Patent Application
20130219940
The present invention relates to an air-conditioning apparatus applicable to, for example, a multi-air-conditioning apparatus for a building or the like.
An example of a conventional air-conditioning apparatus such as a multi-air-conditioning apparatus for buildings is an air-conditioning apparatus that causes a refrigerant to circulate from an outdoor unit to a heat medium relay unit (relay unit) and that causes a heat medium such as water to circulate from the heat medium relay unit to indoor units, so as to reduce the power used to convey the heat medium while causing the heat medium to circulate to the indoor units (for example, Patent Literature 1).
Further, an example of a conventional air-conditioning apparatus that uses a non-azeotropic refrigerant mixture is a chiller air-conditioning apparatus that causes a non-azeotropic refrigerant mixture and a heat medium to flow through a heat exchanger related to heat medium (refrigerant/heat medium heat exchanger) in opposing directions (that is, the flows are in counter flow) to improve heat exchange efficiency (for example, Patent Literature 2).
Further, an example of a conventional air-conditioning apparatus that uses a non-azeotropic refrigerant mixture is a chiller air-conditioning apparatus that causes a non-azeotropic refrigerant mixture and a heat medium to flow through a heat exchanger related to heat medium serving as an evaporator of a refrigerant circuit in parallel in the same direction (that is, the flows are in parallel flow) to prevent freezing of the heat medium while keeping the temperature of the heat medium at the inlet of the heat exchanger related to heat medium constant (for example, Patent Literature 3).
Further, an example of a conventional air-conditioning apparatus that uses a non-azeotropic refrigerant mixture is an air-conditioning apparatus of a heat pump based cold/hot water pumping type configured such that a four-way valve is switched to reverse a refrigerant flow passage of a heat exchanger related to heat medium so that a refrigerant and a heat medium are in parallel flow in the heat exchanger related to heat medium during a cooling operation and a refrigerant and a heat medium are in counter flow in the heat exchanger related to heat medium during a heating operation (for example, Patent Literature 4).
The conventional air-conditioning apparatus described in Patent Literature 1 is configured to cause a refrigerant to circulate between an outdoor unit and a heat medium relay unit and to cause a heat medium such as water to circulate between the heat medium relay unit and indoor units, such that the heat medium relay unit causes heat exchange between the refrigerant and the heat medium such as water. This reduces the power used to convey the heat medium and therefore improves the operation efficiency of the air-conditioning apparatus. However, since the conventional air-conditioning apparatus described in Patent Literature 1 is not presumably designed to use a non-azeotropic refrigerant mixture having a temperature glide between the saturated liquid temperature and the saturated gas temperature at the same pressure, the use of a non-azeotropic refrigerant mixture causes a problem of it not necessarily being possible to provide efficient operation. Further, the conventional air-conditioning apparatus described in Patent Literature 1 cools the heat medium by causing heat exchange between the refrigerant and the heat medium in counter flow. For this reason, in the case of using a non-azeotropic refrigerant mixture having a temperature glide in the heat exchange process, a low-temperature refrigerant undergoes heat exchange with a low-temperature heat medium, and a problem occurs in that the heat medium is prone to freezing if the temperature of the heat medium is low.
The conventional air-conditioning apparatus described in Patent Literature 2 uses a non-azeotropic refrigerant mixture having a temperature glide in the heat exchange process, such that a refrigerant and a heat medium such as water, which flow through a heat exchanger related to heat medium, are always in counter flow. This allows the temperature glide of the refrigerant and the temperature glide of the heat medium to be in the same direction to improve the heat exchange efficiency of the heat exchanger related to heat medium. In the conventional air-conditioning apparatus described in Patent Literature 2, however, since a low-temperature refrigerant undergoes heat exchange with a low-temperature heat medium, a problem occurs in that the heat medium is prone to freezing if the temperature of the heat medium is low.
The conventional air-conditioning apparatus described in Patent Literature 3 uses a non-azeotropic refrigerant mixture having a temperature glide in the heat exchange process, such that a refrigerant and a heat medium such as water, which flow through a heat exchanger related to heat medium, are in parallel flow. For this reason, the conventional air-conditioning apparatus described in Patent Literature 3 can prevent freezing of the heat medium but has a problem in that the heat exchange efficiency of the heat exchanger related to heat medium is not so high.
The conventional air-conditioning apparatus described in Patent Literature 4 uses a non-azeotropic refrigerant mixture having a temperature glide in the heat exchange process, such that the passages of a heat exchanger related to heat medium are switched between counter flow and parallel flow by reversing the refrigerant passage. In the conventional air-conditioning apparatus described in Patent Literature 4, however, since the passages of the heat exchanger related to heat medium are always in parallel flow during the cooling operation, the passages of the heat exchanger related to heat medium are not allowed to be in counter flow even if the temperature of the heat medium is high. Thus, a problem occurs in that the heat exchange efficiency of the heat exchanger related to heat medium may not be improved.
The present invention has been made in order to overcome the foregoing problems, and an object thereof is to provide an air-conditioning apparatus with high energy efficiency and capable of preventing freezing of a heat medium even in the case of using a non-azeotropic refrigerant mixture having a temperature glide between the saturated liquid temperature and the saturated gas temperature at the same pressure.
An air-conditioning apparatus according to the present invention includes a refrigerant circuit in which a compressor, a refrigerant passage switching device that switches a passage of a refrigerant discharged from the compressor, a first heat exchanger, a first expansion device, and a refrigerant flow passage of a second heat exchanger are connected via a refrigerant pipe through which the refrigerant is distributed; a heat medium circuit in which a heat medium flow passage of the second heat exchanger and a heat medium sending device are connected via a heat medium pipe through which a heat medium is distributed, and to which a use side heat exchanger is connected; a heat medium passage reversing device that is disposed in the heat medium circuit and that is capable of switching a direction of the heat medium flowing through the heat medium flow passage of the second heat exchanger between a normal direction and a reverse direction; a controller that controls the heat medium passage reversing device to switch the direction of the heat medium flowing through the heat medium flow passage of the second heat exchanger; and a freezing determination unit that is disposed in the controller and that determines whether or not there is a possibility of freezing of the heat medium flowing through the heat medium flow passage of the second heat exchanger. The refrigerant flowing through the refrigerant circuit is a non-azeotropic refrigerant mixture including two or more components and having a temperature glide between a saturated gas temperature and a saturated liquid temperature at the same pressure. In a condition where the second heat exchanger serves as a cooler that cools the heat medium, the controller controls the heat medium passage reversing device so that, when the freezing determination unit determines that the heat medium flowing through the heat medium flow passage of the second heat exchanger will not be frozen, the refrigerant flowing through the refrigerant flow passage of the second heat exchanger and the heat medium flowing through the heat medium flow passage of the second heat exchanger are in counter flow, and controls the heat medium passage reversing device so that, when the freezing determination unit determines that there is a possibility of freezing of the heat medium flowing through the heat medium flow passage of the second heat exchanger, the refrigerant flowing through the refrigerant flow passage of the second heat exchanger and the heat medium flowing through the heat medium flow passage of the second heat exchanger are in parallel flow.
In an air-conditioning apparatus according to the present invention, when a second heat exchanger serves as a cooler that cools a heat medium, if a freezing determination unit determines that a heat medium flowing through a heat medium flow passage of the second heat exchanger will not be frozen, a refrigerant flowing through a refrigerant flow passage of the second heat exchanger and the heat medium flowing through the heat medium flow passage of the second heat exchanger are in counter flow. Thus, the air-conditioning apparatus according to the present invention can improve the heat exchange efficiency of the second heat exchanger. In the air-conditioning apparatus according to the present invention, furthermore, when the second heat exchanger serves as a cooler that cools the heat medium, if the freezing determination unit determines that there is a possibility of freezing of the heat medium flowing through the heat medium flow passage of the second heat exchanger, the refrigerant flowing through the refrigerant flow passage of the second heat exchanger and the heat medium flowing through the heat medium flow passage of the second heat exchanger are in parallel flow. Thus, the air-conditioning apparatus according to the present invention can cause a high-temperature heat medium to undergo heat exchange with a low-temperature refrigerant and a low-temperature heat medium to undergo heat exchange with a high-temperature heat medium in the second heat exchanger. This can prevent freezing of the heat medium in the second heat exchanger.
In this manner, since a passage in the second heat exchanger is switched in accordance with the state of the heat medium flowing through the second heat exchanger, the air-conditioning apparatus according to the present invention can achieve consistent energy efficiency improvement and freezing prevention.
Embodiment of the present invention will be described with reference to the drawings.
In
The outdoor unit 1 is generally installed in an outdoor space 6, which is an outside space (for example, a roof) of a structure 9 such as a building, and is designed to supply cooling energy or heating energy to the indoor units 2 through the heat medium relay unit 3. The indoor units 2 are installed at positions so as to be able to supply cooling air or heating air to an indoor space 7, which is an inside space (for example, a living room) of the structure 9, and are designed to supply the cooling air or heating air to the indoor space 7, which is an air-conditioned space. The heat medium relay unit 3 includes a housing separated from the outdoor unit 1 and the indoor units 2 such that the heat medium relay unit 3 can be installed at a position different from the outdoor space 6 and the indoor space 7. The heat medium relay unit 3 is connected to the outdoor unit 1 and the indoor units 2 via the refrigerant pipes 4 and the pipes 5, respectively, to transfer the cooling energy or heating energy supplied from the outdoor unit 1 to the indoor units 2.
As illustrated in
In
In
Further, the heat medium relay unit 3 can also be installed in the vicinity of the outdoor unit 1. It should be noted that if the distance from the heat medium relay unit 3 to the indoor units 2 is excessively long, a considerably high power is required to convey the heat medium, resulting in the effect of energy saving being impaired. Furthermore, the numbers of connected outdoor units 1, indoor units 2, and heat medium relay units 3 are not limited to those illustrated in
The outdoor unit 1 has a compressor 10, a first refrigerant passage switching device 11, such as a four-way valve, a heat source side heat exchanger 12, and an accumulator 19, which are connected in series via the refrigerant pipes 4. Here, the heat source side heat exchanger 12 corresponds to a first heat exchanger in the present invention.
The outdoor unit 1 further includes a first connecting pipe 4a, a second connecting pipe 4b, a check valve 13a, a check valve 13b, a check valve 13c, and a check valve 13d. The provision of the first connecting pipe 4a, the second connecting pipe 4b, the check valve 13a, the check valve 13b, the check valve 13c, and the check valve 13d allows the refrigerant to flow into the heat medium relay unit 3 in a constant direction regardless of the operation requested by the indoor units 2.
The outdoor unit 1 further includes a high-low pressure bypass pipe 4c that connects a discharge-side passage and suction-side passage of the compressor 10, an expansion device 14 disposed in the high-low pressure bypass pipe 4c, a refrigerant-refrigerant heat exchanger 27 that causes heat exchange between pipes located before and after the expansion device 14 (in other words, heat exchange between the refrigerant flowing through the high-low pressure bypass pipe 4c on the inlet side of the expansion device 14 and the refrigerant flowing through the high-low pressure bypass pipe 4c on the outlet side of the expansion device 14), a high-pressure side refrigerant temperature detection device 32 and a low-pressure side refrigerant temperature detection device 33 disposed on the inlet side and outlet side of the expansion device 14, respectively, a high-pressure side pressure detection device 37 capable of detecting the high-pressure side pressure of the compressor 10 (that is, the pressure of the refrigerant discharged by the compressor 10), and a low-pressure side pressure detection device 38 capable of detecting the low-pressure side pressure of the compressor 10 (that is, the pressure on the low-pressure side of the compressor 10). The high-pressure side pressure detection device 37 and the low-pressure side pressure detection device 38, which are of a type such as a strain gauge type or a semiconductor type, are used, and the high-pressure side refrigerant temperature detection device 32 and the low-pressure side refrigerant temperature detection device 33, which are of a type such as a thermistor type, are used. Here, the expansion device 14 corresponds to a second expansion device in the present invention.
The compressor 10 is designed to suck in the refrigerant and compress the refrigerant into a high-temperature and high-pressure state, and may include, for example, a capacity-controllable inverter compressor or the like. The first refrigerant passage switching device 11 is designed to switch between the flow of the refrigerant in a heating operation (a heating only operation mode and a heating main operation mode) and the flow of the refrigerant in a cooling operation (a cooling only operation mode and a cooling main operation mode). The heat source side heat exchanger 12 serves as an evaporator in the heating operation, and serves as a condenser (or radiator) in the cooling operation. The heat source side heat exchanger 12 is designed to cause heat exchange between the air supplied from an air-sending device (not illustrated) such as a fan and the refrigerant, and to evaporate and gasify or condense and liquefy the refrigerant. The accumulator 19 is disposed on the suction side of the compressor 10, and is designed to store excess refrigerant.
The check valve 13d is disposed in the refrigerant pipe 4 between the heat medium relay unit 3 and the first refrigerant passage switching device 11, and is designed to permit the flow of the refrigerant only in a certain direction (the direction from the heat medium relay unit 3 to the outdoor unit 1). The check valve 13a is disposed in the refrigerant pipe 4 between the heat source side heat exchanger 12 and the heat medium relay unit 3, and is designed to permit the flow of the refrigerant only in a certain direction (the direction from the outdoor unit 1 to the heat medium relay unit 3). The check valve 13b is disposed in the first connecting pipe 4a, and is designed to distribute the refrigerant discharged from the compressor 10 to the heat medium relay unit 3 in the heating operation. The check valve 13c is disposed in the second connecting pipe 4b, and is designed to distribute the refrigerant returning from the heat medium relay unit 3 to the suction side of the compressor 10 in the heating operation.
The first connecting pipe 4a is designed in the outdoor unit 1 to connect the refrigerant pipe 4 between the first refrigerant passage switching device 11 and the check valve 13d to the refrigerant pipe 4 between the check valve 13a and the heat medium relay unit 3. The second connecting pipe 4b is designed in the outdoor unit 1 to connect the refrigerant pipe 4 between the check valve 13d and the heat medium relay unit 3 to the refrigerant pipe 4 between the heat source side heat exchanger 12 and the check valve 13a. In
In the refrigerant circuit A, a refrigerant mixture containing, for example, tetrafluoropropene, which is represented by chemical formula C3H2F4 (HFO1234yf, which is represented by CF3CF═CH2, HFO1234ze, which is represented by CF3CH═CHF, or the like) and difluoromethane (R32), which is represented by chemical formula CH2F2, circulates. Because the chemical formula has a double bond, tetrafluoropropene is easily decomposed in the atmosphere, and is an environment-friendly refrigerant with a low global warming potential (GWP) (for example, a GWP of 4). However, tetrafluoropropene has a lower density than conventional refrigerants such as R410A. For this reason, in a case where tetrafluoropropene is used alone as a refrigerant, a very large compressor may be required to exert high heating capacity or cooling capacity. In a case where tetrafluoropropene is used alone as a refrigerant, furthermore, thick refrigerant pipes may be required in order to prevent an increase in pressure loss at the pipes. Thus, if tetrafluoropropene is to be used alone as a refrigerant, a high-cost air-conditioning apparatus may be required. Meanwhile, R32 is a comparatively easy-to-use refrigerant because its characteristics are close to those of conventional ones. However, R32 has a GWP of, for example, 675, which is slightly high to use it alone as a refrigerant although the GWP of R32 is smaller than the GWP (for example, 2088) of R410A, which is a conventional refrigerant.
The air-conditioning apparatus 100 according to Embodiment uses a mixture of tetrafluoropropene and R32. Accordingly, the air-conditioning apparatus 100, which has improved characteristics of the refrigerant without greatly increasing GWP and therefore is earth-friendly and efficient, can be achieved. Tetrafluoropropene and R32 may be mixed at a mixture ratio of, for example, 70% to 30% in mass % for use. However, Embodiment is not limited to this mixture ratio.
A refrigerant mixture of tetrafluoropropene and R32 is non-azeotropic refrigerant having different boiling points, where, for example, HFO1234yf, which is a tetrafluoropropene, has a boiling point of −29 degrees C. and R32 has a boiling point of −53.2 degrees C. Due to the presence of a liquid pool, such as the accumulator 19, and the like, the refrigerant circulating in the refrigerant circuit A has time-varying proportions of tetrafluoropropene and R32 (hereinafter referred to as circulation compositions).
Since a non-azeotropic refrigerant has mixture components (for example, HFO1234yf and R32) whose boiling points are different, the saturated liquid temperature and the saturated gas temperature at the same pressure are different. Thus, a P-h diagram as in
In the air-conditioning apparatus 100 according to Embodiment, therefore, the outdoor unit 1 is provided with a refrigerant circulation composition detection device 50. The refrigerant circulation composition detection device 50, which includes the high-low pressure bypass pipe 4c, the expansion device 14, the refrigerant-refrigerant heat exchanger 27, the high-pressure side refrigerant temperature detection device 32, the low-pressure side refrigerant temperature detection device 33, the high-pressure side pressure detection device 37, and the low-pressure side pressure detection device 38, is used to measure the circulation compositions of the refrigerant circulating in the refrigerant circuit A.
A circulation composition measurement method according to Embodiment will be described hereinafter with reference to
As illustrated in
Once the circulation compositions of the refrigerant are determined, the enthalpy of the refrigerant can be calculated from the P-h diagram (
X=(hH−hb)/(hd−hb) (1)
Here, hb denotes the saturated liquid enthalpy at the pressure PL detected by the low-pressure side pressure detection device 38, and hd denotes the saturated gas enthalpy at the pressure PL detected by the low-pressure side pressure detection device 38.
In ST6, the controller 60 determines a saturated gas temperature TLG and a saturated liquid temperature TLL at the pressure PL detected by the low-pressure side pressure detection device 38. The saturated gas temperature TLG and the saturated liquid temperature TLL can be determined on the basis of, for example, the P-h diagram illustrated in
T
L
′=T
LL×(1−X)+TLG×X (2)
In ST7, the controller 60 determines whether or not TL′ is substantially equal to the temperature TL detected by the low-pressure side refrigerant temperature detection device 33 (that is, the controller 60 determines whether or not the difference between them is within a certain range). If the difference between TL′ and TL is greater than the certain range, the controller 60 adjust the assumed circulation compositions α1 and α2 of the two components of the refrigerant (ST8), and repeats the process from ST4. If TL′ and TL are substantially equal, the controller 60 regards circulation compositions as being successfully determined, and then the process ends (ST9).
Accordingly, the circulation compositions of a two-component non-azeotropic refrigerant mixture can be determined by the process described above.
In Embodiment, the enthalpy hH is calculated using the pressure PH detected by the high-pressure side pressure detection device 37. If the isotherm lines are substantially vertical in the subcooled-liquid region in
Even in a three-component non-azeotropic refrigerant mixture, a correlation is established between the proportions of two components among the three components. Thus, once the circulation compositions of two components are assumed, the circulation composition of the other component can be determined, and the circulation compositions can therefore be determined using a similar processing method. In Embodiment, the description has been given taking an example of a two-component refrigerant mixture containing tetrafluoropropene, which is represented by chemical formula C3H2F4 (HFO1234yf, which is represented by CF3CF═CH2, HFO1234ze, which is represented by CF3CH═CHF, or the like) and difluoromethane (R32), which is represented by chemical formula CH2F2, but Embodiment is not limited thereto. Any other two-component refrigerant mixture having different boiling points or a three-component refrigerant mixture including an additional component may be used, and the circulation compositions can be determined using a similar method.
Further, the expansion device 14 may be an electronic expansion valve whose opening degree is variable, or may be a device with a fixed aperture, such as a capillary tube. Further, the refrigerant-refrigerant heat exchanger 27 may be a double-pipe heat exchanger, but is not limited thereto. A plate-type heat exchanger, a micro-channel heat exchanger, or the like may be used, or any type that causes heat exchange between a high-pressure refrigerant and a low-pressure refrigerant may be used. In the illustration of
As described above, once the circulation compositions of the refrigerant circulating in the refrigerant circuit A can be measured, a saturated liquid temperature and a saturated gas temperature at a certain pressure can be calculated. For example, if the pressure of the refrigerant flowing into the heat exchanger is P1, the saturated liquid temperature and the saturated gas temperature at that pressure can be calculated using
On the low-pressure side (the evaporation side), it is possible to determine a saturated liquid temperature, a saturated gas temperature, and so forth without measuring a pressure. More specifically, the temperature of the two-phase refrigerant at the inlet of the evaporator is measured, and is assumed to be the saturated liquid temperature or the temperature of the two-phase refrigerant at a set quality. An inverse calculation of a relational expression (formula into which
While the description has been made here taking an example where the refrigerant is a refrigerant mixture of HFO1234yf (tetrafluoropropene) and R32, Embodiment is not limited thereto. A refrigerant mixture of a refrigerant other tetrafluoropropene, such as HFO1234ze, and R32 or any non-azeotropic refrigerant mixture having a temperature glide between a saturated gas temperature and a saturated liquid temperature at the same pressure, such as R407C, may be used, and similar advantages are achieved.
Each of the indoor units 2 includes a use side heat exchanger 26. The use side heat exchangers 26 are designed to be connected to heat medium flow control devices 25 and first heat medium passage switching devices 23 of the heat medium relay unit 3 via the pipes 5. The use side heat exchangers 26 are designed to cause heat exchange between the air supplied from air-sending devices (not illustrated) such as fans and the heat medium to generate heating air or cooling air to be supplied to the indoor space 7.
In the illustration of
The heat medium relay unit 3 has the two heat exchangers related to heat medium 15, two expansion devices 16, two opening and closing devices 17, two second refrigerant passage switching devices 18, two pumps 21 (heat medium sending devices), four second heat medium passage switching devices 22, four heat medium passage reversing devices 20, the four first heat medium passage switching devices 23, and the four heat medium flow control devices 25. Here, the heat exchangers related to heat medium 15 correspond to a second heat exchanger in the present invention, the expansion devices 16 correspond to a first expansion device in the present invention, the first heat medium passage switching devices 23 correspond to a first heat medium passage switching device in the present invention, and the second heat medium passage switching devices 22 correspond to a second heat medium passage switching device in the present invention.
Each of the two heat exchangers related to heat medium 15 (the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b) serves as a condenser (radiator) or an evaporator, and is designed to cause heat exchange between the refrigerant and the heat medium to transfer the cooling energy or heating energy generated by the outdoor unit 1 and stored in the refrigerant to the heat medium. In other words, each of the two heat exchangers related to heat medium 15 (the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b) is designed to serve as a cooler for cooling the heat medium or a heater for heating the heat medium. The heat exchanger related to heat medium 15a is disposed between an expansion device 16a and a second refrigerant passage switching device 18a in the refrigerant circuit A, and is designed to serve to cool the heat medium in the cooling and heating mixed operation mode. The heat exchanger related to heat medium 15b is disposed between an expansion device 16b and a second refrigerant passage switching device 18b in the refrigerant circuit A, and is designed to serve to heat the heat medium in the cooling and heating mixed operation mode.
Each of the two expansion devices 16 (the expansion device 16a and the expansion device 16b) has functions of a pressure reducing valve and an expansion valve, and is designed to reduce the pressure of the refrigerant and expand the refrigerant. The expansion device 16a is disposed upstream of the heat exchanger related to heat medium 15a in the flow of the refrigerant in the cooling operation. The expansion device 16b is disposed upstream of the heat exchanger related to heat medium 15b in the flow of the refrigerant in the cooling operation. Each of the two expansion devices 16 may include a device whose opening degree is variably controllable, such as an electronic expansion valve.
Each of the two opening and closing devices 17 (an opening and closing device 17a and an opening and closing device 17b) includes a two-way valve or the like, and is designed to open and close the refrigerant pipe 4. The opening and closing device 17a is disposed in the refrigerant pipe 4 on the refrigerant inlet side. The opening and closing device 17b is disposed in a pipe that connects the refrigerant pipes 4 on the refrigerant inlet and outlet sides. Each of the two second refrigerant passage switching devices 18 (a second refrigerant passage switching device 18a and a second refrigerant passage switching device 18b) includes a four-way valve or the like, and is designed to switch the flow of the refrigerant in accordance with the operation mode. The second refrigerant passage switching device 18a is disposed downstream of the heat exchanger related to heat medium 15a in the flow of the refrigerant in the cooling operation. The second refrigerant passage switching device 18b is disposed downstream of the heat exchanger related to heat medium 15b in the flow of the refrigerant in the cooling only operation.
Each of the two pumps 21 (a pump 21a and a pump 21b) is designed to circulate the heat medium passing through the pipe 5. The pump 21a is disposed in the pipe 5 between the heat exchanger related to heat medium 15a and the second heat medium passage switching devices 22. The pump 21b is disposed in the pipe 5 between the heat exchanger related to heat medium 15b and the second heat medium passage switching devices 22. Each of the two pumps 21 may include, for example, a capacity-controllable pump or the like.
Each of the four heat medium passage reversing devices 20 (heat medium passage reversing devices 20a to 20d) includes a three-way valve or the like, and is designed to switch the flow direction of the heat medium in the heat exchangers related to heat medium 15a and 15b. Two of the heat medium passage reversing devices 20 are disposed for each of the heat exchangers related to heat medium 15. In the heat medium passage reversing device 20a, one of the three ways is connected to the pump 21a (heat medium sending device), another of the three ways is connected to one end of the heat exchanger related to heat medium 15a, and the other of the three ways is connected to a passage between the other end of the heat exchanger related to heat medium 15a and the heat medium passage reversing device 20b. In the heat medium passage reversing device 20b, one of the three ways is connected to the other end of the heat exchanger related to heat medium 15a, another of the three ways is connected to a passage between the one end of the heat exchanger related to heat medium 15a and the heat medium passage reversing device 20a, and the other of the three ways is connected to the first heat medium passage switching devices 23a to 23d. The direction of the heat medium to be distributed to the heat exchanger related to heat medium 15a is changed by switching between the heat medium passage reversing device 20a and the heat medium passage reversing device 20b. Here, the heat medium passage reversing device 20a corresponds to a first heat medium passage reversing device in the present invention, and the heat medium passage reversing device 20b corresponds to a second heat medium passage reversing device in the present invention.
Further, in the heat medium passage reversing device 20c, one of the three ways is connected to the pump 21b (heat medium sending device), another of the three ways is connected to one end of the heat exchanger related to heat medium 15b, and the other of the three ways is connected to a passage between the other end of the heat exchanger related to heat medium 15b and the heat medium passage reversing device 20d. In the heat medium passage reversing device 20d, one of the three ways is connected to the other end of the heat exchanger related to heat medium 15b, another of the three ways is connected to a passage between the one end of the heat exchanger related to heat medium 15b and the heat medium passage reversing device 20c, and the other of the three ways is connected to the first heat medium passage switching devices 23a to 23d. The direction of the heat medium to be distributed to the heat exchanger related to heat medium 15b is changed by switching between the heat medium passage reversing device 20c and the heat medium passage reversing device 20d. Here, the heat medium passage reversing device 20c corresponds to the first heat medium passage reversing device in the present invention, and the heat medium passage reversing device 20d corresponds to the second heat medium passage reversing device in the present invention.
Each of the four second heat medium passage switching devices 22 (second heat medium passage switching devices 22a to 22d) includes a three-way valve or the like, and is designed to switch the passage of the heat medium. The second heat medium passage switching devices 22, the number of which corresponds to the number of installed indoor units 2 (here, four), are arranged. In each of the second heat medium passage switching devices 22 one of the three ways is connected to the heat exchanger related to heat medium 15a, another of the three ways is connected to the heat exchanger related to heat medium 15b, and the other of the three ways is connected to the corresponding one of the heat medium flow control devices 25. The second heat medium passage switching devices 22 are disposed on the outlet side of the heat medium passages of the use side heat exchangers 26. The second heat medium passage switching device 22a, the second heat medium passage switching device 22b, the second heat medium passage switching device 22c, and the second heat medium passage switching device 22d are illustrated in this order from bottom to top of the drawing in correspondence with the indoor units 2.
Each of the four first heat medium passage switching devices 23 (first heat medium passage switching devices 23a to 23d) includes a three-way valve or the like, and is designed to switch the passage of the heat medium. The first heat medium passage switching devices 23, the number of which corresponds to the number of installed indoor units 2 (here, four), are arranged. In each of the first heat medium passage switching devices 23, one of the three ways is connected to the heat exchanger related to heat medium 15a, another of the three ways is connected to the heat exchanger related to heat medium 15b, and the other of the three ways is connected to the corresponding one of the use side heat exchangers 26. The first heat medium passage switching devices 23 are disposed on the inlet side of the heat medium passages of the use side heat exchangers 26. The first heat medium passage switching device 23a, the first heat medium passage switching device 23b, the first heat medium passage switching device 23c, and the first heat medium passage switching device 23d are illustrated in this order from bottom to top of the drawing in correspondence with the indoor units 2.
Each of the four heat medium flow control devices 25 (heat medium flow control devices 25a to 25d) includes a two-way valve or the like whose opening area is controllable, and is designed to control the flow rate of the flow in the pipe 5. The heat medium flow control devices 25, the number of which corresponds to the number of installed indoor units 2 (here, four), are arranged. In each of the heat medium flow control devices 25, one is connected to the corresponding one of the use side heat exchangers 26 and the other is connected to the corresponding one of the second heat medium passage switching devices 22. The heat medium flow control devices 25 are disposed on the outlet side of the heat medium passages of the use side heat exchangers 26. The heat medium flow control device 25a, the heat medium flow control device 25b, the heat medium flow control device 25c, and the heat medium flow control device 25d are illustrated in this order from bottom to top of the drawing in correspondence with the indoor units 2. The heat medium flow control devices 25 may be disposed on the inlet side of the heat medium passages of the use side heat exchangers 26.
The heat medium relay unit 3 is further provided with various detection devices (two temperature sensors 31, four temperature sensors 34, four temperature sensors 35, and two pressure sensors 36). Information (temperature information and pressure information) detected by these detection devices is sent to the controller 60, which controls the overall operation of the air-conditioning apparatus 100, to use the information for control such as the driving frequency of the compressor 10, the rotation speed of the air-sending devices (not illustrated), switching of the first refrigerant passage switching device 11, the driving frequency of the pumps 21, switching of the second refrigerant passage switching devices 18, and switching of the passage of the heat medium.
Each of the two temperature sensors 31 (a temperature sensor 31a and a temperature sensor 31b) is designed to detect the temperature of the heat medium flowing out of the corresponding one of the heat exchangers related to heat medium 15, that is, the temperature of the heat medium at the outlet of the corresponding one of the heat exchangers related to heat medium 15, and may include, for example, a thermistor or the like. The temperature sensor 31a is disposed in the pipe 5 on the inlet side of the pump 21a. The temperature sensor 31b is disposed in the pipe 5 on the inlet side of the pump 21b. Here, the temperature sensor 31a and the temperature sensor 31b correspond to a fourth temperature detection device in the present invention.
Each of the four temperature sensors 34 (temperature sensors 34a to 34d) is disposed between the corresponding one of the second heat medium passage switching devices 22 and the corresponding one of the heat medium flow control devices 25. Each of the four temperature sensors 34 is designed to detect the temperature of the heat medium flowing out of the corresponding one of the use side heat exchangers 26, and may include a thermistor or the like. The temperature sensors 34, the number of which corresponds to the number of installed indoor units 2 (here, four), are arranged. The temperature sensor 34a, the temperature sensor 34b, the temperature sensor 34c, and the temperature sensor 34d are illustrated in this order from bottom to top of the drawing in correspondence with the indoor units 2. Here, the temperature sensors 34a to 34d correspond to a third temperature detection device in the present invention.
Each of the four temperature sensors 35 (temperature sensors 35a to 35d) is disposed on the refrigerant inlet or outlet side of the corresponding one of the heat exchangers related to heat medium 15. Each of the four temperature sensors 35 is designed to detect the temperature of the refrigerant flowing into the corresponding one of the heat exchangers related to heat medium 15 or the temperature of the refrigerant flowing out of the corresponding one of the heat exchangers related to heat medium 15, and may include a thermistor or the like. The temperature sensor 35a is disposed between the heat exchanger related to heat medium 15a and the second refrigerant passage switching device 18a. The temperature sensor 35b is disposed between the heat exchanger related to heat medium 15a and the expansion device 16a. The temperature sensor 35c is disposed between the heat exchanger related to heat medium 15b and the second refrigerant passage switching device 18b. The temperature sensor 35d is disposed between the heat exchanger related to heat medium 15b and the expansion device 16b. Here, the temperature sensors 35a to 35d correspond to a first temperature detection device or a second temperature detection device in the present invention.
A pressure sensor 36b is disposed between, similarly to the installation position of the temperature sensor 35d, the heat exchanger related to heat medium 15b and the expansion device 16b, and is designed to detect the pressure of the refrigerant flowing between the heat exchanger related to heat medium 15b and the expansion device 16b. A pressure sensor 36a is disposed between, similarly to the installation position of the temperature sensor 35a, the heat exchanger related to heat medium 15a and the second refrigerant passage switching device 18a, and is designed to detect the pressure of the refrigerant flowing between the heat exchanger related to heat medium 15a and the second refrigerant passage switching device 18a.
Further, the controller 60 includes a microcomputer or the like, and is designed to control the driving frequency of the compressor 10, the rotation speed (including ON/OFF) of the air-sending devices, switching of the first refrigerant passage switching device 11, the driving of the pumps 21, the opening degree of the expansion devices 16, the opening and closing of the opening and closing devices 17, switching of the second refrigerant passage switching devices 18, switching of the heat medium passage reversing devices 20, switching of the second heat medium passage switching devices 22, switching of the first heat medium passage switching devices 23, the opening degree of the heat medium flow control devices 25, and so forth in accordance with the information detected by the various detection devices and instructions from various remote controls to execute operation modes described below. In Embodiment, the controller 60 is divided into a controller 60a and a controller 60b, such that the controller 60a is disposed in the outdoor unit 1 and the controller 60b is disposed in the heat medium relay unit 3. However, the method for installing the controller 60 is not limited to the method illustrated in Embodiment, and the controller 60 may be disposed in only either the outdoor unit 1 or the heat medium relay unit 3. Here, the controller 60a corresponds to a first controller in the present invention, and the controller 60b corresponds to a second controller in the present invention.
The pipes 5 through which the heat medium passes include pipes connected to the heat exchanger related to heat medium 15a and pipes connected to the heat exchanger related to heat medium 15b. The pipes 5 have branching pipes (here, four pipes), the number of which corresponds to the number of indoor units 2 connected to the heat medium relay unit 3. The pipes 5 are connected to the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23. The second heat medium passage switching devices 22 and the first heat medium passage switching devices 23 are controlled to determine whether to cause the heat medium flowing from the heat exchanger related to heat medium 15a to flow into the use side heat exchangers 26 or to cause the heat medium flowing from the heat exchanger related to heat medium 15b to flow into the use side heat exchangers 26.
In the air-conditioning apparatus 100, the refrigerant circuit A is formed by connecting the compressor 10, the first refrigerant passage switching device 11, the heat source side heat exchanger 12, the opening and closing devices 17, the second refrigerant passage switching devices 18, the refrigerant passages of the heat exchangers related to heat medium 15, the expansion devices 16, and the accumulator 19 via the refrigerant pipes 4. Further, the heat medium circuit B is formed by connecting the heat medium passages of the heat exchangers related to heat medium 15, the pumps 21, the second heat medium passage switching devices 22, the heat medium flow control devices 25, the use side heat exchangers 26, and the first heat medium passage switching devices 23 via the pipes 5. That is, a plurality of use side heat exchangers 26 are connected in parallel to each of the heat exchangers related to heat medium 15, thereby making the heat medium circuit B have a plurality of systems.
Therefore, in the air-conditioning apparatus 100, the outdoor unit 1 and the heat medium relay unit 3 are connected through the heat exchangers related to heat medium 15a and 15b disposed in the heat medium relay unit 3, and the heat medium relay unit 3 and the indoor units 2 are also connected through the heat exchangers related to heat medium 15a and 15b. That is, the air-conditioning apparatus 100 causes heat exchange between the refrigerant circulating in the refrigerant circuit A and the heat medium circulating in the heat medium circuit B at the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b.
Subsequently, the operation modes of the air-conditioning apparatus 100 will be described. The air-conditioning apparatus 100 allows each of the indoor units 2 to perform a cooling operation or a heating operation in accordance with an instruction from the indoor unit 2. That is, the air-conditioning apparatus 100 is designed to allow all the indoor units 2 to perform the same operation and also allow each of the indoor units 2 to perform a different operation.
The operation modes of the air-conditioning apparatus 100 include a cooling only operation mode in which all the indoor units 2 in operation perform the cooling operation, a heating only operation mode in which all the indoor units 2 in operation perform the heating operation, a cooling main operation mode in which cooling load is larger, and a heating main operation mode in which heating load is larger. The individual operation modes will be described hereinafter along the flows of the refrigerant and the heat medium.
In the first cooling only operation mode illustrated in
First, the flow of the refrigerant in the refrigerant circuit A will be described.
A low-temperature and low-pressure refrigerant is compressed by the compressor 10 into a high-temperature and high-pressure gaseous refrigerant, which is then discharged. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12 through the first refrigerant passage switching device 11. Then, the gaseous refrigerant is condensed and liquefied by the heat source side heat exchanger 12, while radiating heat to the outdoor air, and then turns into a high-pressure liquid refrigerant. The high-pressure liquid refrigerant flowing out of the heat source side heat exchanger 12 flows out of the outdoor unit 1 through the check valve 13a, and flows into the heat medium relay unit 3 through the refrigerant pipe 4. The flow of the high-pressure liquid refrigerant flowing into the heat medium relay unit 3 is split after it flows through the opening and closing device 17a and then turns into a low-temperature and low-pressure two-phase refrigerant after being expanded by the expansion devices 16a and 16b.
The two-phase refrigerant flows individually into the heat exchangers related to heat medium 15a and 15b serving as evaporators (coolers) from the lower portion of the drawing, and absorbs heat from the heat medium circulating in the heat medium circuit B to cool the heat medium, so that the two-phase refrigerant is turned into a low-temperature and low-pressure gaseous refrigerant. The gaseous refrigerant flowing out of the heat exchangers related to heat medium 15a and 15b from the upper portion of the drawing flow out of the heat medium relay unit 3 through the second refrigerant passage switching devices 18a and 18b, respectively, and again flow into the outdoor unit 1 through the refrigerant pipe 4. The refrigerant flowing into the outdoor unit 1 flow through the check valve 13d, and are again sucked into the compressor 10 through the first refrigerant passage switching device 11 and the accumulator 19.
The circulation compositions of the refrigerant circulating in the refrigerant circuit A are measured by using the refrigerant circulation composition detection device 50 (the high-low pressure bypass pipe 4c, the expansion device 14, the refrigerant-refrigerant heat exchanger 27, the high-pressure side refrigerant temperature detection device 32, the low-pressure side refrigerant temperature detection device 33, the high-pressure side pressure detection device 37, and the low-pressure side pressure detection device 38). The controller 60a in the outdoor unit 1 and the controller 60b in the heat medium relay unit 3 are connected via wire or wirelessly so as to be capable of communicating with each other, and the circulation compositions calculated by the controller 60a in the outdoor unit 1 are transmitted via communication from the controller 60a in the outdoor unit 1 to the controller 60b in the heat medium relay unit 3.
The controller 60b in the heat medium relay unit 3 calculates a saturated liquid temperature and a saturated gas temperature on the basis of the circulation compositions transmitted from the controller 60a in the outdoor unit 1 and the pressure detected by the pressure sensor 36a. Further, the controller 60b in the heat medium relay unit 3 calculates an average temperature of the saturated liquid temperature and the saturated gas temperature to determine an evaporating temperature. Then, the controller 60b in the heat medium relay unit 3 controls the opening degree of the expansion device 16a so that superheat (the degree of superheating) obtained as a temperature difference between the temperature detected by the temperature sensor 35a and the calculated evaporating temperature is kept constant.
Similarly, the controller 60b in the heat medium relay unit 3 controls the opening degree of the expansion device 16b so that superheat (the degree of superheating) obtained as a temperature difference between the temperature detected by the temperature sensor 35c and the calculated evaporating temperature is kept constant.
The evaporating temperature may be determined on the basis of the circulation compositions transmitted from the controller 60a in the outdoor unit 1 and the temperature detected by the temperature sensor 35b (or the temperature sensor 35d). That is, a saturated pressure and a saturated gas temperature may be calculated by assuming that the temperature detected by the temperature sensor 35b is a saturated liquid temperature or the temperature of a set quality, and an average temperature of the saturated liquid temperature and the saturated gas temperature may be calculated to determine an evaporating temperature. Then, the resulting evaporating temperature may be used to control the expansion devices 16a and 16b. In this case, the pressure sensor 36a and the pressure sensor 36b may not necessarily be installed, thus achieving a low-cost system.
Next, the flow of the heat medium in the heat medium circuit B will be described.
In the first cooling only operation mode, cooling energy of the refrigerant is transferred to the heat medium in both the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b, and the chilled heat medium is caused by the pump 21a and the pump 21b to flow in the pipes 5.
The heat medium pressurized by and flowing out of the pump 21a flows into the heat exchanger related to heat medium 15a from the upper portion of the drawing through the heat medium passage reversing device 20a, and is chilled by the refrigerant flowing through the heat exchanger related to heat medium 15a. The chilled heat medium flows out of the heat exchanger related to heat medium 15a from the lower portion of the drawing, and flows through the heat medium passage reversing device 20b, reaching the first heat medium passage switching device 23a and the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15a, are in counter flow. The heat medium pressurized by and flowing out of the pump 21b flows into the heat exchanger related to heat medium 15b from the upper portion of the drawing through the heat medium passage reversing device 20c, and is chilled by the refrigerant flowing through the heat exchanger related to heat medium 15b. The chilled heat medium flows out of the heat exchanger related to heat medium 15b from the lower portion of drawing, and flows through the heat medium passage reversing device 20d, reaching the first heat medium passage switching device 23a and the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15b, are in counter flow.
The heat media pumped out by the pump 21a and the pump 21b merge at each of the first heat medium passage switching device 23a and the first heat medium passage switching device 23b, and the merged heat media flow into the use side heat exchanger 26a and the use side heat exchanger 26b. Then, the heat media absorbs heat from the indoor air in the use side heat exchanger 26a and the use side heat exchanger 26b to cool the indoor space 7. Each of the use side heat exchanger 26a and the use side heat exchanger 26b serves as a cooler, and is configured such that the flow direction of the heat medium and the flow direction of the indoor air are in a counter-flow configuration.
The heat media flowing out of the use side heat exchanger 26a and the use side heat exchanger 26b flow into the heat medium flow control device 25a and the heat medium flow control device 25b, respectively. At this time, due to the action of the heat medium flow control device 25a and the heat medium flow control device 25b, the flow rates of the heat media are controlled to flow rates necessary to compensate for the air conditioning load required indoor, and the resulting heat media flow into the use side heat exchanger 26a and the use side heat exchanger 26b. The heat media flowing out of the heat medium flow control device 25a and the heat medium flow control device 25b are split into flows at the second heat medium passage switching device 22a and the second heat medium passage switching device 22b, respectively, which are again sucked into the pump 21a and the pump 21b.
As described above, in the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b, the refrigerant flows from the lower portion of the drawing to the upper portion of the drawing, and the heat medium flows from the upper portion of the drawing to the lower portion of the drawing, where the refrigerant and the heat medium are in counter flow. Flowing of the refrigerant and the heat medium in a counter-flow manner provides high heat exchange efficiency and improves COP.
Further, if plate-type heat exchangers are used as the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b, flowing of the evaporation-side refrigerant from below to above in the manner illustrated in the drawing causes the evaporated gaseous refrigerant to move upward due to the buoyant force effect, yielding a reduction in the power of the compressor and appropriate distribution of the refrigerant. If plate-type heat exchangers are used as the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b, furthermore, flowing of the heat medium from above to below in the manner illustrated in the drawing causes the chilled heat medium to sink due to the gravitational effect, yielding a reduction in the power of the pumps, which is efficient.
In the pipes 5 of the use side heat exchangers 26, the heat medium flows in the direction from the first heat medium passage switching devices 23 to the second heat medium passage switching devices 22 through the heat medium flow control devices 25. Further, the air conditioning load required for the indoor space 7 can be compensated for by performing control to maintain the differences between the temperature detected by the temperature sensor 31a or the temperature detected by the temperature sensor 31b and the temperatures detected by the temperature sensors 34 at a target value. Either of the temperatures obtained by the temperature sensor 31a and the temperature sensor 31b may be used as the outlet temperatures of the heat exchangers related to heat medium 15, or an average temperature thereof may be used. At this time, the opening degrees of the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23 are set to be an intermediate opening degree so as to reserve the passages of the flows to both the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b.
In the first cooling only operation mode, since it is not necessary to cause the heat medium to flow to a use side heat exchanger 26 having no heat load (including that in a thermostat-off state), the corresponding one of the heat medium flow control devices 25 closes the passage to prevent the heat medium from flowing to the use side heat exchanger 26. In
Here, the determination as to whether or not there is a possibility of freezing of the heat medium in the heat exchangers related to heat medium 15 may be performed, for example, as follows. That is, if at least one of the temperatures detected by the temperature sensor 35a and the temperature sensor 35b is less than or equal to the first set temperature (for example, −3 degrees C.) or if at least one of the temperatures detected by the temperature sensor 34a, the temperature sensor 34b, and the temperature sensor 31a is less than or equal to the second set temperature (for example, 4 degrees C.), a freezing determination unit in the controller 60b determines that there is a possibility of freezing of the heat medium in the heat exchanger related to heat medium 15a. Similarly, if at least one of the temperatures detected by the temperature sensor 35c and the temperature sensor 35d is less than or equal to the first set temperature or if at least one of the temperatures detected by the temperature sensor 34a, the temperature sensor 34b, and the temperature sensor 31b is less than or equal to the second set temperature, the freezing determination unit in the controller 60b determines that there is a possibility of freezing of the heat medium in the heat exchanger related to heat medium 15b.
In the operation modes in Embodiment, the controller 60b determines the first set temperature using, for example, a correspondence table between circulation compositions and the first set temperature or the like on the basis of the circulation compositions transmitted from the controller 60a. Embodiment is not limited to this form, and the first set temperature may also be determined, for example, as follows. For example, the controller 60a may calculate, from the circulation compositions measured by the refrigerant circulation composition detection device 50, a temperature glide of the refrigerant (non-azeotropic refrigerant) in the circulation compositions. Then, the controller 60a may transmit the calculated temperature glide to the controller 60b, and the controller 60b may determine the first set temperature on the basis of the transmitted temperature glide. As described above, the non-azeotropic refrigerant has a refrigerant temperature on the inlet side of the heat exchangers related to heat medium 15 lower than the refrigerant temperature on the outlet side of the heat exchangers related to heat medium 15 when the heat-medium heat exchangers 15 serve as coolers. However, if the refrigerant and heat medium flowing through the heat exchangers related to heat medium 15 are in parallel flow, the temperature of the heat medium to be subjected to heat exchange with the refrigerant on the inlet side of the heat exchangers related to heat medium 15 is higher than that of the heat medium to be subjected to heat exchange with the refrigerant on the outlet side of the heat exchangers related to heat medium 15. That is, the heat medium is less likely to be frozen if the temperature of the refrigerant on the inlet side of the heat exchangers related to heat medium 15 is low. Accordingly, by determining the first set temperature on the basis of temperature glide, it is possible for the controller 60b to set the first set temperature of the temperature sensors 35, which measure the refrigerant temperatures on the inlet side of the heat exchangers related to heat medium 15, to be lower than the first set temperature of the temperature sensors 35, which measure the refrigerant temperatures on the outlet side of the heat exchangers related to heat medium 15. That is, by determining the first set temperature on the basis of temperature glide, it is possible for the controller 60b to set the first set temperature of the temperature sensors 35, which measure the refrigerant temperatures on the inlet side of the heat exchangers related to heat medium 15, and the first set temperature of the temperature sensors 35, which measure the refrigerant temperatures on the outlet side of the heat exchangers related to heat medium 15, to be different values.
In the second cooling only operation mode, the flow of the refrigerant in the refrigerant circuit A is the same as that in the first cooling only operation mode. Further, the flow of the heat medium in the heat medium circuit B is the same as that in the first cooling only operation mode, except the flow of the heat medium around the heat exchangers related to heat medium 15a and 15b. Hereinafter, a description will be given of only a portion of the flow of the heat medium different from that in the first cooling only operation mode.
The heat medium pressurized by and flowing out of the pump 21a flows into the heat exchanger related to heat medium 15a from the lower portion of the drawing through the heat medium passage reversing device 20a, and is chilled by the refrigerant flowing through the heat exchanger related to heat medium 15a. The chilled heat medium flows out of the heat exchanger related to heat medium 15a from the upper portion of the drawing, and flows through the heat medium passage reversing device 20b, reaching the first heat medium passage switching device 23a and the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15a, are in parallel flow. The heat medium pressurized by and flowing out of the pump 21b flows into the heat exchanger related to heat medium 15b from the lower portion of the drawing through the heat medium passage reversing device 20c, and is chilled by the refrigerant flowing through the heat exchanger related to heat medium 15b. The chilled heat medium flows out of the heat exchanger related to heat medium 15b from the upper portion of the drawing, and flows through the heat medium passage reversing device 20d, reaching the first heat medium passage switching device 23a and the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15b, are in parallel flow. The heat media pumped out by the pump 21a and the pump 21b merge at each of the first heat medium passage switching device 23a and the first heat medium passage switching device 23b, and the merged heat media flow into the use side heat exchanger 26a and the use side heat exchanger 26b.
As described above, in the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b, the refrigerant flows from the lower portion of the drawing to the upper portion of the drawing, and the heat medium flows from the lower portion of the drawing to the upper portion of the drawing, where the refrigerant and the heat medium are in parallel flow. Flowing of the refrigerant and the heat medium in a parallel-flow manner does not provide high heat exchange efficiency. In the heat exchangers related to heat medium 15a and 15b, on the contrary, a low-temperature heat medium and a high-temperature refrigerant undergo heat exchange on the outlet side, and a high-temperature heat medium and a low-temperature refrigerant undergo heat exchange on the inlet side, resulting in freezing of the heat medium being less likely to occur and realizing safe operation.
In the heating only operation mode illustrated in
First, the flow of the refrigerant in the refrigerant circuit A will be described.
A low-temperature and low-pressure refrigerant is compressed by the compressor 10 into a high-temperature and high-pressure gaseous refrigerant, which is then discharged. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 10 flows through the first refrigerant passage switching device 11, passing through the first connecting pipe 4a, and flows out of the outdoor unit 1 through the check valve 13b. The high-temperature and high-pressure gaseous refrigerant flowing out of the outdoor unit 1 flows into the heat medium relay unit 3 through the refrigerant pipe 4. The flow of the high-temperature and high-pressure gaseous refrigerant flowing into the heat medium relay unit 3 branches into flows, which enter the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b through the second refrigerant passage switching device 18a and the second refrigerant passage switching device 18b, respectively.
The high-temperature and high-pressure gaseous refrigerant flows into the heat exchangers related to heat medium 15a and 15b serving as condensers (heaters) from the upper portion of the drawing, and is condensed and liquefied, while radiating heat to the heat medium circulating in the heat medium circuit B, and then turns into a high-pressure liquid refrigerant. The liquid refrigerants flowing out of the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b from the lower portion of the drawing are expanded by the expansion device 16a and the expansion device 16b, respectively, and then turns into a low-temperature and low-pressure two-phase refrigerant. The two-phase refrigerant flows out of the heat medium relay unit 3 through the opening and closing device 17b, and again flows into the outdoor unit 1 along the refrigerant pipe 4. The refrigerant flowing into the outdoor unit 1 passes through the second connecting pipe 4b, and flows into the heat source side heat exchanger 12 serving as an evaporator through the check valve 13c.
Then, the refrigerant flowing into the heat source side heat exchanger 12 absorbs heat from outdoor air in the heat source side heat exchanger 12, and is turned into a low-temperature and low-pressure gaseous refrigerant. The low-temperature and low-pressure gaseous refrigerant flowing out of the heat source side heat exchanger 12 is again sucked into the compressor 10 through the first refrigerant passage switching device 11 and the accumulator 19.
The circulation compositions of the refrigerant circulating in the refrigerant circuit A are measured by using the refrigerant circulation composition detection device 50 (the high-low pressure bypass pipe 4c, the expansion device 14, the refrigerant-refrigerant heat exchanger 27, the high-pressure side refrigerant temperature detection device 32, the low-pressure side refrigerant temperature detection device 33, the high-pressure side pressure detection device 37, and the low-pressure side pressure detection device 38). The controller 60a in the outdoor unit 1 and the controller 60b in the heat medium relay unit 3 are connected via wire or wirelessly so as to be capable of communicating with each other, and the circulation compositions calculated by the controller 60a in the outdoor unit 1 are transmitted via communication from the controller 60a in the outdoor unit 1 to the controller 60b in the heat medium relay unit 3.
The controller 60b in the heat medium relay unit 3 calculates a saturated liquid temperature and a saturated gas temperature on the basis of the circulation compositions transmitted from the controller 60a in the outdoor unit 1 and the pressure detected by the pressure sensor 36b. Further, the controller 60b in the heat medium relay unit 3 calculates an average temperature of the saturated liquid temperature and the saturated gas temperature to determine a condensing temperature. Then, the controller 60b in the heat medium relay unit 3 controls the opening degree of the expansion device 16a so that subcool (degree of subcooling) obtained as a temperature difference between the temperature detected by the temperature sensor 35b and the calculated condensing temperature is kept constant.
Similarly, the controller 60b in the heat medium relay unit 3 controls the opening degree of the expansion device 16b so that subcool (degree of subcooling) obtained as a temperature difference between the temperature detected by the temperature sensor 35d and the calculated condensing temperature.
Next, the flow of the heat medium in the heat medium circuit B will be described.
In the heating only operation mode, heating energy of the refrigerant is transferred to the heat medium in both the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b, and the warmed heat medium is caused by the pump 21a and the pump 21b to flow in the pipes 5.
The heat medium pressurized by and flowing out of the pump 21a flows into the heat exchanger related to heat medium 15a from the lower portion of the drawing through the heat medium passage reversing device 20a, and is warmed by the refrigerant flowing through the heat exchanger related to heat medium 15a. The warmed heat medium flows out of the heat exchanger related to heat medium 15a from the upper portion of the drawing, and flows through the heat medium passage reversing device 20b, reaching the first heat medium passage switching device 23a and the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15a, are in counter flow. The heat medium pressurized by and flowing out of the pump 21b flows into the heat exchanger related to heat medium 15b from the lower portion of the drawing through the heat medium passage reversing device 20c, and is warmed by the refrigerant flowing through the heat exchanger related to heat medium 15b. The warmed heat medium flows out of the heat exchanger related to heat medium 15b from the upper portion of the drawing, and flows through the heat medium passage reversing device 20d, reaching the first heat medium passage switching device 23a and the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15b, are in counter flow.
The heat media pumped out by the pump 21a and the pump 21b merge at each of the first heat medium passage switching device 23a and the first heat medium passage switching device 23b, and the merged heat media flow into the use side heat exchanger 26a and the use side heat exchanger 26b. Then, the heat media radiate heat to indoor air in the use side heat exchanger 26a and use side heat exchanger 26b to heat the indoor space 7. Each of the use side heat exchanger 26a and the use side heat exchanger 26b serves as a heater, and is configured such that the flow direction of the heat medium is the same as that when serving as a cooler and the flow direction of the heat medium and the flow direction of the indoor air are in a counter-flow configuration.
The heat media flowing out of the use side heat exchanger 26a and the use side heat exchanger 26b flow into the heat medium flow control device 25a and the heat medium flow control device 25b, respectively. At this time, due to the action of the heat medium flow control device 25a and the heat medium flow control device 25b, the flow rates of the heat media are controlled to flow rates necessary to compensate for the air conditioning load required indoor, and the resulting heat media flow into the use side heat exchanger 26a and the use side heat exchanger 26b. The heat media flowing out of the heat medium flow control device 25a and the heat medium flow control device 25b are split into flows at the second heat medium passage switching device 22a and the second heat medium passage switching device 22b, respectively, which are again sucked into the pump 21a and the pump 21b.
As described above, in the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b, the refrigerant flows from the upper portion of the drawing to the lower portion of the drawing, and the heat medium flows from the lower portion of the drawing to the upper portion of the drawing, where the refrigerant and the heat medium are in counter flow. Flowing of the refrigerant and the heat medium in a counter-flow manner provides high heat exchange efficiency and improves COP.
Further, if plate-type heat exchangers are used as the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b, flowing of the condensing-side refrigerant from above to below in the manner illustrated in the drawing causes the condensed liquid refrigerant to move downward due to the gravitational effect, yielding a reduction in the power of the compressor. If plate-type heat exchangers are used as the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b, furthermore, flowing of the heat medium from below to above in manner illustrated in the drawing causes the warmed heat medium to float due to the buoyant force effect, yielding a reduction in the power of the pumps, which is efficient.
In the pipes 5 of the use side heat exchangers 26, the heat medium flows in the direction from the first heat medium passage switching devices 23 to the second heat medium passage switching devices 22 through the heat medium flow control devices 25. Further, the air conditioning load required for the indoor space 7 can be compensated for by performing control to maintain the differences between the temperature detected by the temperature sensor 31a or the temperature detected by the temperature sensor 31b and the temperatures detected by the temperature sensors 34 at a target value. Either of the temperatures obtained by the temperature sensor 31a and the temperature sensor 31b may be used as the outlet temperatures of the heat exchangers related to heat medium 15, or an average temperature thereof may be used.
At this time, the opening degrees of the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23 are set to be an intermediate opening degree so as to reserve the passages of the flows to both the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b. Furthermore, the flow rates of the heat media flowing through the use side heat exchangers 26 should be controlled using the temperature differences between the inlet and outlet temperatures. The temperatures of the heat media on the inlet side of the use side heat exchangers 26 are substantially the same as the temperatures detected by the temperature sensors 31. Thus, the number of temperature sensors can be reduced by controlling the flow rates of the heat media flowing through the use side heat exchangers 26 using the temperatures detected by the temperature sensors 31, thus achieving a low-cost system.
In the heating only operation mode, since it is not necessary to cause the heat medium to flow to a use side heat exchanger 26 having no heat load (including that in a thermostat-off state), the corresponding one of the heat medium flow control devices 25 closes the passage to prevent the heat medium from flowing to the use side heat exchanger 26. In
In the first cooling main operation mode illustrated in
First, the flow of the refrigerant in the refrigerant circuit A will be described.
A low-temperature and low-pressure refrigerant is compressed by the compressor 10 into a high-temperature and high-pressure gaseous refrigerant, which is then discharged. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 10 flows into the heat source side heat exchanger 12 through the first refrigerant passage switching device 11. Then, the gaseous refrigerant is condensed, while radiating heat to outdoor air in the heat source side heat exchanger 12, and then turns into a two-phase refrigerant. The two-phase refrigerant flowing out of the heat source side heat exchanger 12 flows out of the outdoor unit 1 through the check valve 13a, and flows into the heat medium relay unit 3 through the refrigerant pipe 4. The two-phase refrigerant flowing into the heat medium relay unit 3 flows into the heat exchanger related to heat medium 15b serving as a condenser through the second refrigerant passage switching device 18b.
The two-phase refrigerant flows into the heat exchanger related to heat medium 15b serving as a condenser from the upper portion of the drawing, and is condensed and liquefied, while radiating heat to the heat medium circulating in the heat medium circuit B, and then turns into a liquid refrigerant. The liquid refrigerant flowing out of the heat exchanger related to heat medium 15b from the lower portion of the drawing is expanded by the expansion device 16b and then turns into a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant flows into the heat exchanger related to heat medium 15a serving as an evaporator through the expansion device 16a. The low-pressure two-phase refrigerant flowing into the heat exchanger related to heat medium 15a from the lower portion of the drawing absorbs heat from the heat medium circulating in the heat medium circuit B to cool the heat medium, so that the two-phase refrigerant is turned into a low-pressure gaseous refrigerant. The gaseous refrigerant flows out of the heat exchanger related to heat medium 15a from the upper portion of the drawing, flows out of the heat medium relay unit 3 through the second refrigerant passage switching device 18a, and again flows into the outdoor unit 1 along the refrigerant pipe 4. The refrigerant flowing into the outdoor unit 1 flows through the check valve 13d, and is again sucked into the compressor 10 through the first refrigerant passage switching device 11 and the accumulator 19.
The circulation compositions of the refrigerant circulating in the refrigerant circuit A are measured by using the refrigerant circulation composition detection device 50 (the high-low pressure bypass pipe 4c, the expansion device 14, the refrigerant-refrigerant heat exchanger 27, the high-pressure side refrigerant temperature detection device 32, the low-pressure side refrigerant temperature detection device 33, the high-pressure side pressure detection device 37, and the low-pressure side pressure detection device 38). The controller 60a in the outdoor unit 1 and the controller 60b in the heat medium relay unit 3 are connected via wire or wirelessly so as to be capable of communicating with each other, and the circulation compositions calculated by the controller 60a in the outdoor unit 1 are transmitted via communication from the controller 60a in the outdoor unit 1 to the controller 60b in the heat medium relay unit 3.
The controller 60b in the heat medium relay unit 3 calculates a saturated liquid temperature and a saturated gas temperature on the basis of the circulation compositions transmitted from the controller 60a in the outdoor unit 1 and the pressure detected by the pressure sensor 36a. Further, the controller 60b in the heat medium relay unit 3 calculates an average temperature of the saturated liquid temperature and the saturated gas temperature to determine an evaporating temperature of the heat exchanger related to heat medium 15a. Then, the controller 60b in the heat medium relay unit 3 controls the opening degree of the expansion device 16b so that superheat (degree of superheating) obtained as a temperature difference between the temperature detected by the temperature sensor 35a and the calculated evaporating temperature is kept constant. In addition, the expansion device 16a is fully opened.
The controller 60b in the heat medium relay unit 3 may calculate a saturated liquid temperature and a saturated gas temperature on the basis of the circulation compositions transmitted from the controller 60a in the outdoor unit 1 and the pressure detected by the pressure sensor 36b. Then, the controller 60b in the heat medium relay unit 3 may calculate an average temperature of the saturated liquid temperature and the saturated gas temperature to determine a condensing temperature, and may control the opening degree of the expansion device 16b so that subcool (degree of subcooling) obtained as a temperature difference between the temperature detected by the temperature sensor 35d and the calculated condensing temperature is kept constant. In addition, the expansion device 16b may be fully opened and the expansion device 16a may be used to control superheat or subcool.
A saturated pressure and a saturated gas temperature may be calculated by assuming that the temperature detected by the temperature sensor 35b is a saturated liquid temperature or the temperature of a set quality on the basis of the circulation compositions transmitted via communication from the outdoor unit 1 and the temperature sensor 35b, and an average temperature of the saturated liquid temperature and the saturated gas temperature may be calculated to determine an evaporating temperature. Then, the determined evaporating temperature may be used to control the expansion devices 16a and 16b. In this case, the installation of the pressure sensor 36a may be omitted, thus achieving a low-cost system.
Next, the flow of the heat medium in the heat medium circuit B will be described.
In the first cooling main operation mode, heating energy of the refrigerant is transferred to the heat medium in the heat exchanger related to heat medium 15b, and the warmed heat medium is caused by the pump 21b to flow in the pipes 5. In the first cooling main operation mode, furthermore, cooling energy of the refrigerant is transferred to the heat medium in the heat exchanger related to heat medium 15a, and the chilled heat medium is caused by the pump 21a to flow in the pipes 5.
The heat medium pressurized by and flowing out of the pump 21b flows into the heat exchanger related to heat medium 15b from the lower portion of the drawing through the heat medium passage reversing device 20c, and is warmed by the refrigerant flowing through the heat exchanger related to heat medium 15b. The warmed heat medium flows out of the heat exchanger related to heat medium 15b from the upper portion of the drawing, and flows through the heat medium passage reversing device 20d, reaching the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15b, are in counter flow. The heat medium pressurized by and flowing out of the pump 21a flows into the heat exchanger related to heat medium 15a from the upper portion of the drawing through the heat medium passage reversing device 20a, and is chilled by the refrigerant flowing through the heat exchanger related to heat medium 15a. The chilled heat medium flows out of the heat exchanger related to heat medium 15a from the lower portion of the drawing, and flows through the heat medium passage reversing device 20b, reaching the first heat medium passage switching device 23a. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15a, are in counter flow.
The heat medium transmitted through the first heat medium passage switching device 23b flows into the use side heat exchanger 26b, and radiates heat to indoor air to heat the indoor space 7. Further, the heat medium transmitted through the first heat medium passage switching device 23a flows into the use side heat exchanger 26a, and absorbs heat from indoor air to cool the indoor space 7. At this time, due to the action of the heat medium flow control device 25a and the heat medium flow control device 25b, the flow rates of the heat media are controlled to flow rates necessary to compensate for the air conditioning load required indoor, and the resulting heat media flow into the use side heat exchanger 26a and the use side heat exchanger 26b. The heat medium, whose temperature has been slightly reduced after being transmitted through the use side heat exchanger 26b, passes through the heat medium flow control device 25b and the second heat medium passage switching device 22b, and is again sucked into the pump 21b. The heat medium, whose temperature has been slightly increased after being transmitted through the use side heat exchanger 26a, passes through the heat medium flow control device 25a and the second heat medium passage switching device 22a, and is again sucked into the pump 21a. While the use side heat exchanger 26a serves as a cooler and the use side heat exchanger 26b serves as a heater, both are configured such that the flow direction of the heat medium and the flow direction of the indoor air are in a counter-flow configuration.
During this period, the hot heat medium and the cold heat medium are not mixed due to the action of the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23, and are introduced into a use side heat exchanger 26 having a heating load and a use side heat exchanger 26 having a cooling load, respectively. In the pipes 5 of the use side heat exchangers 26, the heat medium flows in the direction from the first heat medium passage switching devices 23 to the second heat medium passage switching devices 22 through the heat medium flow control devices 25 on both the heating side and the cooling side. Further, the air conditioning load required for the indoor space 7 can be compensated for by performing control to maintain the differences between the temperature detected by the temperature sensor 31b and the temperatures detected by the temperature sensors 34 on the heating side or between the temperatures detected by the temperature sensors 34 and the temperature detected by the temperature sensor 31a on the cooling side at a target value.
As described above, in the heat exchanger related to heat medium 15a serving as a cooler, the refrigerant flows from the lower portion of the drawing to the upper portion of the drawing, and the heat medium flows from the upper portion of the drawing to the lower portion of the drawing, where the refrigerant and the heat medium are in counter flow. Further, in the heat exchanger related to heat medium 15b serving as a heater, the refrigerant flows from the upper portion of the drawing to the lower portion of the drawing, and the heat medium flows from the lower portion of the drawing to the upper portion of the drawing, where the refrigerant and the heat medium are in counter flow. Flowing of the refrigerant and the heat medium in a counter-flow manner provides high heat exchange efficiency and improves COP.
Further, if a plate-type heat exchanger is used as the heat exchanger related to heat medium 15a serving as a cooler, flowing of the evaporation-side refrigerant from below to above in the manner illustrated in the drawing causes the evaporated gaseous refrigerant to move upward due to the buoyant force effect, yielding a reduction in the power of the compressor and appropriate distribution of the refrigerant. If a plate-type heat exchanger is used as the heat exchanger related to heat medium 15a serving as a cooler, furthermore, flowing of the heat medium from above to below in the manner illustrated in the drawing causes the chilled heat medium to sink due to the gravitational effect, yielding a reduction in the power of the pump, which is efficient.
Further, if a plate-type heat exchanger is used as the heat exchanger related to heat medium 15b serving as a heater, flowing of the condensing-side refrigerant from above to below in the manner illustrated in the drawing causes the condensed liquid refrigerant to move downward due to the gravitational effect, yielding a reduction in the power of the compressor. If a plate-type heat exchanger is used as the heat exchanger related to heat medium 15b serving as a heater, furthermore, flowing of the heat medium from below to above in the manner illustrated in the drawing causes the warmed heat medium to float due to the buoyant force effect, yielding a reduction in the power of the pumps, which is efficient.
In the first cooling main operation mode, since it is not necessary to cause the heat medium to flow to a use side heat exchanger 26 having no heat load (including that in a thermostat-off state), the corresponding one of the heat medium flow control devices 25 closes the passage to prevent the heat medium from flowing to the use side heat exchanger 26. In
Here, the determination as to whether or not there is a possibility of freezing of the heat medium in the heat exchanger related to heat medium 15a may be performed, for example, as follows. That is, if at least one of the temperatures detected by the temperature sensor 35a and the temperature sensor 35b is less than or equal to the first set temperature (for example, −3 degrees C.) or at least one of the temperatures detected by the temperature sensor 34a and the temperature sensor 31a is less than or equal to the second set temperature (for example, 4 degrees C.), the freezing determination unit in the controller 60b determines that there is a possibility of freezing of the heat medium in the heat exchanger related to heat medium 15a.
In the second cooling main operation mode, the flow of the refrigerant in the refrigerant circuit A is the same as that in the first cooling main operation mode. Further, the flow of the heat medium in the heat medium circuit B is the same as that in the first cooling main operation mode, except the flow of the heat medium around the heat exchangers related to heat medium 15a and 15b. Thus, a description will be given of only a portion of the flow of the heat medium different from that in the first cooling main operation mode.
The heat medium pressurized by and flowing out of the pump 21b flows into the heat exchanger related to heat medium 15b from the lower portion of the drawing through the heat medium passage reversing device 20c, and is warmed by the refrigerant flowing through the heat exchanger related to heat medium 15b. The warmed heat medium flows out of the heat exchanger related to heat medium 15b from the upper portion of the drawing, and flows through the heat medium passage reversing device 20d, reaching the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15b, are in counter flow. The heat medium pressurized by and flowing out of the pump 21a flows into the heat exchanger related to heat medium 15a from the lower portion of the drawing through the heat medium passage reversing device 20a, and is chilled by the refrigerant flowing through the heat exchanger related to heat medium 15a. The chilled heat medium flows out of the heat exchanger related to heat medium 15a from the upper portion of the drawing, and flows through the heat medium passage reversing device 20b, reaching the first heat medium passage switching device 23a. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15a, are in parallel flow. The hot heat medium and the cold heat medium are not mixed due to the action of the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23, and are introduced into a use side heat exchanger 26 having a heating load and a use side heat exchanger 26 having a cooling load, respectively.
As described above, in the heat exchanger related to heat medium 15b serving as a heater, the refrigerant flows from the upper portion of the drawing to the lower portion of the drawing, and the heat medium flows from the lower portion of the drawing to the upper portion of the drawing, where the refrigerant and the heat medium are in counter flow. Flowing of the refrigerant and the heat medium in a counter-flow manner provides high heat exchange efficiency and improves COP. Further, in the heat exchanger related to heat medium 15a serving as a cooler, the refrigerant flows from the lower portion of the drawing to the upper portion of the drawing, and the heat medium flows from the lower portion of the drawing to the upper portion of the drawing, where the refrigerant and the heat medium are in parallel flow. Flowing of the refrigerant and the heat medium in a parallel-flow manner does not provide high heat exchange efficiency. In the heat exchanger related to heat medium 15a, on the contrary, a low-temperature heat medium and a high-temperature refrigerant undergo heat exchange on the outlet side, and a high-temperature heat medium and a low-temperature refrigerant undergo heat exchange on the inlet side, resulting in freezing of the heat medium being less likely to occur and realizing safe operation.
In the first heating main operation mode illustrated in
First, the flow of the refrigerant in the refrigerant circuit A will be described.
A low-temperature and low-pressure refrigerant is compressed by the compressor 10 into a high-temperature and high-pressure gaseous refrigerant, which is then discharged. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 10 flows through the first refrigerant passage switching device 11, passing through the first connecting pipe 4a, and flows out of the outdoor unit 1 through the check valve 13b. The high-temperature and high-pressure gaseous refrigerant flowing out of the outdoor unit 1 flows into the heat medium relay unit 3 through the refrigerant pipe 4. The high-temperature and high-pressure gaseous refrigerant flowing into the heat medium relay unit 3 flows into the heat exchanger related to heat medium 15b serving as a condenser through the second refrigerant passage switching device 18b.
The gaseous refrigerant flows into the heat exchanger related to heat medium 15b serving as a condenser from the upper portion of the drawing, and is condensed and liquefied, while radiating heat to the heat medium circulating in the heat medium circuit B, into a liquid refrigerant. The liquid refrigerant flowing out of the heat exchanger related to heat medium 15b is expanded by the expansion device 16b into a low-pressure two-phase refrigerant. The low-pressure two-phase refrigerant flows into the heat exchanger related to heat medium 15a serving as an evaporator through the expansion device 16a. The low-pressure two-phase refrigerant flowing into the heat exchanger related to heat medium 15a from the lower portion of the drawing evaporates by absorbing heat from the heat medium circulating in the heat medium circuit B, and cools the heat medium. The low-pressure gaseous refrigerant flows out of the heat exchanger related to heat medium 15a from the upper portion of the drawing, flows out of the heat medium relay unit 3 through the second refrigerant passage switching device 18a, and again flows into the outdoor unit 1 along the refrigerant pipe 4.
The controller 60b in the heat medium relay unit 3 calculates a saturated liquid temperature and a saturated gas temperature on the basis of the circulation compositions transmitted from the controller 60a in the outdoor unit 1 and the pressure detected by the pressure sensor 36b. Further, the controller 60b in the heat medium relay unit 3 calculates an average temperature of the saturated liquid temperature and the saturated gas temperature to determine a condensing temperature. Then, the controller 60b in the heat medium relay unit 3 controls the opening degree of the expansion device 16b so that subcool (degree of subcooling) obtained as a temperature difference between the temperature detected by the temperature sensor 35d and the calculated condensing temperature is kept constant. At this time, the expansion device 16a is fully opened. Note that the expansion device 16b may be fully opened and the expansion device 16a may be used to control subcool.
A saturated pressure and a saturated gas temperature may be calculated by assuming that the temperature detected by the temperature sensor 35b is a saturated liquid temperature or the temperature of a set quality on the basis of the circulation compositions transmitted via communication from the outdoor unit 1 and the temperature sensor 35b, and an average temperature of the saturated liquid temperature and the saturated gas temperature may be calculated to determine an evaporating temperature. Then, the determined evaporating temperature may be used to control the expansion devices 16a and 16b. In this case, the installation of the pressure sensor 36a may be omitted, thus achieving a low-cost system.
Next, the flow of the heat medium in the heat medium circuit B will be described.
In the first heating main operation mode, heating energy of the refrigerant is transferred to the heat medium in the heat exchanger related to heat medium 15b, and the warmed heat medium is caused by the pump 21b to flow in the pipes 5. In the first heating main operation mode, furthermore, cooling energy of the refrigerant is transferred to the heat medium in the heat exchanger related to heat medium 15a, and the chilled heat medium is caused by the pump 21a to flow in the pipes 5.
The heat medium pressurized by and flowing out of the pump 21b flows into the heat exchanger related to heat medium 15b from the lower portion of the drawing through the heat medium passage reversing device 20c, and is warmed by the refrigerant flowing through the heat exchanger related to heat medium 15b. The warmed heat medium flows out of the heat exchanger related to heat medium 15b from the upper portion of the drawing, and flows through the heat medium passage reversing device 20d, reaching the first heat medium passage switching device 23a. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15b, are in counter flow. The heat medium pressurized by and flowing out of the pump 21a flows into the heat exchanger related to heat medium 15a from the upper portion of the drawing through the heat medium passage reversing device 20a, and is chilled by the refrigerant flowing through the heat exchanger related to heat medium 15a. The chilled heat medium flows out of the heat exchanger related to heat medium 15a from the lower portion of the drawing, and flows through the heat medium passage reversing device 20b, reaching the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15a, are in counter flow.
The heat medium transmitted through the first heat medium passage switching device 23a flows into the use side heat exchanger 26a, and radiates heat to indoor air to heat the indoor space 7. Further, the heat medium transmitted through the first heat medium passage switching device 23b flows into the use side heat exchanger 26b, and absorbs heat from indoor air to cool the indoor space 7. At this time, due to the action of the heat medium flow control device 25a and the heat medium flow control device 25b, the flow rates of the heat media are controlled to flow rates necessary to compensate for the air conditioning load required indoor, and the resulting heat media flow into the use side heat exchanger 26a and the use side heat exchanger 26b. The heat medium, whose temperature has been slightly reduced after being transmitted through the use side heat exchanger 26a, passes through the heat medium flow control device 25a and the second heat medium passage switching device 22a, and is again sucked into the pump 21b. The heat medium, whose temperature has been slightly increased after being transmitted through the use side heat exchanger 26b, passes through the heat medium flow control device 25b and the second heat medium passage switching device 22b, and is again sucked into the pump 21a. While the use side heat exchanger 26a serves as a heater and the use side heat exchanger 26b serves as a cooler, both are configured such that the flow direction of the heat medium and the flow direction of the indoor air are in a counter-flow configuration.
During this period, the hot heat medium and the cold heat medium are not mixed due to the action of the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23, and are introduced into a use side heat exchanger 26 having a heating load and a use side heat exchanger 26 having a cooling load, respectively. In the pipes 5 of the use side heat exchangers 26, the heat medium flows in the direction from the first heat medium passage switching devices 23 to the second heat medium passage switching devices 22 through the heat medium flow control devices 25 on both the heating side and the cooling side. Further, the air conditioning load required for the indoor space 7 can be compensated for by performing control to maintain the differences between the temperature detected by the temperature sensor 31b and the temperatures detected by the temperature sensors 34 on the heating side or between the temperatures detected by the temperature sensors 34 and the temperature detected by the temperature sensor 31a on the cooling side at a target value.
As described above, in both the heat exchanger related to heat medium 15a serving as a cooler and the heat exchanger related to heat medium 15b serving as a heater, the refrigerant and the heat medium are in counter flow. Flowing of the refrigerant and the heat medium in a counter-flow manner provides high heat exchange efficiency and improves COP.
Further, if a plate-type heat exchanger is used as the heat exchanger related to heat medium 15a serving as a cooler, flowing of the evaporation-side refrigerant from below to above in the manner illustrated in the drawing causes the evaporated gaseous refrigerant to move upward due to the buoyant force effect, yielding a reduction in the power of the compressor and appropriate distribution of the refrigerant. If a plate-type heat exchanger is used as the heat exchanger related to heat medium 15a serving as a cooler, furthermore, flowing of the heat medium from above to below in the manner illustrated in the drawing causes the chilled heat medium to sink due to the gravitational effect, yielding a reduction in the power of the pump, which is efficient.
Further, if a plate-type heat exchanger is used as the heat exchanger related to heat medium 15b serving as a heater, flowing of the condensing-side refrigerant from above to below in the manner illustrated in the drawing causes the condensed liquid refrigerant to move downward due to the gravitational effect, yielding a reduction in the power of the compressor. If a plate-type heat exchanger is used as the heat exchanger related to heat medium 15b serving as a heater, furthermore, flowing of the heat medium from below to above in the manner illustrated in the drawing causes the warmed heat medium to float due to the buoyant force effect, yielding a reduction in the power of the pumps, which is efficient.
In the first heating main operation mode, since it is not necessary to cause the heat medium to flow to a use side heat exchanger 26 having no heat load (including that in a thermostat-off state), the corresponding one of the heat medium flow control devices 25 closes the passage to prevent the heat medium from flowing to the use side heat exchanger 26. In
Here, the determination as to whether or not there is a possibility of freezing of the heat medium in the heat exchanger related to heat medium 15a may be performed, for example, as follows. That is, if at least one of the temperatures detected by the temperature sensor 35a and the temperature sensor 35b is less than or equal to the first set temperature (for example, −3 degrees C.) or at least one of the temperatures detected by the temperature sensor 34b and the temperature sensor 31a is less than or equal to the second set temperature (for example, 4 degrees C.), the freezing determination unit in the controller 60b determines that there is a possibility of freezing of the heat medium in the heat exchanger related to heat medium 15a. Note that a temperature sensor (fifth temperature detection device) may be provided, for example, in the vicinity of the heat source side heat exchanger 12, and it may be determined that there is a possibility of freezing of the heat medium in the heat exchanger related to heat medium 15a if the ambient air temperature around the heat source side heat exchanger 12 is less than a third set temperature (for example, 0 degrees C.).
In the second heating main operation mode, the flow of the refrigerant in the refrigerant circuit A is the same as that in the first heating main operation mode. Further, the flow of the heat medium in the heat medium circuit B is the same as that in the first heating main operation mode, except the flow of the heat medium around the heat exchangers related to heat medium 15a and 15b. Thus, a description will be given of only a portion of the flow of the heat medium different from that in the first heating main operation mode.
The heat medium pressurized by and flowing out of the pump 21b flows into the heat exchanger related to heat medium 15b from the lower portion of the drawing through the heat medium passage reversing device 20c, and is warmed by the refrigerant flowing through the heat exchanger related to heat medium 15b. The warmed heat medium flows out of the heat exchanger related to heat medium 15b from the upper portion of the drawing, and flows through the heat medium passage reversing device 20d, reaching the first heat medium passage switching device 23a. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15b, are in counter flow. The heat medium pressurized by and flowing out of the pump 21a flows into the heat exchanger related to heat medium 15a from the lower portion of the drawing through the heat medium passage reversing device 20a, and is chilled by the refrigerant flowing through the heat exchanger related to heat medium 15a. The chilled heat medium flows out of the heat exchanger related to heat medium 15a from the upper portion of the drawing, and flows through the heat medium passage reversing device 20b, reaching the first heat medium passage switching device 23b. That is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15a, are in parallel flow. The hot heat medium and the cold heat medium are not mixed due to the action of the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23, and are introduced into a use side heat exchanger 26 having the heating load and a use side heat exchanger 26 having the cooling load, respectively.
As described above, in the heat exchanger related to heat medium 15b serving as a heater, the refrigerant flows from the upper portion of the drawing to the lower portion of the drawing, and the heat medium flows from the lower portion of the drawing to the upper portion of the drawing, where the refrigerant and the heat medium are in counter flow. Flowing of the refrigerant and the heat medium in a counter-flow manner provides high heat exchange efficiency and improves COP. Further, in the heat exchanger related to heat medium 15a serving as a cooler, the refrigerant flows from the lower portion of the drawing to the upper portion of the drawing, and the heat medium flows from the lower portion of the drawing to the upper portion of the drawing, where the refrigerant and the heat medium are in parallel flow. Flowing of the refrigerant and the heat medium in a parallel-flow manner does not provide high heat exchange efficiency. In the heat exchanger related to heat medium 15a, on the contrary, a low-temperature heat medium and a high-temperature refrigerant undergo heat exchange on the outlet side, whereas a high-temperature heat medium and a low-temperature refrigerant undergo heat exchange on the inlet side, resulting in freezing of the heat medium being less likely to occur and realizing safe operation.
As described above, the air-conditioning apparatus 100 according to Embodiment has several operation modes. In these operation modes, a refrigerant flows through the pipes 4 connecting the outdoor unit 1 and the heat medium relay unit 3.
In the several operation modes of the air-conditioning apparatus 100 according to Embodiment, a heat medium such as water or antifreeze flows through the pipes 5 connecting the heat medium relay unit 3 and the indoor units 2.
Next, water temperature difference control in the heat exchangers related to heat medium 15 in the case of using a non-azeotropic refrigerant mixture will be described in detail.
In
The operation in this case will be described in detail with reference to
As illustrated in
Next, a description will be given of a case where the heat exchanger related to heat medium 15a or/and the heat exchanger related to heat medium 15b is used as an evaporator. As illustrated in
At this time, if there is absolutely no pressure loss of the refrigerant in the refrigerant flow passage of the heat exchanger related to heat medium 15, the temperature of the refrigerant increases along a line indicated by a one-dot chain line in
In
As described above, when the heat exchanger related to heat medium 15 serves as an evaporator (cooler), heat exchange efficiency can be improved by controlling the temperature difference of the heat medium flowing through the heat exchanger related to heat medium 15 in accordance with the temperature glide based on the circulation compositions of the refrigerant. In a non-azeotropic refrigerant mixture, however, the circulation compositions of the refrigerant vary depending on the operation state such as an excess amount of refrigerant. Accordingly, the control target value (first target value) of the temperature difference of the heat medium flowing through the heat exchanger related to heat medium 15 (that is, the temperature difference between the temperature sensor 31 and the temperature sensor 34) is not fixed, where an initial value is stored in advance, but varies in accordance with the time-varying operation state, and may be reset. Specifically, the circulation compositions of the refrigerant may be calculated using the refrigerant circulation composition detection device 50, the operation of which has been described previously, and the control target value of the temperature difference of the heat medium flowing through the heat exchanger related to heat medium 15 may be set in accordance with the calculated circulation compositions (or the temperature glide of the refrigerant calculated from the circulation compositions).
When the heat exchanger related to heat medium 15 serves as an evaporator, a two-phase refrigerant having a mixture of a liquid refrigerant and a gaseous refrigerant flows into the refrigerant flow passage of the heat exchanger related to heat medium 15, and the temperature of the refrigerant increases in accordance with an increase in gaseous components during the subsequent evaporation process. At this time, a pressure loss occurs in the refrigerant flowing through the refrigerant flow passage of the heat exchanger related to heat medium 15, and a reduction in temperature by the amount corresponding to the pressure loss occurs. In accordance with the factors described above, the temperature difference between the refrigerant on the outlet side of the heat exchanger related to heat medium 15 and the refrigerant on the inlet side of the inlet-side heat exchanger related to heat medium 15 is determined. The temperature difference between the refrigerant on the outlet side of the heat exchanger related to heat medium 15 and the refrigerant on the inlet side of the heat exchanger related to heat medium 15 is assumed to be, for example, 5 degrees C. If the pressure loss in the refrigerant is excessively high, the performance of the heat exchanger related to heat medium 15 deteriorates. Thus, the heat exchanger related to heat medium 15 according to Embodiment is configured such that the reduction in temperature due to the pressure loss is appropriately 1 to 2 degrees C. Further, the temperature of the heat medium flowing through the heat exchanger related to heat medium 15 is higher than that of the refrigerant, and the temperature difference (average temperature difference) between the heat medium and the refrigerant is approximately 3 to 7 degrees C. In consideration of the foregoing, the control target value of the difference between the inlet and outlet temperatures of the heat medium flowing through the heat exchanger related to heat medium 15 is set to a value substantially equal to the temperature difference between the inlet and outlet temperatures of the refrigerant in the heat exchanger related to heat medium 15, providing high heat exchange efficiency. If the difference between the inlet and outlet temperatures of the refrigerant in the heat exchanger related to heat medium 15 is 5 degrees C., the control target value of the difference between the inlet and outlet temperatures of the heat medium flowing through the heat exchanger related to heat medium 15 may be set to 3 to 7 degrees C.
A pressure loss in the refrigerant is predictable to some extent based on the operation state. Thus, when the heat exchanger related to heat medium 15 serves as an evaporator, for example, if the calculated temperature glide of the refrigerant is 5 degrees C., settings may be made such that the control target value of the heat medium is set to a value in the range from 5 degrees C., which is substantially the same as the calculated temperature glide of the refrigerant, to a slightly larger value, or 7 degrees C., for a significantly small pressure loss in the refrigerant in the heat exchanger related to heat medium 15, and the control target value may be set to 4 degrees C., 3 degrees C., or the like, which is smaller than the calculated temperature glide of the refrigerant for a large pressure loss to some extent. Further, for example, if the calculated temperature glide of the refrigerant is, for example, 7 degrees C., settings may be made such that the control target value of the heat medium is set to a value in the range from 7 degrees C. to 9 degrees C. for a significantly small pressure loss, and the control target value is set to 6 degrees C. or 5 degrees C. for a large pressure loss to some extent. This control is automatically performed by the controller 60b on the basis of the circulation compositions calculated by the controller 60a.
Here, (1) when the heat exchanger related to heat medium 15 serves as a condenser and (2) when the heat exchanger related to heat medium 15 serves as an evaporator and the temperature of the heat medium in the heat medium flow passage and the temperature of the refrigerant in the refrigerant flow passage are higher than the set temperatures described above, flowing of the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15, in a counter-flow manner provides high heat exchange efficiency of the heat exchanger related to heat medium 15. In contrast, (3) when the heat exchanger related to heat medium 15 serves as an evaporator and the temperature of the heat medium in the heat medium flow passage or/and the temperature of the refrigerant in the refrigerant flow passage is less than or equal to the set temperatures described above, flowing of the heat medium and the refrigerant in a counter-flow manner in the heat exchanger related to heat medium 15 may cause the heat medium to be frozen in the heat medium passage, and the heat exchanger related to heat medium 15 can be broken.
Accordingly, if there is a concern that the heat medium will be frozen, in the air-conditioning apparatus 100 according to Embodiment, the passage of the heat medium that is to flow into the heat exchanger related to heat medium 15 serving as an evaporator is reversed so that the flows of the heat medium and the refrigerant are in parallel flow.
When the heat exchanger related to heat medium 15 serves as an evaporator, flowing of the refrigerant and the heat medium in a parallel-flow manner increases the temperature of a non-azeotropic refrigerant mixture in accordance with a two-phase change in the direction from the inlet to the outlet. Then, the heat medium is cooled by the refrigerant, so that the temperature thereof decreases in the direction from the inlet to the outlet. That is, a high-temperature heat medium and a low-temperature refrigerant heat exchange on the inlet side of the heat exchanger related to heat medium 15, and a low-temperature heat medium and a high-temperature refrigerant heat exchange on the outlet side of the heat exchanger related to heat medium 15. The heat medium is more prone to freezing when the temperature is low; nonetheless, a low-temperature heat medium is less likely to be frozen because it undergoes heat exchange with a high-temperature refrigerant.
The difference between the inlet and outlet temperatures of the refrigerant in the heat exchanger related to heat medium 15 may be handled by adjusting the flow rate of the heat medium transmitted through the pump 21. One method for reducing the flow rate of the flow transmitted through the pump 21 is to reduce the frequency to reduce the flow rate when the pump 21 is driven by a brushless DC inverter, an AC inverter, or the like. When the pump 21 is not of an inverter type, the voltage to be applied to the pump 21 may be reduced by switching a resistor or any other method. Alternatively, a valve whose opening area for a passage is variable may be provided on the suction side or discharge side of the pump 21, and the passage area may be reduced to reduce the flow rate of the flow to the pump 21.
In the air-conditioning apparatus 100 having the configuration described above, when the heat exchanger related to heat medium 15 is used as an evaporator, if there is a possibility of freezing of the heat medium, the refrigerant and the heat medium in the heat exchanger related to heat medium 15 are caused to flow in parallel, thereby preventing freezing of the heat medium and providing safe operation.
Further, in the heating main operation, if the ambient air temperature around the heat source side heat exchanger 12 is low, the pressure of the refrigerant in the heat exchanger related to heat medium 15a serving as an evaporator decreases, reducing the temperature. In contrast, the air-conditioning apparatus 100 according to Embodiment operates the second heating main operation mode (that is, the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15a, are in parallel flow) when the ambient air temperature is less than or equal to a set temperature (for example, less than or equal to 0 degrees C.), thereby preventing freezing of the heat medium and providing safe operation.
If the refrigerant and the heat medium, which flow through the heat exchanger related to heat medium 15, are in parallel flow, the set temperature of the heat medium (set temperatures of the temperature sensor 31 and the temperature sensor 34) used as a reference for the freezing determination unit to determine whether there is a possibility of freezing of the heat medium may be set to a fourth set temperature lower than the second set temperature. Further, the control target value of the temperature difference of the heat medium flowing through the heat exchanger related to heat medium 15 (that is, the temperature difference between the temperature sensor 31 and the temperature sensor 34) may be set to a second target value (for example, 0 degrees C.) lower than the first target value. This can increase the flow rate of the heat medium flowing through the heat medium flow passage of the heat exchanger related to heat medium 15, and can prevent the outlet temperature of the heat medium from decreasing, thereby more reliably preventing freezing of the heat medium.
Further, when the heat exchanger related to heat medium 15 is used as a condenser, the regions of the heated gaseous refrigerant and the subcooled-liquid refrigerant in the heat exchanger related to heat medium 15 enlarge to some extent. Thus, the control target value of the temperature difference of the heat medium may be set to a value larger than the calculated temperature glide of the refrigerant. For example, if the calculated temperature glide of the refrigerant is 5 degrees C., the control target value of the temperature difference of the heat medium may be set to a value larger than 5 degrees C., such as 7 degrees C.
The temperature difference between the temperature sensor 31 and the temperature sensor 34 is referred to here as a temperature difference of the heat medium flowing through the heat exchanger related to heat medium 15, or may be referred to as an inlet/outlet temperature difference of the use side heat exchanger 26, where both temperature differences are the same unless heat penetration into the pipe 5, or the like occurs. Alternatively, another temperature sensor may be installed on the inlet side of the use side heat exchanger 26 to control the temperature difference between the temperature detected thereby and that of the temperature sensor 34.
Further, the air-conditioning apparatus 100 according to Embodiment is designed such that if only heating load or cooling load is generated in the use side heat exchangers 26, the opening degrees of the associated second heat medium passage switching devices 22 and the associated first heat medium passage switching devices 23 are set to an intermediate opening degree to allow the heat medium to flow through both the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b. Thus, both the heat exchanger related to heat medium 15a and the heat exchanger related to heat medium 15b can be used for the heating operation or the cooling operation. This can increase the heat transfer area, providing an efficient heating operation or cooling operation.
Further, if both heating load and cooling load are generated in the use side heat exchangers 26, the second heat medium passage switching device 22 and the first heat medium passage switching device 23, which are associated with the use side heat exchanger 26 currently in the heating operation, are switched to the passage connected to the heat exchanger related to heat medium 15b for use in heating, and the second heat medium passage switching device 22 and the first heat medium passage switching device 23, which are associated with the use side heat exchanger 26 currently in the cooling operation, are switched to the passage connected to the heat exchanger related to heat medium 15a for use in cooling. This enables the individual indoor units 2 to freely perform the heating operation and the cooling operation.
In Embodiment, both the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23 are provided. Alternatively, only the first heat medium passage switching devices 23 may allow the individual indoor units 2 to freely perform the heating operation and the cooling operation (to perform a simultaneous cooling and heating operation). At this time, the heat media flowing out of the individual indoor units 2 merge on the way (if the second heat medium passage switching devices 22 are provided, at the positions where the second heat medium passage switching devices 22 are located). That is, a cold heat medium (for example, 10 degrees C.) flowing out of the use side heat exchanger 26 on the cooling side and a hot heat medium (for example, 40 degrees C.) flowing out of the use side heat exchanger 26 on the heating side are caused to merge into an intermediate-temperature heat medium (for example, 25 degrees C.), and the intermediate-temperature heat medium flows into the heat exchangers related to heat medium 15a and 15b. Then, the heat exchanger related to heat medium 15a chills the intermediate-temperature heat medium to generate a cold heat medium (for example, 5 degrees C.), and the heat exchanger related to heat medium 15b chills the intermediate-temperature heat medium to generate a hot heat medium (for example, 45 degrees C.). Thereafter, due to the effect of the first heat medium passage switching devices 23, the cold heat medium flows into the use side heat exchanger 26 on the cooling side and the hot heat medium flows into the use side heat exchanger 26 on the heating side, which are used for the cooling operation and the heating operation, respectively. In this case, since the cold heat medium and the hot heat medium merge into an intermediate-temperature heat medium on the outlet side of the use side heat exchangers 26, waste occurs in terms of the amount of heat. Therefore, both the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23 allow a more efficient operation, whereas only the first heat medium passage switching devices 23 allow a cooling and heating mixed operation at low cost. Note that a structure in which only the second heat medium passage switching devices 22 are provided does not allow a cooling and heating mixed operation.
Further, each of the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23 described in Embodiment may be designed to switch between passages, such as a device capable of switching between three-way passages, such as a three-way valve, or a device formed by combining two devices, each configured to open and close two-way passages, such as opening and closing valves. Further, each of the second heat medium passage switching devices 22 and the first heat medium passage switching devices 23 may be a device capable of changing the flow rates of three-way passages, such as a stepping-motor-driven mixing valve, or may be implemented by, for example, combining two devices each capable of changing the flow rates of two-way passages, such as electronic expansion valves. In this case, water hammer caused by a sudden opening and closing of a passage can also be prevented. In Embodiment, furthermore, the description has been made taking an example where each of the heat medium flow control devices 25 is a two-way valve. Alternatively, each of the heat medium flow control devices 25 may be a control valve having three-way passages, and may be disposed together with bypass pipes that bypass the use side heat exchangers 26.
In addition, each of the heat medium flow control devices 25 may be implemented as an stepping-motor-driven device capable of controlling the flow rate of the flow through a passage, or may be a two-way valve or a three-way valve whose one end is closed. Alternatively, each of the heat medium flow control devices 25 may be implemented as a device that opens and closes two-way passages, such as an opening and closing valve, which is repeatedly turned on and off to control an average flow rate.
Furthermore, each of the heat medium passage reversing devices 20 may not only be a device capable of switching between three-way passages, such a three-way valve, but also be implemented by combining two devices each configured to open and close two-way passages, such as opening and closing valves as illustrated in
Further, each of the second refrigerant passage switching devices 18 is illustrated as a four-way valve, but is not limited thereto. Each of the second refrigerant passage switching device 18 may be configured by using a plurality of two-way passage switching valves or three-way passage switching valves so that the refrigerant flows in the same manner.
The air-conditioning apparatus 100 according to Embodiment has been described as being capable of performing a cooling and heating mixed operation, but is not limited thereto. The air-conditioning apparatus 100, which is configured to include a single heat exchanger related to heat medium 15 and a single expansion device 16, to which a plurality of use side heat exchangers 26 and a plurality of heat medium flow control devices 25 are connected in parallel, and configured to perform only either the cooling operation or the heating operation, would achieve similar advantages.
Further, there is of course no problem if a plurality of devices designed to operate in the same manner are disposed as the heat exchangers related to heat media 15 and the expansion devices 16. Furthermore, the description has been made taking an example where the heat medium flow control devices 25 are incorporated in the heat medium relay unit 3, but Embodiment is not limited thereto. The heat medium flow control devices 25 may be incorporated in the indoor units 2, or may be configured separately from the heat medium relay unit 3 and the indoor units 2.
Further, the heat medium is not limited to water, and may be implemented using, for example, brine (antifreeze), a liquid mixture of brine and water, a liquid mixture of water and anti-corrosive additive, or the like.
Further, each of the heat source side heat exchanger 12 and the use side heat exchangers 26a to 26d is generally equipped with an air-sending device, and the blowing of air often facilitates condensation or evaporation, but is not limited thereto. For example, each of the use side heat exchangers 26a to 26d may be implemented using a device that utilizes radiation, like a panel heater, and the heat source side heat exchanger 12 may be of a water-cooled type that causes heat to move by water or antifreeze. Any structure capable of radiating heat or absorbing heat may be used.
Further, while the description has been made with reference to
Further, the description has been made with reference to
Further, the pumps 21a and 21b are not necessarily single ones, and each of them may be implemented by arranging a plurality of small-capacity pumps in parallel.
1 outdoor unit (heat source unit), 2 (2a, 2b, 2c, 2d) indoor unit, 3 heat medium relay unit, 4 refrigerant pipe, 4a first connecting pipe, 4b second connecting pipe, 4c high-low pressure bypass pipe, 5 pipe, 6 outdoor space, 7 indoor space, 8 space, 9 structure, 10 compressor, 11 first refrigerant passage switching device (four-way valve), 12 heat source side heat exchanger, 13a, 13b, 13c, 13d check valve, 14 expansion device, 15 (15a, 15b) heat exchanger related to heat medium, 16 (16a, 16b) expansion device, 17 (17a, 17b) opening and closing device, 18 (18a, 18b) second refrigerant passage switching device, 19 accumulator, 20 (20a, 20b, 20c, 20d) heat medium passage reversing device, 21 (21a, 21b) pump (heat medium sending device), 22 (22a, 22b, 22c, 22d) second heat medium passage switching device, 23 (23a, 23b, 23c, 23d) first heat medium passage switching device, 25 (25a, 25b, 25c, 25d) heat medium flow control device, 26 (26a, 26b, 26c, 26d) use side heat exchanger, 27 refrigerant-refrigerant heat exchanger, 31 (31a, 31b) temperature sensor, 32 high-pressure side refrigerant temperature detection device, 33 low-pressure side refrigerant temperature detection device, 34 (34a, 34b, 34c, 34d) temperature sensor, 35 (35a, 35b, 35c, 35d) temperature sensor, 36 (36a, 36b) pressure sensor, 37 high-pressure side pressure detection device, 38 low-pressure side pressure detection device, 50 refrigerant circulation composition detection device, 60 (60a, 60b) controller, 100 air-conditioning apparatus, A refrigerant circuit, B heat medium circuit.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/000447 | 1/27/2011 | WO | 00 | 5/1/2013 |
