Patent Application
20120167604
The present invention relates to a refrigeration cycle apparatus in which a refrigerant is injected into a compressor during a compression process.
Conventionally, refrigeration cycle apparatuses in which a refrigerant is injected into a compressor during a compression process have been known. The heating capacity can be increased in such refrigeration cycle apparatuses.
For example, Patent Literature 1 discloses a refrigeration cycle apparatus 850 as shown in
Patent Literature 2 discloses a refrigeration cycle apparatus 900 as shown in
PTL 1JP 61(1986)-197960 A
PTL 2JP 11(1999)-173687 A
Ideally, a gas phase refrigerant and a liquid phase refrigerant are separated from each other completely in a gas-liquid separator. However, in a transition period such as a starting operation, the gas phase refrigerant and the liquid phase refrigerant are not separated completely from each other in the gas-liquid separator and the liquid phase refrigerant is mixed into the gas phase refrigerant in some cases. Such a phenomenon occurs more prominently when the pressure in the gas-liquid separator is closer to a saturation vapor pressure. Thus, there is a possibility of the liquid phase refrigerant being injected into a compressor through an injection passage together with the gas phase refrigerant. When such an injection of the liquid phase refrigerant into the compressor occurs excessively, a problem of liquid compression arises in the compressor.
To deal with this, it is conceivable to close the throttling device 860 provided to the injection passage 859 in the starting operation as disclosed in Patent Literature 1. In this case, however, the effect of increasing the heating capacity by injection cannot be obtained in the starting operation.
The phenomenon in which the liquid phase refrigerant is mixed into the gas phase refrigerant as described above occurs also in a defrosting operation and a stopping operation in the same manner.
The phenomenon as described above hardly is a problem for the refrigeration cycle apparatus 900 disclosed in Patent Literature 2 because carbon dioxide, which reaches a supercritical state on a high pressure side, is used as the refrigerant. That is, Patent Literature 2 neither discloses nor suggests a technical idea of preventing the liquid phase refrigerant from being injected into the compressor through the injection passage.
In view of the foregoing, the present invention is intended to provide a refrigeration cycle apparatus capable of suppressing the liquid compression without shutting an injection passage even in the case of using a refrigerant that does not reach the supercritical state on a high pressure side.
In order to solve the above-mentioned problem, the present invention provides a refrigeration cycle apparatus comprising: a refrigerant circuit including a compressor for compressing a refrigerant, a condenser for condensing the refrigerant compressed in the compressor, a first throttling device for expanding the refrigerant condensed in the condenser, a gas-liquid separator for separating the refrigerant expanded in the first throttling device into a gas phase refrigerant and a liquid phase refrigerant, a second throttling device for expanding the liquid phase refrigerant separated out in the gas-liquid separator, and an evaporator for evaporating the refrigerant expanded in the second throttling device, the refrigerant circuit being a refrigerant circuit through which the refrigerant that does not reach a supercritical state after being compressed in the compressor circulates; an injection passage through which the gas phase refrigerant separated out in the gas-liquid separator is supplied to the compressor during a compression process; a detector for detecting a temperature or a pressure of the refrigerant present on a downstream side of the first throttling device and on an upstream side of the second throttling device in the refrigerant circuit or present in the injection passage; and a controller for decreasing an opening degree of the first throttling device when the controller recognizes, by the detector, that a pressure of the refrigerant flowing into the gas-liquid separator exceeds a specified pressure lower than a saturation vapor pressure, in a starting operation, a defrosting operation or a stopping operation.
In the refrigeration cycle apparatus according to the present invention, the opening degree of the first throttling device is adjusted so that the pressure of the refrigerant flowing into the gas-liquid separator is equal to or lower than a specified pressure lower than a saturation vapor pressure, and thereby the amount of the liquid phase refrigerant injected into the compressor can be suppressed to an extent where the liquid compression is not a problem. This makes it possible to suppress the liquid compression in the starting operation, the defrosting operation or the stopping operation without shutting the injection passage.
Hereinafter, embodiments for carrying out the present invention are described with reference to the drawings.
The configuration of a refrigeration cycle apparatus 100 according to Embodiment 1 of the present invention is described with reference to
The refrigerant circuit 160 is a circuit through which the refrigerant circulates. The refrigerant circuit 160 includes a compressor 101, an indoor heat exchanger 102, an indoor side throttling device 103, a gas-liquid separator 104, an outdoor side throttling device 105, an outdoor heat exchanger 106, and a four-way valve 120 (corresponding to the switching device in Claims). The four-way valve 120 serves to switch between a heating operation and a cooling operation. A first port of the four-way valve 120 is connected to a discharge port of the compressor 101 with a pipe. A fourth port of the four-way valve 120 is connected to a suction port of the compressor 101 with a pipe. A second port of the four-way valve 120 is connected to a third port with a pipe via the indoor heat exchanger 102, the indoor side throttling device 103, the gas-liquid separator 104, the outdoor side throttling device 105, and the outdoor heat exchanger 106.
The injection passage 170 is a passage through which a gas phase refrigerant separated out by the gas-liquid separator 104 is supplied to the compressor 101 during a compression process. The injection passage 170 is provided with a temperature sensor 130 (corresponding to the detector in Claims) for detecting the temperature of the refrigerant flowing through the injection passage 170.
In the present embodiment, a refrigerant that does not reach a supercritical state after being compressed by the compressor 101 is used as the refrigerant. Examples of such a refrigerant include a fluorocarbon refrigerant.
The refrigeration cycle apparatus 100 further includes a controller 108. The controller 108 controls mainly the rotation speed of the compressor 101, the opening degree of the indoor side throttling device 103 and the opening degree of the outdoor side throttling device 105, and the four-way valve 120. The refrigeration cycle apparatus 100 in the present embodiment is characterized by that the controller 108 controls the opening degree of the indoor side throttling device 103 and the opening degree of the outdoor side throttling device 105 based on values detected by the temperature sensor 130. The control is described later in detail.
Next, the flow of the refrigerant in the refrigerant circuit 160 is described. In the heating operation, the four-way valve 120 is switched to a state that allows the refrigerant to flow in the direction indicated by the solid line in
In the heating operation, the refrigerant compressed by the compressor 101 is condensed in the indoor heat exchanger 102. The refrigerant condensed in the indoor heat exchanger 102 is expanded in the indoor side throttling device 103. The refrigerant expanded in the indoor side throttling device 103 is separated into a gas phase refrigerant and a liquid phase refrigerant in the gas-liquid separator 104. The liquid phase refrigerant separated out in the gas-liquid separator 104 is expanded in the outdoor side throttling device 105. The refrigerant expanded in the outdoor side throttling device 105 is evaporated in the outdoor heat exchanger 106. The refrigerant that has evaporated in the outdoor heat exchanger 106 is drawn into the compressor 101. In this case, the indoor heat exchanger 102 serves as a condenser and the outdoor heat exchanger 106 serves as an evaporator.
In the cooling operation, the refrigerant circulates through the compressor 101, the outdoor heat exchanger 106, the outdoor side throttling device 105, the gas-liquid separator 104, the indoor side throttling device 103 and the indoor heat exchanger 102 in this order. In this case, the indoor heat exchanger 102 serves as an evaporator and the outdoor heat exchanger 106 serves as a condenser.
Next, the state of the refrigerant flowing through the refrigerant circuit 160 and the injection passage 170 is described with reference to the Mollier diagram in
The low pressure refrigerant (State A) drawn into the compressor 101 is compressed to have an intermediate pressure (State B) and merged into the refrigerant supplied from the injection passage 170 (State C), and then compressed further to have a high temperature and a high pressure (State D). The high temperature, high pressure refrigerant discharged from the compressor 101 flows into the condenser and is cooled and condensed therein (State E). The high pressure refrigerant flowed out of the condenser is expanded by the first throttling device to have an intermediate pressure (State F). This refrigerant is separated into a refrigerant (State I) containing a gas phase refrigerant as a main component and a liquid phase refrigerant (State G) in the gas-liquid separator 104. The refrigerant containing the gas phase refrigerant as a main component flows into the injection passage 170. The liquid phase refrigerant flows into the second throttling device. The liquid phase refrigerant that has flowed into the second throttling device is expanded further and turns into a low pressure refrigerant (State H). Thereafter, the low pressure refrigerant is evaporated in the evaporator to be gaseous (State A), and then passes through the four-way valve 120 and is drawn into the compressor 101 again. The refrigerant containing the gas phase refrigerant as a main component separated in the gas-liquid separator 104 passes through the injection passage 170 and is drawn into the compressor 101 during the compression process.
Ideally, the refrigerant separated in the gas-liquid separator 104 and flowing into the injection passage 170 contains no liquid phase component (that is, the refrigerant is in State J in
Mixing of the liquid phase refrigerant into the gas phase refrigerant in the gas-liquid separator 104 occurs more prominently when the pressure, referred to as State F in
In the present embodiment, the controller 108 decreases the opening degree of the first throttling device and increases the opening degree of the second throttling device when the controller 108 recognizes, by the temperature sensor 130, that the pressure of the refrigerant flowing into the gas-liquid separator 104 exceeds the specified pressure in the starting operation. Hereinafter, the control in the present embodiment is described with reference to the flow chart in
The controller 108 set the opening degree of the first throttling device and the opening degree of the second throttling device to specified opening degrees, and then starts running the refrigeration cycle apparatus to perform the starting operation.
First, the controller 108 determines the large/small relationship between a time T that has elapsed from the start of the operation and a threshold value T1 (5 minutes, for example) (Step S201). If the relationship of T>T1 holds (YES in Step S201), the sequence proceeds to Step S202 and the controller 108 ends the starting operation. If the relationship of T>T1 does not hold (NO in Step S201), the sequence proceeds to Step S211 and the controller 108 continues the starting operation. The time T that has elapsed from the start of the operation can be measured by a timer 109 provided to the controller 108.
In Step S202, a shifting operation is performed to set the opening degree of the first throttling device and the opening degree of the second throttling device to opening degrees suitable for a normal operation, and then the sequence proceeds to Step S203 and the controller 108 performs the normal operation.
In Step S211, the temperature sensor 130 detects a temperature Ti of the refrigerant flowing through the injection passage 170.
Subsequently, the controller 108 determines the large/small relationship between the temperature Ti and a threshold value Ti1 defined in advance (10° C., for example) (Step S212). In the present embodiment, if the relationship of Ti>Ti1 holds, the controller 108 determines that the pressure of the refrigerant flowing into the gas-liquid separator 104 exceeds the specified pressure lower than the saturation vapor pressure. If the relationship of Ti>Ti1 holds (YES in Step S212), the controller 108 decreases the opening degree of the first throttling device by ΔA1 and increases the opening degree of the second throttling device by ΔA2 (Step S213), and the sequence returns to Step S201. If the relationship of Ti>Ti1 does not hold (NO in Step S212), the sequence returns to Step S201. That is, the controller 108 monitors Ti in the starting operation, and if Ti is larger than Ti1, decreases gradually the opening degree of the first throttling device and increases gradually the opening degree of the second throttling device until Ti becomes equal to or smaller than Ti1.
The control in accordance with the flow chart in
The effect of the control in accordance with the flow chart in
As shown in
In the present embodiment, the control is performed based on the temperature Ti of the refrigerant in the injection passage 170, but it can also be performed based on another value. For example, the opening degree of the first throttling device and the opening degree of the second throttling device may be controlled based on the temperature of the refrigerant between the first throttling device and the gas-liquid separator 104 or between the gas-liquid separator 104 and the second throttling device in the refrigerant circuit 160, or the temperature of the refrigerant in the gas-liquid separator 104.
It also is possible to detect, using a pressure sensor instead of the temperature sensor, the pressure of the refrigerant in the injection passage 170 or the pressure of the refrigerant present on the downstream side of the first throttling device and on the upstream side of the second throttling device in the refrigerant circuit 160 so as to control the opening degree of the first throttling device and the opening degree of the second throttling device based on this value.
In the present embodiment, both of the opening degree of the first throttling device and the opening degree of the second throttling device are controlled. This makes it possible to suppress the variation in the pressure difference between a pressure on the high pressure side and a pressure on the low pressure side in the refrigeration cycle. Moreover, by controlling both of the opening degree of the first throttling device and the opening degree of the second throttling device, it also is possible to adjust the degree of dryness of the refrigerant flowing into the compressor 101 via the evaporator to an appropriate value. Thereby, the heating capacity of the refrigeration cycle apparatus 100 can be enhanced. However, the controller 108 may only decrease gradually the opening degree of the first throttling device while keeping the opening degree of the second throttling device constant. This also can suppress the liquid compression.
The four-way valve (switching device) 120 may be omitted. This makes the configuration of the refrigeration cycle apparatus simple, and advantageous from the viewpoints of maintenance and cost. In the case where the four-way valve 120 is omitted, and the flowing direction of the refrigerant is fixed as in a refrigeration cycle apparatus constituting a water heater or the like, a fixed throttling device may be used as the second throttling device. This makes the configuration further simpler.
In the present embodiment, the injection passage 170 is provided with no injection throttling device. Thereby, an advantageous configuration is achieved from the view point of cost. However, even in the case where an injection throttling device is provided (for emergency, etc.), the above-mentioned control may be performed while the injection throttling device is kept open.
In the present embodiment, the controller 108 determines whether to end the starting operation or not based on a rate of change with time, ΔTc, in a temperature Tc of the refrigerant flowing through the condenser.
The control of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in
The flow chart shown in
First, the temperature sensor 131 detects the temperature Tc of the refrigerant flowing through the condenser in Step S401, and the sequence proceeds to Step S402. The temperature Tc is stored in the controller 108 each time.
In Step S402, the rate of change with time, ΔTc, in the temperature of the refrigerant flowing through the condenser is calculated from the detected temperature Tc, a temperature Tc′ detected one time step earlier and stored in the controller 108, and a time step Δt.
In Step S403, the large/small relationship between the calculated rate of change with time, ΔTc, and a threshold value ΔTc1 is determined. If the relationship of ΔTe<ΔTc1 holds (YES in Step S403), the sequence proceeds to Step S202. If the relationship of ΔTc<ΔTc1 does not hold (No in Step S403), the sequence proceeds to Step S211.
The control in accordance with the flow chart in
In the present embodiment, the controller 108 determines whether to end the starting operation or not based on a rate of change with time, ΔTe, in a temperature Te of the refrigerant flowing through the evaporator.
The control of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in
The flow chart shown in
First, the temperature sensor 133 detects the temperature Te of the refrigerant flowing through the evaporator in Step S501, and the sequence proceeds to Step S502. The temperature Te is stored in the controller 108 each time.
In Step S502, the rate of change with time, ΔTe, in the temperature of the refrigerant flowing through the condenser is calculated from the detected temperature Te, a temperature Te′ detected one time step earlier and stored in the controller 108, and the time step At.
In Step S503, the large/small relationship between the calculated rate of change with time, ΔTe, and a threshold value ΔTe1 is determined. If the relationship of ΔTe<ΔTe1 holds (YES in Step S503), the sequence proceeds to Step S202. If the relationship of ΔTe<ΔTe1 does not hold (NO in Step S503), the sequence proceeds to Step S211.
The control in accordance with the flow chart in
Although the controls described in the above-mentioned Embodiments are provided to prevent the liquid compression in the starting operation, they are applicable to prevent the liquid compression in other operations as well.
In the defrosting operation, for example, the liquid phase refrigerant is likely to be injected into the compressor 101. Also, in the stopping operation, the drawing temperature in the compressor 101 lowers, the amount of the liquid phase component contained in the refrigerant increases, and the liquid compression is likely to occur. Also in these operations, the liquid compression can be suppressed by the same configuration as that of the refrigeration cycle apparatus 100 in
The controller 108 starts the defrosting operation when, for example, the temperature of the outdoor heat exchanger 106 becomes equal to or lower than a specified temperature (−5° C., for example).
First, in Step S601, the controller 108 determines the large/small relationship between a time T that has elapsed from the start of the defrosting operation and a threshold value T2 (10 minutes, for example). If the relationship of T>T2 holds (YES in Step S601), the sequence proceeds to Step S602 and the controller 108 ends the defrosting operation. If the relationship of T>T2 does not hold (NO in Step S601), the sequence proceeds to Step S611 and the controller 108 continues the defrosting operation. The time T that has elapsed from the start of the operation can be measured by the timer 109 provided to the controller 108.
The controller 108 performs the shifting operation in Step S602, and then the sequence proceeds to Step S603 to perform the normal operation.
In Step S611, the temperature sensor 130 detects the temperature Ti of the refrigerant in the injection passage 170.
Subsequently, the controller 108 determines the large/small relationship between the temperature Ti and the threshold value Ti1 defined in advance (Step S612). If the relationship of Ti>Ti1 holds (YES in Step S612), the controller 108 decreases the opening degree of the first throttling device by ΔA1 and increases the opening degree of the second throttling device by ΔA2 (Step S613), and the sequence returns to Step S601. If the relationship of Ti>Ti1 does not hold (NO in Step S612), the sequence returns to Step S601.
The control in accordance with the flow chart in
In the flow chart in
Next,
First, in Step S701, the controller 108 determines the large/small relationship between a time T that has elapsed from the start of the stopping operation and a threshold value T3 (3 minutes, for example). If the relationship of T>T3 holds (YES in Step S701), the sequence proceeds to Step S702 and the controller 108 ends the stopping operation. If the relationship of T>T3 does not hold (NO in Step S701), the sequence proceeds to Step S711 and the controller 108 continues the stopping operation. The time T that has elapsed from the start of the operation can be measured by the timer 109 provided to the controller 108.
In Step S711, the temperature sensor 130 detects the temperature Ti of the refrigerant in the injection passage 170.
Subsequently, the controller 108 determines the large/small relationship between the temperature Ti and the threshold value Ti1 defined in advance (Step S712). If the relationship of Ti>Ti1 holds (YES in Step S712), the controller 108 decreases the opening degree of the first throttling device by ΔA1 and increases the opening degree of the second throttling device by ΔA2 (Step S713), and the sequence returns to Step S701. If the relationship of Ti>Ti1 does not hold (NO in Step S712), the sequence returns to Step S701.
The controlling in accordance with the flow chart in
In each of the defrosting operation and the stopping operation, instead of performing the control based on the temperature Ti of the refrigerant in the injection passage 170, it also is possible to perform the control based on another value. For example, the opening degree of the first throttling device and the opening degree of the second throttling device may be controlled based on the temperature of the refrigerant between the first throttling device and the gas-liquid separator 104 or between the gas-liquid separator 104 and the second throttling device in the refrigerant circuit 160, or the temperature of the refrigerant in the gas-liquid separator 104. That is, the opening degree of the first throttling device and the opening degree of the second throttling device may be controlled based on the temperature of the refrigerant present on the downstream side of the first throttling device and on the upstream side of the second throttling device in the refrigerant circuit 160, or the temperature of the refrigerant in the injection passage 107.
It also is possible to detect, using a pressure sensor instead of the temperature sensor, the pressure of the refrigerant in the injection passage 170 or the pressure of the refrigerant present on the downstream side of the first throttling device and on the upstream side of the second throttling device in the refrigerant circuit 160 so as to control the opening degree of the first throttling device and the opening degree of the second throttling device based on this value.
The controller 108 may only decrease gradually the opening degree of the first throttling device while keeping the opening degree of the second throttling device constant. The four-way valve (switching device) 120 may be omitted. Also, with the four-way valve 120 being omitted, a fixed throttling device may be used as the second throttling device
(Control in Normal Operation)
When controlled as mentioned above, the refrigeration cycle apparatus can perform the starting operation, the defrosting operation and the stopping operation in which the liquid compression hardly occurs while the effect of injection is exhibited. In the normal operation, the refrigeration cycle apparatus preferably is operated as described in First Normal Operation, Second Normal Operation, Third Normal Operation, or Fourth Normal Operation below. Thereby, it is possible to suppress an abnormal increase in the pressure of the refrigerant on the high pressure side in the refrigeration cycle in the normal operation, and to achieve the effect of enhancing the heating capacity by injection while preventing the liquid refrigerant from being injected into the compressor.
(First Normal Operation)
The first normal operation is described with reference to a refrigeration cycle apparatus 150 (
A fluorocarbon refrigerant is used as the refrigerant also in the refrigeration cycle apparatus 150. However, the effect of the first normal operation is exhibited even when a refrigerant, such as carbon dioxide, that reaches a supercritical state after being compressed by the compressor 101 is used as the refrigerant. Thus, the term “radiator” is used instead of the term “condenser” hereinafter.
The state of the refrigerant flowing through the refrigerant circuit 160 and the injection passage 170 in the refrigeration cycle apparatus 150 in the first normal operation are described with reference to the Mollier diagram in
The low pressure refrigerant (State 0) drawn into the compressor 101 is compressed to have an intermediate pressure (State P) and merged into the refrigerant supplied from the injection passage 170 (State Q), and then compressed further to have a high temperature and a high pressure (State R). The high temperature, high pressure refrigerant discharged from the compressor 101 flows into the radiator and is cooled and radiates heat therein (state S). The high pressure refrigerant flowed out of the radiator is expanded by the first throttling device to have an intermediate pressure (State T). This refrigerant is separated into a gas phase refrigerant and a liquid phase refrigerant (State U) in the gas-liquid separator 104. The gas phase refrigerant flows into the injection passage 170. The liquid phase refrigerant flows into the second throttling device. The liquid phase refrigerant that has flowed into the second throttling device is expanded further and turns into a low pressure refrigerant (State V). Thereafter, the low pressure refrigerant is evaporated in the evaporator to be gaseous (State O), and then passes through the four-way valve 120 and is drawn into the compressor 101 again. The gas phase refrigerant separated out in the gas-liquid separator 104 passes through the injection passage 170 and is drawn into the compressor 101 during the compression process.
In the first normal operation, the controller 108 controls the rotation speed of the compressor 102 in accordance with, for example, a load required by a user, and adjusts the opening degrees of the first throttling device and the second throttling device so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is equal to the specified pressure stored in advance.
In the first normal operation, the pressure (the pressure in State R and State S in
In the first normal operation, the controller 108 controls the opening degree of the indoor side throttling device 103 and the opening degree of the outdoor side throttling device 105 based on a value detected by the temperature sensor 131 (high pressure side detector) capable of measuring the temperature of the refrigerant in the indoor heat exchanger 102 that functions as the radiator in the heating operation. This control may be performed while the output of the compressor 101 is kept constant, or may be performed while the output of the compressor 101 is being changed. Moreover, the control may be performed concurrently with the control of another device. In the refrigeration cycle apparatus 150 shown in
Hereinafter, the control of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in
First, in Step S261, the temperature sensor 131 detects a temperature Th of the refrigerant flowing through the radiator.
Subsequently, the controller 108 determines the large/small relationship between the temperature Th detected in Step 261 and a threshold value Th1 (55° C., for example) defined in advance (Step S262). If the relationship of Th>Th1 holds (YES in Step S262), the sequence proceeds to Step S263 and the controller 108 shifts the operating state from the steady operation to the high-pressure-side abnormality eliminating operation. If the relationship of Th>Th1 does not hold (NO in Step S262), the sequence returns to Step S261. That is, in the first normal operation, the determination of whether to shift the operating state to the high-pressure-side abnormality eliminating operation is made according to the large/small comparison between Th and Th1. Step S261 and Step S262 are in the flow of the steady operation.
In Step S263 (main step), the controller 108 increases the opening degree of the first throttling device by ΔA3 and increases the opening degree of the second throttling device by ΔA4, and the sequence proceeds to Step S264. Here, ΔA3 and the ΔA4 are set to values that cause no increase in the pressure of the refrigerant in the gas-liquid separator 104 even if Step S263 is performed. Such ΔA3 and ΔA4 can be determined by an experiment, etc. conducted in advance.
In Step S264, the temperature sensor 131 detects once again the temperature Th of the refrigerant flowing through the radiator. In Step S265, the controller 108 determines the large/small relationship between the temperature Th detected in Step 264 and the threshold value Th1 defined in advance. If the relationship of Th>Th1 holds (YES in Step S265), the sequence returns to Step S263 and the controller 108 continues the high-pressure-side abnormality eliminating operation. If the relationship of Th>Th1 does not hold (NO in Step S265), the sequence returns to Step S261 (comes back to the steady operation) and the controller 108 ends the high-pressure-side abnormality eliminating operation. That is, in the first normal operation, the determination of whether to end the high-pressure-side abnormality eliminating operation is made according to the large/small comparison between Th and Th1.
As described above, in the first normal operation, the controller 108 monitors the temperature Th of the refrigerant flowing through the radiator in the steady operation, and shifts the operating state to the high-pressure-side abnormality eliminating operation if the relationship of Th>Th1 holds. Thereafter, the controller 108 increases gradually the opening degree of the first throttling device and increases gradually the opening degree of the second throttling device until the relationship of Th>Th1 fails to hold.
The control in accordance with the flow chart in
The effect of the control in accordance with the flow chart in
When the pressure of the refrigerant on the high pressure side in the refrigeration cycle is excessively high, it is conceivable to deal with it by increasing only the opening degree of the throttling device on the upstream side of the gas-liquid separator. This can lower the pressure of the refrigerant on the high pressure side. On the other hand, however, this increases the pressure of the refrigerant in the gas-liquid separator. When the pressure of the refrigerant in the gas-liquid separator exceeds the saturation vapor pressure, the liquid refrigerant is injected into the compressor.
In the case where the injection passage 170 is provided with an opening and closing valve as is described in JP 2009-180427 A, for example, it is possible to prevent the liquid refrigerant from being injected into the compressor by closing the opening and closing valve. However, this makes it impossible to obtain the effect of increasing the heating capacity by injection.
In contrast, the control in accordance with the flow chart in
(Second Normal Operation)
Also in the second normal operation, when the pressure of the refrigerant on the high pressure side in the refrigeration cycle becomes excessively high, the high-pressure-side abnormality eliminating operation is performed so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is kept equal to or lower than the saturation vapor pressure while the pressure on the high pressure side in the refrigeration cycle is lowered, as in the first normal operation.
In the high-pressure-side abnormality eliminating operation in the second normal operation, the controller 108 controls the opening degree of the first throttling device and the opening degree of the second throttling device based on the temperature Tcom detected by the temperature sensor 132. Hereinafter, the control (the high-pressure-side abnormality eliminating operation) of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in
First, in Step S361, the temperature sensor 132 detects the temperature Tcom of the refrigerant discharged from the compressor 101.
Subsequently, the controller 108 determines the large/small relationship between the temperature Tcom detected in Step 361 and a threshold value Tcom1 (120° C., for example) defined in advance (Step S362). If the relationship of Tcom>Tcom1 holds (YES in Step S362), the sequence proceeds to Step S363 and the controller 108 shifts the operating state from a steady operation to the high-pressure-side abnormality eliminating operation. If the relationship of Tcom>Tcom1 does not hold (NO in Step S362), the sequence returns to Step S361. That is, in the second normal operation, the determination of whether to shift the operating state to the high-pressure-side abnormality eliminating operation is made according to the large/small comparison between Tcom and Tcom1.
In Step S363, the controller 108 increases the opening degree of the first throttling device by ΔA3 and increases the opening degree of the second throttling device by ΔA4, and the sequence proceeds to Step S364. ΔA3 and the ΔA4 are the same as in the first normal operation. In Step S364, the temperature sensor 132 detects once again the temperature Tcom of the refrigerant discharged from the compressor 101. In Step S365, the controller 108 determines the large/small relationship between the temperature Tcom detected in Step 364 and the threshold value Tcom1 defined in advance. If the relationship of Tcom>Tcom1 holds (YES in Step S365), the sequence returns to Step S363 and the controller 108 continues the high-pressure-side abnormality eliminating operation. If the relationship of Tcom>Tcom1 does not hold (NO in Step S365), the sequence returns to Step S361 (the operating state comes back to the steady operation) and the controller 108 ends the high-pressure-side abnormality eliminating operation. That is, in the second normal operation, the determination of whether to end the high-pressure-side abnormality eliminating operation is made according to the large/small comparison between Tcom and Tcom1.
As described above, in the second normal operation, the controller 108 monitors the temperature Tcom of the refrigerant discharged from the compressor 101 in the steady operation, and shifts the operating state to the high-pressure-side abnormality eliminating operation if the relationship of Tcom>Tcom1 holds. Thereafter, the controller 108 increases gradually the opening degree of the first throttling device and increases gradually the opening degree of the second throttling device until the relationship of Tcom>Tcom1 fails to hold.
The control in accordance with the flow chart in
In the first normal operation, the determination of whether to shift the operating state to the high-pressure-side abnormality eliminating operation and the determination of whether to end the high-pressure-side abnormality eliminating operation are made based on the temperature Th of the refrigerant flowing through the radiator. In the second normal operation, these determinations are made based on the temperature Tcom of the refrigerant discharged from the compressor 101. However, the determinations can also be made based on another value. For example, the determinations may also be made based on the temperature of the refrigerant present between the radiator and the first throttling device in the refrigerant circuit 160.
It also is possible to detect, using a pressure sensor instead of the temperature sensor, the pressure of the refrigerant present on the downstream side of the compressor 101 and on the upstream side of the first throttling device in the refrigerant circuit 160 and make the determinations based on this value.
It also is possible to refer to both of the temperature Th of the refrigerant flowing through the radiator and the temperature Tcom of the refrigerant discharged from the compressor 101 by using both of the temperature sensor 131 and the temperature sensor 132. For example, the determination of whether to shift the operating state to the high-pressure-side abnormality eliminating operation and the determination of whether to end the high-pressure-side abnormality eliminating operation may also be made depending on whether one of the relationship of Th>Th1 and the relationship of Tcom>Tcom1 holds. This makes it possible to perform an operation with higher safety than those of the first normal operation and the second normal operation.
In the first normal operation and the second normal operation, the four-way valve (switching device) 120 may be omitted when the refrigeration cycle apparatus 150 and the refrigeration cycle apparatus 250 are used in an application other than air conditioner. This makes the configurations of the refrigeration cycle apparatuses simple, and advantageous from the viewpoints of maintenance and cost.
(Third Normal Operation)
Also in the third normal operation, when the pressure of the refrigerant on the high pressure side in the refrigeration cycle becomes excessively high, the high-pressure-side abnormality eliminating operation is performed so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is kept equal to or lower than the saturation vapor pressure while the pressure on the high pressure side in the refrigeration cycle is lowered, as in the first normal operation and the second normal operation. In the high-pressure-side abnormality eliminating operation in the third normal operation, the controller 108 controls the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) based on the temperature Th detected by the temperature sensor 131.
When the pressure (temperature, in another word) of the refrigerant flowing through the evaporator decreases excessively, the performance of the evaporator may not be exhibited sufficiently due to frost formation on the evaporator, etc. Therefore, in the third normal operation, a low-pressure-side abnormality eliminating operation for raising the pressure of the refrigerant flowing through the evaporator is performed when the pressure of the refrigerant flowing through the evaporator is determined to be lower than the specified value even in the case where it is determined not to perform the high-pressure-side abnormality eliminating operation. In the low-pressure-side abnormality eliminating operation in the third normal operation, the controller 108 controls the opening degree of the second throttling device based on the temperature Te detected by the temperature sensor 133.
Hereinafter, the high-pressure-side abnormality eliminating operation and the low-pressure-side abnormality eliminating operation performed by the controller 108 are described with reference to the flow chart shown in
If the relationship of Th>Th1 does not hold in Step S262 (NO in Step S262), the sequence proceeds to Step S471.
In Step S471, the temperature sensor 133 detects the temperature Te of the refrigerant flowing through the evaporator.
Subsequently, in Step S472, the controller 108 determines the large/small relationship between the temperature Te and a threshold value Te2 (5° C., for example) defined in advance. If the relationship of Te<Te2 holds (YES in Step S472), the sequence proceeds to Step S473 and the controller 108 shifts the operating state to the low-pressure-side abnormality eliminating operation. If the relationship of Te<Te2 does not hold (NO in Step S472), the sequence returns to Step S261. In this way, in the third normal operation, the determination of whether to shift the operating state to the low-pressure-side abnormality eliminating operation is made according to the large/small comparison between Te and Te2.
In Step S473, the controller 108 increases the opening degree of the second throttling device by ΔA5 and the sequence proceeds to Step S474. Here, ΔA5 can be an arbitrary value. In Step S474, the temperature sensor 133 detects once again the temperature Te of the refrigerant flowing through the evaporator. In Step S475, the controller 108 determines the large/small relationship between the temperature Te detected in Step S474 and the threshold value Te2 defined in advance. If the relationship of Te<Te2 holds (YES in Step S475), the sequence returns to Step S473 and the controller 108 continues the low-pressure-side abnormality eliminating operation. If the relationship of Te<Te2 does not hold (NO in Step S475), the sequence returns to Step S261 (the operating state comes back to the steady operation) and the controller 108 ends the low-pressure-side abnormality eliminating operation. That is, in the third normal operation, the determination of whether to end the low-pressure-side abnormality eliminating operation is made according to the large/small comparison between Te and Te2.
In the control in accordance with the flow chart in
In the third normal operation, the determinations of whether to shift the operating state to the high-pressure-side abnormality eliminating operation and whether to end the high-pressure-side abnormality eliminating operation are made based on the temperature Th of the refrigerant flowing through the radiator. However, the determinations may be made based on the temperature of the refrigerant discharged from the compressor 101, as in the second normal operation.
Moreover, although the determination of whether to perform the low-pressure-side abnormality eliminating operation is made based on the temperature Te of the refrigerant flowing through the evaporator in the third normal operation, it can be made based on another value. For example, it is possible to measure the temperature of the refrigerant drawn into the compressor 101 by the temperature sensor and compare the detected temperature with another threshold value so as to make the determination based on this. That is, the temperature sensor may be provided at any position as long as it is on the downstream side of the second throttling device and on the upstream side of the compressor 101, where the refrigerant has a low pressure.
It also is possible to detect, using a pressure sensor instead of the temperature sensor, the pressure of the refrigerant present on the downstream side of the second throttling device and on the upstream side of the compressor 101 in the refrigerant circuit 160 so as to determine whether to perform the low-pressure-side abnormality eliminating operation based on this value.
(Fourth Normal Operation)
Also in the fourth normal operation, when the pressure of the refrigerant on the high pressure side in the refrigeration cycle becomes excessively high, the high-pressure-side abnormality eliminating operation is performed so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is kept equal to or lower than the saturation vapor pressure while the pressure on the high pressure side in the refrigeration cycle is lowered, as in the first normal operation, the second normal operation, and the third normal operation. In the high-pressure-side abnormality eliminating operation in the fourth normal operation, the controller 108 controls the opening degree of the first throttling device and the opening degree of the second throttling device based on the temperature Th detected by the temperature sensor 131, a temperature Tec detected by the temperature sensor 134, and a pressure Pi detected by the pressure sensor 140.
Hereinafter, the control (high-pressure-side abnormality eliminating operation) of the opening degree of the indoor side throttling device 103 (first throttling device) and the opening degree of the outdoor side throttling device 105 (second throttling device) performed by the controller 108 is described with reference to the flow chart shown in
The flow chart shown in
In the fourth normal operation, the controller 108 increases the opening degree of the first throttling device by ΔA3 and increases the opening degree of the second throttling device by ΔA4 in Step S263, and the sequence proceeds to Step S564. In the fourth normal operation, the values of ΔA3 and ΔA4 can be arbitrary values.
The temperature sensor 134 detects the temperature Tec of the refrigerant flowing out of the radiator in Step S564, and the sequence proceeds to Step S565.
In Step S565, the controller 108 determines a saturation vapor pressure Pi6 based on the temperature Th detected in Step S261 and the temperature Tec detected in Step S564. A table or the like can be used when determining the saturation vapor pressure Pi6.
Subsequently, in Step S566, the pressure sensor 140 detects the pressure Pi of the refrigerant in the gas-liquid separator 104 and the sequence proceeds to Step S567.
In Step S567, the controller 108 determines the large/small relationship between the pressure Pi and the saturation vapor pressure Pi6. If the relationship of Pi>Pi6 holds (YES in Step S567), the sequence proceeds to Step S568 and the controller 108 decreases the opening degree of the first throttling device by ΔA6 and increase the opening degree of the second throttling device by ΔA7, and the sequence proceeds to Step S264. If the relationship of Pi>Pi6 does not hold (NO in Step S567), the sequence proceeds to Step S264. Since ΔA6 is smaller than ΔA3, the pressure of the refrigerant flowing through the radiator (that is, the pressure on the high pressure side) is lowered even in the case where both controls of Step S263 and Step S568 are performed.
The control in accordance with the flow chart in
Furthermore, the control in accordance with the flow chart in
Moreover, in the first normal operation, the second normal operation, and the third normal operation, it is necessary to set the pressure of the refrigerant flowing into the gas-liquid separator 104 to be equal to or lower than the saturation vapor pressure in a reliable manner only by Step S263 (or by Step S363). Therefore, it is preferable to set the amount of change ΔA4 in the opening degree of the second throttling device to be somewhat larger than an amount of change ΔA4 determined by experiment, etc. That is, the pressure of the refrigerant flowing into the gas-liquid separator 104 may be lower than needed. In contrast, in the fourth normal operation, it is possible to keep reliably the pressure of the refrigerant flowing into the gas-liquid separator 104 equal to or lower than the saturation vapor pressure by Step S564 to Step S568. Therefore, the amount of change ΔA4 in Step S263 can be smaller in the fourth normal operation than that in the first normal operation, the second normal operation, and the third normal operation. This makes it possible to control the opening degree of the second throttling device so that the pressure of the refrigerant flowing into the gas-liquid separator 104 is equal to or lower than the saturation vapor pressure and close to the saturation vapor pressure. As a result, the refrigeration cycle apparatus can be operated more effectively.
Instead of detecting the temperature Th of the refrigerant flowing through the radiator by the temperature sensor 131, it is possible to detect the pressure of the refrigerant present on the downstream side of the compressor 101 and on the upstream side of the first throttling device in the refrigerant circuit 160 so as to determine whether to shift the operating state to the high-pressure-side abnormality eliminating operation and whether to end the high-pressure-side abnormality eliminating operation based on this value. Thereby, the saturation vapor pressure can be determined also from this value and the temperature Tec.
In the fourth normal operation, the pressure sensor 140 provided in the gas-liquid separator 104 detects directly the pressure Pi of the refrigerant in the gas-liquid separator 104, but the pressure Pi does not necessarily have to be detected directly. For example, the pressure Pi of the refrigerant in the gas-liquid separator 104 may be determined indirectly from the pressure or temperature of the refrigerant present between the first throttling device and the gas-liquid separators 104 or between the gas-liquid separator 104 and the second throttling device in the refrigerant circuit 160, or from the pressure or temperature of the refrigerant in the injection passage 170.
Moreover, although the saturation vapor pressure Pi6 is determined from the detected temperature Th and temperature Tec in the fourth normal operation, a value in accordance with the value detected by the temperature sensor 131 may be used as the saturation vapor pressure Pi6, for example. This simplifies the control performed by the controller 108, making it possible to obtain a useful configuration from the view point of computer resource.
The first normal operation to the fourth normal operation described above can be summarized as follows.
That is, it is preferable that the refrigeration cycle apparatus capable of performing the normal operation include: the refrigerant circuit including the compressor for compressing the refrigerant, the radiator that allows the refrigerant compressed in the compressor to radiate heat, the first throttling device for expanding the refrigerant that has radiated heat in the radiator, the gas-liquid separator for separating the refrigerant expanded in the first throttling device into the gas phase refrigerant and the liquid phase refrigerant, the second throttling device for expanding the liquid phase refrigerant separated out in the gas-liquid separator, and the evaporator for evaporating the refrigerant expanded in the second throttling device; the injection passage through which the gas phase refrigerant separated out in the gas-liquid separator is supplied to the compressor during the compression process; a high pressure side detector for detecting the temperature or the pressure of the refrigerant present on the downstream side of the compressor and on the upstream side of the first throttling device in the refrigerant circuit; and the controller for performing the high-pressure-side abnormality eliminating operation in which when the value detected by the high pressure side detector exceeds the specified value, the controller increases the opening degree of the first throttling device and increases the opening degree of the second throttling device so as to lower the high pressure of the refrigeration cycle while keeping the pressure of the refrigerant in the gas-liquid separator equal to or lower than the saturation vapor pressure.
This configuration makes it possible to increase the opening degree of the first throttling device to lower the pressure of the refrigerant on the high pressure side in the refrigeration cycle when the pressure of the refrigerant on the high pressure side in the refrigeration cycle is excessively high. Furthermore, in the above-mentioned refrigeration cycle apparatus, not only the opening degree of the first throttling device but also the opening degree of the second throttling device is increased. When the opening degree of the second throttling device is increased, the pressure of the refrigerant in the gas-liquid separator is lowered. That is, by increasing the opening degree of the first throttling device as well as the opening degree of the second throttling device, it is possible to suppress an increase in the pressure of the refrigerant in the gas-liquid separator while lowering the pressure of the refrigerant on the high pressure side in the refrigeration cycle, so that the pressure of the refrigerant in the gas-liquid separator is kept equal to or lower than the saturation vapor pressure. Accordingly, it is possible to suppress an abnormal increase in the pressure on the high pressure side in the refrigeration cycle, and to inject the refrigerant into the compressor while preventing the liquid refrigerant from being injected into the compressor.
Preferably, the above-mentioned refrigeration cycle apparatus further includes the low pressure side detector for detecting the temperature or the pressure of the refrigerant present on the downstream side of the second throttling device and on the upstream side of the compressor in the refrigerant circuit, and if the value detected by the low pressure side detector is smaller than the specified value, the controller performs the low-pressure-side abnormality eliminating operation for increasing gradually the opening degree of the second throttling device even in the case where it does not perform the high-pressure-side abnormality eliminating operation.
Preferably, in the above-mentioned refrigeration cycle apparatus, the controller repeats, in the high-pressure-side abnormality eliminating operation, the main step of increasing the opening degree of the first throttling device by the specified amount of ΔA3 and increasing the opening degree of the second throttling device by the specified amount of ΔA4 until the value detected by the high pressure side detector falls below the specified value.
In the above-mentioned refrigeration cycle apparatus, it is preferable that the high pressure side detector is a radiator temperature sensor for detecting the temperature of the refrigerant flowing through the radiator. Preferably, the above-mentioned refrigeration cycle apparatus further includes the pressure sensor for detecting the pressure of the refrigerant in the gas-liquid separator, and the radiator outlet temperature sensor for detecting the temperature of the refrigerant flowing out of the radiator. Preferably, the controller calculates the saturation vapor pressure of the refrigerant flowing into the gas-liquid separator from the values detected by the radiator temperature sensor and the radiator outlet temperature sensor and determines whether the pressure detected by the pressure sensor exceeds the saturation vapor pressure every time when performing the main step, and when the pressure detected by the pressure sensor exceeds the saturation vapor pressure, the controller decreases the opening degree of the first throttling device by a value smaller than ΔA3 and increases further the opening degree of the second throttling device.
The refrigeration cycle apparatus according to the present invention can be utilized as a refrigeration cycle apparatus for various applications, such as hot water supply and air conditioning.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-200744 | Sep 2010 | JP | national |
| 2010-200745 | Sep 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/003578 | 6/23/2011 | WO | 00 | 3/14/2012 |
