Patent Application
20190056160
The present invention relates to an air-conditioning apparatus which is applied to, for example, a multi-air-conditioning apparatus for a building.
When an air-conditioning apparatus performs a heating operation during winter season, water vapor in the air adheres to a heat exchanger in a heat source, and frost is formed on the heat exchanger. If the frost still adheres to the heat exchanger, the heating capacity lowers. Therefore, generally, a defrost operation is performed by an outdoor unit during an interval between heating operations to melt the frost adhering to the heat exchanger, to thereby achieve a stable heating capacity.
When the defrost operation is performed, the frost formed on the heat exchanger is melted into defrost water, which flows to a lower part of the heat exchanger. In a cold region, the temperature of such defrost water is low, and the temperature of outside air is extremely low. Therefore, in the cold region, in the case where such a defrost operation is performed in an air-conditioning apparatus, defrost water sometimes refreezes when it flows to a lower part of a heat exchanger. In order to prevent the defrost water from being refrozen, a bypass is provided at a lowermost part of the heat exchanger, and refrigerant having a high pressure and a high temperature is made to flow into the bypass (patent literature 1).
Patent Literature: Japanese Unexamined Patent Application Publication No. 2006-64381
In many cases, as multi-air-conditioning apparatuses for a building, plural air-conditioning apparatuses are used. In this case, outdoor units of the air-conditioning apparatuses are arranged side by side, that is, they are arranged such that side surfaces of any adjacent two of them face each other. In the case where plural outdoor units are densely installed, the distance between side surfaces of any adjacent two of the outdoor units is only several centimeters. During the above defrost operation, fans of the outdoor units of the air-conditioning apparatuses are stopped, and only outside air thus passes through the outdoor units. Therefore, in multi-air-conditioning apparatuses, in the case where plural outdoor units are densely installed, during the defrost operation, outside air more greatly influences upon front and rear surfaces of the outdoor units than upon the side surfaces of the outdoor units, which are spaced from each other by a slight distance. As a result, defrost water tends to refreeze on the front and rear surfaces of the outdoor units.
Also, in many cases, the external shape of an outdoor unit is a substantially cuboid as a whole. The influence of outside air upon the outdoor unit varies from one surface of the outdoor unit to another surface thereof, since the surfaces of the outdoor unit have different areas. Furthermore, the temperature of refrigerant at part of the above bypass which is the farthest from a header of the heat exchanger is lower than the temperature of refrigerant at any of the other parts of the bypass. Therefore, in a single heat exchanger, the temperature of a bypass for preventing refreeze is not uniform over the bypass, a drainage performance is easily worsened, and there is a possibility that refreeze will occur, and whether or not refreeze occurs depends on the distance between part of the bypass and the header.
The present invention has been made to solve the above problem, and an object of the invention is to improve a defrosting efficiency during a defrost operation in a multi-air-conditioning apparatus in which plural outdoor units are installed, and to prevent defrost water from being refrozen.
An air-conditioning apparatus according to an embodiment of the present invention includes: an outdoor unit including a compressor, a flow-path switching unit and plural heat-source-side heat exchangers, the compressor, the flow-path switching unit and the heat-source-side heat exchangers being connected by pipes; and an indoor unit connected to the outdoor unit to air-condition a target space, wherein the outdoor unit includes: plural bypasses each having ends one of which is, in connection by pipes in the outdoor unit, connected to a discharge side of the compressor, and the other of which is connected to a suction side of the compressor, the bypasses being configured to cause refrigerant to flow through lower parts of the plural heat-source-side heat exchangers during a defrost operation of the air-conditioning apparatus; and flow-rate adjusting mechanisms respectively provided in the plural bypasses to adjust flow rates of refrigerant flowing into the plural bypasses.
In the air-conditioning apparatus according to the embodiment of the present invention, the plural bypasses configured to cause the refrigerant to flow through lower parts of the plural heat-source-side heat exchangers during the defrost operation are provided with flow-rate adjusting mechanisms for adjusting the flow rates of the refrigerant flowing into the bypasses. Therefore, in the multi-air-conditioning apparatus for a building, even in the case where the outdoor units are densely installed, the flow-rate adjusting mechanisms are made to function in accordance with the states of the installation of the outdoor units, whereby defrost water generated during the defrost operation can be reliably prevented from being refrozen.
Refrigeration cycle devices according to embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the embodiments, which will be described below. With respect to the figures to be referred to, there is a case where the size of each of structural elements is different from that of an actual apparatus.
The outdoor unit 20 includes a compressor 1, a flow-path switching unit 2 such as a four-way valve, heat-source-side heat exchangers 3a and 3b and an accumulator 5, which are connected by pipes. The compressor 1 sucks refrigerant, compresses it to cause it to have a high temperature and a high pressure, and transfers it to a refrigerant circuit. The compressor is provided as, for example, an inverter compressor the capacity of which can be controlled. The flow-path switching unit 2 switches the flow of refrigerant between the flow of refrigerant in a heating operation mode and the flow of refrigerant in a cooling operation mode. The heat-source-side heat exchangers 3a and 3b function as evaporators in the heating operation mode and function as radiators in the cooling operation mode and a defrost operation mode, and cause heat exchange to be performed between the refrigerant and air supplied by an air-sending device such as a fan (not shown). The heat-source-side heat exchangers 3a and 3b are connected in parallel by refrigerant pipes in the outdoor unit 20. The heat-source-side heat exchangers 3a and 3b are formed in an L-shape as their outer shape, and are arranged to form a rectangular frame as a whole in a housing of the outdoor unit 20. The accumulator 5 is installed on a suction side of the compressor 1, and accumulates surplus refrigerant which generates because of the difference between the heating operation mode and the cooling operation mode, and surplus refrigerant which generates because of a change in a transient operation.
Bypasses 6a and 6b are connected to pipes in the outdoor unit 20. In the pipes in the outdoor unit 20, one of the ends of each of the bypasses 6a and 6b is connected to the discharge side of the compressor 1, and the other is connected to the suction side thereof. Furthermore, the bypass 6a extends through lower part of the heat-source-side heat exchanger 3a, and the bypass 6b extends through lower part of the heat-source-side heat exchanger 3b. Also, the bypasses 6a and 6b are connected by pipes to a solenoid valve 4 which serves as an opening/closing unit. The refrigerant in the pipes does not flow into the bypasses 6a and 6b when the solenoid valve 4 is closed, and flows into the bypasses 6a and 6b when the solenoid valve 4 is opened. The bypasses 6a and 6b and the solenoid valve 4 are used to prevent melted frost from being refrozen after the defrost operation of the air-conditioning apparatus 100.
In the indoor unit 10a, a use-side heat exchanger (indoor-side heat exchanger) 12a and an expansion unit 11a are connected in series to each other. In the indoor unit 10b, a use-side heat exchanger 12b and an expansion unit 11b are connected in series to each other. In the indoor unit 10c, a use-side heat exchanger 12c and an expansion unit 11c are connected in series to each other. In the indoor unit 10d, a use-side heat exchanger 12d and an expansion unit 11d are connected in series to each other. The use-side heat exchangers 12a, 12b, 12c and 12d function as condensers in the heating operation mode, and function as evaporators in the cooling operation mode, causes heat exchange to be performed between refrigerant and air supplied by the air-sending device (not shown) such as a fan, and generates air for cooling or air for heating, which is to be supplied to a to-be-air-conditioned space. The expansion units 11a, 11b, 11c and 11d have functions of pressure reducing valves and expansion valves, and reduce the pressure of the refrigerant and expand the refrigerant, and they are also provided as, for example, electronic expansion valves whose opening degrees can be controlled to be changed. In the air-conditioning apparatus 100, the four indoor units 10a, 10b, 10c and 10d are connected in parallel. This, however, is a mere example, and the number of indoor units is not limited to four.
Each of operation modes of the air-conditioning apparatus 100 will be described.
In the use-side heat exchangers 12a, 12b, 12c and 12d, the gas refrigerant having the high temperature and high pressure exchanges heat with air supplied from the air-sending device not shown, and thus becomes liquid refrigerant. The use-side heat exchangers 12a, 12b, 12c and 12d function as condensers, which transfer heat to the ambient air, and reduce the temperature of the refrigerant in pipes in the heat exchangers. The liquid refrigerant flows out from the use-side heat exchangers 12a, 12b, 12c and 12d as liquid refrigerant having a high temperature and a high pressure, and is expanded and reduced in pressure by the expansion units 11a, 11b, 11c and 11d to become two-phase gas-liquid refrigerant having a low temperature and a low pressure, and then the two-phase gas-liquid refrigerant flows from the indoor units 10a, 10b, 10c and 10d. After flowing from the indoor units 10a, 10b, 10c and 10d, the two-phase gas-liquid refrigerant flows into the outdoor unit 20 through the pipe B. After flowing into the outdoor unit 20, in the heat-source-side heat exchangers 3a and 3b, the two-phase gas-liquid refrigerant exchanges heat with air supplied by the air-sending device (not shown) to become gas refrigerant having a low temperature and a low pressure. The heat-source-side heat exchangers 3a and 3b function as evaporators that receive heat from the ambient air and evaporate the refrigerant in the pipes. After flowing from the heat-source-side heat exchangers 3a and 3b, the gas refrigerant flows into the accumulator 5 through pipes and the flow-path switching unit 2 in the outdoor unit 20. The refrigerant having flown into the accumulator 5 is separated into liquid refrigerant and gas refrigerant, and the gas refrigerant is sucked into the compressor 1.
When the heating operation is continued at a low external temperature (at an evaporating temperature of 0 degrees C. or less), frost forms on surfaces of the heat-source-side heat exchangers 3a and 3b. This is because with moisture contained in air to be subjected to heat exchange at the heat-source-side heat exchangers 3a and 3b, dew condensation occurs at the surfaces of the heat-source-side heat exchangers 3a and 3b, which serve as evaporators, and the temperature of outside air is low, as a result of which frost forms. When the quantity of frost forming on the heat-source-side heat exchangers 3a and 3b increases, the thermal resistance increases, and the quantity of air decreases. Consequently, pipe temperatures (evaporating temperatures) in the heat-source-side heat exchangers 3a and 3b lower, and the heating capacity cannot be sufficiently fulfilled. It is therefore necessary to perform defrosting to remove the frost.
In the indoor units 10a, 10b, 10c and 10d, the liquid refrigerant is expanded and reduced in pressure by the respective expansion units 11a, 11b, 11c and 11d to become two-phase gas-liquid refrigerant having a low temperature and a low pressure. The two-phase gas-liquid refrigerant flows from the indoor units 10a, 10b, 10c and 10d without being subjected to heat exchange at the use-side heat exchangers 12a, 12b, 12c and 12d. After flowing from the indoor units 10a, 10b, 10c and 10d, the two-phase gas-liquid refrigerant re-flows into the outdoor unit 20 through the pipe A. In the outdoor unit 20, the two-phase gas-liquid refrigerant passes through the flow-path switching unit 2, and flows into the accumulator 5. The refrigerant having flown into the accumulator 5 is separated into liquid refrigerant and gas refrigerant, and the gas refrigerant is re-sucked into the compressor 1.
In ordinary cases, the defrost operation is ended when it is confirmed that the entire frost adhering to the heat-source-side heat exchangers 3a and 3b is completely melted, on the basis of results of detection by temperature detection units (not shown) provided at the heat-source-side heat exchangers 3a and 3b. When the defrost operation is ended, the flow-path switching unit 2 is switched, and the operation to be performed is returned to the above heating operation. It is determined to end the defrost operation, for example, by detecting an increase in the temperatures of the pipes in the heat-source-side heat exchangers 3a and 3b, which is caused by removal of the entire frost.
In order to prevent frost from being refrozen after the defrost operation, there is a case where it is necessary to consider an influence of an environment in which the air-conditioning apparatus 100, which causes refrigerant to be circulated using the bypasses 6a and 6b as illustrated in
As illustrated in
For example, in the case where wind flows as illustrated in
In ordinary cases, in the case where the air-conditioning apparatus is in the cooling operation or the heating operation, the air-sending device is operated to cause wind to forcefully pass through the heat-source-side heat exchangers. However, in the defrost operation described above, the air-sending devices of the outdoor units are stopped. During the defrost operation, if wind flows as illustrated in
In forced convection, a value obtained by multiplying the velocity of wind by 0.5 is proportional to a thermal conductivity. Therefore, when the wind velocity increases by A times, a heat radiation amount increases by √A times. Therefore, in the defrost operation mode, if wind flows as illustrated in
When the solenoid valve 4 is opened, and an opening degree of the electronic expansion valve 7a reaches a predetermined opening degree, gas refrigerant having a high temperature and a high pressure starts to flow into the bypass 6a. After flowing into the bypass 6a, the gas refrigerant having the high temperature and high pressure exchanges heat with defrost water, at the lower part of the heat-source-side heat exchanger 3a. As a result, while liquefying, the gas refrigerant having the high temperature and high pressure heats the bypass 6a of the heat-source-side heat exchanger 3a. Thus, the defrost water is prevented from being refrozen. When the solenoid valve 4 is opened, and the opening degree of the electronic expansion valve 7b reaches a predetermined opening degree, the gas refrigerant having the high temperature and high pressure starts to flow into the bypass 6b. After flowing into the bypass 6b, the gas refrigerant having the high temperature and high pressure exchanges heat with defrost water, at the lower part of the heat-source-side heat exchanger 3b. As a result, while liquefying, the gas refrigerant having the high temperature and high pressure heats the bypass 6b of the heat-source-side heat exchanger 3b. Thus, the defrost water is prevented from being refrozen.
As described above, according to embodiment 1, in addition to control of opening of the solenoid valve 4, control of the opening degrees of the electronic expansion valves 7a and 7b based on the detection results of the thermistors 8a and 8b is performed, and the flow rates of refrigerant to the bypasses 6a and 6b are adjusted in accordance with ambient environments of the heat-source-side heat exchangers 3a and 3b. In other words, the defrosting capacities of the heat-source-side heat exchangers 3a and 3b are adjusted in accordance with the ambient environments thereof. Therefore, the flow rates of the refrigerant to the bypasses 6a and 6b can be optimized in accordance with defrosting loads on the bypasses 6a and 6b. As a result, even if the influences of wind of outside air upon the surfaces of the heat-source-side heat exchangers 3a and 3b vary in accordance with the positions of the outdoor units in the dense installation as described with reference to
The following description is given by referring to by way of example the case where the plural outdoor units 20 in the multi-air-conditioning apparatus for a building are densely installed, and wind of outside air flows in the direction indicated in
The inlet 13a of the bypass 6a of the heat-source-side heat exchanger 3a is located close to the surface 16a onto which the wind flows. Refrigerant gas having a high temperature flows into part of the surface 16a of the heat-source-side heat exchanger 3a. On the other hand, the inlet 14a of the bypass 6b of the heat-source-side heat exchanger 3b is located on a side of a side surface thereof which is orthogonal to the surface 16b onto which the wind flows. The refrigerant gas passes through part of the side surface of the heat-source-side heat exchanger 3b, and flows into part of the surface 16b. Thus, the temperature of the refrigerant gas flowing into the part of the surface 16b of the heat-source-side heat exchanger 3b lowers, as compared with the temperature of the refrigerant gas flowing into the part of the surface 16a of the heat-source-side heat exchanger 3a. Therefore, the defrosting capacity of the heat-source-side heat exchanger 3b needs to be set higher than the defrosting capacity of the heat-source-side heat exchanger 3a. In embodiment 2, the flow resistance of the pipe resistor 15b is set lower than the flow resistance of the pipe resistor 15a.
In such a manner, according to embodiment 2, in the dense installation in the multi-air-conditioning apparatus for a building, in the case where it is known which of the defrosting capacities requisite for the heat-source-side heat exchangers 3a and 3b of each of the outdoor units 20 is greater or smaller, pipe resistors 15a and 15b whose flow resistances are set in accordance with the requisite defrosting capacities are provided.
According to embodiment 2, it is possible to reduce increasing of the number of components. Therefore, in the dense installation, in the case where it is known which of defrosting capacities which are requisite for the heat-source-side heat exchangers 3a and 3b in accordance with the position of each of installed outdoor units is greater or smaller, the defrost water at the heat-source-side heat exchangers 3a and 3b can be prevented from being refrozen, at the same time as the product cost is reduced.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/064006 | 5/11/2016 | WO | 00 |
