JPWO2018189826A1 - Refrigeration cycle equipment - Google Patents

Abstract

The refrigeration cycle apparatus includes a refrigerant circuit in which a compressor, a heat source side heat exchanger, a first expansion valve, a second expansion valve, and a load side heat exchanger are connected via a refrigerant pipe. A cooling operation in which the exchanger functions as an evaporator and a heating operation in which the load-side heat exchanger functions as a condenser can be performed. Between the first expansion valve and the second expansion valve, a refrigerant pipe is provided. The refrigerant circuit includes a first bypass circuit connected in parallel with the first expansion valve in the refrigerant flow, and a first reverse circuit provided in the first bypass circuit. A stop valve, a second bypass circuit connected in parallel with the second expansion valve in the refrigerant flow, and a second check valve provided in the second bypass circuit are provided.

Description

  The present invention relates to a refrigeration cycle apparatus including two expansion valves connected in series.

  Patent Document 1 describes a refrigeration air conditioning system having a refrigerant leakage detection function. This refrigeration air conditioning system is based on past data relating to the past refrigerant amount of the refrigeration cycle and new data relating to the refrigerant amount after the refrigeration cycle has been stopped and started a plurality of times from the past time point. Determining means for determining the refrigerant leakage. This document describes that the liquid phase area ratio of the condenser is used as an index for determining the shortage of the refrigerant amount. The liquid phase area ratio of the condenser is calculated based on the refrigerant supercooling degree of the condenser, the outside air temperature, the discharge enthalpy of the compressor, the low pressure liquid specific heat of the refrigerant, and the like.

International Publication No. 2008/035418

  In general, in the refrigeration cycle, the amount of refrigerant required during cooling operation differs from the amount of refrigerant required during heating operation. For this reason, in the operation mode with a small amount of necessary refrigerant, excess liquid refrigerant is stored in a liquid storage container such as an accumulator or a receiver. When the refrigerant leaks in a state where the liquid refrigerant is stored in the liquid reservoir, there is no difference in the operation state of the refrigeration cycle before and after the refrigerant leaks unless all the liquid refrigerant in the liquid reservoir is vaporized. Therefore, when the leakage of the refrigerant is determined based on the operation status data of the refrigeration cycle as in the refrigeration air conditioning system of Patent Document 1, the larger the amount of excess refrigerant stored in the liquid reservoir, the more the refrigerant leaks. It takes a long time until a leak is detected. That is, there is a problem that the larger the amount of excess refrigerant stored in the liquid storage container, the greater the amount of refrigerant leakage.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a refrigeration cycle apparatus that can reduce the amount of surplus refrigerant.

  A refrigeration cycle apparatus according to the present invention includes a refrigerant circuit in which a compressor, a heat source side heat exchanger, a first expansion valve, a second expansion valve, and a load side heat exchanger are connected via a refrigerant pipe, and the refrigerant circuit Is capable of performing a cooling operation in which the load-side heat exchanger functions as an evaporator, and a heating operation in which the load-side heat exchanger functions as a condenser, and the first expansion valve and the second expansion valve The valve is connected via a liquid pipe which is a part of the refrigerant pipe, and the refrigerant circuit includes a first bypass circuit connected in parallel with the first expansion valve in the flow of the refrigerant. A first check valve provided in the first bypass circuit and allowing a refrigerant flow in a direction from the heat source side heat exchanger to the load side heat exchanger via the liquid pipe; A second bypass circuit connected in parallel with the second expansion valve in the refrigerant flow; And a second check valve that is provided in the second bypass circuit and allows a refrigerant flow in a direction from the load side heat exchanger to the heat source side heat exchanger via the liquid pipe. , At least one of them is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the density of the refrigerant | coolant in the liquid pipe at the time of cooling operation and the density of the refrigerant | coolant in the liquid pipe at the time of heating operation can be closely approached. Therefore, the amount of refrigerant necessary during the cooling operation and the amount of refrigerant necessary during the heating operation can be made closer, so that the amount of excess refrigerant can be reduced.

It is a refrigerant circuit diagram which shows schematic structure of the refrigerating-cycle apparatus 1 which concerns on Embodiment 1 of this invention. It is a ph diagram which shows the state of the refrigerant at the time of air conditioning operation of refrigeration cycle device 1 concerning Embodiment 1 of the present invention. It is a ph diagram which shows the state of the refrigerant at the time of heating operation of refrigerating cycle device 1 concerning Embodiment 1 of the present invention. FIG. 6 is a ph diagram illustrating a refrigerant state during cooling operation of a refrigeration cycle apparatus in which the first bypass circuit 11 and the first check valve 27 are not provided as a comparative example of the first embodiment of the present invention. FIG. 6 is a ph diagram illustrating a refrigerant state during heating operation of a refrigeration cycle apparatus in which the second bypass circuit 12 and the second check valve are not provided as a comparative example of the first embodiment of the present invention. It is a flowchart which shows an example of the refrigerant | coolant leak detection process performed in the leak detection part in the refrigeration cycle apparatus 1 which concerns on Embodiment 1 of this invention. It is a flowchart which shows the other example of the refrigerant | coolant leak detection process performed in the leak detection part in the refrigeration cycle apparatus 1 which concerns on Embodiment 1 of this invention.

Embodiment 1 FIG.
A refrigeration cycle apparatus according to Embodiment 1 of the present invention will be described. FIG. 1 is a refrigerant circuit diagram showing a schematic configuration of a refrigeration cycle apparatus 1 according to the present embodiment. In the present embodiment, an air conditioner is illustrated as the refrigeration cycle apparatus 1.

  As shown in FIG. 1, the refrigeration cycle apparatus 1 has a refrigerant circuit 10 that circulates refrigerant. In the refrigerant circuit 10, a compressor 21, a refrigerant flow switching device 22, a heat source side heat exchanger 23, a first expansion valve 24, a second expansion valve 25, and a load side heat exchanger 26 are sequentially annularly arranged through a refrigerant pipe. It has a connected configuration. The refrigerant circuit 10 is configured to be able to switch between a cooling operation in which the load-side heat exchanger 26 functions as an evaporator and a heating operation in which the load-side heat exchanger 26 functions as a condenser. The refrigerant circuit 10 may be provided with a liquid storage container for storing excess refrigerant.

  In addition, the refrigeration cycle apparatus 1 includes, for example, an outdoor unit 30 that is installed outdoors, and an indoor unit 40 that is installed indoors, for example. The outdoor unit 30 accommodates at least the heat source side heat exchanger 23. In the outdoor unit 30 of the present embodiment, in addition to the heat source side heat exchanger 23, a compressor 21, a refrigerant flow switching device 22, and a first expansion valve 24 are accommodated. The indoor unit 40 accommodates at least the load side heat exchanger 26. In the indoor unit 40 of the present embodiment, the second expansion valve 25 is accommodated in addition to the load-side heat exchanger 26.

  The outdoor unit 30 and the indoor unit 40 are connected via an extension pipe 51 and an extension pipe 52 that are part of the refrigerant pipe. One end of the extension pipe 51 is connected to the outdoor unit 30 via the joint portion 31. The other end of the extension pipe 51 is connected to the indoor unit 40 via the joint portion 41. The refrigerant flow switching device 22 of the outdoor unit 30 and the load side heat exchanger 26 of the indoor unit 40 are connected via a refrigerant pipe including an extension pipe 51. The refrigerant pipe between the refrigerant flow switching device 22 and the load-side heat exchanger 26 is a gas pipe that mainly circulates the gas refrigerant.

  One end of the extension pipe 52 is connected to the outdoor unit 30 via the joint portion 32. The other end of the extension pipe 52 is connected to the indoor unit 40 via the joint portion 42. The first expansion valve 24 of the outdoor unit 30 and the second expansion valve 25 of the indoor unit 40 are connected via a refrigerant pipe including an extension pipe 52. The refrigerant pipe between the first expansion valve 24 and the second expansion valve 25 is a liquid pipe that mainly circulates the liquid refrigerant.

  The compressor 21 is a fluid machine that sucks and compresses a low-pressure gas refrigerant and discharges it as a high-pressure gas refrigerant. As the compressor 21, for example, an inverter-driven compressor capable of adjusting the rotation speed is used. The refrigerant flow switching device 22 switches the flow direction of the refrigerant in the refrigerant circuit 10 between the cooling operation and the heating operation. For example, a four-way valve is used as the refrigerant flow switching device 22.

  The heat source side heat exchanger 23 is a heat exchanger that functions as a condenser during cooling operation and functions as an evaporator during heating operation. In the heat source side heat exchanger 23, heat exchange is performed between the refrigerant circulating inside and the outdoor air blown by an outdoor fan (not shown).

  The first expansion valve 24 is a valve that depressurizes the refrigerant on the outdoor unit 30 side. The second expansion valve 25 is a valve that depressurizes the refrigerant on the indoor unit 40 side. The first expansion valve 24 and the second expansion valve 25 are connected to each other in series in the refrigerant circuit 10. As the 1st expansion valve 24 and the 2nd expansion valve 25, the electronic expansion valve which can adjust an opening degree by control of the control part 100 mentioned later is used.

  The load-side heat exchanger 26 is a heat exchanger that functions as an evaporator during cooling operation and functions as a condenser during heating operation. In the load side heat exchanger 26, heat exchange is performed between the refrigerant circulating in the interior and the indoor air blown by an indoor fan (not shown).

  The refrigerant circuit 10 is provided with a first bypass circuit 11 that is connected in parallel with the first expansion valve 24 in the flow of the refrigerant and that circulates the refrigerant without passing through the first expansion valve 24. The first bypass circuit 11 is provided with a first check valve 27. The first check valve 27 allows the refrigerant flow in the direction from the heat source side heat exchanger 23 toward the load side heat exchanger 26 via the liquid pipe including the extension pipe 52 and blocks the refrigerant flow in the reverse direction. Is configured to do. The first bypass circuit 11 and the first check valve 27 are accommodated in the outdoor unit 30.

  In addition, the refrigerant circuit 10 is provided with a second bypass circuit 12 that is connected in parallel with the second expansion valve 25 in the flow of the refrigerant and distributes the refrigerant without passing through the second expansion valve 25. A second check valve 28 is provided in the second bypass circuit 12. The second check valve 28 allows the refrigerant flow in the direction from the load side heat exchanger 26 to the heat source side heat exchanger 23 via the liquid pipe including the extension pipe 52 and blocks the reverse refrigerant flow. Is configured to do. The second bypass circuit 12 and the second check valve 28 are accommodated in the indoor unit 40.

  As the refrigerant circulating in the refrigerant circuit 10, for example, a combustible refrigerant is used. Here, the flammable refrigerant is a refrigerant having a flammability at or above a slight combustion level (for example, 2 L or more in the ASHRAE 34 classification). In addition, as the refrigerant circulating in the refrigerant circuit 10, a nonflammable refrigerant or a toxic refrigerant may be used.

  The control unit 100 includes a microcomputer that includes a CPU, a ROM, a RAM, an I / O port, and the like. The control unit 100 is based on detection signals from various sensors provided in the refrigerant circuit 10, operation signals from the operation unit, and the like, the compressor 21, the refrigerant flow switching device 22, the first expansion valve 24, and the second expansion. The operation of the entire refrigeration cycle apparatus 1 including the operation of the valve 25 is controlled. The control unit 100 may be provided in the outdoor unit 30 or may be provided in the indoor unit 40. In addition, the control unit 100 may include an outdoor unit control unit provided in the outdoor unit 30 and an indoor unit control unit provided in the indoor unit 40 and capable of communicating with the outdoor unit control unit. The control unit 100 also functions as a leak detection unit described later.

  Next, the operation of the refrigeration cycle apparatus 1 will be described. First, the operation during the cooling operation will be described. A solid line arrow in FIG. 1 indicates the flow direction of the refrigerant during the cooling operation. During the cooling operation, the refrigerant circuit 10 is configured such that the refrigerant flow path of the refrigerant flow switching device 22 is switched under the control of the control unit 100 and the high-pressure refrigerant discharged from the compressor 21 flows into the heat source side heat exchanger 23. Is done. Further, during the cooling operation, the first expansion valve 24 is controlled to be fully opened, for example, and the second expansion valve 25 is controlled so that the degree of superheat of the refrigerant sucked into the compressor 21 approaches a target value (for example, 4K). Is done. The compressor 21 is controlled such that the high pressure side pressure (for example, discharge pressure) and the low pressure side pressure (for example, suction pressure) of the refrigerant circuit 10 approach the target values. The outdoor fan is controlled so that the temperature difference between the condensation temperature of the heat source side heat exchanger 23 and the outside air temperature is constant.

  FIG. 2 is a ph diagram showing the state of the refrigerant during the cooling operation of the refrigeration cycle apparatus 1 according to the present embodiment. A thick line in FIG. 2 and FIGS. 3 to 5 described later represents a pressure drop due to a pressure loss in the extension pipe 51 or the extension pipe 52. As shown in FIGS. 1 and 2, the high-temperature and high-pressure gas refrigerant (point A in FIG. 2) discharged from the compressor 21 flows into the heat source side heat exchanger 23 via the refrigerant flow switching device 22. . During the cooling operation, the heat source side heat exchanger 23 functions as a condenser. That is, in the heat source side heat exchanger 23, heat exchange is performed between the refrigerant circulating in the interior and the outdoor air blown by the outdoor fan, and the heat of condensation of the refrigerant is radiated to the outdoor air. As a result, the refrigerant flowing into the heat source side heat exchanger 23 is condensed and becomes a high-pressure liquid refrigerant (point B in FIG. 2). The high-pressure liquid refrigerant flowing out of the heat source side heat exchanger 23 passes through the first check valve 27 or the fully opened first expansion valve 24 and the extension pipe 52, and the second expansion valve 25 of the indoor unit 40. (Point C in FIG. 2). In the refrigerant circuit 10 of the present embodiment, the first bypass circuit 11 and the first check valve 27 are provided in parallel with the first expansion valve 24, so that the pressure loss in the refrigerant piping in the outdoor unit 30 is reduced. It can be suppressed. Therefore, the liquid refrigerant flowing from the heat source side heat exchanger 23 is reduced in pressure mainly due to the pressure loss in the extension pipe 52, but flows into the second expansion valve 25 with the liquid single phase. Since the second check circuit 28 is provided in the second bypass circuit 12, the liquid refrigerant is prevented from flowing into the second bypass circuit 12.

  The liquid refrigerant that has flowed into the second expansion valve 25 is decompressed and becomes a low-pressure two-phase refrigerant (point D in FIG. 2). The low-pressure two-phase refrigerant decompressed by the second expansion valve 25 flows into the load side heat exchanger 26. During the cooling operation, the load side heat exchanger 26 functions as an evaporator. That is, in the load-side heat exchanger 26, heat exchange is performed between the refrigerant circulating in the interior and the indoor air blown by the indoor fan, and the evaporation heat of the refrigerant is absorbed from the indoor air. Thereby, the refrigerant flowing into the load-side heat exchanger 26 evaporates to become a low-pressure gas refrigerant (point E in FIG. 2). Further, the air blown by the indoor fan is cooled by the heat absorbing action of the refrigerant. The low-pressure gas refrigerant evaporated in the load-side heat exchanger 26 is decompressed mainly by the pressure loss in the extension pipe 52 via the extension pipe 51 and the refrigerant flow switching device 22 and is sucked into the compressor 21. (Point F in FIG. 2). The refrigerant sucked into the compressor 21 is compressed into a high-temperature and high-pressure gas refrigerant (point A in FIG. 2). In the cooling operation, the above cycle is continuously repeated.

  Next, operation during heating operation will be described. The broken line arrows in FIG. 1 indicate the flow direction of the refrigerant during the heating operation. During the heating operation, the refrigerant circuit 10 is configured such that the refrigerant flow path of the refrigerant flow switching device 22 is switched under the control of the control unit 100 and the high-pressure refrigerant discharged from the compressor 21 flows into the load-side heat exchanger 26. Is done. Further, during the heating operation, the second expansion valve 25 is controlled to be in a fully open state, for example, and the first expansion valve 24 is controlled so that the superheat degree of the refrigerant sucked into the compressor 21 approaches a target value (for example, 4K). Is done. The compressor 21 is controlled such that the high pressure side pressure (for example, discharge pressure) and the low pressure side pressure (for example, suction pressure) of the refrigerant circuit 10 approach the target values. The outdoor fan is controlled so that the temperature difference between the evaporation temperature of the heat source side heat exchanger 23 and the outside air temperature is constant.

  FIG. 3 is a ph diagram showing the state of the refrigerant during the heating operation of the refrigeration cycle apparatus 1 according to the present embodiment. As shown in FIGS. 1 and 3, the high-temperature and high-pressure gas refrigerant discharged from the compressor 21 (point A in FIG. 3) mainly passes through the refrigerant flow switching device 22 and the extension pipe 51, and mainly the extension pipe 51. The pressure is reduced due to the pressure loss at, and flows into the load-side heat exchanger 26 of the indoor unit 40 (point B in FIG. 3). During the heating operation, the load side heat exchanger 26 functions as a condenser. That is, in the load side heat exchanger 26, heat exchange is performed between the refrigerant circulating in the interior and the indoor air blown by the indoor fan, and the condensation heat of the refrigerant is radiated to the indoor air. As a result, the refrigerant flowing into the load-side heat exchanger 26 is condensed and becomes a high-pressure liquid refrigerant (point C in FIG. 3). Further, the indoor air blown by the indoor fan is heated by the heat dissipation action of the refrigerant.

  The high-pressure liquid refrigerant that has flowed out of the load-side heat exchanger 26 passes through the second check valve 28 or the fully opened second expansion valve 25 and the extension pipe 52, and then passes through the first expansion valve 24 of the outdoor unit 30. (Point D in FIG. 3). Since the second bypass circuit 12 and the second check valve 28 are provided in parallel with the second expansion valve 25 in the refrigerant circuit 10 of the present embodiment, the pressure loss in the refrigerant pipe in the indoor unit 40 is reduced. It can be suppressed. Accordingly, the liquid refrigerant that has flowed out of the load-side heat exchanger 26 is reduced in pressure mainly due to the pressure loss in the extension pipe 52, but flows into the first expansion valve 24 in the liquid single phase. Since the first check circuit 27 is provided with the first check circuit 27, the liquid refrigerant is prevented from flowing into the first bypass circuit 11.

  The liquid refrigerant that has flowed into the first expansion valve 24 is decompressed and becomes a low-pressure two-phase refrigerant (point E in FIG. 3). The low-pressure two-phase refrigerant decompressed by the first expansion valve 24 flows into the heat source side heat exchanger 23. During the heating operation, the heat source side heat exchanger 23 functions as an evaporator. That is, in the heat source side heat exchanger 23, heat exchange is performed between the refrigerant circulating in the interior and the outdoor air blown by the outdoor fan, and the evaporation heat of the refrigerant is absorbed from the outdoor air. As a result, the refrigerant flowing into the heat source side heat exchanger 23 evaporates and becomes a low-pressure gas refrigerant (point F in FIG. 3). The low-pressure gas refrigerant flowing out from the heat source side heat exchanger 23 is sucked into the compressor 21 via the refrigerant flow switching device 22. The refrigerant sucked into the compressor 21 is compressed into a high-temperature and high-pressure gas refrigerant (point A in FIG. 3). In the heating operation, the above cycle is continuously repeated.

  As described above, in the present embodiment, the liquid single-phase refrigerant flows through the liquid pipe (for example, the extension pipe 52) in both the cooling operation and the heating operation. Thereby, the following effects are obtained.

For example, in a refrigeration cycle apparatus in which only an indoor unit is provided with an expansion valve and an outdoor unit is not provided with an expansion valve, the liquid phase refrigerant before being depressurized by the expansion valve is circulated through the liquid pipe during cooling operation, and during heating operation. The two-phase refrigerant after being depressurized by the expansion valve flows through the liquid pipe. The density of the liquid phase refrigerant is about 1050 kg / m ³ , and the density of the two-phase refrigerant after being decompressed by the expansion valve is about 150 kg / m ³ . For this reason, the density difference Δρ between the refrigerant in the liquid pipe during the cooling operation and the refrigerant in the liquid pipe during the heating operation is about 900 kg / m ³ . The product of the density difference Δρ and the internal volume of the liquid pipe generally corresponds to the difference between the necessary refrigerant amount during the cooling operation and the necessary refrigerant amount during the heating operation, that is, the amount of excess refrigerant during the heating operation. When the density difference Δρ is 900 kg / m ³ and the internal volume of the liquid pipe is 5 L, the amount of surplus refrigerant during heating operation is 4.5 kg.

  Excess refrigerant is stored in a liquid storage container provided in the refrigerant circuit. If the refrigerant leaks from the refrigerant circuit while the liquid refrigerant is stored in the liquid storage container, no difference appears in the detection values of various sensors provided in the refrigerant circuit, and the liquid refrigerant liquid level in the liquid storage container It only drops. When the leakage progresses and all the liquid refrigerant in the liquid storage container is vaporized, a difference from the value before the refrigerant leakage appears in the value such as the degree of supercooling at the outlet of the condenser. Therefore, as the amount of surplus refrigerant increases, it may take a longer time from the occurrence of refrigerant leakage until the leakage is detected, and thus the amount of refrigerant leakage tends to increase. For example, in the above example, 4.5 kg or more of the refrigerant leaks from when the refrigerant leaks until the leak is detected.

  In the present embodiment, since the liquid phase refrigerant flows through the liquid pipe in both the cooling operation and the heating operation, there is a difference in density between the refrigerant in the liquid pipe during the cooling operation and the refrigerant in the liquid pipe during the heating operation. Does not occur. Thereby, since the required refrigerant quantity at the time of air_conditionaing | cooling operation and the required refrigerant quantity at the time of heating operation can be closely approached, the quantity of surplus refrigerant | coolant can be reduced. Moreover, the amount of refrigerant required during the cooling operation and the amount of refrigerant required during the heating operation can be made to coincide with each other, so that the amount of excess refrigerant can be made substantially zero.

  Furthermore, according to the present embodiment, since the amount of surplus refrigerant can be reduced, when refrigerant leakage occurs, the difference between before and after refrigerant leakage appears more quickly in the detection values of various sensors provided in the refrigerant circuit. . For this reason, the leakage of the refrigerant can be detected at an early stage. Therefore, even when refrigerant leakage occurs, the amount of refrigerant leakage can be further reduced.

  In the present embodiment, since the amount of excess refrigerant can be reduced, it is possible to reduce the capacity of the liquid storage container or to omit the installation of the liquid storage container.

  FIG. 4 is a ph diagram showing the refrigerant state during the cooling operation of the refrigeration cycle apparatus in which the first bypass circuit 11 and the first check valve 27 are not provided as a comparative example of the present embodiment. . In FIG. 4, the section from point B to point G represents the pressure drop due to the pressure loss at the first expansion valve 24, and the section from point G to point C is the pressure due to the pressure loss at the extension pipe 52. It represents a decline. Generally, a throttle is provided in the flow path inside the electronic expansion valve. Therefore, even if the electronic expansion valve is controlled to be fully opened, the pressure loss at the electronic expansion valve is relatively large. As shown in FIG. 4, when the pressure loss at the first expansion valve 24 is large during the cooling operation, the liquid refrigerant is two-phased in the middle of the extension pipe 52. Therefore, in this case, the refrigerant in the liquid pipe at the time of cooling operation cannot be made into a liquid single phase.

  In contrast, in the present embodiment, the first bypass circuit 11 and the first check valve 27 are provided in parallel with the first expansion valve 24. For this reason, in the cooling operation, in addition to the flow path passing through the first expansion valve 24, a flow path that bypasses the first expansion valve 24 is formed. Thereby, since the pressure loss between the outlet of the heat source side heat exchanger 23 and the inlet of the extension pipe 52 can be reduced, the refrigerant in the liquid pipe during the cooling operation can be more reliably maintained in the liquid single phase.

  FIG. 5 is a ph diagram illustrating a refrigerant state during heating operation of a refrigeration cycle apparatus in which the second bypass circuit 12 and the second check valve 28 are not provided as a comparative example of the present embodiment. . In FIG. 5, the section from point C to point G represents the pressure drop due to the pressure loss at the second expansion valve 25, and the section from point G to point D is the pressure due to the pressure loss at the extension pipe 52. It represents a decline. As shown in FIG. 5, when the pressure loss at the second expansion valve 25 is large during the heating operation, the liquid refrigerant is two-phased in the middle of the extension pipe 52. Therefore, in this case, the refrigerant in the liquid pipe at the time of heating operation cannot be made into a liquid single phase.

  On the other hand, in the present embodiment, the second bypass circuit 12 and the second check valve 28 are provided in parallel with the second expansion valve 25. For this reason, in the heating operation, in addition to the flow path passing through the second expansion valve 25, a flow path that bypasses the second expansion valve 25 is formed. Thereby, since the pressure loss between the outlet of the load side heat exchanger 26 and the inlet of the extension pipe 52 can be reduced, the refrigerant in the liquid pipe during the heating operation can be more reliably maintained in the liquid single phase.

  Here, the refrigerant circuit 10 according to the present embodiment is provided with both a set of the first bypass circuit 11 and the first check valve 27 and a set of the second bypass circuit 12 and the second check valve 28. It has been. However, the refrigerant circuit 10 is provided with at least one of a set of the first bypass circuit 11 and the first check valve 27 and a set of the second bypass circuit 12 and the second check valve 28. That's fine. For example, in the cooling operation, even if the first bypass circuit 11 and the first check valve 27 are not provided, the refrigerant in the liquid pipe can be maintained as a liquid single phase or a two-phase refrigerant having a dryness close to 0 (for example, When the pressure loss of the first expansion valve 24 is relatively small), the set of the first bypass circuit 11 and the first check valve 27 may not necessarily be provided. On the other hand, when heating operation is performed, even if the second bypass circuit 12 and the second check valve 28 are not provided, the refrigerant in the liquid pipe can be maintained as a single-phase liquid or a two-phase refrigerant whose dryness is close to 0 (for example, When the pressure loss of the second expansion valve 25 is relatively small), the set of the second bypass circuit 12 and the second check valve 28 may not necessarily be provided.

  FIG. 6 is a flowchart illustrating an example of the refrigerant leakage detection process executed by the leakage detection unit (for example, the control unit 100) in the refrigeration cycle apparatus 1 according to the present embodiment. The refrigerant leakage detection process is repeatedly executed at predetermined time intervals during operation of the refrigeration cycle apparatus 1.

  In step S <b> 1 of FIG. 6, the control unit 100 determines the condenser (for example, the heat source side heat exchanger 23 during the cooling operation and the load side heat exchange during the heating operation based on the detection values of various sensors provided in the refrigerant circuit 10. The degree of supercooling of the refrigerant at the outlet of the vessel 26) is calculated.

  In step S2, the control unit 100 determines whether or not the calculated degree of supercooling is within a set range. The data of the setting range of the degree of supercooling is stored in advance in the ROM of the control unit 100. When the refrigerant leaks, for example, the degree of supercooling at the condenser outlet decreases. For this reason, the leakage of the refrigerant can be detected based on the degree of supercooling at the condenser outlet. If it is determined that the degree of supercooling is within the set range, the process ends. If it is determined that the degree of supercooling is not within the set range, the process proceeds to step S3.

  In step S3, the control unit 100 notifies the notification unit that the refrigerant has leaked. As the notification unit, for example, a display unit provided in the indoor unit 40 or the outdoor unit 30 can be used.

  When refrigerant leakage occurs, the degree of supercooling at the outlet of the condenser changes compared to before the refrigerant leakage. In the present embodiment, since the amount of excess refrigerant can be reduced, the change in the degree of supercooling when the refrigerant leaks occurs more quickly. For this reason, the leakage of the refrigerant can be detected earlier, and the occurrence of the leakage of the refrigerant can be notified earlier. Further, in the present embodiment, the leakage of the refrigerant can be detected using a smaller number of sensors. Instead of the degree of supercooling at the condenser outlet, the leakage of the refrigerant may be detected based on another parameter having a correlation with the degree of supercooling.

  FIG. 7 is a flowchart illustrating another example of the refrigerant leakage detection process executed by the leakage detection unit (for example, the control unit 100) in the refrigeration cycle apparatus 1 according to the present embodiment.

  In step S <b> 11 of FIG. 7, the control unit 100 estimates the amount of refrigerant in the refrigerant circuit 10 based on detection values of various sensors provided in the refrigerant circuit 10 and information stored in advance. The refrigerant amount in the refrigerant circuit 10 is estimated based on the internal volume of each element of the refrigerant circuit 10 and the refrigerant density of each element, as described in, for example, Japanese Patent Application Laid-Open No. 2012-229893. In the method described in the publication, the amount of refrigerant other than the excess refrigerant and the amount of excess refrigerant are calculated, and the total amount of refrigerant is obtained by adding the amount of refrigerant other than excess refrigerant and the amount of excess refrigerant. Is calculated. However, in the present embodiment, since the amount of surplus refrigerant can be reduced, the amount of refrigerant other than the surplus refrigerant can be estimated as the total refrigerant amount.

  In step S12, the control unit 100 determines whether or not the estimated refrigerant amount is within the set range. Data on the refrigerant amount setting range is stored in advance in the ROM of the control unit 100. If it is determined that the refrigerant amount is within the set range, the process is terminated. If it is determined that the refrigerant amount is not within the set range, the process proceeds to step S13.

  In step S13, the control unit 100 notifies the notification unit that the refrigerant has leaked.

  In the present embodiment, since the amount of surplus refrigerant can be reduced, leakage of the refrigerant can be detected early based on the amount of refrigerant other than the surplus refrigerant. Further, since the leakage of the refrigerant can be detected based on the amount of the refrigerant other than the surplus refrigerant, the liquid level detection sensor for the liquid storage container necessary for calculating the amount of the surplus refrigerant can be omitted. Therefore, the cost of the refrigeration cycle apparatus 1 can be reduced.

  As described above, in the refrigeration cycle apparatus 1 according to the present embodiment, the compressor 21, the heat source side heat exchanger 23, the first expansion valve 24, the second expansion valve 25, and the load side heat exchanger 26 are refrigerant pipes. The refrigerant circuit 10 is connected through the. The refrigerant circuit 10 can execute a cooling operation in which the load-side heat exchanger 26 functions as an evaporator and a heating operation in which the load-side heat exchanger 26 functions as a condenser. The first expansion valve 24 and the second expansion valve 25 are connected via a liquid pipe (for example, an extension pipe 52) that is a part of the refrigerant pipe. The refrigerant circuit 10 is provided with a first bypass circuit 11 connected in parallel with the first expansion valve 24 in the refrigerant flow, and the first bypass circuit 11, and is loaded from the heat source side heat exchanger 23 via a liquid pipe. A set of a first check valve 27 that allows a refrigerant flow in a direction toward the side heat exchanger 26, a second bypass circuit 12 connected in parallel with the second expansion valve 25 in the refrigerant flow, A second check valve 28 provided in the bypass circuit 12 and allowing a refrigerant flow in a direction from the load side heat exchanger 26 to the heat source side heat exchanger 23 via the liquid pipe, At least one of the above is provided.

  According to this configuration, the density of the refrigerant in the liquid pipe during the cooling operation can be made closer to the density of the refrigerant in the liquid pipe during the heating operation. For example, when a set of the first bypass circuit 11 and the first check valve 27 is provided, the refrigerant in the liquid pipe during the cooling operation can be more reliably maintained in the liquid single phase. For example, when the set of the 2nd bypass circuit 12 and the 2nd non-return valve 28 is provided, the refrigerant | coolant in the liquid pipe at the time of heating operation can be more reliably maintained to a liquid single phase. In both the cooling operation and the heating operation, the refrigerant in the liquid pipe is a single-phase liquid or a two-phase refrigerant whose dryness is close to 0, so that the refrigerant amount necessary for the cooling operation and the refrigerant amount necessary for the heating operation are brought closer. be able to. Therefore, the amount of excess refrigerant can be reduced.

  In the refrigeration cycle apparatus 1 according to the present embodiment, a liquid single-phase refrigerant flows through the liquid pipe in both the cooling operation and the heating operation.

  According to this configuration, since the density of the refrigerant in the liquid pipe during the cooling operation and the density of the refrigerant in the liquid pipe during the heating operation can be matched, the amount of refrigerant required during the cooling operation and the heating operation are necessary. It is possible to make the amount of the refrigerant closer. Therefore, the amount of surplus refrigerant can be reduced.

  In addition, the refrigeration cycle apparatus 1 according to the present embodiment further includes a leakage detection unit (for example, the control unit 100) that detects the leakage of the refrigerant from the refrigerant circuit 10. The leakage detection unit is configured to detect refrigerant leakage based on the degree of refrigerant supercooling at the condenser outlet of the refrigerant circuit 10 or a parameter having a correlation with the degree of supercooling.

  In the present embodiment, since the amount of excess refrigerant can be reduced, the change in the degree of supercooling when the refrigerant leaks occurs more quickly. For this reason, according to the said structure, the leakage of a refrigerant | coolant can be detected earlier.

  In addition, the refrigeration cycle apparatus 1 according to the present embodiment further includes a leakage detection unit (for example, the control unit 100) that detects the leakage of the refrigerant from the refrigerant circuit 10. The leakage detection unit is configured to estimate the amount of refrigerant in the refrigerant circuit 10 and detect refrigerant leakage based on the estimated amount of refrigerant.

  In the present embodiment, since the amount of excess refrigerant can be reduced, leakage of the refrigerant can be detected based on the amount of refrigerant other than the excess refrigerant. Therefore, since the liquid level detection sensor of the liquid storage container necessary for calculating the amount of surplus refrigerant can be omitted, the cost of the refrigeration cycle apparatus 1 can be reduced. In addition, since the leakage of the refrigerant is detected based on the refrigerant amount estimated using the refrigerant physical properties and the like, it is possible to suppress the variation due to the difference in the operation state, and to improve the detection accuracy. Therefore, it is possible to more reliably detect refrigerant leakage even if the amount of leakage is very small.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, in the said embodiment, although the air conditioning apparatus was mentioned as an example as the refrigerating cycle apparatus 1, this invention is applicable also to other refrigerating cycle apparatuses, such as a hot-water supply apparatus.

  In the above embodiment, the refrigeration cycle apparatus 1 including one outdoor unit 30 and one indoor unit 40 is taken as an example. However, the refrigeration cycle apparatus includes a plurality of outdoor units 30. Alternatively, a plurality of indoor units 40 may be provided.

  DESCRIPTION OF SYMBOLS 1 Refrigeration cycle apparatus, 10 Refrigerant circuit, 11 1st bypass circuit, 12 2nd bypass circuit, 21 Compressor, 22 Refrigerant flow path switching device, 23 Heat source side heat exchanger, 24 1st expansion valve, 25 2nd expansion valve , 26 Load side heat exchanger, 27 1st check valve, 28 2nd check valve, 30 Outdoor unit, 31, 32 Joint part, 40 Indoor unit, 41, 42 Joint part, 51, 52 Extension piping, 100 Control Department.

Claims (4)

A compressor, a heat source side heat exchanger, a first expansion valve, a second expansion valve, and a load side heat exchanger are provided with a refrigerant circuit connected via a refrigerant pipe,
The refrigerant circuit can perform a cooling operation in which the load-side heat exchanger functions as an evaporator and a heating operation in which the load-side heat exchanger functions as a condenser.
The first expansion valve and the second expansion valve are connected via a liquid pipe that is a part of the refrigerant pipe,
In the refrigerant circuit,
A first bypass circuit connected in parallel with the first expansion valve in the flow of the refrigerant, and provided in the first bypass circuit, from the heat source side heat exchanger to the load side heat exchanger via the liquid pipe A set of a first check valve that allows the flow of refrigerant in the direction of travel;
A second bypass circuit connected in parallel with the second expansion valve in the flow of the refrigerant, and provided in the second bypass circuit, from the load side heat exchanger to the heat source side heat exchanger via the liquid pipe A refrigeration cycle apparatus provided with at least one of a set of a second check valve that allows a flow of refrigerant in a direction toward it.   The refrigeration cycle apparatus according to claim 1, wherein a liquid single-phase refrigerant flows through the liquid pipe in both the cooling operation and the heating operation. Further comprising a leakage detection unit for detecting refrigerant leakage from the refrigerant circuit;
The said leakage detection part is comprised so that the leakage of a refrigerant | coolant may be detected based on the parameter which has a correlation with the supercooling degree of the refrigerant | coolant at the condenser exit of the said refrigerant circuit, or the said supercooling degree. Item 3. The refrigeration cycle apparatus according to Item 2. Further comprising a leakage detection unit for detecting refrigerant leakage from the refrigerant circuit;
The refrigeration cycle apparatus according to claim 1 or 2, wherein the leakage detection unit is configured to estimate a refrigerant amount in the refrigerant circuit and detect refrigerant leakage based on the estimated refrigerant amount.

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