JP7507963B2 - Refrigeration Cycle Equipment - Google Patents

Description

The present disclosure relates to a refrigeration cycle device.

In recent years, due in part to the ongoing reduction in the Global Warming Potential (GWP) regulation value, development of refrigeration cycle devices using non-azeotropic refrigerants is progressing. Japanese Utility Model Publication No. 62-025644 (Patent Document 1) proposes a refrigeration cycle device using a non-azeotropic refrigerant, in which a compressor, a condenser, a pressure reducer, a first evaporator, a second evaporator, and a gas-liquid separator are connected, and the gaseous refrigerant separated by the gas-liquid separator is guided to the suction side of the compressor, and the liquid refrigerant separated by the gas-liquid separator is guided to the second evaporator.

Japanese Utility Model Publication No. 62-025644

According to the technology described in Patent Document 1, the refrigerant is separated into gaseous refrigerant and liquid refrigerant by a gas-liquid separator, and the liquid refrigerant is then guided to a second evaporator, thereby improving the operating efficiency of the refrigeration cycle. However, Patent Document 1 discloses a technology in which the gas-liquid separator is applied exclusively to the evaporator. For this reason, there is an issue that the technology cannot be fully utilized in a system in which the heat exchanger functions not only as an evaporator but also as a condenser.

The present disclosure has been made to solve such problems, and aims to provide a refrigeration cycle device that can improve operating efficiency by utilizing a gas-liquid separator regardless of whether the heat exchanger functions as an evaporator or a condenser.

The present disclosure relates to a refrigeration cycle device. The refrigeration cycle device includes a compressor, a first heat exchanger, a second heat exchanger, a third heat exchanger, an expansion device, a gas-liquid separator, a first flow rate control device, and a switching device. The switching device is configured to switch the refrigerant circulation path between a first route corresponding to a first operation mode and a second route corresponding to a second operation mode. In the first route, the refrigerant flows through the compressor, the first heat exchanger, the expansion device, the second heat exchanger, and the gas-liquid separator in that order, and the liquid refrigerant discharged from the gas-liquid separator flows into the third heat exchanger, and the gas-state refrigerant discharged from the gas-liquid separator passes through the first flow rate control device and merges with the refrigerant discharged from the third heat exchanger at a first junction, and the refrigerant merged at the first junction flows into the compressor. In the second route, the refrigerant flows in the order of the compressor, the second heat exchanger, and the gas-liquid separator, the gas-state refrigerant discharged from the gas-liquid separator flows into the third heat exchanger via the first flow control device, the liquid-state refrigerant discharged from the gas-liquid separator merges with the refrigerant discharged from the third heat exchanger at the second junction point, and the refrigerant merged at the second junction point flows in the order of the expansion device, the first heat exchanger, and the compressor.

According to the refrigeration cycle device disclosed herein, it is possible to improve operating efficiency by utilizing a gas-liquid separator regardless of whether the heat exchanger functions as an evaporator or a condenser.

1 is a refrigerant circuit diagram showing a configuration of a refrigeration cycle device (first embodiment). FIG. FIG. 4 is a diagram showing a flow of a refrigerant in a first operation mode of the refrigeration cycle device (first embodiment). FIG. 4 is a diagram showing a flow of a refrigerant in a second operation mode of the refrigeration cycle device (first embodiment). A ph diagram showing the change in state of the refrigerant in the first operation mode (embodiment 1). A ph diagram showing the change in state of the refrigerant in the second operation mode (embodiment 1). 4 is a flowchart for explaining control by the control device in a first operation mode (first embodiment). 5 is a flowchart for explaining control by the control device in a second operation mode (first embodiment). FIG. 11 is a refrigerant circuit diagram showing a configuration of a refrigeration cycle device (Embodiment 2). FIG. 11 is a refrigerant circuit diagram showing a configuration of a refrigeration cycle device (third embodiment). 13 is a flowchart for explaining control by the control device in the second operation mode (Embodiment 3).

Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are designated by the same reference numerals and their description will not be repeated.

Embodiment 1.
1 is a refrigerant circuit diagram showing the configuration of a refrigeration cycle apparatus 100 according to embodiment 1. The refrigeration cycle apparatus 100 includes a refrigerant circuit including at least a compressor 1, an expansion device 3, a four-way valve 4, a gas-liquid separator 6, a first heat exchanger 10, a second heat exchanger 20, a third heat exchanger 30, a first flow control device 51, and a control device 90.

The first heat exchanger 10 is mounted on the indoor unit. The second heat exchanger 20 and the third heat exchanger 30 are mounted on the outdoor unit. A gas-liquid separator 6 is disposed between the second heat exchanger 20 and the third heat exchanger 30. This configuration is equivalent to a configuration in which the heat exchanger on the outdoor unit side is divided into two heat exchangers and a gas-liquid separator 6 is disposed between one heat exchanger and the other heat exchanger.

The second heat exchanger 20 has a first port P1 and a second port P2. The third heat exchanger 30 has a third port P3 and a fourth port P4.

The gas-liquid separator 6 has an inlet port P61, a gas exhaust port P62, and a liquid exhaust port P63. A first flow control device 51 that adjusts the flow rate of the refrigerant is provided between the gas exhaust port P62 and the third heat exchanger 30. The first flow control device 51 has a valve for adjusting the flow rate of the refrigerant. The first flow control device 51 changes the flow rate of the refrigerant by adjusting the opening degree of the valve.

The inlet port P61 receives the refrigerant discharged from the second port P2 of the second heat exchanger 20. The gas outlet port P62 is connected to the third port P3 of the third heat exchanger 30 via the first flow control device 51. The gas outlet port P62 discharges the refrigerant in gas state from the gas-liquid separator 6. The liquid outlet port P63 is connected to the fourth port P4 of the third heat exchanger 30. The liquid outlet port P63 discharges the refrigerant in liquid state from the gas-liquid separator 6.

Hereinafter, refrigerant in a gaseous state will be referred to as a gas refrigerant, and refrigerant in a liquid state will be referred to as a liquid refrigerant. In addition, in situations where it is not necessary to mention whether the refrigerant is in a gaseous or liquid state, the term refrigerant will simply be used.

The four-way valve 4 has a first switching port P41, a second switching port P42, a third switching port P43, and a fourth switching port P44. The discharge port of the compressor 1 is connected to the first switching port P41, and the suction port of the compressor 1 is connected to the second switching port P42.

The refrigerant circuit of the refrigeration cycle device 100 is provided with a first check valve 41, a second check valve 42, a third check valve 43, and a fourth check valve 44.

The first check valve 41 is provided between the fourth switching port P44 of the four-way valve 4 and point a shown in Figure 1 on the refrigerant circuit. Point a corresponds to the first junction where the refrigerant discharged from the third port P3 of the third heat exchanger 30 and the refrigerant discharged from the first flow control device 51 join. The first check valve 41 blocks the flow of refrigerant from the fourth switching port P44 toward the first junction a.

The second check valve 42 is provided between the fourth switching port P44 of the four-way valve 4 and the first port P1 of the second heat exchanger 20. The second check valve 42 blocks the flow of refrigerant from the expansion device 3 to the fourth switching port P44 of the four-way valve 4.

The third check valve 43 is provided between the fourth switching port P44, the expansion device 3, and the first port P1 of the second heat exchanger 20. The third check valve 43 blocks the flow of refrigerant from the fourth switching port to the expansion device 3.

The fourth check valve 44 is provided between the expansion device 3 and point b on the refrigerant circuit shown in Figure 1. Point b corresponds to the second junction where the refrigerant discharged from the fourth port P4 of the third heat exchanger 30 and the refrigerant discharged from the liquid discharge port P63 of the gas-liquid separator 6 join together. The fourth check valve 44 blocks the flow of refrigerant from the expansion device 3 to the second junction b.

The four-way valve 4 changes between a first state and a second state. In the first state, the first switching port P41 and the third switching port P43 communicate with each other, and the second switching port P42 and the fourth switching port P44 communicate with each other. In the second state, the first switching port P41 and the fourth switching port P44 communicate with each other, and the second switching port P42 and the third switching port P43 communicate with each other.

The four-way valve 4 switches the direction in which the refrigerant discharged from the compressor 1 flows through the flow path by changing between a first state and a second state. The four-way valve 4, the first check valve 41, the second check valve 42, the third check valve 43, and the fourth check valve 44 function to switch the order in which the refrigerant circulates between the first order and the second order. This switches the operation mode of the refrigeration cycle device 100 between the first operation mode and the second operation mode.

In the first operation mode, high-pressure refrigerant flows into the first heat exchanger 10. In the second operation mode, low-pressure refrigerant flows into the first heat exchanger 10. When the first heat exchanger 10 is installed in an indoor unit, the first operation mode corresponds to heating operation, and the second operation mode corresponds to cooling operation. The control device 90 sets the four-way valve 4 to a first state in the first operation mode, and sets the four-way valve 4 to a second state in the second operation mode.

A switching device 40 for switching the operation mode is configured by the four-way valve 4, the first check valve 41, the second check valve 42, the third check valve 43, and the fourth check valve 44. The switching device 40 switches the route through which the refrigerant discharged from the compressor 1 circulates between a first route corresponding to the first operation mode and a second route corresponding to the second operation mode.

The refrigerant circuit of the refrigeration cycle device 100 is provided with a number of temperature sensors including a first temperature sensor 71, a second temperature sensor 72 and a third temperature sensor 73.

The first temperature sensor 71 is provided on the side of the gas-liquid separator 6 where the gaseous refrigerant is discharged. More specifically, the first temperature sensor 71 is provided between the side of the gas-liquid separator 6 where the gaseous refrigerant is discharged and the first flow control device 51.

The second temperature sensor 72 is provided on the third port P3 side of the third heat exchanger 30. More specifically, the second temperature sensor 72 is provided between the third port P3 side of the third heat exchanger 30 and the first junction a.

The third temperature sensor 73 is provided on the fourth port P4 side of the third heat exchanger 30. More specifically, the third temperature sensor 73 is provided between the fourth port P4 side of the third heat exchanger 30 and the second junction b.

The control device 90 includes a processor 91 and a memory 92. The memory 92 includes a ROM (Read Only Memory) and a RAM (Random Access Memory). The processor 91 deploys a program stored in the ROM into the RAM or the like and executes it. The program stored in the ROM is a program in which the processing procedures of the control device 90 are written.

The control device 90 controls each device in the refrigeration cycle device 100 according to a program stored in the memory 92. For example, the control device 90 controls the compressor 1, the expansion device 3, the four-way valve 4, and the first flow control device 51.

Next, the flow of the refrigerant in the first and second operating modes will be described. As will be made clear by the following description, in the present disclosure, in both the first and second paths, when the compressor 1 is used as the starting point, the second heat exchanger 20 is located upstream of the refrigerant, and the third heat exchanger 30 is located downstream of the refrigerant.

In this disclosure, a non-azeotropic refrigerant mixture such as R466A will be used as an example of a refrigerant. A non-azeotropic refrigerant mixture is formed by mixing two or more refrigerants with different boiling points. For this reason, a non-azeotropic refrigerant mixture is characterized in that a deviation occurs between the saturated gas temperature and the saturated liquid temperature under a certain pressure. In general, the saturated gas temperature is higher than the saturated liquid temperature. Such a temperature difference is called a temperature gradient.

When a temperature gradient exists, there is a risk of temperature bias occurring within the heat exchanger, resulting in a deterioration in operating efficiency. This disclosure proposes a configuration that can improve operating performance while reducing pressure loss when a non-azeotropic refrigerant mixture is used. In particular, this disclosure proposes a configuration that can be applied to both the first and second operating modes.

In the refrigeration cycle device 100, the heat exchanger in the outdoor unit is divided into a second heat exchanger 20 on the upstream side and a third heat exchanger 30 on the downstream side, and a gas-liquid separator 6 is arranged in the flow path between the second heat exchanger 20 and the third heat exchanger 30. Furthermore, in the refrigeration cycle device 100, the operating capacity is improved by flowing liquid refrigerant or gas refrigerant to the downstream third heat exchanger 30 depending on the operating mode. Note that the refrigerant applicable to the refrigeration cycle device 100 is not limited to a non-azeotropic refrigerant mixture.

<Refrigerant flow in first operation mode>
Fig. 2 is a diagram showing the flow of refrigerant in a first operation mode of the refrigeration cycle apparatus 100. The flow of refrigerant in the first operation mode will be described with reference to Fig. 2. In the first operation mode, the control device 90 controls the four-way valve 4 so that the flow paths shown by the solid lines in Fig. 2 are formed in the four-way valve 4.

At this time, the refrigerant flows through the refrigerant circuit of the refrigeration cycle apparatus 100 as shown by the arrows due to the action of the switching device 40 including the four-way valve 4. That is, the refrigerant discharged from the compressor 1 flows through the first heat exchanger 10, the expansion device 3, the second heat exchanger 20, and the gas-liquid separator 6 in this order via the first switching port P41 and the third switching port P43 of the four-way valve 4. Then, the liquid refrigerant discharged from the liquid discharge port P63 of the gas-liquid separator 6 flows into the third heat exchanger 30 from the fourth port P4.

Meanwhile, the gas refrigerant discharged from the gas discharge port P62 of the gas-liquid separator 6 passes through the first flow control device 51 and heads toward the first junction a shown in Fig. 2. The refrigerant discharged from the third port P3 of the third heat exchanger 30 also flows into the first junction a. The refrigerant that merges from two directions at the first junction a flows through the four-way valve 4 to the suction port of the compressor 1.

The first refrigerant path in the first operating mode is configured by the refrigerant path outlined above. That is, in the first path, the refrigerant flows through the compressor 1, the first heat exchanger 10, the expansion device 3, the second heat exchanger 20, and the gas-liquid separator 6 in that order, and then the liquid refrigerant discharged from the gas-liquid separator 6 flows into the third heat exchanger 30, while the gas refrigerant discharged from the gas-liquid separator 6 passes through the first flow control device 51 and merges with the refrigerant discharged from the third heat exchanger 30 at the first junction a. The refrigerant that merges at the first junction a flows into the compressor 1.

Next, the flow of refrigerant in the first operating mode will be explained in more detail. In the first operating mode, the first heat exchanger 10 on the indoor unit side functions as a condenser, and the second heat exchanger 20 and the third heat exchanger 30 on the outdoor unit side function as evaporators. The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the first heat exchanger 10 on the indoor unit side after passing through the four-way valve 4.

The gas refrigerant that flows into the first heat exchanger 10 condenses by releasing heat to the air in the room. As a result, the refrigerant liquefies within the first heat exchanger 10. The refrigerant discharged from the first heat exchanger 10 flows into the expansion device 3. The expansion device 3 is equipped with a valve for adjusting the degree of expansion of the refrigerant. The refrigerant discharged from the first heat exchanger 10 expands in the expansion device 3 and changes into a two-phase refrigerant in which gas and liquid are mixed.

The two-phase refrigerant discharged from the expansion device 3 flows from the first port P1 through the third check valve 43 into the second heat exchanger 20 on the outdoor unit side. The flow of refrigerant from the expansion device 3 toward the second junction point b is blocked by the fourth check valve 44.

In the second heat exchanger 20, a portion of the two-phase refrigerant evaporates, and the two-phase refrigerant with a higher dryness is discharged from the second port P2 of the second heat exchanger 20. The two-phase refrigerant discharged from the second port P2 flows into the gas-liquid separator 6 from the inlet port P61 and is separated into gas refrigerant and liquid refrigerant.

The liquid refrigerant separated in the gas-liquid separator 6 is discharged from the liquid discharge port P63. The liquid refrigerant discharged from the liquid discharge port P63 flows into the third heat exchanger 30 from the fourth port P4. At this time, the liquid refrigerant discharged from the liquid discharge port P63 does not flow to the expansion device 3 side through the fourth check valve 44. This is because the pressure of the liquid refrigerant discharged from the liquid discharge port P63 is lower than the pressure of the refrigerant flowing from the expansion device 3 toward the third check valve 43. The pressure difference corresponds to the pressure loss between the second heat exchanger 20 part and the third check valve 43 part.

The third temperature sensor 73 detects the temperature of the liquid refrigerant flowing from the fourth port P4 into the third heat exchanger 30. The temperature detected by the third temperature sensor 73 is transmitted to the control device 90.

On the other hand, the gas refrigerant separated in the gas-liquid separator 6 is discharged from the gas discharge port P62. The gas refrigerant discharged from the gas discharge port P62 does not flow into the third heat exchanger 30, but travels through the first flow control device 51 toward the first junction a downstream of the third heat exchanger 30. As a result, of the second heat exchanger 20 and the third heat exchanger 30 in the outdoor unit, liquid refrigerant flows into the third heat exchanger 30, which is downstream, and gas refrigerant does not flow into it.

The first temperature sensor 71 detects the temperature of the gas refrigerant separated in the gas-liquid separator 6. The temperature detected by the first temperature sensor 71 is transmitted to the control device 90. This temperature is equivalent to the saturated gas temperature of the refrigerant that flows into the gas-liquid separator 6. The control device 90 estimates the pressure inside the gas-liquid separator 6 from the temperature detected by the first temperature sensor 71.

In the third heat exchanger 30, the liquid refrigerant exchanges heat with the outside air and gasifies. In this way, since no gas refrigerant flows into the third heat exchanger 30, no temperature gradient occurs within the third heat exchanger 30. As a result, no temperature bias occurs within the third heat exchanger 30. The refrigerant gasified within the third heat exchanger 30 is discharged from the third port P3.

The second temperature sensor 72 detects the temperature of the gas refrigerant discharged from the third port P3. The temperature detected by the second temperature sensor 72 is transmitted to the control device 90. The temperature detected by the second temperature sensor 72 corresponds to the outlet temperature of the evaporator in the first operating mode. The control device 90 estimates the degree of superheat (SH: Super Heat) at the evaporator outlet based on the temperature detected by the first temperature sensor 71 and the temperature detected by the second temperature sensor 72.

The gas refrigerant discharged from the third port P3 of the third heat exchanger 30 merges with the gas refrigerant discharged from the first flow control device 51 at the first merging point a. The gas refrigerant merged from two directions flows into the suction side of the compressor 1 through the first check valve 41 and the four-way valve 4. At this time, the gas refrigerant does not flow through the second check valve 42 to the second heat exchanger 20. This is because the pressure of the gas refrigerant between the first check valve 41 and the four-way valve 4 is lower than the pressure of the refrigerant in the first port P1 portion of the second heat exchanger 20. The pressure difference corresponds to the pressure loss between the second heat exchanger 20 and the first check valve 41.

<Refrigerant flow in second operation mode>
Fig. 3 is a diagram showing the flow of the refrigerant in the second operation mode of the refrigeration cycle apparatus 100. The flow of the refrigerant in the second operation mode will be described with reference to Fig. 3. In the second operation mode, the control device 90 controls the four-way valve 4 so that the flow paths shown by the solid lines in Fig. 3 are formed in the four-way valve 4.

At this time, the refrigerant flows through the refrigerant circuit of the refrigeration cycle apparatus 100 as shown by the arrows due to the action of the switching device 40 including the four-way valve 4. That is, the refrigerant discharged from the compressor 1 flows through the first switching port P41 and the fourth switching port P44 of the four-way valve 4, to the second heat exchanger 20 and the gas-liquid separator 6 in that order. Thereafter, the gas refrigerant discharged from the gas discharge port P62 of the gas-liquid separator 6 flows through the first flow control device 51 and into the third heat exchanger 30 from the third port P3.

Meanwhile, the liquid refrigerant discharged from the liquid discharge port P63 of the gas-liquid separator 6 merges with the refrigerant discharged from the fourth port P4 of the third heat exchanger 30 at the second junction b. The refrigerant that merges at the second junction b flows in order through the expansion device 3 and the first heat exchanger 10, and then flows via the four-way valve 4 to the suction port of the compressor 1.

The second refrigerant path in the second operating mode is configured by the refrigerant path outlined above. That is, in the second path, the refrigerant flows through the compressor 1, the second heat exchanger 20, and the gas-liquid separator 6 in that order, and then the gas-state refrigerant discharged from the gas-liquid separator 6 flows into the third heat exchanger 30 via the first flow control device 51, while the liquid-state refrigerant discharged from the gas-liquid separator 6 merges with the refrigerant discharged from the third heat exchanger 30 at the second junction b, and then the refrigerant that merges at the second junction b flows through the expansion device 3, the first heat exchanger 10, and the compressor 1 in that order.

Next, the flow of refrigerant in the second operation mode will be described in more detail. In the second operation mode, the first heat exchanger 10 on the indoor unit side functions as an evaporator, and the second heat exchanger 20 and the third heat exchanger 30 on the outdoor unit side function as condensers. After passing through the four-way valve 4, the high-temperature, high-pressure gas refrigerant flows from the first port P1 through the second check valve 42 into the second heat exchanger 20 on the outdoor unit side. The flow of refrigerant from the four-way valve 4 toward the first junction a is blocked by the first check valve 41.

The gas refrigerant that flows into the second heat exchanger 20 condenses by releasing heat to the outside air, and changes into a two-phase refrigerant in which gas and liquid are mixed. The two-phase refrigerant discharged from the second port of the second heat exchanger 20 flows into the gas-liquid separator 6 from the inlet port P61, and is separated into gas refrigerant and liquid refrigerant.

The gas refrigerant separated in the gas-liquid separator 6 is discharged from the gas discharge port P62. The gas refrigerant discharged from the gas discharge port P62 flows into the third heat exchanger 30 from the third port P3 through the first flow control device 51. At this time, the gas refrigerant discharged from the first flow control device 51 does not flow through the first check valve 41 to the fourth switching port P44 side of the four-way valve 4. This is because the pressure of the gas refrigerant discharged from the first flow control device 51 is lower than the pressure of the refrigerant at the fourth switching port P44 of the four-way valve 4. The pressure difference corresponds to the pressure loss between the four-way valve 4 and the first check valve 41.

On the other hand, the liquid refrigerant separated in the gas-liquid separator 6 is discharged from the liquid discharge port P63. The liquid refrigerant discharged from the liquid discharge port P63 does not flow into the third heat exchanger 30, but heads toward the downstream side of the third heat exchanger 30. As a result, of the second heat exchanger 20 and the third heat exchanger 30 in the outdoor unit, gas refrigerant flows into the third heat exchanger 30 on the downstream side, and liquid refrigerant does not flow into it.

In the third heat exchanger 30, the gas refrigerant exchanges heat with the outside air and condenses. As a result, the refrigerant liquefies in the third heat exchanger 30. In this way, since no liquid refrigerant flows into the third heat exchanger 30, no temperature gradient occurs in the third heat exchanger 30. As a result, no temperature bias occurs in the third heat exchanger 30.

The liquid refrigerant discharged from the fourth port P4 of the third heat exchanger 30 merges with the liquid refrigerant discharged from the liquid discharge port P63 of the gas-liquid separator 6 at the second junction point b. The liquid refrigerant merged at the second junction point b flows into the expansion device 3 through the fourth check valve 44. At this time, the liquid refrigerant does not flow through the third check valve 43 to the second heat exchanger 20. This is because the refrigerant pressure in the fourth check valve 44 is lower than the refrigerant pressure in the first port P1 of the second heat exchanger 20. The pressure difference corresponds to the pressure loss in the second heat exchanger 20, the first flow control device 51, and the fourth check valve 44.

The refrigerant that flows into the expansion device 3 expands and then flows into the first heat exchanger 10 on the indoor unit side. The refrigerant that flows into the first heat exchanger 10 evaporates by absorbing heat from the indoor air, and then flows into the suction side of the compressor 1 through the four-way valve 4.

The flow of refrigerant in the first and second operating modes is as described above. In the refrigeration cycle device 100, the first check valve 41 and the second check valve 42 form a first valve mechanism. The third check valve 43 and the fourth check valve 44 form a second valve mechanism.

In the first operating mode in which the four-way valve 4 is in the first state, the first valve mechanism connects the expansion device 3 to the first port P1 of the second heat exchanger 20 and blocks communication between the expansion device 3 and the fourth port P4 of the third heat exchanger 30.

In the first operating mode, the first valve mechanism opens the flow of refrigerant from the first junction a to the fourth switching port P44 and blocks the flow of refrigerant from the expansion device 3 to the fourth switching port P44. Furthermore, in the second operating mode, the first valve mechanism opens the flow of refrigerant from the fourth switching port P44 to the second heat exchanger 20 and blocks the flow of refrigerant from the fourth switching port P44 to the first junction a.

In the first operating mode, the second valve mechanism opens the flow of refrigerant from the expansion device 3 to the second heat exchanger 20 and blocks the flow of refrigerant from the expansion device 3 to the second junction point b, and in the second operating mode, opens the flow of refrigerant from the second junction point b to the expansion device 3 and blocks the flow of refrigerant from the fourth switching port P44 to the expansion device 3.

<ph diagram in first operation mode>
4 is a ph diagram showing changes in the state of the refrigerant in the first operation mode. FIG. 4 will be described with reference to FIG.

Here, hout, hout', hg, hl, hin, and hsep shown in Fig. 4 correspond to Poout, Poout', Pog, Pol, Poin, and Posep in Fig. 2, respectively. For example, the enthalpy at the position Poin in the refrigerant circuit in Fig. 2 corresponds to hin shown in Fig. 4.

The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 is condensed by the first heat exchanger 10. The refrigerant then changes to two phases, gas refrigerant and liquid refrigerant, in the expansion device 3 before flowing into the second heat exchanger 20. The enthalpy of the refrigerant at this time is hin. A two-phase refrigerant with a higher dryness is discharged from the second heat exchanger 20. The discharged two-phase refrigerant flows into the gas-liquid separator 6. The enthalpy of the refrigerant at this time is hsep.

The two-phase refrigerant that flows into the gas-liquid separator 6 is separated into gas refrigerant and liquid refrigerant in the gas-liquid separator 6. The gas refrigerant discharged from the gas-liquid separator 6 flows toward the first flow control device 51. The enthalpy of the gas refrigerant at this time is hg. On the other hand, the gas refrigerant discharged from the gas-liquid separator 6 flows toward the third heat exchanger 30. The enthalpy of the liquid refrigerant at this time is hl.

Here, if the amount of refrigerant flowing into the gas-liquid separator 6 is X [kg/hr], the amount of gas refrigerant discharged from the gas-liquid separator 6 is Y [kg/hr], and the amount of liquid refrigerant discharged from the gas-liquid separator 6 is Z [kg/hr], then X = Y + Z holds. At this time, the evaporation capacity is expressed by the following formula (1).

Here, the flow rate X is determined by the rotation speed of the compressor 1, the suction density of the compressor 1, etc. The flow rates Y and Z are determined by the opening degree of the first flow control device 51 attached to the gas refrigerant outlet side of the gas-liquid separator 6. The enthalpy hsep of the refrigerant flowing into the gas-liquid separator 6 can be adjusted by the size, air volume, etc. of the second heat exchanger 20 functioning as an evaporator. Therefore, the evaporation capacity can be improved by adjusting the opening degree of the first flow control device 51 while taking into account changes in the composition of the refrigerant.

The liquid refrigerant that flows into the third heat exchanger 30 exchanges heat with the outside air and gasifies. As a result, the enthalpy of the refrigerant discharged from the third heat exchanger 30 becomes hout'. The gas refrigerant discharged from the third heat exchanger 30 merges with the gas refrigerant discharged from the first flow control device 51 at the merge point a. The enthalpy of the gas refrigerant at this time becomes hout. The gas refrigerant then returns to the compressor 1 through the four-way valve 4.

In the first operating mode, by using the gas-liquid separator 6, only liquid refrigerant flows to the third heat exchanger 30. Therefore, the flow rate of the refrigerant flowing to the third heat exchanger 30 can be reduced (Z = X - Y) compared to when the entire amount of two-phase refrigerant including gas refrigerant and liquid refrigerant flows to the third heat exchanger 30. As a result, the pressure loss can be reduced compared to when the entire amount of two-phase refrigerant flows to the third heat exchanger 30.

Furthermore, because only liquid refrigerant, which has a higher density than gas refrigerant, flows into the third heat exchanger 30, the dryness fraction at the inlet of the third heat exchanger 30 is almost zero. This allows the flow velocity of the refrigerant flowing through the third heat exchanger 30 to be reduced compared to when two-phase refrigerant is flowed. As a result, pressure loss can be improved from the perspective of flow velocity as well.

Here, consider the case where multiple flow paths are provided in the downstream third heat exchanger 30. In this case, when a two-phase non-azeotropic refrigerant consisting of a gas refrigerant and a liquid refrigerant is passed through the third heat exchanger 30, the gas refrigerant flows through the flow paths at a relatively high position, and the liquid refrigerant flows through the flow paths at a relatively low position. This is because there is a density difference between the gas refrigerant and the liquid refrigerant. Then, the temperature gradient of the non-azeotropic refrigerant causes a bias in the refrigerant temperature. However, in this embodiment, only liquid refrigerant with a dryness of approximately 0 is passed through the third heat exchanger 30. Such liquid refrigerant is not easily affected by gravity or flow bias. Therefore, by passing only the liquid refrigerant through the third heat exchanger 30, the flow rate of the refrigerant in each flow path can be made uniform. As a result, according to this embodiment, the bias in the refrigerant temperature due to the temperature gradient can be improved.

According to this embodiment, the amount of liquid refrigerant flowing through the third heat exchanger 30 can be controlled by adjusting the opening of the first flow control device 51. For example, when the rotation speed of the compressor 1 and the opening of the expansion device 3 are constant and the opening of the first flow control device 51 is increased, the amount of gas refrigerant bypassed to the outlet side of the third heat exchanger 30 functioning as an evaporator increases, and the amount of liquid refrigerant flowing through the third heat exchanger 30 decreases.

When the amount of liquid refrigerant flowing through the third heat exchanger 30 is reduced, it is expected that the refrigerant will completely evaporate and gasify inside the third heat exchanger 30. In this case, the degree of superheat at the outlet of the third heat exchanger 30 will increase. On the other hand, when the opening degree of the first flow control device 51 is reduced, the amount of liquid refrigerant flowing into the third heat exchanger 30 increases, so that the liquid refrigerant does not completely gasify inside the third heat exchanger 30. As a result, the degree of superheat decreases. Therefore, by adjusting the opening degree of the first flow control device 51 and increasing or decreasing the amount of gas refrigerant bypassed, the degree of superheat at the outlet of the third heat exchanger 30 can be controlled to an optimal value.

The degree of superheat at the outlet of the third heat exchanger 30 can be estimated based on the temperature detected by the first temperature sensor 71 and the temperature detected by the second temperature sensor 72. Since a non-azeotropic refrigerant mixture has a temperature gradient, it is difficult to estimate the saturation temperature from the temperature of the refrigerant in a two-phase state, but the degree of superheat can be more accurately estimated based on the temperature of the gas refrigerant that has been converted into a single-phase state by the gas-liquid separator 6.

<P-H diagram in second operation mode>
5 is a ph diagram showing changes in the state of the refrigerant in the second operation mode. FIG. 5 will be described with reference to FIG.

Here, hout, hout', hg, hl, hin, and hsep in Figure 5 correspond to Poout, Poout', Pog, Pol, Poin, and Posep in Figure 3, respectively.

The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows into the second heat exchanger 20. The enthalpy of the refrigerant at this time is hin. The refrigerant that flows into the second heat exchanger 20 condenses and is discharged as a two-phase refrigerant. The two-phase refrigerant discharged from the second heat exchanger 20 flows into the gas-liquid separator 6. The enthalpy of the refrigerant at this time is hsep.

The two-phase refrigerant that flows into the gas-liquid separator 6 is separated into gas refrigerant and liquid refrigerant in the gas-liquid separator 6. The gas refrigerant discharged from the gas-liquid separator 6 passes through the first flow control device 51 and heads toward the third heat exchanger 30. The enthalpy of the gas refrigerant before the first flow control device 51 is hg. On the other hand, the liquid refrigerant discharged from the gas-liquid separator 6 heads toward the downstream side of the third heat exchanger 30. The enthalpy of the liquid refrigerant at this time is hl.

Here, if the amount of refrigerant flowing into the gas-liquid separator 6 is X [kg/hr], the amount of gas refrigerant discharged from the gas-liquid separator 6 is Y [kg/hr], and the amount of liquid refrigerant discharged from the gas-liquid separator 6 is Z [kg/hr], then X = Y + Z holds, as in the case of the first operating mode. At this time, the condensation capacity is expressed by the following equation (2).

The gas refrigerant that flows into the third heat exchanger 30 exchanges heat with the outside air and condenses. As a result, the enthalpy of the refrigerant discharged from the third heat exchanger 30 becomes hout'. The refrigerant discharged from the third heat exchanger 30 merges with the liquid refrigerant discharged from the gas-liquid separator 6 at the second junction b. The enthalpy of the refrigerant at this time becomes hout. The refrigerant then expands in the expansion device 3, flows into the first heat exchanger 10, evaporates, and returns to the compressor 1 through the four-way valve 4.

In the second operating mode, by using the gas-liquid separator 6, only gas refrigerant flows to the third heat exchanger 30. Therefore, the flow rate of the refrigerant flowing to the third heat exchanger 30 can be reduced compared to when the entire amount of the two-phase refrigerant including gas refrigerant and liquid refrigerant flows to the third heat exchanger 30. As a result, the pressure loss can be reduced compared to when the entire amount of the two-phase refrigerant flows to the third heat exchanger 30.

In the second operating mode, when a non-azeotropic refrigerant mixture flows into the second heat exchanger 20 on the outdoor unit side, the refrigerant with a high boiling point is preferentially condensed in the second heat exchanger 20 over the refrigerant with a low boiling point. Therefore, most of the gas refrigerant in the gas-liquid separator 6 is a refrigerant with a low boiling point, and most of the liquid refrigerant in the gas-liquid separator 6 is a refrigerant with a high boiling point. In the second operating mode, only the gas refrigerant separated in the gas-liquid separator 6 is flowed to the third heat exchanger 30, so that it is the refrigerant with a low boiling point that is condensed in the third heat exchanger 30.

In this way, by using the gas-liquid separator 6 in the second operating mode, it is possible to flow a refrigerant with a large amount of low boiling point components to the downstream third heat exchanger 30 out of the second heat exchanger 20 and the third heat exchanger 30. Here, if the theoretical coefficient of performance of the refrigerant with the low boiling point components is higher than that of the refrigerant with the high boiling point components, the efficiency of the refrigeration cycle can be improved.

In the second operating mode, as in the first operating mode, the amount of refrigerant flowing to the third heat exchanger 30 can be adjusted by adjusting the opening of the first flow control device 51 while taking into account changes in the composition of the refrigerant. For example, if the opening of the first flow control device 51 is increased while the rotation speed of the compressor 1 and the opening of the expansion device 3 are kept constant, the amount of gas refrigerant flowing to the third heat exchanger 30 increases.

When the amount of gas refrigerant flowing to the third heat exchanger 30 increases, the liquid level in the gas-liquid separator 6 rises. As a result, the degree of supercooling (SC: Super cool) at the outlet of the third heat exchanger 30 decreases. On the other hand, when the opening degree of the first flow control device 51 is reduced, the degree of supercooling increases. Therefore, by adjusting the opening degree of the first flow control device 51 and increasing or decreasing the amount of gas refrigerant flowing to the third heat exchanger 30, the degree of supercooling at the outlet of the third heat exchanger 30 can be controlled to an optimal value.

The degree of subcooling at the outlet portion of the third heat exchanger 30 can be estimated based on the temperature detected by the first temperature sensor 71 and the temperature detected by the third temperature sensor 73.

<Control of the control device in the first operation mode>
6 is a flow chart for explaining the control of the control device 90 in the first operation mode. First, the control device 90 changes the rotation speed of the compressor 1 (step S1). The rotation speed of the compressor 1 is determined by the difference between the temperature set by the remote control of the indoor unit and the room temperature, etc. The control device 90 changes the rotation speed of the compressor 1 to an appropriate value.

Next, the control device 90 adjusts the opening degree of the expansion device 3 (step S2).
Next, the control device 90 calculates the degree of supercooling (SC: Super cool) at the outlet of the first heat exchanger 10 functioning as a condenser (step S3). The degree of supercooling at the outlet of the first heat exchanger 10 can be calculated, for example, from the temperature at the outlet of the first heat exchanger 10 and the pressure of the first heat exchanger 10. Therefore, it is preferable to appropriately arrange a sensor for detecting the temperature and a sensor for detecting the pressure in the refrigerant circuit.

Next, the control device 90 determines whether the degree of subcooling at the outlet of the first heat exchanger 10 functioning as a condenser is within the target region (step S4). When the control device 90 determines that the degree of subcooling at the outlet of the first heat exchanger 10 is not within the target region, in step S2, the control device 90 again adjusts the opening degree of the expansion device 3.

In this way, in step S2, the control device 90 repeatedly adjusts the opening degree of the expansion device 3 until the degree of subcooling at the outlet of the first heat exchanger 10 falls within the target region set for each rotation speed of the compressor 1. Here, the target value region is the target value ± the target error.

When the control device 90 determines in step S4 that the degree of subcooling at the outlet of the first heat exchanger 10 is within the target range, it adjusts the opening degree of the first flow control device 51 (step S5).

Next, the control device 90 calculates the degree of superheat (SH) at the outlet of the third heat exchanger 30, which functions as an evaporator (step S6). At this time, the control device 90 calculates the degree of superheat at the outlet of the third heat exchanger 30 based on the temperature detected by the first temperature sensor 71 and the temperature detected by the second temperature sensor 72.

Next, the control device 90 determines whether the degree of superheat at the outlet of the third heat exchanger 30 functioning as an evaporator is within the target range (step S7). When the control device 90 determines that the degree of superheat at the outlet of the third heat exchanger 30 is not within the target range, in step S5, the control device 90 again adjusts the opening degree of the first flow control device 51.

In this way, in step S5, the control device 90 repeatedly adjusts the opening degree of the first flow control device 51 until the degree of superheat at the outlet of the third heat exchanger 30 falls within the target region set for each rotation speed of the compressor 1. When the control device 90 determines that the degree of superheat at the outlet of the third heat exchanger 30 is within the target region, it ends the process.

When the rotation speed of the compressor 1 is within a specified rotation speed range, the control device 90 may close the flow path by setting the opening degree of the first flow control device 51 to zero, and allow the gas refrigerant to flow to the third heat exchanger 30. In this case, the control device 90 checks whether the rotation speed of the compressor 1 is within the specified rotation speed range each time the rotation speed of the compressor 1 changes.

As explained above using the flowchart shown in Figure 6, in the first operating mode, the control device 90 calculates the degree of superheat of the third heat exchanger 30 based on the detection value of the first temperature sensor 71 and the detection value of the second temperature sensor 72, and controls the degree of superheat of the third heat exchanger 30 by adjusting the opening degree of the first flow control device 51.

<Control of the control device in the second operation mode>
7 is a flow chart for explaining the control of the control device 90 in the second operation mode. First, the control device 90 changes the rotation speed of the compressor 1 in the same manner as in the process of step S1 (step S11).

When the rotation speed of the compressor 1 is changed, the control device 90 adjusts the opening degree of the expansion device 3 so that the discharge temperature of the compressor 1 is within the target range (step S12). The discharge temperature of the compressor 1 can be determined, for example, based on the detection value of a temperature sensor provided at the discharge portion of the compressor 1. Next, the control device 90 determines whether the discharge temperature of the compressor 1 is within the target range (step S13). When the control device 90 determines that the discharge temperature of the compressor 1 is not within the target range, in step S12, it again adjusts the opening degree of the expansion device 3.

When the control device 90 determines in step S13 that the discharge temperature of the compressor 1 is within the target range, it adjusts the opening degree of the first flow control device 51 (step S14).

Next, the control device 90 calculates the degree of subcooling at the outlet of the third heat exchanger 30, which functions as a condenser (step S15). At this time, the control device 90 calculates the degree of subcooling at the outlet of the third heat exchanger 30 based on the temperature detected by the first temperature sensor 71 and the temperature detected by the third temperature sensor 73.

Next, the control device 90 determines whether the degree of subcooling at the outlet of the third heat exchanger 30, which functions as a condenser, is within a target region set for each rotation speed of the compressor 1 (step S16). When the control device 90 determines that the degree of subcooling at the outlet of the third heat exchanger 30 is not within the target region, in step S14, it again adjusts the opening degree of the first flow control device 51.

In this way, in step S14, the control device 90 repeatedly adjusts the opening degree of the first flow control device 51 until the degree of subcooling at the outlet of the third heat exchanger 30 falls within the target region set for each rotation speed of the compressor 1. When the control device 90 determines that the degree of subcooling at the outlet of the third heat exchanger 30 is within the target region, it ends the process.

As explained above using the flowchart shown in Figure 7, in the second operating mode, the control device 90 calculates the degree of subcooling of the third heat exchanger 30 based on the detection value of the first temperature sensor 71 and the detection value of the third temperature sensor 73, and controls the degree of subcooling of the third heat exchanger 30 by adjusting the opening degree of the first flow control device 51.

As described above, the refrigeration cycle device 100 according to the first embodiment improves the operating capacity by flowing liquid refrigerant or gas refrigerant to the downstream third heat exchanger 30 depending on the operating mode. Therefore, the refrigeration cycle device 100 can improve the operating efficiency of the refrigeration cycle in both the first and second operating modes. In other words, the refrigeration cycle device 100 can improve the operating efficiency by utilizing the gas-liquid separator 6 even when the second heat exchanger 20 and the third heat exchanger 30 on the outdoor unit side function as either an evaporator or a condenser. In particular, when a non-azeotropic mixed refrigerant is used, the effect of improving the operating efficiency of the refrigeration cycle can be enhanced.

Embodiment 2.
Next, a second embodiment will be described with reference to Fig. 8. Fig. 8 is a refrigerant circuit diagram showing a configuration of a refrigeration cycle apparatus 110 according to the second embodiment. The refrigeration cycle apparatus 110 according to the second embodiment is different from the refrigeration cycle apparatus 100 according to the first embodiment in the configuration of a switching device. The refrigeration cycle apparatus 110 according to the second embodiment includes a switching device 400 including a first three-way valve 45 and a second three-way valve 46.

The first three-way valve 45 is provided between the fourth switching port P44, the second heat exchanger 20, and the first junction a. The first three-way valve 45 switches the connection destination of the fourth switching port P44 between the second heat exchanger 20 and the first junction a.

The second three-way valve 46 is provided between the expansion device 3, the second heat exchanger 20, and the second junction b. The second three-way valve 46 switches the connection of the expansion device 3 between the second heat exchanger 20 and the second junction b.

In the first operation mode, the control device 90 controls the four-way valve 4, the first three-way valve 45, and the second three-way valve 46 so that the flow path shown by the solid lines in Figure 8 is formed. As a result, the refrigerant circulates through the refrigerant circuit in the same order as that shown in Figure 2. In the second operation mode, the control device 90 controls the four-way valve 4 as shown in Figure 3, and switches the connection mode of the first three-way valve 45 and the second three-way valve 46 to the mode shown by the dashed lines in Figure 8. As a result, the refrigerant circulates through the refrigerant circuit in the same order as that shown in Figure 3.

The first three-way valve 45 has a function similar to that of the first check valve 41 and the second check valve 42 of the refrigeration cycle apparatus 100 according to embodiment 1. The second three-way valve 46 has a function similar to that of the third check valve 43 and the fourth check valve 44 of the refrigeration cycle apparatus 100 according to embodiment 1. Therefore, in embodiment 2, the first valve mechanism is constituted by the first three-way valve 45, and the second valve mechanism is constituted by the second three-way valve 46.

The first valve mechanism according to the first embodiment is composed of a first check valve 41 and a second check valve 42. On the other hand, the first valve mechanism according to the second embodiment is composed of a first three-way valve 45. The second valve mechanism according to the first embodiment is composed of a third check valve 43 and a fourth check valve 44. On the other hand, the second valve mechanism according to the second embodiment is composed of a second three-way valve 46. Therefore, according to the second embodiment, the number of parts can be reduced compared to the first embodiment.

Embodiment 3.
9 is a refrigerant circuit diagram showing a configuration of a refrigeration cycle apparatus 120 according to embodiment 3. The refrigeration cycle apparatus 120 according to embodiment 3 further includes a second flow control device 52 and a fourth temperature sensor 74, as compared with the refrigeration cycle apparatus 100 according to embodiment 1.

The second flow control device 52 is provided between the side of the gas-liquid separator 6 from which the liquid refrigerant is discharged and the second junction b. The fourth temperature sensor 74 is provided between the side of the gas-liquid separator 6 from which the liquid refrigerant is discharged and the second flow control device 52.

In this way, by providing a mechanism capable of adjusting the flow rate at the part where the liquid refrigerant is discharged from the gas-liquid separator 6, the control device 90 can more precisely adjust the amount of gas refrigerant and liquid refrigerant discharged from the gas-liquid separator 6.

In addition, because the first temperature sensor 71 detects the temperature of the gas refrigerant, when calculating the saturation temperature of the liquid refrigerant using the detection value of the first temperature sensor 71, it is necessary to take into account the temperature gradient of the non-azeotropic refrigerant mixture. However, in the refrigeration cycle device 120 according to the third embodiment, the saturation temperature of the liquid refrigerant can be directly detected by the fourth temperature sensor 74. Therefore, the control device 90 can more accurately calculate the degree of subcooling based on the detection value of the third temperature sensor 73 and the detection value of the fourth temperature sensor 74.

Figure 10 is a flowchart for explaining the control of the control device 90 in the second operating mode according to embodiment 3. The flowchart shown in Figure 10 differs from the flowchart shown in Figure 7 only in that step S24 is provided instead of step S14.

The processes in steps S21 to S23 in Figure 10 are similar to those in steps S11 to S13 in Figure 7, so their explanation will not be repeated here.

In step S24, the control device 90 adjusts the opening degree of the first flow control device 51 and the second flow control device 52.

Next, the control device 90 calculates the degree of subcooling at the outlet of the third heat exchanger 30, which functions as a condenser (step S25). At this time, the control device 90 calculates the degree of subcooling at the outlet portion of the third heat exchanger 30 based on the temperature detected by the third temperature sensor 73 and the temperature detected by the fourth temperature sensor 74. This allows the control device 90 to calculate the degree of subcooling more accurately than when the control device 90 calculates the degree of subcooling at the outlet portion of the third heat exchanger 30 based on the temperature detected by the first temperature sensor 71 and the temperature detected by the third temperature sensor 73.

Next, the control device 90 determines whether the degree of subcooling at the outlet of the third heat exchanger 30, which functions as a condenser, is within the target region set for each rotation speed of the compressor 1 (step S26). When the control device 90 determines that the degree of subcooling at the outlet of the third heat exchanger 30 is not within the target region, in step S24, the control device 90 again adjusts the opening degree of the first flow control device 51 and the second flow control device 52.

In this way, in step S24, the control device 90 repeatedly adjusts the opening degree of the first flow control device 51 and the second flow control device 52 until the degree of subcooling at the outlet of the third heat exchanger 30 falls within the target region set for each rotation speed of the compressor 1. When the control device 90 determines that the degree of subcooling at the outlet of the third heat exchanger 30 is within the target region, it ends the process.

In the third embodiment, the first valve mechanism is composed of the first check valve 41 and the second check valve 42, and the second valve mechanism is composed of the third check valve 43 and the fourth check valve 44. However, the first valve mechanism may be composed of the first three-way valve 45, and the second valve mechanism may be composed of the second three-way valve 46.

(summary)
The present embodiment will be summarized below.

(1) The present disclosure relates to a refrigeration cycle device. The refrigeration cycle device (100) includes a compressor (1), a first heat exchanger (10), a second heat exchanger (20), a third heat exchanger (30), an expansion device (3), a gas-liquid separator (6), a first flow control device (51), and a switching device (40) configured to switch a refrigerant circulation path between a first route corresponding to a first operation mode and a second route corresponding to a second operation mode. In the first route, the refrigerant flows through the compressor (1), the first heat exchanger (10), the expansion device (3), the second heat exchanger (20), and the gas-liquid separator (6) in that order, and then the liquid refrigerant discharged from the gas-liquid separator (6) flows into the third heat exchanger (30), and the gaseous refrigerant discharged from the gas-liquid separator (6) passes through the first flow control device (51) and merges with the refrigerant discharged from the third heat exchanger (30) at a first junction (a). The refrigerant merged at the first junction (a) flows into the compressor (1). In the second route, the refrigerant flows through the compressor (1), the second heat exchanger (20), and the gas-liquid separator (6) in this order. The gas-state refrigerant discharged from the gas-liquid separator (6) flows into the third heat exchanger (30) via the first flow control device (51). The liquid-state refrigerant discharged from the gas-liquid separator (6) merges with the refrigerant discharged from the third heat exchanger (30) at the second junction (b). The refrigerant merged at the second junction (b) flows through the expansion device (3), the first heat exchanger (10), and the compressor (1) in this order.

By adopting such a configuration, the operating efficiency of the refrigeration cycle can be improved in both the first and second operating modes. In other words, the operating efficiency can be improved by utilizing the gas-liquid separator whether the heat exchanger functions as an evaporator or a condenser. In particular, when a non-azeotropic refrigerant mixture is used, the effect of improving the operating efficiency of the refrigeration cycle can be enhanced.

(2) The switching device (40) includes a four-way valve (4), a first valve mechanism (41, 42), and a second valve mechanism (43, 44). The four-way valve (4) has a first switching port (P41), a second switching port (P42), a third switching port (P43), and a fourth switching port (P44), and the discharge port of the compressor (1) is connected to the first switching port (P41) and the suction port of the compressor (1) is connected to the second switching port (P42). In a first operating mode, the four-way valve (4) connects the first switching port (P41) to the third switching port (P43) and connects the second switching port (P42) to the fourth switching port (P44), and in a second operating mode, connects the first switching port (P41) to the fourth switching port (P44) and connects the second switching port (P42) to the third switching port (P43). The first valve mechanism (41, 42) opens the flow of refrigerant from the first junction (a) to the fourth switching port (P44) and blocks the flow of refrigerant from the expansion device (3) to the fourth switching port (P44) in a first operation mode, and opens the flow of refrigerant from the fourth switching port (P44) to the second heat exchanger (20) and blocks the flow of refrigerant from the fourth switching port (P44) to the first junction (a) in a second operation mode. The second valve mechanism (43, 44) opens the flow of refrigerant from the expansion device (3) to the second heat exchanger (20) in the first operation mode and blocks the flow of refrigerant from the expansion device (3) to the second junction (b) in the second operation mode.

(3) The first valve mechanism (41, 42) includes a first check valve (41) provided between the fourth switching port (P44) and the first junction (a) and blocking the flow of refrigerant from the fourth switching port (P44) to the first junction (a), and a second check valve (42) provided between the expansion device (3), the fourth switching port (P44), and the second heat exchanger (20) and blocking the flow of refrigerant from the expansion device (3) to the fourth switching port (P44). The second valve mechanism (43, 44) includes a third check valve (43) that is provided between the fourth switching port (P44), the expansion device (3), and the second heat exchanger (20) and blocks the flow of refrigerant from the fourth switching port (P44) to the expansion device (3), and a fourth check valve (44) that is provided between the expansion device and the second junction (b) and blocks the flow of refrigerant from the expansion device (3) to the second junction (b).

(4) The first valve mechanism may be constituted by a first three-way valve (45). The second valve mechanism may be constituted by a second three-way valve (46). The first three-way valve (45) is provided between the fourth switching port (P44), the second heat exchanger (20), and the first junction (a), and switches the connection destination of the fourth switching port (P44) between the second heat exchanger (20) and the first junction (a). The second three-way valve (46) is provided between the expansion device (3), the second heat exchanger (20), and the second junction (b), and switches the connection destination of the expansion device (3) between the second heat exchanger (20) and the second junction (b).

(5) The refrigeration cycle device further includes a first temperature sensor (71) provided between the side (P62) of the gas-liquid separator (6) where the gaseous refrigerant is discharged and the first flow rate control device (51), a second temperature sensor (72) provided between the third heat exchanger (30) and the first junction (a), and a control device (90) that controls the first flow rate control device (51). In the first operation mode, the control device (90) calculates the degree of superheat of the third heat exchanger (30) based on the detection value of the first temperature sensor (71) and the detection value of the second temperature sensor (72) (step S6), and controls the degree of superheat of the third heat exchanger (30) by adjusting the opening degree of the first flow rate control device (51) (steps S5 to S7).

(6) The refrigeration cycle device may further include a third temperature sensor (73) provided between the third heat exchanger (30) and the second junction (b). In the second operation mode, the control device (90) calculates the degree of subcooling of the third heat exchanger (30) based on the detection value of the first temperature sensor (71) and the detection value of the third temperature sensor (73) (step S15), and controls the degree of subcooling of the third heat exchanger (30) by adjusting the opening degree of the first flow rate control device (51) (steps S14 to S16).

(7) The refrigeration cycle device may further include a second flow control device (52) provided between the side (P63) of the gas-liquid separator (6) where the liquid refrigerant is discharged and the second junction (b), a third temperature sensor (73) provided between the third heat exchanger (30) and the second junction (b), and a fourth temperature sensor (74) provided between the side (P63) of the gas-liquid separator (6) where the liquid refrigerant is discharged and the second flow control device (52). In the second operation mode, the control device (90) calculates the degree of subcooling of the third heat exchanger (30) based on the detection value of the third temperature sensor (73) and the detection value of the fourth temperature sensor (74) (step S25), and controls the degree of subcooling of the third heat exchanger (30) by adjusting the opening degree of the first flow control device (51) and the second flow control device (52) (steps S24 to S26).

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims, not by the description of the embodiments above, and is intended to include all modifications within the meaning and scope of the claims.

1 Compressor, 3 Expansion device, 4 Four-way valve, 6 Gas-liquid separator, 10 First heat exchanger, 20 Second heat exchanger, 30 Third heat exchanger, 40 Switching device, 41 First check valve, 42 Second check valve, 43 Third check valve, 44 Fourth check valve, 45 First three-way valve, 46 Second three-way valve, 51 First flow control device, 52 Second flow control device, 71 First temperature sensor, 72 Second temperature sensor, 73 Third temperature sensor, 74 Fourth temperature sensor, 90 Control device, 91 Processor, 92 Memory, 100, 110, 120 Refrigeration cycle device, 400 Switching device, P1 First port, P2 Second port, P3 Third port, P4 Fourth port, P41 First switching port, P42 Second switching port, P43 Third switching port, P44 Fourth switching port, P61 inlet port, P62 gas exhaust port, P63 liquid exhaust port.

Claims (6)

A refrigeration cycle device,
A compressor;
A first heat exchanger;
A second heat exchanger;
A third heat exchanger;
An expansion device;
A gas-liquid separator;
A first flow control device;
a switching device configured to switch a refrigerant circulation path between a first route corresponding to a first operation mode and a second route corresponding to a second operation mode,
In the first route,
The refrigerant flows through the compressor, the first heat exchanger, the expansion device, the second heat exchanger, and the gas-liquid separator in this order,
The refrigerant in a liquid state discharged from the gas-liquid separator flows into the third heat exchanger,
The refrigerant in a gas state discharged from the gas-liquid separator passes through the first flow control device and merges with the refrigerant discharged from the third heat exchanger at a first junction point,
The refrigerant that has joined at the first joining point flows into the compressor,
In the second route,
The refrigerant flows through the compressor, the second heat exchanger, and the gas-liquid separator in this order.
The refrigerant in a gas state discharged from the gas-liquid separator passes through the first flow control device and flows into the third heat exchanger,
The refrigerant in a liquid state discharged from the gas-liquid separator merges with the refrigerant discharged from the third heat exchanger at a second junction point,
The refrigerant that has joined at the second joining point flows through the expansion device, the first heat exchanger, and the compressor in this order,
The switching device is
A four-way valve,
A first valve mechanism;
a second valve mechanism;
the four-way valve has a first switching port, a second switching port, a third switching port, and a fourth switching port, the first switching port is connected to a discharge port of the compressor, and the second switching port is connected to a suction port of the compressor,
The four-way valve is
In the first operation mode, the first switching port and the third switching port are communicated with each other, and the second switching port and the fourth switching port are communicated with each other;
In the second operation mode, the first switching port and the fourth switching port are communicated with each other, and the second switching port and the third switching port are communicated with each other;
The first valve mechanism includes:
in the first mode of operation, opening the flow of the refrigerant from the first junction to the fourth switch port and blocking the flow of the refrigerant from the expansion device to the fourth switch port;
In the second operating mode, the flow of the refrigerant from the fourth switching port to the second heat exchanger is opened, and the flow of the refrigerant from the fourth switching port to the first junction is blocked;
The second valve mechanism includes:
in the first mode of operation, opening the flow of the refrigerant from the expansion device to the second heat exchanger and blocking the flow of the refrigerant from the expansion device to the second junction;
the flow of the refrigerant from the second junction to the expansion device is opened and the flow of the refrigerant from the fourth switching port to the expansion device is blocked in the second operation mode . The first valve mechanism includes:
a first check valve provided between the fourth switching port and the first junction and configured to block the flow of the refrigerant from the fourth switching port toward the first junction;
a second check valve provided between the expansion device, the fourth switching port, and the second heat exchanger, the second check valve blocking the flow of the refrigerant from the expansion device to the fourth switching port;
The second valve mechanism includes:
a third check valve provided between the fourth switching port, the expansion device, and the second heat exchanger, the third check valve blocking the flow of the refrigerant from the fourth switching port to the expansion device;
2. The refrigeration cycle apparatus according to claim 1 , further comprising: a fourth check valve provided between the expansion device and the second junction point and configured to block a flow of the refrigerant from the expansion device to the second junction point. The first valve mechanism is constituted by a first three-way valve,
the second valve mechanism is constituted by a second three-way valve,
the first three-way valve is provided between the fourth switching port, the second heat exchanger, and the first junction, and switches a connection destination of the fourth switching port between the second heat exchanger and the first junction;
2. The refrigeration cycle apparatus according to claim 1, wherein the second three-way valve is provided between the expansion device, the second heat exchanger, and the second junction, and switches a connection destination of the expansion device between the second heat exchanger and the second junction. a first temperature sensor provided between a side of the gas-liquid separator from which the refrigerant in a gas state is discharged and the first flow rate control device;
a second temperature sensor provided between the third heat exchanger and the first junction;
A control device for controlling the first flow rate control device,
The control device includes:
In the first operation mode, a degree of superheat of the third heat exchanger is calculated based on a detection value of the first temperature sensor and a detection value of the second temperature sensor;
The refrigeration cycle apparatus according to any one of claims 1 to 3 , wherein the degree of superheat of the third heat exchanger is controlled by adjusting an opening degree of the first flow control device. Further comprising a third temperature sensor provided between the third heat exchanger and the second junction,
The control device includes:
In the second operation mode, a degree of subcooling of the third heat exchanger is calculated based on a detection value of the first temperature sensor and a detection value of the third temperature sensor;
The refrigeration cycle apparatus according to claim 4 , wherein the degree of subcooling of the third heat exchanger is controlled by adjusting an opening degree of the first flow rate control device. a second flow control device provided between a side of the gas-liquid separator from which the refrigerant in a liquid state is discharged and the second junction;
a third temperature sensor provided between the third heat exchanger and the second junction;
a fourth temperature sensor provided between a side of the gas-liquid separator from which the refrigerant in a liquid state is discharged and the second flow control device;
The control device includes:
In the second operation mode, a degree of subcooling of the third heat exchanger is calculated based on a detection value of the third temperature sensor and a detection value of the fourth temperature sensor;
The refrigeration cycle apparatus according to claim 4 , wherein the degree of subcooling of the third heat exchanger is controlled by adjusting opening degrees of the first flow rate control device and the second flow rate control device.

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