JP7474911B1 - Refrigeration Cycle Equipment - Google Patents

Abstract

A refrigeration cycle device includes an economizer circuit that reduces the pressure of a refrigerant branched from a refrigerant path between a condenser and an evaporator using an economizer expansion valve and merges the refrigerant with a refrigerant reduced to an intermediate pressure in a compressor, a subcooling circuit that reduces the pressure of a refrigerant branched from a refrigerant path between the condenser and an evaporator using a subcooling expansion valve and merges the refrigerant with a suction side refrigerant of the compressor, a first temperature sensor that detects a first refrigerant temperature of the refrigerant discharged from the compressor, and a controller that adjusts the opening of the economizer expansion valve and the opening of the subcooling expansion valve, wherein the controller sets the opening of the subcooling expansion valve to a first opening when the compressor has a first rotation speed, and sets the opening of the subcooling expansion valve to a second opening greater than the first opening when the compressor has a second rotation speed greater than the first rotation speed, thereby controlling the opening of the economizer expansion valve in accordance with the first refrigerant temperature.

Description

The present invention relates to a refrigeration cycle device.

In recent years, issues of energy depletion and global warming have been attracting attention, and there is a demand for refrigerants used in refrigerators and air conditioners that have a high COP (Coefficient of Performance) and a low environmental impact. In particular, there is a lot of attention on the issue of global warming, and there is a demand for refrigerants that have a low direct impact, i.e., GWP (Global Warming Potential), and a low indirect impact, i.e., energy consumption, due to leakage.

Known means for improving the performance of refrigerators and other devices include economizers, which can reduce the input power to the compressor, and subcooling bypass technologies, which can reduce pressure loss mainly on the low-pressure side.

JP 2009-204244 A

There was a desire to improve operating efficiency by using an economizer and subcooling bypass.

The present invention has been developed in consideration of such problems and aims to improve the operating efficiency of refrigeration cycle equipment.

The present invention is a refrigeration cycle device, comprising: an economizer circuit for reducing the pressure of a refrigerant branched from a refrigerant path between a condenser and an evaporator by an economizer expansion valve and for allowing the refrigerant to merge with refrigerant reduced to an intermediate pressure in a compressor; a subcooling circuit for reducing the pressure of the refrigerant branched from the refrigerant path between the condenser and the evaporator by a subcooling expansion valve and for allowing the refrigerant to merge with refrigerant on a suction side of the compressor; a first temperature sensor for detecting a first refrigerant temperature of the refrigerant discharged from the compressor; and a control unit for adjusting an opening degree of the economizer expansion valve and an opening degree of the subcooling expansion valve, the control unit sets the opening of the subcooling expansion valve to a first opening, and when the rotation speed is a second rotation speed greater than the first rotation speed, sets the opening of the subcooling expansion valve to a second opening greater than the first opening, and controls the opening of the economizer expansion valve in accordance with the first refrigerant temperature, the economizer circuit and the subcooling circuit are connected to a common heat exchanger, and when the rotation speed is a third rotation speed, the control unit merges the refrigerant flowing through the common heat exchanger with refrigerant on a suction side of the compressor, and when the rotation speed is a fourth rotation speed smaller than the third rotation speed, the control unit merges the refrigerant flowing through the common heat exchanger with refrigerant at an intermediate pressure of the compressor.

Another aspect of the present invention is a refrigeration cycle device comprising: an economizer circuit that reduces the pressure of a refrigerant branched from a refrigerant path between a condenser and an evaporator using an economizer expansion valve and merges it with refrigerant that has been reduced to an intermediate pressure in a compressor; a subcooling circuit that reduces the pressure of a refrigerant branched from the refrigerant path between the condenser and the evaporator using a subcooling expansion valve and merges it with the refrigerant on the suction side of the compressor; a first temperature sensor that detects a first refrigerant temperature of the refrigerant discharged from the compressor; a second temperature sensor that detects a second refrigerant temperature of the refrigerant between the subcooling circuit and the evaporator; and a control unit that adjusts the opening of the economizer expansion valve and the opening of the subcooling expansion valve, wherein the control unit controls the opening of the subcooling expansion valve based on the second refrigerant temperature and controls the opening of the economizer expansion valve based on the first refrigerant temperature, and a mixed refrigerant with a temperature gradient is used as the refrigerant.

According to the present invention, the operating efficiency of a refrigeration cycle device can be improved.

1 is a diagram showing a refrigeration cycle device according to a first embodiment. 4 is a flowchart showing a control according to the first embodiment. FIG. 6 is a diagram showing a refrigeration cycle device according to a second embodiment. 10 is a flowchart showing a control according to a second embodiment. This is a p-h diagram. FIG. 13 is a diagram showing an economizer circuit, a subcooling circuit, and a common heat exchanger according to a third embodiment. FIG. 13 is a diagram showing an economizer circuit, a subcooling circuit, and a common heat exchanger in a case where the bypass is dominant. FIG. 13 is a diagram showing an economizer circuit, a subcooling circuit, and a common heat exchanger according to a fourth embodiment. FIG. 13 is a diagram showing an economizer circuit, a subcooling circuit, and a common heat exchanger in a case where the bypass is dominant.

First Embodiment
FIG 1 is a diagram showing a refrigeration cycle apparatus 1 according to a first embodiment. The refrigeration cycle apparatus 1 is used in a refrigerator or an air conditioner. In the refrigeration cycle apparatus 1 according to this embodiment, the refrigerant is a mixed refrigerant having a temperature gradient. An example of such a mixed refrigerant is R448A. However, the refrigerant may be a single refrigerant.

The refrigeration cycle device 1 includes a condenser (heat source side heat exchanger) 11, an expansion valve 12, an evaporator (load side heat exchanger) 13, a compressor 14, an economizer circuit 20, and a subcooling circuit 30. The refrigerant exchanges heat with the surroundings in the condenser 11 and changes from a high-temperature gas to a liquid. The refrigerant then passes through the economizer circuit 20 and the subcooling circuit 30, is depressurized in the expansion valve 12, and exchanges heat with the surroundings in the evaporator 13 and changes from a liquid to a low-temperature, low-pressure gas. The refrigerant is then compressed in the compressor 14 and discharged from the compressor 14 as a high-temperature, high-pressure gas.

In the economizer circuit 20, an economizer heat exchanger 21 is provided in the mainstream path 101, and an economizer expansion valve 22 is provided in the first branch path 102. A portion of the liquid refrigerant that has undergone heat exchange in the condenser 11 flows through the first branch path 102 and is reduced in pressure to the intermediate pressure of the compressor 14 by the economizer expansion valve 22. The reduced-pressure liquid refrigerant is vaporized by heat exchange with the mainstream refrigerant in the economizer heat exchanger 21, and flows into the middle of the compressor 14 via the injection path 103. In the compressor 14, the gas refrigerant flowing through the mainstream path 101 and the gas refrigerant that has been reduced in pressure to the intermediate pressure and that has flowed in from the injection path 103 merge. This reduces the amount of refrigerant that the compressor 14 draws in the mainstream, thereby reducing the input (power) of the compressor 14.

In the supercooling circuit 30, a subcooling heat exchanger 31 is provided in the mainstream path 101, and a subcooling expansion valve 32 is provided in the second branch path 104. A part of the refrigerant that has exchanged heat in the condenser 11 and passed through the mainstream path 101 of the economizer circuit 20 flows through the second branch path 104 and is depressurized to the suction pressure of the compressor 14 by the subcooling expansion valve 32. The depressurized refrigerant is vaporized by heat exchange with the mainstream refrigerant in the subcooling heat exchanger 31, and flows into the piping on the suction side of the compressor 14 (the piping of the mainstream path 101) through the subcooling bypass 105. The gas refrigerant in the subcooling bypass 105 merges with the refrigerant flowing through the mainstream path 101 on the suction side of the compressor 14. This reduces the refrigerant flow rate flowing through the mainstream via the expansion valve 12 and the load side heat exchanger 13, thereby reducing pressure loss.

The refrigeration cycle device 1 of this embodiment uses both the economizer circuit 20 and the subcooling circuit 30. The refrigeration cycle device 1 of this embodiment includes a control unit 40 that controls the opening of the economizer expansion valve 22 to control the economizer circuit 20, and further controls the opening of the subcooling expansion valve 32 to control the subcooling circuit 30. Furthermore, in the refrigeration cycle device 1, a first temperature sensor 51 is provided in the piping between the compressor 14 and the condenser 11 on the discharge side of the compressor 14. The control unit 40 acquires the first refrigerant temperature, which is the temperature of the refrigerant discharged from the compressor 14, detected by the first temperature sensor 51, and performs control based on the first refrigerant temperature.

Figure 2 is a flowchart showing the control by the control unit 40. When control is started, first, in step S100, the control unit 40 acquires the rotation speed of the compressor 14. Next, in step S102, the control unit 40 sets the opening degree of the supercooling expansion valve 32 based on the rotation speed. Specifically, the control unit 40 controls the opening degree of the supercooling expansion valve 32 so that it becomes larger as the rotation speed increases. For example, the control unit 40 increases the opening degree of the supercooling expansion valve 32 by a fixed amount each time the rotation speed increases by a fixed amount.

The higher the rotation speed of the compressor 14, the greater the pressure loss. Therefore, in this embodiment, the higher the rotation speed, the greater the opening of the subcooling expansion valve 32 in the subcooling circuit 30, and the amount of refrigerant passing through the subcooling bypass 105 is increased, thereby reducing the refrigerant flow rate passing through the load side heat exchanger 13. This makes it possible to reduce pressure loss.

In addition, the control unit 40 sets the opening degree of the supercooling expansion valve 32 to a first opening degree when the rotational speed is a first rotational speed, and sets the opening degree of the supercooling expansion valve 32 to a second opening degree greater than the first opening degree when the rotational speed is a second rotational speed greater than the first rotational speed, and the specific control for this purpose is not limited to the embodiment.

Next, in step S104, the control unit 40 acquires the first refrigerant temperature from the first temperature sensor 51. Next, in step S106, the control unit 40 compares the first refrigerant temperature with a first temperature threshold. It is assumed that the first temperature threshold is set in advance. When liquid refrigerant flows into the subcooling bypass 105, the discharge temperature of the compressor 14 decreases. This first temperature threshold is a temperature for detecting such a state.

If the first refrigerant temperature is lower than the first temperature threshold (Y in step S106), the control unit 40 reduces the opening of the economizer expansion valve 22 (step S108) and then proceeds to step S112. In step S108, the control unit 40 reduces the opening of the economizer expansion valve 22 by a certain amount, for example.

On the other hand, if the first refrigerant temperature is equal to or higher than the first temperature (N in step S106), the control unit 40 sets the opening of the economizer expansion valve 22 according to the opening of the subcooling expansion valve 32 (step S110), and then proceeds to step S112. The lower the rotation speed of the compressor 14, the smaller the opening of the subcooling expansion valve 32 is set to, and in response, the opening of the economizer expansion valve 22 is set to a larger value. In this way, the opening of the economizer expansion valve 22 is controlled based on the opening of the subcooling expansion valve 32.

In step S112, the control unit 40 determines whether or not to end the control. If the air conditioning operation has ended, the control unit 40 determines to end the control. If the control unit 40 determines to end the control (Y in step S112), it ends the control. If the control unit 40 determines not to end the control (N in step S112), the process proceeds to step S100 and the control continues.

As described above, in order to reduce pressure loss, the opening of the subcooling expansion valve 32 of the subcooling circuit 30 is adjusted according to the rotation speed of the compressor 14. However, if the opening of the subcooling expansion valve 32 becomes too large as the rotation speed of the compressor 14 increases, liquid refrigerant flows into the subcooling bypass 105, leading to a decrease in performance of the subcooling circuit 30. In order to prevent a decrease in performance of the subcooling circuit 30, it is necessary to reduce the opening of the economizer expansion valve 22. This reduces the amount of refrigerant flowing into the injection flow path 103, reduces the cooling of the refrigerant flowing through the mainstream path 101 of the economizer circuit 20, increases the temperature of the mainstream path 101 flowing into the subcooling heat exchanger 31, and increases the amount of heat exchange in the subcooling heat exchanger 31.

Liquid return in the subcooling bypass 105 appears as a decrease in the discharge temperature from the compressor 14. Therefore, in this embodiment, the control unit 40 monitors the first refrigerant temperature, which corresponds to the discharge temperature, and when the first refrigerant temperature is equal to or lower than the first temperature threshold, the opening of the economizer expansion valve 22 is reduced. This reduces the cooling of the refrigerant in the mainstream path 101 of the economizer circuit 20, and increases the temperature of the refrigerant flowing into the subcooling circuit 30. Therefore, the amount of heat exchanged in the subcooling heat exchanger 31 can be increased.

Furthermore, when the rotation speed of the compressor 14 is relatively low, the effect of reducing pressure loss is small. Therefore, in this case, the control unit 40 controls the opening of the subcooling expansion valve 32 to be smaller, while at the same time increasing the opening of the economizer expansion valve 22. In other words, when the rotation speed of the compressor 14 is relatively low, the injection amount is increased. This makes it possible to increase the effect of reducing the input of the compressor 14 by the economizer circuit 20.

As described above, the refrigeration cycle device 1 of the first embodiment adjusts the opening degree of the economizer expansion valve 22 and the opening degree of the subcooling expansion valve 32. This optimizes the effect of reducing pressure loss by the subcooling circuit 30 and the effect of reducing the input of the compressor 14 by the economizer circuit 20, thereby improving the operating efficiency of the refrigeration cycle device 1.

Second Embodiment
Next, with reference to Fig. 3, the refrigeration cycle apparatus 2 according to the second embodiment will be described, mainly focusing on the differences from the refrigeration cycle apparatus 1 according to the first embodiment. The refrigeration cycle apparatus 2 according to the second embodiment includes a second temperature sensor 52 in addition to the first temperature sensor 51. The second temperature sensor 52 is installed in a pipe between the supercooling circuit 30 and the expansion valve 12, and detects a second refrigerant temperature, which is the temperature of the refrigerant flowing between the supercooling circuit 30 and the expansion valve 12. In the refrigeration cycle apparatus 2 according to the second embodiment, the refrigerant is a mixed refrigerant with a temperature gradient. An example of such a mixed refrigerant is R448A.

In the refrigeration cycle device 2 of this embodiment, the control unit 40 controls the opening degree of the subcooling expansion valve 32 based on the second refrigerant temperature detected by the second temperature sensor 52, and further controls the opening degree of the economizer expansion valve 22 based on the first refrigerant temperature.

Figure 4 is a flowchart showing the control by the control unit 41 of the refrigeration cycle device 2 according to the second embodiment. When the control is started, first, in step S200, the control unit 41 acquires the second refrigerant temperature from the second temperature sensor 52. Next, in step S202, the control unit 41 sets the opening degree of the subcooling expansion valve 32 based on the second refrigerant temperature. Specifically, when the second refrigerant temperature is higher than the target refrigerant temperature, the control unit 41 increases the opening degree of the subcooling expansion valve 32. For example, the control unit 41 increases the opening degree of the subcooling expansion valve 32 by a certain amount. Here, the target refrigerant temperature is set by the control unit 41 according to the operating state, etc. In addition, the control unit 41 may adjust the opening degree of the subcooling expansion valve 32 according to the difference between the target refrigerant temperature and the second refrigerant temperature.

Next, in step S204, the control unit 41 acquires the first refrigerant temperature from the first temperature sensor 51. Next, in step S206, the control unit 41 compares the first refrigerant temperature with a first temperature threshold. It is assumed that the first temperature threshold is set in advance. If the first refrigerant temperature is smaller than the first temperature threshold (Y in step S206), the control unit 41 reduces the opening of the economizer expansion valve 22 to a smaller value (step S208), and then proceeds to step S212. In step S208, the control unit 41 reduces the opening of the economizer expansion valve 22 by a certain amount, for example.

On the other hand, if the first refrigerant temperature is equal to or higher than the first temperature threshold (N in step S206), the control unit 41 sets the opening of the economizer expansion valve 22 according to the opening of the subcooling expansion valve 32 (step S210), and then proceeds to step S212. The lower the rotation speed of the compressor 14, the smaller the opening of the subcooling expansion valve 32 is set to, and in response, the opening of the economizer expansion valve 22 is set to a larger value.

In step S212, the control unit 41 determines whether or not to end the control. If the air conditioning operation has ended, the control unit 41 determines to end the control. If the control unit 41 determines to end the control (Y in step S212), it ends the control. If the control unit 41 determines not to end the control (N in step S212), the process proceeds to step S100 and the control continues.

In the refrigeration cycle device 2 of this embodiment, a mixed refrigerant with a temperature gradient is used as the refrigerant. By lowering the liquid temperature of such a non-azeotropic mixed refrigerant, the refrigerant temperature flowing into the evaporator 13 can be lowered, the temperature difference with the air that is the subject of heat exchange can be increased, and the amount of heat exchange can be increased.

Figure 5 is a pH diagram of R448A. In R448, the refrigerant temperature flowing into the evaporator 13 is -42°C, but it can be lowered to -46°C. In this way, in the case of a mixed refrigerant, even if the evaporation pressure does not change, it is possible to lower the evaporation temperature, improving the performance of the refrigeration cycle device 2. On the other hand, for example, when adjusting the heat exchange amount to be equivalent to the heat exchange amount at an evaporation temperature of -42°C, the inflow refrigerant temperature is lowered to -46°C, but the average temperature of the refrigerant can be set to -42°C, making it possible to increase the evaporation pressure. In other words, the pressure difference during the compression process can be reduced, and the input to the compressor 14 can be reduced.

The effect of lowering the temperature of the liquid refrigerant is greater in the subcooling heat exchanger 31 than in the economizer heat exchanger 21. Therefore, as described above, the refrigeration cycle device 2 of this embodiment adjusts the opening degree of the subcooling expansion valve 32 according to the second refrigerant temperature, which is the temperature of the liquid refrigerant. On the other hand, even in this embodiment, if the opening degree of the subcooling expansion valve 32 becomes too large, liquid refrigerant flows into the subcooling bypass 105, which appears as a decrease in the discharge temperature from the compressor 14. Therefore, similar to the control in the first embodiment, the control unit 41 reduces the opening degree of the economizer expansion valve 22 when the first refrigerant temperature corresponding to the discharge temperature is equal to or lower than the first temperature threshold value.

As described above, the refrigeration cycle device 2 of the second embodiment adjusts the opening degree of the economizer expansion valve 22 and the opening degree of the subcooling expansion valve 32. This optimizes the effect of reducing pressure loss by the subcooling circuit 30 and the effect of reducing the power consumption of the compressor 14 by the economizer circuit 20, thereby improving the operating efficiency of the refrigeration cycle device 2.

Third Embodiment
Next, the refrigeration cycle apparatus 3 according to the third embodiment will be described, focusing mainly on the differences from the other embodiments. The refrigeration cycle apparatus 3 according to the third embodiment further includes a common heat exchanger that is used in common in the economizer circuit and the subcooling circuit. The flow rate is limited by simply adjusting the opening degree of the economizer heat exchanger 21 and the subcooling heat exchanger 31. On the other hand, if the sizes of these heat exchangers 21 and 31 are increased, the entire refrigeration cycle apparatus 3 becomes large, which is not preferable. Therefore, the refrigeration cycle apparatus 3 in this embodiment includes a common heat exchanger 400 that can be used as the economizer heat exchanger and the subcooling heat exchanger.

6 is a diagram showing an economizer circuit 200, a subcooling circuit 300, and a common heat exchanger 400 in a refrigeration cycle device 3 according to a third embodiment. A first branch point 121, a second branch point 122, and a third branch point 123 are provided in this order in the mainstream path 101.

An economizer circuit 200 is provided in the mainstream path 101 downstream of the third branch point 123. The third diversion path 133 branched at the third branch point 123 further branches. As a result, the mainstream refrigerant passes through the economizer heat exchanger 21, the common heat exchanger 400, and the subcooling heat exchanger 31. The refrigerant that passes through these heat exchangers then merges and flows to the load side heat exchanger 13.

The first branch path 131, which branches off at the first branch point 121, is provided with a subcooling expansion valve 32, and downstream of that, a fourth branch point 124 is provided. One path branching off at the fourth branch point 124 connects to the subcooling bypass 105 via the subcooling heat exchanger 31. The other path is provided with a first check valve 401, then passes through a common heat exchanger 400, and further branches off at a fifth branch point 125. The one path is provided with a second opening/closing valve 412, which is connected downstream between the subcooling heat exchanger 31 and the subcooling bypass 105. The other path is provided with a second check valve 402, which is connected downstream between the economizer heat exchanger 21 and the injection flow path 103.

The second branch path 132 branching off at the second branch point 122 is provided with an economizer expansion valve 22, and downstream of that, a sixth branch point 126 is provided. One path branching off at the sixth branch point 126 connects to the injection flow path 103 via the economizer heat exchanger 21. The other path is provided with a first on-off valve 411, and downstream of that, connects between the first check valve 401 and the common heat exchanger 400.

When the rotation speed of the compressor 14 is equal to or lower than a preset rotation speed threshold, the control unit 40 gives priority to the economizer and uses the common heat exchanger 400 as an economizer heat exchanger. Here, it is assumed that the rotation speed threshold is set in advance. As shown in FIG. 6, the control unit 40 closes the first check valve 401 and opens the first opening/closing valve 411. The control unit 40 also closes the second opening/closing valve 412 and opens the second check valve 402.

In this case, the refrigerant on the mainstream path 101 side flows in parallel into the economizer heat exchanger 21, the subcooling heat exchanger 31, and the common heat exchanger 400 that functions as an economizer heat exchanger. The refrigerant on the mainstream path 101 side that passes through these is cooled in each heat exchanger 21, 31, 400, and after merging, flows toward the load side heat exchanger 13 side, i.e., the expansion valve 12.

On the other hand, the refrigerant decompressed by the economizer expansion valve 22 branches at the sixth branch point 126 and flows in parallel into the economizer heat exchanger 21 and the common heat exchanger 400 functioning as an economizer heat exchanger. The flowing refrigerant is heated in each heat exchanger 21, 400 and injected. The refrigerant decompressed by the subcooling expansion valve 32 evaporates in the subcooling heat exchanger 31 and is bypassed to the suction side of the compressor 14 via the subcooling bypass 105. In this way, even if a large amount of refrigerant flows through the economizer circuit 200, in addition to the economizer heat exchanger 21, the common heat exchanger 400 functions as an economizer heat exchanger, so that insufficient evaporation can be prevented.

In addition, when the rotation speed of the compressor 14 is greater than the rotation speed threshold, the control unit 40 prioritizes bypass and uses the common heat exchanger 400 as a subcooling heat exchanger. Specifically, as shown in FIG. 7, the control unit 40 opens the first check valve 401 and closes the first opening/closing valve 411. In addition, the control unit 40 opens the second opening/closing valve 412 and closes the second check valve 402.

In this case, part of the high-pressure refrigerant flowing out of the condenser 11 flows toward the economizer expansion valve 22 and the subcooling expansion valve 32. The remaining refrigerant on the mainstream path 101 side flows in parallel into the economizer heat exchanger 21, the subcooling heat exchanger 31, and the common heat exchanger 400 that functions as a subcooling heat exchanger. The refrigerant that passes through these is cooled in each heat exchanger 21, 31, 400, and after merging, flows toward the load side heat exchanger 13, i.e., the expansion valve 12.

On the other hand, the refrigerant decompressed by the economizer expansion valve 22 flows into the economizer heat exchanger 21, where it is heated, evaporated, and injected. The refrigerant decompressed by the subcooling expansion valve 32 branches at the fourth branch point 124 and flows in parallel into the subcooling heat exchanger 31 and the common heat exchanger 400, which functions as a subcooling heat exchanger. The flowing refrigerant is heated and evaporated in these heat exchangers 31 and 400, and is bypassed to the suction side of the compressor 14 via the subcooling bypass 105. In this way, even if a large amount of refrigerant flows into the subcooling circuit 300, the common heat exchanger 400 functions as a subcooling heat exchanger in addition to the subcooling heat exchanger 31, so that liquid refrigerant can be prevented from flowing into the subcooling bypass 105.

As described above, the common heat exchanger 400 can be switched and used, thereby improving the operating efficiency of the refrigeration cycle device 3.

Fourth Embodiment
Next, the refrigeration cycle apparatus 4 according to the fourth embodiment will be described, focusing mainly on the differences from the other embodiments. The refrigeration cycle apparatus 4 according to the fourth embodiment includes a common heat exchanger, similar to the refrigeration cycle apparatus 3 according to the third embodiment. The refrigeration cycle apparatus 3 according to the third embodiment is configured to switch the low-pressure side circuit between an injection flow path and a subcooling bypass. In contrast, in the refrigeration cycle apparatus 4 according to the fourth embodiment, the high-pressure side circuit is also switched between an injection flow path and a subcooling bypass.

Figure 8 is a diagram showing the economizer circuit 210, the subcooling circuit 310, and the common heat exchanger 410 in the refrigeration cycle device 4 according to the fourth embodiment. The main path 501 is provided with an eleventh branch point 521 and a twelfth branch point 522 in this order.

The economizer circuit 210 is provided in the mainstream path 501 downstream of the 12th branch point 522. The 12th split path 532 branched at the 12th branch point 522 passes through the common heat exchanger 410 and then merges with the mainstream path 501 at a position between the economizer circuit 210 and the subcooling circuit 310. In this path, the 11th opening/closing valve 611 is provided between the 12th branch point 522 and the common heat exchanger 410. In this path, the path on the outlet side of the common heat exchanger 410 is provided with the 13th branch path 523. One path branched at the 13th branch path 523 is provided with the 12th check valve 602, which is connected downstream to the mainstream path 501 on the outlet side of the economizer heat exchanger 21. The other path is provided with the 12th opening/closing valve 612, which is connected downstream to the mainstream path 501 on the outlet side of the subcooling heat exchanger 31.

On the other hand, the 11th branch path 531 branching off at the 11th branch point 521 is provided with an economizer expansion valve 22, and downstream of that, a 14th branch point 524 is provided. One of the paths branching off at the 14th branch point 524 passes through the economizer heat exchanger 21 and connects to the injection path 103. The other path is provided with a 13th opening/closing valve 613, and downstream of that, connects to the common heat exchanger 410. The path on the outlet side of the common heat exchanger 410 is provided with a 15th branch point 525. One of the paths branching off at the 15th branch point 525 is provided with a 14th check valve 604, and downstream of that, connects between the economizer heat exchanger 21 and the injection path 103. The other path is provided with a 14th opening/closing valve 614, and downstream of that, connects between the subcooling heat exchanger 31 and the subcooling bypass 105.

The mainstream path 501 on the outlet side of the economizer heat exchanger 21 is provided with a 16th branch point 526 and a 17th branch point 527 in this order. The mainstream path 501 that passes through the 16th branch point 526 and the 17th branch point 527 further passes through the subcooling heat exchanger 31 and connects to the load side heat exchanger 13 side, i.e., the expansion valve 12. The 13th branch path 533 that branches off at the 17th branch point 527 is provided with an 11th check valve 601, and connects to the 12th branch path 532 downstream.

The 14th branch path 534 branched off at the 16th branch point 526 is provided with a subcooling expansion valve 32, and downstream of that, an 18th branch point 528 is provided. One path branched off at the 18th branch point 528 passes through the subcooling heat exchanger 31 and connects to the subcooling bypass 105. The other path is provided with a 13th check valve 603, and downstream of that, connects between the 13th opening/closing valve 613 and the common heat exchanger 410.

When the rotation speed of the compressor 14 is equal to or lower than a preset rotation speed threshold, the control unit 40 prioritizes the economizer and uses the common heat exchanger 410 as an economizer heat exchanger. Specifically, as shown in FIG. 8, the control unit 40 closes the 11th check valve 601 and the 13th check valve 603 and opens the 12th check valve 602 and the 14th check valve 604. The control unit 40 also opens the 11th opening/closing valve 611 and the 13th opening/closing valve 613 and closes the 12th opening/closing valve 612 and the 14th opening/closing valve 614.

In this case, a portion of the high-pressure refrigerant flowing out of the condenser 11 branches off at the 11th branch point 521 to the 11th branch path 531 as refrigerant for injection. The remaining refrigerant flows in parallel into the economizer heat exchanger 21 and the common heat exchanger 410 functioning as an economizer heat exchanger. The refrigerants that flow into the economizer heat exchanger 21 and the common heat exchanger 410 merge after heat exchange cooling. A portion of the merged refrigerant branches off at the 16th branch point 526 to the 14th branch path 534 as refrigerant for supercooling, and is then cooled in the subcooling heat exchanger 31 and flows to the load side.

On the other hand, the refrigerant decompressed by the economizer expansion valve 22 flows in parallel into the economizer heat exchanger 21 and the common heat exchanger 410 that functions as an economizer heat exchanger, where it is heated and evaporated in the heat exchanger, and then injected. Also, the refrigerant decompressed by the subcooling expansion valve 32 evaporates in the subcooling heat exchanger 31 and is bypassed to the suction side of the compressor 14. With this configuration, the economizer circuit and the subcooling circuit can be switched even on the high pressure side.

When the rotation speed of the compressor 14 is greater than the rotation speed threshold, the control unit 40 uses the bypass as a bypass and uses the common heat exchanger 400 as a subcooling heat exchanger. Specifically, as shown in FIG. 9, the control unit 40 opens the 11th check valve 601 and the 13th check valve 603 and closes the 12th check valve 602 and the 14th check valve 604. The control unit 40 also closes the 11th opening/closing valve 611 and the 13th opening/closing valve 613 and opens the 12th opening/closing valve 612 and the 14th opening/closing valve 614.

In this case, the high-pressure refrigerant flowing out of the condenser 11 flows only into the economizer heat exchanger 21. The refrigerant flowing out of the economizer heat exchanger 21 flows in parallel into the subcooling heat exchanger 31 and the common heat exchanger 410 functioning as a subcooling heat exchanger. The refrigerant decompressed by the economizer expansion valve 22 enters the economizer heat exchanger 21, where it is heated and evaporated in the heat exchanger, and then injected. On the other hand, the refrigerant decompressed by the subcooling expansion valve 32 flows into the subcooling heat exchanger 31 and the common heat exchanger 410 functioning as a subcooling heat exchanger, where it evaporates in the heat exchanger, and is bypassed to the suction side of the compressor 14.

As described above, in the fourth embodiment, the common heat exchanger 400 can be switched and used, thereby improving the operating efficiency of the refrigeration cycle device 4.

The present invention is not limited to the specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims, for example by applying a modified version of one embodiment to another embodiment.

In such a first modified example, the timing of each process in the control by the control unit is not limited to the embodiment. For example, the process of acquiring the rotation speed of the compressor 14 and the process of acquiring the first refrigerant temperature (the discharge temperature of the compressor) may be executed simultaneously, or the first refrigerant temperature may be acquired first.

As a second modified example, the configuration of the refrigeration cycle device equipped with a common heat exchanger described in the third and fourth embodiments is one example. The refrigeration cycle device equipped with a common heat exchanger may be configured so that the common heat exchanger can be switched and used, and the specific configuration for this is not limited to the embodiments.

1 to 4 Air conditioner 11 Heat source side heat exchanger 12 Expansion valve 13 Load side heat exchanger 14 Compressor 20, 200, 210 Economizer circuit 21 Economizer heat exchanger 22 Economizer expansion valve 30, 300, 310 Subcooling circuit 31 Subcooling heat exchanger 32 Subcooling expansion valve 40, 41 Control unit 51 First temperature sensor 52 Second temperature sensor 101 Main flow path 102 First branch flow path 103 Injection flow path 104 Second branch flow path 105 Subcooling bypass 400, 410 Common heat exchanger

Claims (4)

an economizer circuit in which a refrigerant branched from a refrigerant path between a condenser and an evaporator is decompressed by an economizer expansion valve and merged with the refrigerant decompressed to an intermediate pressure in a compressor;
a subcooling circuit in which a refrigerant branched from the refrigerant path between the condenser and the evaporator is decompressed by a subcooling expansion valve and merged with the refrigerant on the intake side of the compressor;
a first temperature sensor for detecting a first refrigerant temperature of the refrigerant discharged from the compressor;
a control unit that adjusts an opening degree of the economizer expansion valve and an opening degree of the subcooling expansion valve,
The control unit is
When the rotation speed of the compressor is a first rotation speed, the opening degree of the subcooling expansion valve is set to a first opening degree;
When the rotation speed is a second rotation speed that is greater than the first rotation speed, the opening degree of the subcooling expansion valve is set to a second opening degree that is greater than the first opening degree;
controlling an opening degree of the economizer expansion valve in response to the first refrigerant temperature;
the economizer circuit and the subcooling circuit are connected to a common heat exchanger;
The control unit is
When the rotation speed is a third rotation speed, the refrigerant flowing through the common heat exchanger is merged with the refrigerant on the intake side of the compressor,
the refrigerant flowing through the common heat exchanger is merged with an intermediate-pressure refrigerant in the compressor when the rotational speed is a fourth rotational speed that is lower than the third rotational speed . The refrigeration cycle device according to claim 1, wherein the control unit increases the opening degree of the subcooling expansion valve as the rotation speed increases. The control unit is
The refrigeration cycle apparatus according to claim 1 , wherein an opening degree of the economizer expansion valve is reduced when the first refrigerant temperature is lower than a first temperature threshold value. The refrigeration cycle device according to claim 1, wherein the refrigerant is a mixed refrigerant with a temperature gradient.

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