WO2023176697A1

WO2023176697A1 - Refrigeration cycle device

Info

Publication number: WO2023176697A1
Application number: PCT/JP2023/009143
Authority: WO
Inventors: 佑廣崎
Original assignee: 株式会社富士通ゼネラル
Priority date: 2022-03-16
Filing date: 2023-03-09
Publication date: 2023-09-21
Also published as: JP2023136032A

Abstract

Provided is a refrigeration cycle device that uses a non-azeotropic refrigerant mixture and is able to suppress the formation of frost on an evaporator. This refrigeration cycle comprises an air conditioner (1) that is equipped with a refrigerant circuit (2) in which a compressor (12), an indoor heat exchanger (7), an expansion valve (14), and an outdoor heat exchanger (13) are sequentially connected, and in which a non-azeotropic refrigerant mixture circulates, and has: a bypass line (17) connected in parallel to a liquid-side pipe (16) connecting the outflow side of the indoor heat exchanger (7) and the inflow side of the outdoor heat exchanger (13); a receiver (22) provided in the bypass line (17); a first flow rate adjustment valve (20) and a second flow rate adjustment valve (21) for adjusting the amount of refrigerant flowing into the receiver (22); and a control unit (3) for controlling the expansion valve (14), the first flow rate adjustment valve (20), and the second flow rate adjustment valve (21). The control unit (3) controls the first flow rate adjustment valve (20) and the second flow rate adjustment valve (21) on the basis of a refrigerant inlet temperature, and adjusts the amount of liquid refrigerant flowing into the outdoor heat exchanger (13).

Description

Refrigeration cycle equipment

The present invention relates to a refrigeration cycle device, and particularly to a refrigeration cycle device using a non-azeotropic mixed refrigerant.

In recent years, in view of global environmental issues, it has been desired to use refrigerants that do not have a negative impact on the global environment as the working fluid of refrigeration cycle devices. Non-azeotropic mixed refrigerants are being considered as candidates for the refrigerant, and Patent Document 1 discloses an air conditioner as a refrigeration cycle device using a non-azeotropic mixed refrigerant as a refrigerant. A refrigeration cycle device using this non-azeotropic mixed refrigerant, like a refrigeration cycle device using a single refrigerant, includes a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in this order. When an air conditioner using a refrigerant circuit using this non-azeotropic mixed refrigerant performs heating operation, the condenser serves as an indoor user-side heat exchanger, and the evaporator serves as an outdoor heat source-side heat exchanger. The refrigerant discharged from the compressor exchanges heat with indoor air in the heat exchanger on the user side and condenses, is decompressed in the expansion valve, exchanges heat with outdoor air in the heat exchanger on the heat source side, and evaporates. It is sucked into the compressor. In an air conditioner using a conventional refrigeration cycle device using a single refrigerant, the condensation temperature of the refrigerant in the user-side heat exchanger and the evaporation temperature in the heat source-side heat exchanger are constant. On the other hand, in the case of a non-azeotropic mixed refrigerant, due to its properties, the temperature of the refrigerant changes when it condenses in the heat exchanger on the user side and when it evaporates in the heat exchanger on the heat source side. It has the characteristic of That is, the refrigerant temperature is not constant in the user-side heat exchanger and the heat source-side heat exchanger, and a temperature gradient occurs.

Japanese Patent Application Publication No. 2000-161805

Therefore, when heating operation is performed in the air conditioner shown in Patent Document 1, the refrigerant inlet temperature of the heat source side heat exchanger that functions as an evaporator becomes lower than the refrigerant outlet temperature. The amount of heat exchanged between the refrigerant and outdoor air in the heat source side heat exchanger depends on the temperature difference between the refrigerant temperature and the outdoor air temperature. In order to improve the heating capacity, the opening degree of the expansion valve is controlled so that the temperature difference is sufficiently increased on the refrigerant outlet side of the heat source side heat exchanger so that the refrigerant outlet temperature is lowered, but the refrigerant inlet temperature drops excessively. do. Therefore, for example, during heating operation of the air conditioner, when the outside air temperature is low such as in winter, there is a problem that frost is likely to form at the refrigerant inlet portion of the heat source side heat exchanger.

In view of the above problems, an object of the present invention is to provide a refrigeration cycle device that uses a non-azeotropic mixed refrigerant and can suppress frost formation on the evaporator.

One aspect of the present invention is a refrigeration cycle device including a refrigerant circuit in which a compressor, a condenser, a pressure reducing means, and an evaporator are connected in sequence and a non-azeotropic mixed refrigerant circulates as a refrigerant. a bypass path connected in parallel to the liquid side piping connecting the inflow side of the evaporator; a refrigerant storage means provided in the bypass path; a flow rate adjustment means for adjusting the amount of refrigerant flowing into the refrigerant storage means; It has an inlet temperature detection means for detecting the refrigerant inlet temperature, which is the temperature of the refrigerant flowing into the evaporator, and a control means for controlling the pressure reduction means and the flow rate adjustment means. This is a refrigeration cycle device that controls a flow rate adjusting means to adjust the amount of gas-liquid two-phase refrigerant flowing into an evaporator.

According to the present invention, it is possible to provide a refrigeration cycle device that uses a non-azeotropic mixed refrigerant and can suppress frost formation on the evaporator.

1 is a refrigeration circuit diagram of an air conditioner according to an embodiment of the present invention. FIG. 3 is a Mollier diagram showing a state in which no refrigerant is stored in the refrigerant storage means in the air conditioner according to the embodiment of the present invention. FIG. 3 is a control flow diagram of the air conditioner according to the embodiment of the present invention. It is an explanatory view showing the state of a refrigerant storage means in an air conditioner concerning an embodiment of the present invention. It is an explanatory view showing the state of a refrigerant storage means in an air conditioner concerning an embodiment of the present invention. It is an explanatory view showing the state of a refrigerant storage means in an air conditioner concerning an embodiment of the present invention. It is an explanatory view showing the state of a refrigerant storage means in an air conditioner concerning an embodiment of the present invention. FIG. 2 is a Mollier diagram showing a state in which refrigerant is stored in the refrigerant storage means in the air conditioner according to the embodiment of the present invention. FIG. 3 is a refrigeration circuit diagram of an air conditioner according to another embodiment of the present invention.

Below, embodiments of the refrigeration cycle device according to the present invention will be described in detail based on the drawings. Note that the present invention is not limited to this embodiment.

An air conditioner 1 that is an embodiment of a refrigeration cycle device according to the present invention will be described. FIG. 1 is a refrigeration circuit diagram of an air conditioner 1 according to this embodiment. FIG. 2 is a Mollier diagram in a state where no refrigerant is stored in the receiver 22, which will be described later, in the air conditioner 1 of this embodiment.

With reference to FIG. 1, an air conditioner 1 according to the present embodiment will be described. FIG. 1 shows a refrigerant circuit diagram of an air conditioner 1 in this embodiment. The air conditioner 1 includes a refrigerant circuit 2 and a control unit 3, and is capable of cooling operation and heating operation. In the refrigerant circuit 2, a non-azeotropic mixed refrigerant circulates as a refrigerant. The non-azeotropic mixed refrigerant is, for example, a mixed refrigerant of R32 and R1234yf. The refrigerant circuit 2 includes an outdoor unit 11 placed outdoors and an indoor unit 5 placed indoors. The outdoor unit 11 includes a compressor 12 connected by a refrigerant pipe 4, a four-way valve 15, an outdoor heat exchanger 13, and an expansion valve 14 as a pressure reducing means. The indoor unit 5 includes an indoor heat exchanger 7 connected to the refrigerant pipe 4. A bypass passage 17, which will be described later, is connected in parallel to the refrigerant pipe 4 that connects the indoor heat exchanger 7 and the outdoor heat exchanger 13. The outdoor unit 11 includes a blower (not shown) for sending outside air to the outdoor heat exchanger 13 , and the indoor unit 5 includes an indoor fan (not shown) for sending indoor air to the indoor heat exchanger 7 . The four-way valve 15 is a switching valve that is connected to the discharge side of the compressor 12 and changes the flow direction of the refrigerant circulating through the refrigerant circuit 2 between cooling operation and heating operation. During cooling operation, refrigerant discharged from the compressor 12 flows through the four-way valve 15 to the outdoor heat exchanger 13, the expansion valve 14, the indoor heat exchanger 7, the four-way valve 15, and the suction side of the compressor 12. During heating operation, refrigerant discharged from the compressor 12 flows through the four-way valve 15 to the indoor heat exchanger 7, the expansion valve 14, the outdoor heat exchanger 13, the four-way valve 15, and the suction side of the compressor 12.

The flow of refrigerant in the refrigerant circuit 2 during heating operation will be explained. In FIG. 1, solid arrows indicate the flow of refrigerant during heating operation. During heating operation, the gas refrigerant, which has been compressed by the compressor 12 and has become high temperature and high pressure, flows through the indoor heat exchanger 7 via the four-way valve 15. The high-temperature, high-pressure gas refrigerant flowing through the indoor heat exchanger 7 exchanges heat with indoor air blown by the indoor fan, radiates heat, and condenses to become a high-temperature, high-pressure liquid refrigerant. The indoor air is heated by exchanging heat with the high-temperature, high-pressure gas refrigerant. The liquid refrigerant that has passed through the indoor heat exchanger 7 and radiated heat is reduced in pressure by the expansion valve 14 and becomes a low-temperature, low-pressure gas-liquid two-phase refrigerant. The low-temperature, low-pressure gas-liquid two-phase refrigerant flows through the outdoor heat exchanger 13, and as it passes through the outdoor heat exchanger 13, it exchanges heat with the outside air blown by the blower, absorbs heat from the outside air, and evaporates, resulting in low-temperature, low-pressure refrigerant. becomes a gas refrigerant. The gas refrigerant that has absorbed heat returns to the compressor 12 via the four-way valve 15 and is again compressed to high temperature and high pressure.

The flow of refrigerant in the refrigerant circuit 2 during cooling operation will be explained. The flow of refrigerant during cooling operation is the opposite of that during heating operation. In FIG. 1, broken arrows indicate the flow of refrigerant during cooling operation. During cooling operation, the gas refrigerant, which has been compressed by the compressor 12 and becomes high temperature and high pressure, flows through the outdoor heat exchanger 13 via the four-way valve 15. The high-temperature, high-pressure gas refrigerant flowing through the outdoor heat exchanger 13 exchanges heat with the outside air blown by the outdoor fan, radiates heat, and condenses to become a high-temperature, high-pressure liquid refrigerant. The liquid refrigerant that has passed through the outdoor heat exchanger 13 and radiated heat is reduced in pressure by the expansion valve 14 and becomes a low-temperature, low-pressure gas-liquid two-phase refrigerant. The low-temperature, low-pressure gas-liquid two-phase refrigerant flows through the indoor heat exchanger 7, and as it passes through the indoor heat exchanger 7, it exchanges heat with the indoor air blown by the blower, and absorbs the heat of the indoor air. It evaporates and becomes a low-temperature, low-pressure gas refrigerant. When the gas-liquid two-phase refrigerant evaporates, it removes heat from the indoor air and cools the indoor air. The gas refrigerant that has absorbed heat from the indoor air returns to the compressor 12 via the four-way valve 15 and is again compressed to high temperature and high pressure.

In the case of heating operation, the indoor heat exchanger 7 functions as a condenser, and the outdoor heat exchanger 13 functions as an evaporator. In the case of cooling operation, the outdoor heat exchanger 13 functions as a condenser, and the indoor heat exchanger 7 functions as an evaporator. The refrigerant pipe 4 that connects the indoor heat exchanger 7 and the outdoor heat exchanger 13 through the expansion valve 14 is a refrigerant pipe that connects the indoor heat exchanger 7 and the outdoor heat exchanger 13 because the liquid refrigerant after condensation flows therethrough. The piping 4 is defined as a liquid side piping 16 in this embodiment.

Next, a characteristic configuration of the refrigerant circuit 2 in this embodiment will be described. A bypass passage 17 is connected in parallel to the liquid side pipe 16 that connects the indoor heat exchanger 7 and the outdoor heat exchanger 13. The bypass path 17 is connected to the liquid side pipe 16 at a first branch part 18 on the indoor heat exchanger 7 side, and is connected to the liquid side pipe 16 at a second branch part 19 on the outdoor heat exchanger 13 side. The expansion valve 14 is arranged between the first branch part 18 and the second branch part 19 of the liquid side pipe 16. A receiver 22 (refrigerant storage means) for storing refrigerant is connected to the bypass path 17. A first flow rate adjustment valve 20 that adjusts the flow rate of the refrigerant flowing through the bypass path 17 is provided between the first branch portion 18 of the bypass path 17 and the receiver 22 . The first flow rate regulating valve 20 can also function as an expansion valve. A second flow rate regulating valve 21 that adjusts the opening degree of the bypass passage 17 is provided between the second branch portion 19 of the bypass passage 17 and the receiver 22 . The first flow rate adjustment valve 20 and the second flow rate adjustment valve 21 serve as flow rate adjustment means for adjusting the amount of refrigerant flowing into the receiver 22. Note that the second flow rate regulating valve 21 can also function as an expansion valve. An inlet temperature sensor 25 is arranged on the outdoor heat exchanger 13 side of the liquid side pipe 16 to detect the temperature of the refrigerant inlet flowing into the outdoor heat exchanger 13. The inlet temperature sensor 25 is an inlet temperature detection means in the present invention. In this embodiment, during heating operation, in the refrigerant circuit 2, the compressor 12, the four-way valve 15, the indoor heat exchanger 7, the expansion valve 14 in the liquid side pipe 16, the outdoor heat exchanger 13, the four-way valve 15, the compressor 12 The circuit composed of the following is referred to as the main circuit 8.

Next, the state of the refrigerant in the refrigerant circuit 2 will be explained with reference to the Mollier diagram in FIG. 2. The Mollier diagram in FIG. 2 is a Mollier diagram during heating operation. Symbols O to R shown in FIG. 2 indicate the following states. O is the state of the refrigerant before it passes through the outdoor heat exchanger 13 and is sucked into the compressor 12. P is the state of the refrigerant before it is compressed by the compressor 12 and flows into the indoor heat exchanger 7. Q is the state of the refrigerant before it passes through the indoor heat exchanger 7, condenses, and passes through the expansion valve 14. R is the state of the refrigerant before it passes through the expansion valve 14 and flows into the outdoor heat exchanger 13. The broken lines are isothermal lines, the lower broken line indicates 0°C, and the upper broken line indicates the outside temperature of 10°C.

In the refrigerant circuit 2 used in the air conditioner 1 of this embodiment, a non-azeotropic mixed refrigerant circulates as a refrigerant. Therefore, in the case of a single refrigerant, if the pressure is constant within the saturated region, the temperature will also be constant, but with a non-azeotropic mixed refrigerant, even within the saturated region, there will be an isothermal line as shown by the broken line in Figure 2. Even if the pressure is constant, the temperature changes. When the heating operation is started, as shown in FIG. 2, the temperature of the refrigerant before passing through the expansion valve 14 and flowing into the outdoor heat exchanger 13 is -2°C, which is lower than 0°C. Further, the temperature of the refrigerant passing through the outdoor heat exchanger 13 is 6°C, and the difference from the outside temperature of 10°C is 4°C. If the heating operation continues in this state, frost will likely form at the refrigerant inlet of the outdoor heat exchanger 13. In order to avoid frost formation at the refrigerant inlet of the outdoor heat exchanger 13, if the opening degree of the expansion valve 14 is controlled to be large, the temperature of the refrigerant before it flows into the outdoor heat exchanger 13 can be increased. . However, in that case, the temperature of the refrigerant passing through the outdoor heat exchanger 13 also rises, making it impossible to create a sufficient temperature difference from the outside air temperature. Therefore, in order to improve the heating capacity, it is necessary to increase the temperature difference between the refrigerant temperature and the outside air temperature on the refrigerant outlet side of the outdoor heat exchanger 13 as well. Therefore, in this embodiment, the control unit 3 performs the following control.

FIG. 3 is a control flow diagram. First, as an initial state at the start of heating operation, the first flow rate adjustment valve 20 and the second flow rate adjustment valve 21 are closed (ST1). Therefore, during heating operation, all the refrigerant that has passed through the indoor heat exchanger 7 that functions as a condenser passes through the expansion valve 14, and the refrigerant that has passed through the expansion valve 14 and has become low temperature and low pressure is transferred to the outdoor heat exchanger that functions as an evaporator. 13. When the heating operation continues from the initial state at the start of the heating operation, the temperature of the refrigerant flowing into the outdoor heat exchanger 13 becomes -2° C. as shown in FIG. 2. Next, the temperature of the refrigerant immediately before flowing into the outdoor heat exchanger 13 (inlet temperature) is detected based on the inlet temperature sensor 25, and it is determined whether the inlet temperature is higher than a predetermined value (ST2). In this embodiment, the predetermined value is -1°C (minus 1°C). The predetermined value is set to -1°C because if the refrigerant continues to flow into the outdoor heat exchanger 13 at -1°C, there is a high possibility that frost will form on the inlet side of the outdoor heat exchanger 13. Since the temperature of the refrigerant flowing into the outdoor heat exchanger 13 is -2°C, the inlet temperature is below the predetermined value of -1°C.

Next, when the inlet temperature falls below the predetermined value of -1°C (N in ST2), the control unit 3 opens the first flow rate adjustment valve 20 and the second flow rate adjustment valve 21 to increase the amount of refrigerant circulating through the main circuit 8. is adjusted to perform refrigerant amount adjustment control to adjust the amount of refrigerant flowing into the outdoor heat exchanger 13 (ST3). At this time, the opening degree of the first flow rate adjustment valve 20 is made larger than the opening degree of the second flow rate adjustment valve 21. As a result, the refrigerant that has passed through the indoor heat exchanger 7 and flowed through the liquid side piping 16 flows into the bypass passage 17 and accumulates in the receiver 22, so that the amount of refrigerant circulating through the main circuit 8 is reduced. When the amount of refrigerant circulating through the main circuit 8 decreases, the refrigerant pressure in the indoor heat exchanger 7 decreases and the condensing temperature decreases. When the condensation temperature decreases, the temperature difference between indoor air becomes smaller, and therefore the enthalpy difference during the condensation process becomes smaller. FIG. 5 is a Mollier diagram showing a state in which refrigerant is stored in the receiver 22. When the refrigerant amount adjustment control is performed from the heating operation state shown in FIG. 2, the enthalpy of the refrigerant in the refrigerant expansion process indicated by Q and R moves to the right. That is, the enthalpy difference between the condensation process and the evaporation process is reduced. Therefore, by performing the refrigerant amount adjustment control, the enthalpy difference is reduced, so that the refrigerant inlet temperature, which was -2°C during heating operation, becomes 0°C. Note that the refrigerant amount adjustment control may be a control in which the first flow rate adjustment valve 20 is opened and the second flow rate adjustment valve 21 is closed. However, in order to quickly store the refrigerant in the receiver 22, it is desirable that the refrigerant flow through the liquid side piping 16 in the main circuit 8 more easily than through the bypass path 17, so while gradually opening the second flow rate regulating valve 21, It is desirable to gradually reduce the opening degree of the expansion valve 14.

Next, the control unit 3 determines whether the degree of dryness of the refrigerant on the outlet side of the indoor heat exchanger 7 exceeds a predetermined value (for example, 0.2) (ST4). The degree of dryness is calculated based on the refrigerant pressure and refrigerant temperature on the outlet side of the indoor heat exchanger 7. The refrigerant pressure and refrigerant temperature on the outlet side of the indoor heat exchanger 7 are detected by an outlet pressure sensor 26 and an outlet temperature sensor 27 provided on the outlet side of the indoor heat exchanger 7. Dryness is the proportion of the amount of gas phase refrigerant in a refrigerant in a gas-liquid two-phase state, and in the Mollier diagram, the dryness approaches 1 as it approaches the saturated vapor line on the right, and approaches the saturated liquid line on the left. As time goes by, it approaches 0. In the case of a single refrigerant, if the pressure is constant within the saturated region, the temperature is also constant, so dryness cannot be determined from pressure and temperature alone, but in the case of a non-azeotropic mixed refrigerant, within the saturated region, It can be determined because the isotherm line is sloped.

If the degree of dryness exceeds the predetermined value of 0.2 (Y in ST4), the control unit 3 makes the opening degree of the first flow rate regulating valve 20 smaller than the opening degree of the second flow rate regulating valve 21 (ST5). . Alternatively, control may be performed in which the first flow rate adjustment valve 20 is fully closed and the second flow rate adjustment valve 21 is fully opened. If the degree of dryness exceeds the predetermined value of 0.2, the ratio of gas phase refrigerant flowing into the expansion valve 14 increases, resulting in a decrease in controllability of the expansion valve and an increased risk of generating refrigerant noise. Therefore, the control shown in step ST5 is performed. As a result, the refrigerant accumulated in the receiver 22 returns to the main circuit 8 side, and the amount of refrigerant circulating through the main circuit 8 increases. When the amount of refrigerant circulating through the main circuit 8 increases, the refrigerant pressure in the indoor heat exchanger 7 increases, and the condensing temperature increases. As the condensation temperature rises, the temperature difference in the indoor air increases, which increases the enthalpy difference during the condensation process.

Next, the control from step ST2 to step ST3 described above will be explained in more detail using FIGS. 4A to 4D.

FIG. 4A shows a state in which heating operation has started. When the heating operation is started, the first flow rate regulating valve 20 and the second flow rate regulating valve 21 are closed, so that the refrigerant does not pass through the bypass path 17 but entirely passes through the liquid side pipe 16. In this state, the state is as shown in the Mollier diagram shown in FIG. 2, and the temperature of the refrigerant before passing through the expansion valve 14 and flowing into the outdoor heat exchanger 13 is -2°C, which is lower than 0°C. It is in a state.

When the control unit 3 determines that the temperature of the refrigerant before flowing into the outdoor heat exchanger 13 is below the predetermined value of -1°C, the control unit 3 closes the first flow rate adjustment valve 20 and the second flow rate adjustment valve as shown in FIG. 4B. Open valve 21. By opening the first flow rate adjustment valve 20 and the second flow rate adjustment valve 21, the amount of refrigerant flowing into the outdoor heat exchanger 13 increases, and the refrigerant sucked into the compressor 12 becomes slightly moist, making the compressor 12 reliable. There is a risk of lowering sexuality. However, since the opening degree of the expansion valve 14 is restricted by control (for example, target discharge temperature control) that maintains the state of the refrigerant sucked into the compressor 12 in an appropriate state, a decrease in reliability can be suppressed. At this time, the opening degree of the first flow rate adjustment valve 20 is made larger than the opening degree of the second flow rate adjustment valve 21. With this control, the refrigerant flowing through the refrigerant circuit 2 flows into the bypass path 17 side. Further, since the opening degree of the first flow rate adjustment valve 20 is made larger than the opening degree of the second flow rate adjustment valve 21, the refrigerant is stored in the receiver 22.

Next, when the degree of dryness exceeds the predetermined value of 0.2 (Y in ST4 in FIG. 3), the control unit 3 adjusts the opening degree of the first flow rate regulating valve 20 to the second flow rate, as shown in FIG. 4C. The opening degree of the valve 21 should be smaller than that of the valve 21. At this time, the opening degree of the first flow rate regulating valve 20 is made smaller than the opening degree of the expansion valve 14. In this case, it is assumed that valves having the same diameter are used as the first flow rate regulating valve 20, the second flow rate regulating valve 21, and the expansion valve 14. When using valves of different diameters, the second flow rate adjustment means 21 is equipped with a sensor for detecting the temperature of the refrigerant flowing out of the second flow rate adjustment means 21 and a sensor for detecting the temperature of the refrigerant flowing out of the expansion valve 14. The opening degree is controlled so that the temperature of the refrigerant that flows out is low. This control prevents the flow rate of refrigerant flowing through the main circuit 8 from decreasing too much.

Next, when the temperature of the refrigerant before flowing into the outdoor heat exchanger 13 becomes higher than a predetermined value of −1° C., the control unit 3 controls the first flow rate regulating valve 20 and the second flow rate control valve as shown in FIG. 4D. Close the regulating valve 21. As a result, the amount of refrigerant circulating through the refrigerant circuit 2 becomes smaller than when the temperature of the refrigerant flowing into the outdoor heat exchanger 13 during heating operation is -2°C. Therefore, the enthalpy of the refrigerant during the expansion process of the refrigerant can be moved to the right.

Next, an air conditioner 40 that is another embodiment will be described using FIG. 6. The difference between the air conditioner 1 of the first embodiment and the air conditioner 40 of other embodiments is that a gas-liquid separator 32 is used instead of the receiver 22, and a first three-way valve is used instead of the first flow rate regulating valve 20. 30, except that the second expansion valve 31 is used instead of the second flow rate adjustment valve 21, and the other points are the same. The same reference numerals are used for common configurations, and explanations of the common configurations are omitted.

A characteristic configuration of the refrigerant circuit 2 in the air conditioner 40 in another embodiment will be described. A bypass passage 17 is connected in parallel to the liquid side pipe 16 that connects the indoor heat exchanger 7 and the outdoor heat exchanger 13. The bypass path 17 is connected to the liquid side piping 16 at the first three-way valve 30 on the indoor heat exchanger 7 side, and connected to the liquid side piping 16 on the outdoor heat exchanger 13 side. The expansion valve 14 is arranged between the first three-way valve 30 of the liquid side pipe 16 and the indoor heat exchanger 7. The bypass passage 17 includes a gas-liquid separator 32 for separating the refrigerant into a liquid-phase refrigerant and a gas-phase refrigerant and storing the liquid-phase refrigerant, and a gas-liquid separator 32 disposed closer to the outdoor heat exchanger 13 than the gas-liquid separator 32. The second expansion valve 31 is connected thereto. Note that the second expansion valve 31 allows the refrigerant to flow from the bypass path 17 side to the liquid side piping 16 side. The gas-liquid separator 32 may be a refrigerant storage means having a gas-liquid separation function. The first three-way valve 30 and the second expansion valve 31 serve as flow rate adjusting means for adjusting the amount of refrigerant flowing into the gas-liquid separator 32.

Next, control of the air conditioner 40 in another embodiment will be described. First, as an initial state at the start of heating operation, the first three-way valve 30 is switched to a state in which the refrigerant that has passed through the expansion valve 14 does not flow to the bypass path 17 side. Further, the opening degree of the second expansion valve 31 is in a fully closed state. Therefore, the refrigerant that has passed through the indoor heat exchanger 7 and the expansion valve 14 and has become low temperature and low pressure flows through the liquid side pipe 16 into the outdoor heat exchanger 13 that functions as an evaporator. When the heating operation continues from the initial state at the start of the heating operation, the temperature of the refrigerant flowing into the outdoor heat exchanger 13 becomes -2° C. as shown in FIG. 2. Next, the temperature of the refrigerant just before it flows into the outdoor heat exchanger 13 (inlet temperature) is detected based on the inlet temperature sensor 25, and it is determined whether the inlet temperature is higher than a predetermined value. In this embodiment, the predetermined value is -1°C (minus 1°C). The predetermined value is set to -1°C because if the refrigerant continues to flow into the outdoor heat exchanger 13 at -1°C, there is a possibility that frost will form on the inlet side of the outdoor heat exchanger 13. Since the temperature of the refrigerant flowing into the outdoor heat exchanger 13 is -2°C, the inlet temperature of the outdoor heat exchanger 13 is below the predetermined value of -1°C.

Next, when the inlet temperature falls below the predetermined value of −1° C., the control unit 3 fully opens the expansion valve 14 so that the refrigerant that has passed through the expansion valve 14 flows to the bypass path 17 side. Switch the three-way valve 30. Further, the control unit 3 controls the opening degree of the second expansion valve 31 from a fully closed state to an appropriate opening degree. That is, the second expansion valve 31 takes over the process of expanding the refrigerant, which was performed by the expansion valve 14. Thereby, the refrigerant that has passed through the expansion valve 14 flows into the bypass path 17 and then into the gas-liquid separator 32. The refrigerant that has flowed into the gas-liquid separator 32 is separated into a gas-phase refrigerant and a liquid-phase refrigerant, and the liquid-phase refrigerant accumulates in the gas-liquid separator 32, and only the gas-phase refrigerant flows through the liquid side piping 16 and is transferred to the outdoor heat exchanger. 13. This reduces the amount of refrigerant circulating through the refrigerant circuit 2. When the amount of refrigerant circulating through the refrigerant circuit 2 decreases, the refrigerant pressure in the indoor heat exchanger 7 decreases and the condensing temperature decreases. When the condensation temperature decreases, the temperature difference between indoor air becomes smaller, and therefore the enthalpy difference during the condensation process becomes smaller. FIG. 5 is a Mollier diagram showing a state in which liquid phase refrigerant is stored in the gas-liquid separator 32. When the refrigerant amount adjustment control is performed from the heating operation state shown in FIG. 2, the enthalpy of the refrigerant in the refrigerant expansion process indicated by Q and R moves to the right. That is, the enthalpy difference between the condensation process and the evaporation process is reduced. Therefore, by performing the refrigerant amount adjustment control, the enthalpy difference is reduced, so that the refrigerant inlet temperature, which was -2°C during heating operation, becomes 0°C.

Next, the control unit 3 determines whether the degree of dryness of the refrigerant on the outlet side of the indoor heat exchanger 7 exceeds a predetermined value (for example, 0.2). The degree of dryness is calculated based on the refrigerant pressure and refrigerant temperature on the outlet side of the indoor heat exchanger 7. The refrigerant pressure and refrigerant temperature on the outlet side of the indoor heat exchanger 7 are detected by an outlet pressure sensor 26 and an outlet temperature sensor 27 provided on the outlet side of the indoor heat exchanger 7. Dryness is the proportion of the amount of gas phase refrigerant in the refrigerant in the gas-liquid two-phase state.In the Mollier diagram, the dryness approaches 1 as it approaches the dry saturated vapor line on the right, and approaches the saturated liquid line on the left. As it approaches, it approaches 0. In the case of a single refrigerant, if the pressure is constant within the saturated region, the temperature is also constant, so dryness cannot be determined from pressure and temperature alone, but in the case of a non-azeotropic mixed refrigerant, within the saturated region, It can be determined because the isotherm line is sloped.

If the degree of dryness exceeds the predetermined value of 0.2, the first three-way valve 30 is switched to a state in which the refrigerant that has passed through the expansion valve 14 does not flow to the bypass path 17 side. Further, the opening degree of the expansion valve 14 is controlled from a fully open state to an appropriate opening degree. That is, the expansion valve 14 takes over the process of expanding the refrigerant, which was performed by the second expansion valve 31. If the degree of dryness exceeds the predetermined value of 0.2, the ratio of gas phase refrigerant flowing into the expansion valve 14 increases, resulting in a decrease in controllability of the expansion valve and an increased risk of generating refrigerant noise. Therefore, it is necessary to suppress a decrease in the performance of the air conditioner 1. By switching the first three-way valve 30, the refrigerant that has passed through the expansion valve 14 no longer flows to the bypass path 17 side. On the other hand, the high-pressure liquid refrigerant accumulated in the gas-liquid separator 32 returns to the main circuit 8 side, where the pressure has become low due to the pressure reduction by the expansion valve 14, due to the pressure difference, so the amount of refrigerant circulating through the main circuit 8 increases. When the amount of refrigerant circulating through the main circuit 8 increases, the refrigerant pressure in the indoor heat exchanger 7 increases, and the condensing temperature increases. As the condensation temperature rises, the temperature difference in the indoor air increases, which increases the enthalpy difference during the condensation process.

In the embodiments described above, an air conditioner has been described as an example of a refrigeration cycle device using a non-azeotropic refrigerant mixture, but a refrigeration cycle device using a non-azeotropic refrigerant mixture is not limited to an air conditioner. Any refrigeration cycle device equipped with a refrigerant circuit may be used, and for example, a heat pump type water heater installed outdoors may be used.

Although the description has been made with reference to a limited number of embodiments, the scope of rights is not limited thereto, and modifications to the embodiments based on the above disclosure will be obvious to those skilled in the art.

DESCRIPTION OF SYMBOLS 1...Air conditioner, 2...Refrigerant circuit, 3...Control unit, 4...Refrigerant piping, 5...Indoor unit, 7...Indoor heat exchanger, 8...Main circuit, 11...Outdoor unit, 12...Compressor, 13... Outdoor heat exchanger, 14... expansion valve, 15... four-way valve, 16... liquid side piping, 17... bypass path, 18... first branch part, 19... second branch part, 20... first flow rate adjustment valve, 21... Second flow rate adjustment valve, 25... Inlet temperature sensor, 26... Outlet pressure sensor, 27... Outlet temperature sensor, 30... First three-way valve, 31... Second expansion valve, 32... Gas-liquid separator, 40... Air conditioner

Claims

In a refrigeration cycle device equipped with a refrigerant circuit in which a compressor, a condenser, a pressure reducing means, and an evaporator are sequentially connected and a non-azeotropic mixed refrigerant circulates as a refrigerant,
a bypass path connected in parallel to a liquid side pipe connecting the outflow side of the condenser and the inflow side of the evaporator;
a refrigerant storage means provided in the bypass passage;
Flow rate adjustment means for adjusting the amount of refrigerant flowing into the refrigerant storage means;
inlet temperature detection means for detecting a refrigerant inlet temperature that is the temperature of the refrigerant flowing into the evaporator;
control means for controlling the pressure reduction means and the flow rate adjustment means;
The refrigeration cycle device is characterized in that the control means controls the flow rate adjustment means based on the refrigerant inlet temperature of the evaporator to adjust the amount of gas-liquid two-phase refrigerant flowing into the evaporator.
The pressure reducing means is provided between a branch part where the bypass path branches in the liquid side piping and a merging part where the bypass path joins,
The flow rate adjustment means includes a first flow rate adjustment valve that is provided upstream of the refrigerant storage means in the bypass passage and can adjust the opening degree, and a first flow rate adjustment valve that is provided downstream of the refrigerant storage means in the bypass passage and can adjust the opening degree. The refrigeration cycle apparatus according to claim 1, further comprising an adjustable second flow rate regulating valve.
The control means opens the first flow rate adjustment valve when the refrigerant inlet temperature of the evaporator becomes equal to or lower than a predetermined value while the first flow rate adjustment valve and the second flow rate adjustment valve are closed. The second flow rate adjustment valve is maintained in a closed state, or the second flow rate adjustment valve is opened and the opening degree of the first flow rate adjustment valve is made larger than the opening degree of the second flow rate adjustment valve. The refrigeration cycle device according to claim 2.
When the degree of dryness of the refrigerant on the outlet side of the condenser exceeds a predetermined value, the control means closes the first flow rate adjustment valve and opens the second flow rate adjustment valve, or closes the first flow rate adjustment valve. 4. The refrigeration cycle apparatus according to claim 3, wherein the valve is opened and the opening degree of the first flow rate regulating valve is made smaller than the opening degree of the second flow rate regulating valve.
The pressure reducing means is provided upstream of a branch part where the bypass path branches in the liquid side piping,
The flow rate adjustment means is a three-way valve provided at the branch part where the bypass path branches in the liquid side piping or the merging part where the bypass path joins,
The refrigeration cycle device according to claim 1, wherein the refrigerant storage means has a gas-liquid separation function.
The refrigeration cycle device according to claim 5, wherein the control means switches the three-way valve to the bypass path side when the refrigerant inlet temperature of the evaporator becomes equal to or lower than a predetermined value.