Refrigeration cycle and air conditioner

Abstract

[Problem] To provide a refrigeration cycle and an air conditioner that suppress a disproportionation reaction in a non-azeotropic refrigerant mixture containing a refrigerant having a property of causing a disproportionation reaction. [Solution] This refrigeration cycle includes a compressor 103, an indoor heat exchanger 201, and an outdoor heat exchanger 107, and a refrigerant circulates in the refrigeration cycle. The refrigerant is a non-azeotropic refrigerant mixture containing a first refrigerant having a property of causing a disproportionation reaction and a second refrigerant having a property of not causing a disproportionation reaction. When the compressor 103 is stopped, a composition ratio of the first refrigerant in an evaporator-side pipe of the compressor 103 is higher than a composition ratio of the first refrigerant in a discharge-side pipe of the compressor 103, and the refrigeration cycle includes a check valve 103c for preventing backflow of the refrigerant.

Description

Refrigeration cycle and air conditioning device

[0001] The present invention relates to a refrigeration cycle and an air conditioner that suppress the occurrence of a disproportionation reaction.

[0002] In order to reduce the environmental impact, it has been proposed to use a refrigerant with a low global warming potential (GWP) in a refrigeration cycle. In recent years, refrigerant mixtures, particularly non-azeotropic refrigerant mixtures, have attracted attention as low GWP refrigerants.

[0003] Some refrigerants contained in the refrigeration cycle of an air conditioner can undergo disproportionation reactions. When a non-azeotropic refrigerant mixture is used in the refrigeration cycle, the proportion of refrigerants that have the property of causing disproportionation reactions increases in a part of the refrigeration cycle, making the disproportionation reactions more likely to occur.

[0004] In this regard, Japanese Patent No. 6289611 (Patent Document 1) discloses a technology for suppressing the rotation speed of the compressor at the start of the compressor based on a disproportionation reaction pressure value calculated from the discharge gas temperature of the refrigerant discharged from the compressor and the condenser outlet temperature of the refrigerant flowing out of a first heat exchanger functioning as a condenser. According to Patent Document 1, a refrigeration cycle apparatus is provided that enables safe operation even when using a working refrigerant whose main component is a refrigerant that has the property of causing a disproportionation reaction.

[0005] However, in Patent Document 1, if the pressure and temperature are not sufficiently reduced by suppressing the compressor rotation speed, the disproportionation reaction cannot be suppressed. For example, in the case of a scroll compressor, regardless of the rotation speed, the refrigerant drawn in at the suction pressure is compressed to the discharge pressure based on the compression ratio set by the scroll tooth profile, making the disproportionation reaction more likely to occur. Furthermore, suppressing the rotation speed reduces the amount of refrigerant circulating, which reduces the efficiency of air conditioning.

[0006] Therefore, there is a need for a new technique to suppress the disproportionation reaction.

[0007] Patent No. 6289611

[0008] The present invention has been made in consideration of the above-mentioned problems in the conventional technology, and an object of the present invention is to provide a refrigeration cycle and an air conditioner that suppress disproportionation reactions in a non-azeotropic refrigerant mixture that contains a refrigerant that has the property of causing a disproportionation reaction.

[0009] That is, according to the present invention, there is provided a refrigeration cycle comprising a compressor, an evaporator, and a condenser, and in which a refrigerant circulates, wherein the refrigerant is a non-azeotropic refrigerant mixture containing a first refrigerant having a property of causing a disproportionation reaction and a second refrigerant having a property of not causing a disproportionation reaction, wherein when the compressor is stopped, the composition ratio of the first refrigerant in the evaporator-side piping of the compressor is higher than the composition ratio of the first refrigerant in the discharge-side piping, and the refrigeration cycle comprises a check valve for preventing backflow of the refrigerant.

[0010] According to the present invention, it is possible to provide a refrigeration cycle and an air conditioner that suppress disproportionation reactions in a non-azeotropic refrigerant mixture containing a refrigerant that has the property of causing a disproportionation reaction.

[0011] The present invention relates to an air conditioner, a refrigerant cycle, and a compressor, and a check valve for the air conditioner.

[0012] The present invention will be described below with reference to embodiments, but the present invention is not limited to the embodiments described below. In the drawings referred to below, the same reference numerals will be used for common elements, and their description will be omitted as appropriate.

[0013] 1 is a diagram showing the schematic configuration of an air conditioner 1 of this embodiment. The air conditioner 1 of this embodiment is mainly composed of an outdoor unit 100 and an indoor unit 200. The outdoor unit 100 is composed of a four-way valve 101, an accumulator 102, a compressor 103, an oil separator 104, a solenoid valve 105, a discharge check valve 106, an outdoor heat exchanger 107, an outdoor fan 108, a cooling expansion valve 109, a receiver 110, and a heating expansion valve 111. The indoor unit 200 is composed of an indoor heat exchanger 201 and an indoor fan 202.

[0014] The operation of the refrigeration cycle in this embodiment will now be described with reference to Fig. 1. The following description will be made taking the refrigeration cycle when the air conditioning apparatus 1 is in cooling operation as an example. The solid arrows in Fig. 1 indicate the flow of refrigerant during cooling operation, and the solid lines in the four-way valve 101 indicate the connection relationship of the refrigerant path during cooling operation. Therefore, when the air conditioning apparatus 1 is in heating operation, the refrigerant flows in the direction opposite to the arrows in Fig. 1, and the connection of the refrigerant path in the four-way valve 101 is also indicated by the dashed lines.

[0015] When the air conditioner 1 is in cooling operation, low-temperature, low-pressure liquid refrigerant flows from the outdoor unit 100 into the indoor unit 200. The low-temperature refrigerant that has flowed into the indoor unit 200 flows into the indoor heat exchanger 201. The indoor heat exchanger 201 operates as an evaporator during cooling operation, exchanging heat between the low-temperature, low-pressure liquid refrigerant and air blown by the indoor fan 202. The indoor unit 200 can lower the temperature of the indoor space by discharging the air that has undergone heat exchange. The refrigerant that has undergone heat exchange and flows out of the indoor heat exchanger 201 is a mixture of low-temperature, low-pressure gas refrigerant and liquid refrigerant, and flows to the outdoor unit 100 through a refrigerant pipe.

[0016] The refrigerant that flows into the outdoor unit 100 flows through a four-way valve 101 to an accumulator 102. The accumulator 102 is installed on the suction side of a compressor 103 and separates the refrigerant into gas and liquid. By providing the accumulator 102, liquid compression in the compressor 103 is prevented, and the dryness of the refrigerant drawn into the compressor 103 is appropriately adjusted.

[0017] The refrigerant then flows from the accumulator 102 to the compressor 103. The low-temperature, low-pressure gas refrigerant is compressed in the compressor 103 and discharged as high-temperature, high-pressure gas refrigerant. A portion of the refrigerant discharged from the compressor 103 flows to the bypass circuit side including the solenoid valve 105 and flows to the accumulator 102. The solenoid valve 105 can control the amount of refrigerant flowing through the bypass circuit.

[0018] The refrigerant discharged from the compressor 103 flows into the oil separator 104, where the refrigerant is separated from the oil. The oil separated in the oil separator 104 passes through the path indicated by the dashed line in the direction of the dashed arrow in Fig. 1 and is returned to the oil reservoir of the compressor 103.

[0019] The refrigerant separated in the oil separator 104 flows into the outdoor heat exchanger 107 via the discharge check valve 106 and the four-way valve 101. In the outdoor heat exchanger 107, heat is exchanged between the refrigerant flowing therethrough and the outside air sent in by the outdoor fan 108. During cooling operation, the outdoor heat exchanger 107 operates as a condenser, and discharges the refrigerant as a high-temperature liquid through heat exchange. During heating operation, the outdoor heat exchanger 107 operates as an evaporator.

[0020] The liquid refrigerant, now at a high temperature, is expanded in volume by the cooling expansion valve 109, and its temperature is reduced by being decompressed. The cooled refrigerant is temporarily stored in the receiver 110, and then flows into the indoor unit 200.

[0021] The air conditioner 1 can perform air conditioning by a refrigeration cycle in which a refrigerant circulates as shown in FIG.

[0022] Next, the refrigerant used in this embodiment will be described. In recent years, from the viewpoint of reducing environmental impact, there has been a demand for the use of refrigerants with low global warming potential (GWP). Examples of next-generation low-GWP refrigerants include R1234yf, R1132(E), and R1123. Refrigeration cycles using mixtures of these refrigerants have also been developed, and this embodiment uses a non-azeotropic refrigerant mixture.

[0023] A non-azeotropic refrigerant mixture is a mixture of multiple refrigerants, and refers to a refrigerant that has the properties of a simple mixture of refrigerants, with the dew point and boiling point of each refrigerant being separate across the entire composition range. When a non-azeotropic refrigerant mixture is used in a refrigeration cycle, the composition constantly fluctuates within the refrigeration cycle. For example, the composition ratio of a certain refrigerant may be high at one position in the refrigeration cycle and low at another position. Therefore, it is preferable to lower the composition of refrigerants that may cause disproportionation reactions near energy sources that may trigger disproportionation reactions.

[0024] FIG. 2 is a diagram illustrating the composition of the non-azeotropic refrigerant mixture included in the refrigeration cycle of this embodiment. FIG. 2 shows a mixed refrigerant of R1132(E) and R1234yf as an example of the non-azeotropic refrigerant mixture used in this embodiment. The composition of the non-azeotropic refrigerant mixture used in this embodiment is assumed to be R% (R<50) of R1132(E) and (100-R)% of R1234yf. The composition of the non-azeotropic refrigerant mixture can be set arbitrarily, but from the perspective of suppressing disproportionation reactions, it is preferable to set the refrigerant that can cause disproportionation reactions (R1132(E) in the example of FIG. 2) to 50% or less and the refrigerant that does not cause disproportionation reactions (R1234yf in the example of FIG. 2) to 50% or more. Examples of refrigerants that do not cause disproportionation reactions include R1234yf and R1234ze, but this does not particularly limit the embodiment.

[0025] A refrigerant obtained by mixing R1132(E) and R1234yf at ratios of 31.5% (±2%) and 68.5% (±2%), respectively, is sometimes referred to as R474B. In the embodiment described below, R474B is used as a non-azeotropic refrigerant mixture, but this does not limit the embodiment. Therefore, a non-azeotropic refrigerant mixture other than R474B may also be used.

[0026] In R474B, R1234yf is more likely to liquefy than R1132(E). When R474B, a mixture of R1132(E) and R1234yf, is used in a refrigeration cycle, the refrigerant separates into gas and liquid phases. As shown in Figure 2, the mixture ratio (R) of R1132(E) in the liquid phase region becomes higher than the mixture ratio (R) in the initial state.Ｌ ) is lower, and the mixture ratio (R Ｇ ) is higher. That is, as shown in FIG. Ｇ >R>R Ｌ The relationship is as follows.

[0027] Incidentally, gas-phase R1132(E) is prone to disproportionation reactions. Therefore, it is preferable that the ratio of gas-phase R1132(E) is low near an energy source that can trigger a disproportionation reaction, i.e., an energy source that can cause an explosive reaction. In a refrigeration cycle, an example of an energy source that can trigger a disproportionation reaction is a short circuit of the copper wire that forms the motor winding of the compressor 103. In particular, when a gas refrigerant with a high mixing ratio of R1132(E) flows into the compressor 103, it is compressed to high pressure in the compression chamber, making the disproportionation reaction more likely to occur. Therefore, it is preferable to prevent a gas refrigerant with a high mixing ratio of R1132(E) from flowing into the compression chamber.

[0028] Therefore, in this embodiment, a check valve is provided to suppress the unintended inflow of gas refrigerant and make the disproportionation reaction less likely to occur. The configuration of the compressor 103 in this embodiment will be described below with reference to FIG. 3. FIG. 3 is a cross-sectional view showing the configuration of the compressor 103 in this embodiment. FIG. 3(A) shows a cross-sectional view of the entire compressor 103, and FIG. 3(B) shows an enlarged cross-sectional view of a portion of the compressor 103. Note that the following description will be given taking a scroll-type driven compressor 103 as an example.

[0029] As shown in Fig. 3A, the compressor 103 compresses the refrigerant drawn in through a refrigerant suction pipe 103a in a compression chamber and discharges the refrigerant as a high-temperature, high-pressure gas refrigerant from a refrigerant discharge pipe 103b. The arrows in Fig. 3A indicate the flow of the refrigerant.

[0030] Fig. 3(B) is an enlarged view of the area indicated by the dashed rectangle in Fig. 3(A). As shown in Fig. 3(B), the compressor 103 in this embodiment is provided with a check valve 103c in a refrigerant suction pipe 103a.

[0031] Since refrigerant with excessively high temperature and pressure is prone to disproportionation reactions, the disproportionation reactions can be suppressed by preventing an increase in the R1132(E) mixture ratio. In particular, if a refrigerant with a high R1132(E) mixture ratio flows into the compression chamber or the sealed container while the compressor 103 is stopped, the disproportionation reactions are likely to occur when the compressor 103 is started. Therefore, in this embodiment, the disproportionation reactions are suppressed by providing a check valve 103c in the refrigerant suction pipe 103a.

[0032] Fig. 4 is a diagram showing the configuration of the check valve 103c in this embodiment. Fig. 4 is an enlarged view of the area indicated by the dashed rectangle in Fig. 3(B). Fig. 4(A) shows the state of the check valve 103c when the compressor 103 is operating, and Fig. 4(B) shows the state of the check valve 103c when the compressor 103 is stopped.

[0033] The check valve 103c of this embodiment is mainly composed of a valve base 401, a valve spring 402, and a seal member 403. The valve base 401 of this embodiment is made of a metal material such as stainless steel (SUS), and the seal member 403 is fixed to it. The seal member 403 of this embodiment is provided on the end face of the refrigerant suction tube 103a and is made of a resin material. By using this material, the seal member 403 can be tightly attached to the refrigerant suction tube 103a when they come into contact with each other, thereby preventing refrigerant from flowing in.

[0034] When the compressor 103 is operating, as shown in Fig. 4A, the check valve 103c is pushed down by the refrigerant being drawn in, creating a gap between the refrigerant suction pipe 103a and the seal member 403. Therefore, the refrigerant is drawn in through the path indicated by the arrows in Fig. 4A and introduced into the compression chamber.

[0035] Furthermore, when the compressor 103 is stopped, the check valve 103c of this embodiment contacts the refrigerant suction pipe 103a and the seal member 403 due to the force of the valve spring 402 expanding, as shown in FIG. 4B , thereby blocking the refrigerant path. In this way, the check valve 103c operates while the compressor 103 is stopped, closing the path through which refrigerant flows into the compression chamber and the enclosed space of the compressor 103, thereby suppressing disproportionation reactions. That is, when the compressor 103 is stopped, a liquid-phase non-azeotropic refrigerant mixture accumulates on the evaporator side (the refrigerant suction pipe 103a side), and the gas phase contains a high ratio of R1132(E), which is prone to disproportionation reactions. At this time, the check valve 103c prevents the gas-phase refrigerant on the evaporator side from flowing into the compression chamber and the enclosed space of the compressor 103 due to the pressure difference between the evaporator side and the condenser side when the compressor 103 is stopped. Therefore, the composition ratio of R1132(E) in the evaporator-side piping of compressor 103 becomes higher than the composition ratio of R1132(E) in the discharge-side piping, and when compressor 103 starts operating again, it is possible to prevent the gas refrigerant from being compressed in the compression chamber with a high R1132(E) mixture ratio, thereby suppressing the disproportionation reaction. When compressor 103 starts operating, the liquid phase on the evaporator side decreases as operation progresses, and the mixture ratio of R1132(E), which is prone to cause disproportionation reactions in the gas phase, decreases.

[0036] 3, the embodiment has been described using a scroll compressor 103 as an example, but the present invention is not limited to the scroll compressor, and a rotary compressor 103, for example, may also be used. In the case of the rotary compressor 103, a discharge valve is provided in the compression mechanism, and the discharge valve also functions as a check valve. By providing a discharge valve in the compression mechanism, it is possible to prevent the inflow of gas refrigerant with a high mixture ratio of R1132(E), which is prone to disproportionation reactions, from the evaporator, thereby suppressing the disproportionation reaction of the non-azeotropic refrigerant mixture.

[0037] Furthermore, the location where the check valve 103c is provided is not limited to the refrigerant suction pipe 103a or the refrigerant discharge pipe 103b of the compressor 103, and a discharge check valve 106 may be provided as a component constituting the refrigeration cycle, as shown in Fig. 1. By providing the discharge check valve 106 between the compressor 103 and the condenser (or the outdoor heat exchanger 107 in the case of cooling operation), it is possible to prevent the inflow of gas refrigerant with a high mixture ratio of R1132(E), which is prone to disproportionation reactions, from the evaporator, and to suppress the disproportionation reactions of the non-azeotropic refrigerant mixture.

[0038] Furthermore, in order to efficiently suppress the disproportionation reaction, in addition to providing the check valve 103c, the degree of superheat of the refrigerant flowing into the compressor 103 may be set to 0 Kelvin or higher. By setting the degree of superheat of the refrigerant to 0 Kelvin or higher, the proportion of liquid phase on the evaporator side can be reduced, and the mixing ratio of gas phase R1132(E) can be lowered. In a preferred embodiment, in order to adjust the degree of superheat of the refrigerant, for example, the accumulator 102 may be provided with a heater for adjusting the temperature of the refrigerant in the accumulator 102. This allows the degree of superheat of the gas refrigerant flowing into the compressor 103 to be 0 Kelvin or higher, and in combination with the check valve 103c, the disproportionation reaction can be efficiently suppressed.

[0039] According to the embodiments of the present invention described above, it is possible to provide a refrigeration cycle and an air conditioner that suppress disproportionation reactions in a non-azeotropic refrigerant mixture that contains a refrigerant that has the property of causing a disproportionation reaction.

[0040] The present invention has been described above using embodiments, but the present invention is not limited to the above-described embodiments, and any embodiment that can be conceived by a person skilled in the art is included in the scope of the present invention as long as it exhibits the functions and effects of the present invention.

[0041] DESCRIPTION OF SYMBOLS 1...Air conditioner 100...Outdoor unit 101...Four-way valve 102...Accumulator 103...Compressor 103a: Refrigerant suction pipe 103b: Refrigerant discharge pipe 103c: Check valve 104...Oil separator 105...Solenoid valve 106...Discharge check valve 107...Outdoor heat exchanger 108...Outdoor fan 109...Cooling expansion valve 110...Receiver 111...Heating expansion valve 200...Indoor unit 201...Indoor heat exchanger 202...Indoor fan 401...Valve base 402...Valve spring 403...Sealing member

Claims

1. A refrigeration cycle comprising a compressor, an evaporator, and a condenser, in which a refrigerant circulates, wherein the refrigerant is a non-azeotropic refrigerant mixture containing a first refrigerant that has the property of causing a disproportionation reaction and a second refrigerant that does not have the property of causing a disproportionation reaction, wherein when the compressor is stopped, the composition ratio of the first refrigerant in the evaporator-side piping of the compressor is higher than the composition ratio of the first refrigerant in the discharge-side piping, and the refrigeration cycle comprises a check valve that prevents backflow of the refrigerant.

2. The refrigeration cycle according to claim 1, wherein the non-azeotropic refrigerant mixture has a composition of the first refrigerant of 50% or less and a composition of the second refrigerant of 50% or more.

3. The refrigeration cycle according to claim 2, wherein the first refrigerant is R1132(E) and the second refrigerant is R1234yf or R1234ze.

4. The refrigeration cycle according to claim 1, wherein the check valve is provided in a suction pipe of the compressor for the refrigerant.

5. The refrigeration cycle according to claim 4, wherein the check valve is configured so that a seal member contacts the suction pipe via a valve spring.

6. The refrigeration cycle according to claim 5, wherein the portion of the sealing member that comes into contact with the suction pipe is made of a resin material.

7. The refrigeration cycle according to claim 1, wherein the check valve is a discharge check valve provided at a discharge portion of the gas compressed in the compression chamber of the compressor.

8. The refrigeration cycle according to claim 1, wherein the check valve is provided between the compressor and the condenser.

9. The refrigeration cycle according to claim 1, further comprising an accumulator connected to the refrigerant intake side of the compressor and separating the refrigerant into a gas phase and a liquid phase, the accumulator having a heater for adjusting an internal temperature.

10. The refrigeration cycle according to claim 9, wherein the degree of superheat of the gas refrigerant drawn into the compressor is 0 Kelvin or higher when the compressor is started.

11. An air conditioner equipped with the refrigeration cycle according to any one of claims 1 to 10.

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