Refrigeration cycle device

Abstract

[Problem] To further reduce the volume of a heat-absorbing material while preventing the occurrence of a disproportionation reaction in a refrigeration cycle device using a refrigerant that could induce a disproportionation reaction. [Solution] A refrigeration cycle device using a refrigerant that could induce a disproportionation reaction, wherein: the refrigeration cycle device comprises a compressor for compressing refrigerant; a heat absorption member for absorbing heat by means of melting latent heat is disposed in a refrigerant passage through which the refrigerant flows; and the melting point of the heat absorption member is higher than the maximum discharge temperature of the compressor, and is lower than the maximum value of a start temperature at which the refrigerant could induce the disproportionation reaction at a temperature that corresponds to each discharge pressure within a discharge pressure range of the compressor.

Description

Refrigeration Cycle Equipment

[0001] The present invention relates to a refrigeration cycle device.

[0002] Trifluoroethylene (HFO-1123), trans-1,2-difluoroethylene (HFO1132(E)), cis-1,2-difluoroethylene (HFO1132(Z)), and 1,1-difluoroethylene (R1132a), which have unsaturated bonds between carbon atoms within their molecules, are known to have high chemical reactivity due to the intramolecular double bonds. In particular, these refrigerants alone or mixed refrigerants containing these refrigerants at a certain concentration or higher are known to undergo autodecomposition reactions (called disproportionation reactions). Autodecomposition reactions are a phenomenon in which, when a certain amount of energy, such as from a discharge, is applied under high temperature and pressure conditions, the refrigerant decomposes and generates heat, resulting in an explosive reaction. When this autodecomposition reaction occurs, the sudden increase in pressure can cause the location of the autodecomposition reaction within the refrigeration unit to explode, potentially posing a danger to the area around the refrigeration unit.

[0003] On the other hand, these refrigerants and mixed refrigerants containing these refrigerants at a certain concentration or higher have pressure levels similar to the refrigerants R32 and R410A that are widely used in refrigeration equipment such as air conditioners, and compared to HFC refrigerants such as R32 and R410A, the refrigerant molecules are less stable and have a shorter lifespan in the atmosphere, resulting in extremely low ODP (Ozone Depletion Potential) and GWP (Global Warming Potential).

[0004] The Kigali Amendment to the Montreal Protocol, the European F-gas regulations, and Japan's Fluorocarbon Emissions Control Act call for a reduction in GWP beyond that of the refrigerant R32 (GWP 675) used in refrigeration equipment and air conditioners. Therefore, it is necessary to reduce the environmental impact of refrigeration equipment by using refrigerant mixtures that include refrigerants with unsaturated bonds.

[0005] Patent Document 1 discloses a technology in which a liquid or solid endothermic agent is provided in a refrigeration system to cause an endothermic reaction at a specific temperature in order to suppress or mitigate a disproportionation reaction even under high-temperature conditions. Patent Document 2 also discloses a technology in which a refrigeration system using a refrigerant that may cause a disproportionation reaction is provided in a refrigerant circuit with an endothermic part having a melting point of 1000°C or higher and a heat capacity of 6.5 J / K or higher.

[0006] JP 2020-38014 A JP 2022-27634 A

[0007] However, there has been a demand for reducing the volume of the endothermic material due to space limitations within the refrigeration equipment while suppressing the disproportionation reaction.

[0008] The present invention has been made in view of the above problems, and aims to reduce the volume of an endothermic material in a refrigeration cycle device that uses a refrigerant that may cause a disproportionation reaction.

[0009] The present invention provides a refrigeration cycle device that uses a refrigerant that may undergo a disproportionation reaction, the device comprising a compressor that compresses the refrigerant, and a heat-absorbing member that absorbs heat by latent heat of fusion, disposed in a refrigerant path through which the refrigerant flows, the heat-absorbing member having a melting point that is higher than the maximum discharge temperature of the compressor and lower than the maximum value of the initiation temperature, which is the temperature at which the refrigerant may undergo a disproportionation reaction, at a temperature corresponding to each discharge pressure within the discharge pressure range of the compressor.

[0010] According to the present invention, in a refrigeration cycle device that uses a refrigerant that may cause a disproportionation reaction, the volume of the endothermic material can be made smaller.

[0011] Fig. 1 is a diagram showing a refrigeration cycle device; Fig. 2 is a diagram showing the relationship between the discharge pressure of a compressor and the starting temperature of a disproportionation reaction; Fig. 3 is a diagram showing a heat-absorbing member housed inside a compressor; Fig. 4 is a diagram showing a heat-absorbing member housed in a container; Fig. 5 is a diagram showing the arrangement of a heat-absorbing member according to a first modified example; Fig. 6 is a diagram showing the arrangement of a heat-absorbing member according to a second modified example.

[0012] FIG. 1 is a diagram showing a refrigeration cycle apparatus 1 according to this embodiment. The refrigeration cycle apparatus 1 is used in a refrigerator or an air conditioner. The refrigeration cycle apparatus 1 includes a heat source side apparatus 10 and a user side apparatus 20. The heat source side apparatus 10 and the user side apparatus 20 are connected by a liquid connection pipe 50 and a gas connection pipe 51. The heat source side apparatus 10 includes a compressor 11, a condenser 12, a liquid receiver 13, and an accumulator 15. The user side apparatus 20 includes an evaporator 31 and a pressure reducing mechanism 33.

[0013] The compressor 11 compresses low-temperature, low-pressure gas refrigerant and discharges it as high-temperature, high-pressure gas refrigerant. This gas refrigerant exchanges heat with another medium, such as air or water, in the condenser 12, thereby condensing the gas refrigerant. Excess refrigerant, depending on the operating state, is stored in the receiver 13. The refrigerant then flows through the liquid connection pipe 50 via the liquid check valve 16 and expands into a liquid or two-phase gas-liquid low-temperature, low-pressure refrigerant in the pressure reduction mechanism 33 of the user-side device 20. The refrigerant then exchanges heat with another medium, such as air or water, in the evaporator 31 to provide cooling to spaces or objects. The evaporated low-temperature, low-pressure refrigerant, which is highly dry, saturated, or superheated, passes through the gas check valve 17 and gas connection pipe 51 and travels to the user-side heat source device 10. To prevent the refrigerant from being drawn into the compressor 11 in a two-phase gas-liquid state and causing malfunctions in the compressor 11, gas-liquid separation is performed in the accumulator 15. As a result, even if liquid refrigerant suddenly flows to the suction side of the compressor 11 during transient operation, the quality of the refrigerant is adjusted to an appropriate level or higher, ensuring the reliability of the compressor 11.

[0014] The refrigerant used in the refrigeration cycle apparatus 1 is a refrigerant that may undergo a disproportionation reaction. Examples of such refrigerants include single refrigerants that have unsaturated bonds between carbon atoms in their molecules, such as trifluoroethylene (HFO-1123), trans-1,2-difluoroethylene (HFO1132(E)), cis-1,2-difluoroethylene (HFO1132(Z)), and 1,1-difluoroethylene (R1132a), as well as mixed refrigerants containing these refrigerants at a certain concentration or higher. These refrigerants are known to undergo autodecomposition reactions (also called disproportionation reactions). Autodecomposition reactions are a phenomenon in which, under high-temperature and high-pressure conditions, when a certain amount of energy, such as from a discharge, is applied, the refrigerant decomposes explosively and generates heat. When this autodecomposition reaction occurs, a sudden increase in pressure can cause the refrigeration cycle apparatus 1 to explode at the location where the autodecomposition reaction occurs.

[0015] The refrigerant to be mixed with the refrigerant that may cause a disproportionation reaction is preferably selected from HFCs (hydrofluorocarbons), fluoropropenes, CO2, hydrocarbons, etc. When selecting a component to be mixed with the refrigerant that may cause a disproportionation reaction from these, it is desirable to adjust the composition ratio from the viewpoints of the GWP of the refrigerant mixture, the capacity of the refrigeration cycle device to be used, the vapor pressure and temperature gradient of the refrigerant mixture, and the flammability and toxicity of the refrigerant mixture, in consideration of the required temperature range.

[0016] Examples of HFCs include difluoromethane (HFC32), pentafluoroethane (HFC125), 1,1,2,2-tetrafluoroethane (HFC134), 1,1,1,2-tetrafluoroethane (HFC134a), trifluoroethane (HFC143a), difluoroethane (HFC152a), 1,1,1,2,3,3,3-heptafluoropropane (HFC227ea), 1,1,1,3,3,3-hexafluoropropane (HFC236fa), 1,1,1,3,3-pentafluoropropane (HFC245fa), and 1,1,1,3,3-pentafluorobutane (HFC365mfc). Examples of fluoropropenes include 3,3,3-trifluoropropene (HFO1243zf), 1,3,3,3-tetrafluoropropene (HFO1234ze), and 2,3,3,3-tetrafluoropropene (HFO1234yf).

[0017] To prevent such disproportionation reactions, the refrigeration cycle apparatus 1 of this embodiment includes a heat-absorbing member disposed in the refrigerant path Q through which the refrigerant flows. The heat-absorbing member absorbs heat by fusion latent heat. The melting point of the heat-absorbing member is described below. FIG. 2 is a graph showing the relationship between refrigerant temperature and refrigerant pressure, at which a disproportionation reaction can occur in the compressor 11, for a mixed refrigerant containing a certain concentration of molecules with carbon-carbon unsaturated bonds within the molecule. A disproportionation reaction occurs when discharge energy, such as a spark or short circuit, is applied to the refrigerant after the temperature and pressure reach region A in the graph. It is desirable that the disproportionation reaction region A for a single refrigerant or mixed refrigerant at which a disproportionation reaction can occur is equal to or higher than the maximum discharge temperature Tdmax during normal operation. In conventional air conditioners, Tdmax is typically 120°C or lower, including temperature protection control. As shown in FIG. 2, the onset temperature of the disproportionation reaction decreases as the discharge pressure of the compressor 11 increases. The melting point of the heat-absorbing member is assumed to be lower than the maximum onset temperature within the onset temperature range corresponding to the discharge pressure range of the compressor 11. This allows heat absorption to begin before the disproportionation reaction begins. The melting point of the heat absorption member is set to be higher than the maximum discharge temperature of the compressor 11. This makes it possible to prevent heat absorption from beginning in a low temperature range where the disproportionation reaction cannot occur.

[0018] Under these conditions, the heat-absorbing material is preferably a material with a melting point of 150°C or higher but lower than 300°C. The heat-absorbing material itself undergoes a disproportionation reaction when the ambient temperature rises. Examples of heat-absorbing materials include resins containing nylon 66, polyethylene terephthalate (PET), nylon 12, and polypropylene (PP). These materials are relatively readily available and are easy to install in the refrigeration cycle device 1 from a cost perspective. The melting points of nylon 66, polyethylene terephthalate (PET), nylon 12, and polypropylene (PP), respectively, are 267°C, 255°C, 176°C, and 168°C. It is desirable to select a material with a melting point of less than 300°C, as with these materials. If a material with a melting point higher than this is selected, the endothermic effect time during which the heat absorbed during the disproportionation reaction is limited to sensible heat change will be long, resulting in a reduced disproportionation reaction suppression effect. For this reason, heat-absorbing materials with a melting point higher than this are not preferable.

[0019] Furthermore, due to the flow inside the compressor 11, refrigerant oil circulates from the compressor discharge pipe together with the refrigerant, at a maximum of about 5 wt % of the refrigerant mass circulation amount. Therefore, these endothermic materials come into contact with both the refrigerant and the refrigerant oil within the refrigeration cycle device. Therefore, it is desirable to select among these endothermic materials one that has low reactivity with the refrigerant and the refrigerant oil, and that has little effect on the sliding parts of the compressor and on piping corrosion, even though the total acid number of the refrigerant oil increases due to decomposition of the refrigerant or deterioration of the endothermic material itself.

[0020] The heat-absorbing member is preferably disposed in the high-pressure side of the refrigerant path Q through which the refrigerant flows. The high-pressure side path runs from the compressor 11 to the pressure-reducing mechanism 33 via the condenser 12 and the receiver 13. The refrigerant constantly circulates within the refrigeration cycle apparatus 1 during operation. During this process, high-temperature, high-pressure, superheated refrigerant passes from the compressor 11, which compresses the refrigerant, to the inlet of the condenser 12 and the pressure-reducing mechanism 33. In the condenser, the refrigerant exchanges heat with another medium, such as air or water, and dissipates heat, condensing into a high-pressure liquid refrigerant. Therefore, among the factors that cause disproportionation reactions in the refrigeration cycle, high-temperature and high-pressure conditions occur inside the compressor, the piping from the compressor to the condenser inlet, and the condenser. In a refrigeration cycle apparatus equipped with a four-way valve capable of switching between cooling and heating, high-temperature, high-pressure refrigerant may flow through the piping connecting the compressor to the four-way valve, the four-way valve, the four-way valve to the condenser during heating, and the piping and condenser to the condenser during cooling. It is desirable to provide the heat absorbing material at some or all of the locations in the refrigeration cycle.

[0021] FIG. 3 is a schematic cross-sectional view of the compressor 11. The compressor 11 may be a high-pressure chamber type scroll compressor or rotary compressor. FIG. 3 shows a cross-sectional view of a scroll compressor. In these compressors, high-temperature, high-pressure refrigerant flows through the chamber after compression from the discharge port of the compression chamber and finally flows out of the compressor discharge pipe into the refrigeration cycle. Therefore, a relatively high-temperature, high-pressure refrigerant is always present inside the compressor during the refrigeration cycle. Since the amount of high-temperature, high-pressure refrigerant dissolved in the refrigeration oil is reduced, the problem of the refrigeration oil being diluted by the refrigerant and the viscosity of the oil supplying the sliding parts decreasing is avoided. On the other hand, when the refrigerant temperature and pressure exceed a certain level, the possibility of a disproportionation reaction occurring within the refrigerant itself increases. In this embodiment, the heat-absorbing member is disposed inside the compressor 11. The compressor 11 mainly contains a compression mechanism 105 having a fixed scroll 106 and a revolving scroll 107, a shaft 110 that causes the revolving scroll 107 to revolve, and a motor 104 that drives the shaft 110, all housed in a sealed container 103.

[0022] The fixed scroll 106 and the orbiting scroll 107 are fitted together to form a compression chamber 109. The orbiting motion of the orbiting scroll 107 reduces the volume of the compression chamber 109, thereby performing compression. During compression, the orbiting motion of the orbiting scroll 107 draws a refrigerant gas working fluid into the compression chamber 109 through the suction port 101 and discharges the working fluid into a discharge space through the discharge port 106a of the fixed scroll 106. The working fluid discharged into the discharge space then flows into the space 103a in which the motor 104 is located, and is then discharged from the sealed container 103 to the refrigeration cycle via the discharge pipe 102. Refrigeration oil is stored at the bottom of the compressor. The refrigeration oil is supplied to each bearing from the bottom of the compressor through a flow path inside the shaft. The refrigeration oil is preferably selected from polyvinyl ether oil, polyol ester oil, and polyalkylene glycol oil based on its solubility with the refrigerant and the required viscosity for lubrication.

[0023] A disproportionation reaction occurs when three conditions—high temperature, high pressure, and energy—are met. During operation of the refrigeration cycle apparatus 1, the inside of the compressor 11 is at high temperature and pressure. Therefore, when energy is applied, a disproportionation reaction occurs. Meanwhile, inside the compressor 11, in the coil windings 115 arranged above and below the motor 104, short circuits may occur between the windings due to adhesion of wear particles generated by poor compressor sliding or damage to the winding coating, potentially resulting in the input of energy. Therefore, the heat absorption member 200 is disposed near the coil windings 115. In the example shown in FIG. 3 , the heat absorption member 200 is disposed above the upper winding 115 and below the lower winding 115. This reduces heat generation associated with the disproportionation reaction.

[0024] Furthermore, as shown in FIG. 4 , the heat absorption member 200 is housed in a container 300 and placed inside the compressor 11. The container 300 is made of a material, such as metal, with a higher melting point than the heat absorption member 200. This allows the heat absorption member 200 to be installed for a long period equivalent to the product life. This reduces the frequency with which the heat absorption member 200 comes into contact with refrigerant or refrigeration oil during normal operation. Furthermore, in this case, the volume of the heat absorption member 200 housed in the container 300 is smaller than the volume of the container 300. More preferably, the volume of the heat absorption member 200 is set so that it does not exceed the volume of the container 300 even when the heat absorption member 200 melts and expands. Furthermore, the container 300 is provided with a hole 302. This prevents the container 300 from bursting.

[0025] For example, the linear expansion coefficient of PA is approximately 8 to 10 × 10 －５ / °C. In order to prevent the refrigerant from dissolving into the refrigeration oil even when the compressor is stopped for an extended period of time, a heater or other means of heating is often provided to prevent extreme temperature drops. It is desirable to enclose the absorbing member 200 in a container, taking into account the volume change that occurs when the temperature rises from room temperature (15 to 30°C) to around 150 to 300°C, at which point a disproportionation reaction can occur inside the compressor. It is desirable to enclose the heat absorbing member 200 in a container, taking into account that the volume change rate that must be taken into account is ΔV = α × (T - 15) or less, where α is the linear expansion coefficient of the heat absorbing member 200 and T is the melting point of the heat absorbing member 200.

[0026] As described above, in the refrigeration cycle apparatus 1 of this embodiment, a heat absorption member that absorbs heat by latent heat of fusion is disposed in the refrigerant path, thereby preventing the occurrence of a disproportionation reaction. Furthermore, because a material that absorbs heat by latent heat of fusion is used as the heat absorption member, the amount of heat that can be absorbed per unit area can be increased compared to when a material that absorbs heat by sensible heat change is used. Therefore, the volume of the heat absorption member can be made smaller compared to when a heat absorption member that absorbs heat by sensible heat change is used. This improves the ease of mounting the heat absorption member in the refrigeration cycle apparatus 1.

[0027] It should be noted that the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims, such as applying a modified example of one embodiment to another embodiment.

[0028] In such a first modified example, the heat absorption member may be disposed inside the compressor 11, and the position of the heat absorption member inside is not limited to that described in the embodiment. As another example, as shown in FIG. 5 , the heat absorption member 200 may be disposed near the connection terminal 117 to which the coil is connected in the compressor 11. In the example shown in FIG. 5 , the heat absorption member 200 is disposed above the connection terminal 117. There is a possibility that a spark may occur at the connection terminal 117, and energy may be input. In contrast, by disposing the heat absorption member 200 near the connection terminal 117, it is possible to reduce heat generation associated with the disproportionation reaction.

[0029] As a second modified example, the heat absorption member 200 may be disposed on the outer wall of the compressor 11. For example, as shown in Fig. 6 , the heat absorption member 200 may be disposed so as to surround the periphery of the cylindrical sealed container 103 in a circular shape. In the example shown in Fig. 6 , the heat absorption member 200 is disposed on the outer wall corresponding to the motor 104 and the winding portion 115. For example, if there is not enough space inside the compressor 11 to dispose the heat absorption member 200, it is preferable to dispose the heat absorption member 200 on the outer wall of the compressor 11 in this manner.

[0030] As a third modification, the heat-absorbing member may be provided inside or on the outer wall of the receiver 13, which is installed on the high-pressure side of the refrigerant path. Alternatively, as another example, the heat-absorbing member may be provided inside or on the outer wall of the heat transfer tube of the condenser 12. The heat-absorbing member may also be provided inside or on the outer wall of a high-pressure side pipe, such as the pipe between the condenser 12 and the receiver 13. When the heat-absorbing member is provided inside the heat transfer tube or pipe, it is preferable to make the inner diameter of the portion where the heat-absorbing member is provided larger than the inner diameter of the portion where the heat-absorbing member is not provided. This prevents an increase in pressure loss.

[0031] REFRIGERATION CYCLE DEVICE 10 HEAT SOURCE SIDE DEVICE 11 COMPRESSOR 12 CONDENSER 13 RECEIVER 15 ACCUMULATOR 20 USE SIDE DEVICE 31 EVAPORATOR 33 DECOMPRESSION MECHANISM 101 SUCTION PORT 102 DISCHARGE PIPE 103 ENCLOSED CONTAINER 103a SPACE 104 MOTOR 105 COMPRESSION MECHANISM 106 FIXED SCROLL 106a DISCHARGE PORT 107 ORBITING SCROLL 110 SHAFT 115 WINDING PORTION 117 CONNECTION TERMINAL 200 HEAT ABSORPTION MEMBER

Claims

1. A refrigeration cycle device that uses a refrigerant that may cause a disproportionation reaction, comprising: a compressor that compresses the refrigerant; a heat absorption member that absorbs heat by latent heat of fusion is disposed in a refrigerant path through which the refrigerant flows; and the melting point of the heat absorption member is higher than the maximum discharge temperature of the compressor and, at temperatures corresponding to each discharge pressure within the discharge pressure range of the compressor, is lower than the maximum value of a start temperature at which the refrigerant may cause a disproportionation reaction.

2. A refrigeration cycle device as described in claim 1, wherein the melting point of the heat absorbing member is 150°C or higher and lower than 300°C.

3. The refrigeration cycle device according to claim 1, wherein the heat absorbing member is disposed on the high pressure side of the inside of the compressor, the outer wall of the compressor, or the refrigerant path.

4. The refrigeration cycle device according to claim 1, wherein the heat absorbing member is made of a resin including nylon 66, polyethylene terephthalate (PET), nylon, and polypropylene (PP).

5. The refrigeration cycle device according to claim 1, wherein the heat absorbing member is housed in a container.

6. A refrigeration cycle apparatus according to claim 5, wherein the heat absorbing member is accommodated in the container in an amount smaller than the capacity of the container.

7. The refrigeration cycle device according to claim 1, wherein the compressor is a high-pressure chamber type compressor.

Images