WO2025069137A1 - Refrigeration cycle device - Google Patents

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

The present invention relates to a refrigeration cycle device.

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 in their molecules, are known to have high chemical reactivity due to the double bonds in their molecules. 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 is applied under high temperature and pressure conditions, such as from a discharge, the refrigerant decomposes and generates heat, causing an explosive reaction. When this autodecomposition reaction occurs, the sudden increase in pressure can cause the location of the autodecomposition reaction inside the refrigeration equipment to explode, posing a risk to the area around the refrigeration equipment.

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 air conditioners and other refrigeration equipment, and compared to HFC refrigerants such as R32 and R410A, the refrigerant molecules are less stable and their lifespan in the atmosphere is shorter, resulting in extremely low ODP (Ozone Depletion Potential) and GWP (Global Warming Potential).

The Kigali Amendment to the Montreal Protocol, the European F-gas regulations, and Japan's Act on Rational Use of Fluorocarbons, 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 mixed refrigerants that contain these refrigerants with unsaturated bonds.

Patent Document 1 discloses a technology in which a liquid or solid heat absorbing agent is provided in a refrigeration system to suppress or mitigate disproportionation reactions even under high temperature conditions, and an endothermic reaction occurs at a specific temperature. Patent Document 2 describes the provision of a heat absorbing part with a melting point of 1000°C or higher and a heat capacity of 6.5 J/K or higher in the refrigeration circuit in a refrigeration system that uses a refrigerant that may cause a disproportionation reaction.

JP 2020-38014 A JP 2022-27634 A

However, there was a demand to reduce the volume of the endothermic material due to space restrictions inside the refrigeration equipment while suppressing the disproportionation reaction.

The present invention was developed in consideration of these problems, and aims to reduce the volume of heat absorbing material in a refrigeration cycle device that uses a refrigerant that may cause a disproportionation reaction.

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

According to the present invention, the volume of the heat absorbing material can be reduced in a refrigeration cycle device that uses a refrigerant that may cause a disproportionation reaction.

FIG. 1 is a diagram showing a refrigeration cycle device. FIG. 4 is a diagram showing the relationship between the discharge pressure of a compressor and the initiation temperature of a disproportionation reaction. FIG. 2 is a diagram showing a heat absorbing member housed inside the compressor. FIG. 2 is a diagram showing a heat absorbing member housed in a container. FIG. 11 is a diagram showing an arrangement of a heat absorbing member according to a first modified example. FIG. 13 is a diagram showing an arrangement of a heat absorbing member according to a second modified example.

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

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. As a result, the gas refrigerant condenses. 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 low-temperature, low-pressure refrigerant in liquid or gas-liquid two-phase 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 cool a space or object. The evaporated low-temperature, low-pressure refrigerant with a high dryness, or in a saturated or superheated state, passes through the gas check valve 17 and passes through the gas connection pipe 51 to the user side heat source device 10. In order to prevent the refrigerant from being sucked into the compressor 11 in a gas-liquid two-phase state and causing malfunctions in the compressor 11, gas-liquid separation is performed in the accumulator 15. This ensures the reliability of the compressor 11 by adjusting the dryness level to an appropriate level even if liquid refrigerant suddenly flows to the suction side of the compressor 11 during transient operation.

Refrigerants that may cause disproportionation reactions are used as the refrigerant for the refrigeration cycle device 1. Examples of such refrigerants include single refrigerants that have unsaturated bonds between carbon atoms in the molecule, such as trifluoroethylene (HFO-1123), trans-1,2-difluoroethylene (HFO1132(E)), cis-1,2-difluoroethylene (HFO1132(Z)), and 1,1-difluoroethylene (R1132a), or mixed refrigerants that contain a certain concentration or more of these refrigerants. These refrigerants are known to cause autodecomposition reactions (called disproportionation reactions). Autodecomposition reactions are a phenomenon in which the decomposition reaction of the refrigerant generates heat and causes an explosive reaction when a certain amount of energy, such as discharge, is applied under high temperature and high pressure conditions. When this autodecomposition reaction occurs, the sudden increase in pressure may cause the location of the autodecomposition reaction in the refrigeration cycle device 1 to burst.

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

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).

In order to prevent such disproportionation reactions, in the refrigeration cycle device 1 of this embodiment, a heat absorbing member is placed in the refrigerant path Q through which the refrigerant flows. The heat absorbing member is a member that absorbs heat by the latent heat of fusion. Here, the melting point of the heat absorbing member will be explained. FIG. 2 is a graph showing the relationship between the refrigerant temperature and the refrigerant pressure at which the disproportionation reaction of the compressor 11 may occur in a mixed refrigerant containing a certain concentration of molecules having carbon-carbon unsaturated bonds in the molecule. When the temperature and pressure reach the region A in the figure and discharge energy such as a spark or short is given to the refrigerant, a disproportionation reaction occurs. It is desirable that the disproportionation reaction occurrence region A of a single refrigerant or a mixed refrigerant that may cause a disproportionation reaction is equal to or higher than the maximum discharge temperature Tdmax during normal operation. In conventional air conditioners, Tdmax is usually 120°C or less, including temperature protection control. As shown in FIG. 2, the starting temperature of the disproportionation reaction decreases as the discharge pressure of the compressor 11 increases. The melting point of the heat absorbing member is lower than the maximum value of the start temperature in the start temperature range corresponding to the discharge pressure range of the compressor 11. This allows the endotherm to start before the disproportionation reaction starts. Also, the melting point of the heat absorbing member is higher than the maximum discharge temperature of the compressor 11. This makes it possible to prevent the endotherm from starting in a low temperature range where the disproportionation reaction cannot occur.

Under these conditions, it is preferable that the heat absorbing member is a material with a melting point of 150°C or higher and less than 300°C. When the ambient temperature rises, the heat absorbing member itself undergoes a disproportionation reaction. Examples of heat absorbing members include resins containing nylon 66, polyethylene terephthalate (PET), nylon 12, and polypropylene (PP). These materials are relatively easy to obtain, and are easy to install in the refrigeration cycle device 1 in terms of cost. Here, the melting points of nylon 66, polyethylene terephthalate (PET), nylon 12, and polypropylene (PP) are 267°C, 255°C, 176°C, and 168°C, respectively. It is preferable to select a material with a melting point of less than 300°C, like these substances. If a material with a melting point higher than this is selected, the heat absorption time during which the heat absorption at the time of the disproportionation reaction occurs is only a sensible heat change will be long, and the disproportionation reaction suppression effect will be reduced. For this reason, heat absorbing materials with a melting point higher than this are not preferable.

In addition, due to the internal flow of the compressor 11, refrigeration oil, at a maximum of about 5 wt% of the circulating mass of the refrigerant, also circulates from the compressor discharge piping together with the refrigerant. Therefore, these endothermic materials come into contact with the refrigerant as well as the refrigeration 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 refrigeration oil, that causes an increase in the total acid value of the refrigeration oil due to decomposition of the refrigerant or deterioration of the endothermic material itself, and that has little effect on the sliding parts of the compressor and corrosion of the piping.

The heat absorbing member is preferably arranged in the high-pressure side of the refrigerant path Q through which the refrigerant flows. The high-pressure side path is the path from the compressor 11 to the pressure reducing mechanism 33 via the condenser 12 and the receiver 13. The refrigerant always circulates in the refrigeration cycle device 1 while the refrigeration cycle device 1 is in operation. At this time, a high-temperature, high-pressure, superheated refrigerant passes from the compressor 11 that compresses the refrigerant to the condenser 12 and the inlet of the pressure reducing mechanism 33, and in the condenser, the refrigerant exchanges heat with another medium such as air or water and releases heat, condensing it into a high-pressure liquid refrigerant. For this reason, 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 inside the condenser. In a refrigeration cycle device equipped with a four-way valve that can switch between cooling and heating, there is a possibility that high-temperature, high-pressure refrigerant will 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 of the condenser during cooling. It is desirable to provide heat absorbing materials at some or all of the above locations in the refrigeration cycle.

Figure 3 is a schematic cross-sectional view of the compressor 11. A scroll compressor or a rotary compressor of a high-pressure chamber type is used as the compressor 11. Figure 3 shows a cross-sectional view of a scroll compressor. In these compressors, the high-temperature and high-pressure refrigerant flows through the chamber from the discharge port of the compression chamber after compression and finally flows out from the discharge pipe of the compressor into the refrigeration cycle. Therefore, a relatively high-temperature and high-pressure refrigerant is always present inside the compressor during the refrigeration cycle. Since the amount of high-temperature and high-pressure refrigerant that dissolves in the refrigeration oil is reduced, the problem of the refrigeration oil being diluted by the refrigerant and the oil viscosity at the sliding parts being reduced is avoided. On the other hand, when the refrigerant becomes hotter and more pressured than a certain level, the possibility of a disproportionation reaction occurring in the refrigerant itself increases. In this embodiment, the heat-absorbing member is arranged inside the compressor 11. The compressor 11 mainly contains a compression mechanism 105 having a fixed scroll 106 and an orbiting scroll 107, a shaft 110 that orbits the orbiting scroll 107, and a motor 104 that drives the shaft 110, all housed in a sealed container 103.

The fixed scroll 106 and the orbiting scroll 107 are joined together to form a compression chamber 109, and the orbiting scroll 107 rotates to reduce the volume of the compression chamber 109, thereby performing compression. In compression, the orbiting scroll 107 rotates to suck the working fluid, refrigerant gas, into the compression chamber 109 through the suction port 101, and the sucked working fluid is discharged from the discharge port 106a of the fixed scroll 106 into the discharge space. The working fluid discharged into the discharge space then flows into the space 103a in which the motor 104 is located, and is further discharged from the sealed container 103 to the refrigeration cycle through the discharge pipe 102. In addition, 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. It is preferable that the refrigeration oil is selected from polyvinyl ether oil, polyol ester oil, and polyalkylene glycol oil according to its solubility with the refrigerant and the required viscosity during lubrication.

When the three conditions of high temperature, high pressure, and energy are met, a disproportionation reaction occurs. When the refrigeration cycle device 1 is in operation, the inside of the compressor 11 is at high temperature and high pressure. Therefore, when energy is applied, a disproportionation reaction occurs. On the other hand, inside the compressor 11, in the coil windings 115 arranged above and below the motor 104, a short circuit may occur between the windings due to adhesion of wear powder generated by poor sliding of the compressor or damage to the winding coating, and energy may be input. Therefore, the heat absorption member 200 is arranged near the coil windings 115. In the example shown in FIG. 3, the heat absorption member 200 is arranged above the upper winding 115 and below the lower winding 115. This makes it possible to reduce heat generation associated with the disproportionation reaction.

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

For example, the linear expansion coefficient of PA is approximately 8 to 10 x 10 ^-5 /°C. In order to avoid the refrigerant from dissolving in the refrigeration oil even when the compressor is stopped for a long period of time, a heater or other overheating means is often provided to avoid extreme temperature drops. It is desirable to store the absorbing member 200 in a container, taking into consideration the volume change when the temperature rises from room temperature (15 to 30 degrees) to around 150°C to 300°C, which is a temperature at which a disproportionation reaction can occur inside the compressor. It is desirable to seal the heat absorbing member 200 in a container, taking into consideration that the volume change rate ΔV = α x (T-15) or less should be considered when the linear expansion coefficient of the heat absorbing member 200 is α and the temperature change until melting is the melting point T of the heat absorbing member 200.

As described above, in the refrigeration cycle device 1 of this embodiment, a heat absorbing member that absorbs heat due to latent heat of fusion is arranged in the refrigerant path, so that the occurrence of a disproportionation reaction can be prevented. Furthermore, because a material that absorbs heat due to latent heat of fusion is used as the heat absorbing member, the amount of heat that can be absorbed per unit area can be increased compared to when a material that absorbs heat due to sensible heat change is used. Therefore, the volume of the heat absorbing member can be made smaller compared to when a heat absorbing member that absorbs heat due to sensible heat change is used. This improves the mountability of the heat absorbing member in the refrigeration cycle device 1.

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

As a first such modified example, the heat absorbing member may be disposed inside the compressor 11, and the position of the heat absorbing member inside is not limited to that of the embodiment. As another example, as shown in FIG. 5, the heat absorbing 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 absorbing member 200 is disposed above the connection terminal 117. At the connection terminal 117, a spark may occur, and energy may be input. In response to this, by disposing the heat absorbing member 200 near the connection terminal 117, the heat generation associated with the disproportionation reaction can be reduced.

As a second modified example, the heat absorbing member 200 may be disposed on the outer wall of the compressor 11. For example, as shown in FIG. 6, the heat absorbing 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 absorbing member 200 is disposed on the outer wall corresponding to the motor 104 and the winding section 115. For example, if there is not enough space inside the compressor 11 to place the heat absorbing member 200, it is preferable to dispose the heat absorbing member 200 on the outer wall of the compressor 11 in this manner.

As a third modified example, the heat absorbing member may be provided inside or on the outer wall of the receiver 13 installed on the high pressure side of the refrigerant path, or as another example, on the 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 pipe on the high pressure side, 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 part where the heat absorbing member is provided larger than the inner diameter of the part where the heat absorbing member is not provided. This makes it possible to prevent pressure loss from becoming large.

Reference Signs List 1 Refrigeration cycle device 10 Heat source side device 11 Compressor 12 Condenser 13 Receiver 15 Accumulator 20 Use side device 31 Evaporator 33 Pressure reducing mechanism 101 Suction port 102 Discharge pipe 103 Closed container 103a Space 104 Motor 105 Compression mechanism 106 Fixed scroll 106a Discharge port 107 Rotating scroll 110 Shaft 115 Winding portion 117 Connection terminal 200 Heat absorbing member

Claims (7)

A refrigeration cycle device using a refrigerant that may cause a disproportionation reaction,
A compressor that compresses the refrigerant,
a heat absorbing member that absorbs heat by latent heat of fusion is disposed in a refrigerant path through which the refrigerant flows;
a melting point of the heat absorption member is higher than a maximum discharge temperature of the compressor and is lower than a maximum value of a start temperature at which the refrigerant can undergo a disproportionation reaction at a temperature corresponding to each discharge pressure within a discharge pressure range of the compressor. The refrigeration cycle device according to claim 1, wherein the melting point of the heat absorbing member is 150°C or higher and lower than 300°C. The refrigeration cycle device according to claim 1, wherein the heat absorbing member is disposed inside the compressor, on the outer wall of the compressor, or on the high-pressure side of the refrigerant path. 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). The refrigeration cycle device according to claim 1, wherein the heat absorbing member is housed in a container. The refrigeration cycle device according to claim 5, wherein the heat absorbing member is contained in the container in an amount smaller than the capacity of the container. The refrigeration cycle device according to claim 1, wherein the compressor is a high-pressure chamber type compressor.

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