Hybrid refrigerant, method for producing same, and use thereof

Abstract

The application provides a mixed refrigerant, a preparation method and application thereof. The working temperature of the mixed refrigerant comprises-60 DEG C to-45 DEG C; the mixed refrigerant is composed of a first component, a second component and a third component; the first component is CO2; the second component is difluoromethane; and the third component is one of 1,1-difluoroethane, trans-1,3,3,3-tetrafluoropropene, cis-1,3,3,3-tetrafluoropropene or trans-1-chloro-3,3,3-trifluoropropene. The mixed refrigerant of the application improves environmental protection and safety while keeping the system stable, and the overall performance is better than that of difluoromethane, so that the environmental protection and safety are improved; meanwhile, the refrigerant has good evaporation characteristics at low temperature (-45 DEG C), so that the self-recovery heat pump system loaded with the mixed refrigerant is suitable for hot water supply under extremely low temperature working conditions.

Description

Technical Field

[0001] This invention relates to the field of refrigeration technology, and more specifically, to a mixed refrigerant, its preparation method, and its application. Background Technology

[0002] Air source heat pumps, used for heating or hot water supply, are more energy-efficient than traditional electric, gas, or coal-fired boilers. In extremely cold northern regions, temperatures can reach as low as -45°C, while hot water temperatures can exceed 55°C. Under these extreme conditions, air source heat pumps using conventional refrigerants such as difluoromethane (R32) or R410A (composed of difluoromethane and pentafluoroethane) cannot operate normally due to excessively low evaporation pressure and excessively high pressure ratio. While methods like injecting gas to increase enthalpy or using a two-stage compression cycle offer limited temperature improvement, cascade compression cycles result in complex and costly systems, and transcritical carbon dioxide cycles require specialized compressors and other equipment, leading to high costs.

[0003] After gas-liquid separation, the high-boiling-point and low-boiling-point refrigerants in the self-cascade cycle achieve self-heating, requiring only a single conventional compressor to provide heating across a large temperature span, resulting in a relatively simple system structure. However, existing self-cascade heat pump systems primarily use mixed refrigerants, mainly hydrocarbons or traditional hydrofluorocarbons, which generally suffer from high gas per watt (GWP), significant flammability risks, insufficient low-temperature performance, and poor system compatibility. Therefore, there is an urgent need to develop a novel mixed refrigerant that enables the self-cascade cycle to provide heating across a large temperature span up to -45°C. Summary of the Invention

[0004] The main objective of this invention is to provide a mixed refrigerant, its preparation method, and its application, in order to solve the problems of high GWP, high flammability risk, insufficient low-temperature performance, and poor system compatibility of mixed refrigerants used in existing self-cascade heat pump systems.

[0005] To achieve the above objectives, according to one aspect of the present invention, a mixed refrigerant is provided, the operating temperature of which includes -60°C to -45°C; the mixed refrigerant is composed of a first component, a second component, and a third component, wherein the first component is CO2, the second component is difluoromethane, and the third component is one of 1,1-difluoroethane, trans-1,3,3,3-tetrafluoropropene, cis-1,3,3,3-tetrafluoropropene, or trans-1-chloro-3,3,3-trifluoropropene.

[0006] Furthermore, in the mixed refrigerant, the weight percentage of the first component is 10-30%, the weight percentage of the second component is 50-75%, and the weight percentage of the third component is 10-25%.

[0007] Furthermore, in the mixed refrigerant, the weight percentage of the first component is 10-25%, the weight percentage of the second component is 50-75%, and the third component is 1,1-difluoroethane, with the weight percentage of 1,1-difluoroethane being 10-25%.

[0008] Furthermore, in the mixed refrigerant, the weight percentage of the first component is 10-25%, the weight percentage of the second component is 50-75%, and the third component is trans-1,3,3,3-tetrafluoropropylene, with the weight percentage of trans-1,3,3,3-tetrafluoropropylene being 10-25%.

[0009] Furthermore, in the mixed refrigerant, the weight percentage of the first component is 10-30%, the weight percentage of the second component is 50-70%, and the third component is cis-1,3,3,3-tetrafluoropropylene, with the weight percentage of cis-1,3,3,3-tetrafluoropropylene being 10-25%.

[0010] Furthermore, in the mixed refrigerant, the weight percentage of the first component is 15-30%, the weight percentage of the second component is 50-70%, and the third component is trans-1-chloro-3,3,3-trifluoropropylene, with the weight percentage of trans-1-chloro-3,3,3-trifluoropropylene being 10-25%.

[0011] Further, in the mixed refrigerant, the weight percentage of the first component is 10-25%, the weight percentage of the second component is 60-75%, and the weight percentage of 1,1-difluoroethane is 10-15%; or, the weight percentage of the first component is 10-25%, the weight percentage of the second component is 60-75%, and the weight percentage of trans-1,3,3,3-tetrafluoropropylene is 10-15%; or, the weight percentage of the first component is 15-30%, the weight percentage of the second component is 50-70%, and the weight percentage of cis-1,3,3,3-tetrafluoropropylene is 10-20%; or, the weight percentage of the first component is 15-30%, the weight percentage of the second component is 50-70%, and the weight percentage of trans-1-chloro-3,3,3-trifluoropropylene is 10-25%.

[0012] Furthermore, the mixed refrigerant has a GWP value ≤ 525, a bubble point temperature at normal pressure ≤ -61.6℃, a relative Qv of 1.03~1.58 compared to difluoromethane, and a COP ≥ 1.36.

[0013] According to another aspect of the present invention, a method for preparing the above-mentioned mixed refrigerant is provided, comprising the following steps: mixing the components of the mixed refrigerant in a liquid phase state at room temperature and pressure according to their respective weight percentages to obtain the mixed refrigerant.

[0014] According to another aspect of the present invention, a self-cascading heat pump system is provided, the self-cascading heat pump system comprising a refrigerant, the refrigerant comprising the above-described mixed refrigerant.

[0015] By applying the technical solution of this invention, carbon dioxide, difluoromethane, and one of the following components—1,1-difluoroethane, trans-1,3,3,3-tetrafluoropropene, cis-1,3,3,3-tetrafluoropropene, or trans-1-chloro-3,3,3-trifluoropropene—are synergistically combined to obtain a mixed refrigerant. This mixed refrigerant significantly improves environmental friendliness and safety while maintaining system operational stability. Its overall performance is superior to that of difluoromethane, effectively avoiding the environmental and usage risks associated with traditional refrigerants due to their high GWP or flammability. Simultaneously, the refrigerant exhibits excellent evaporation characteristics at extremely low temperatures (-45°C), adapting to the separation and synergistic requirements of high and low boiling point components in a self-cascade cycle. This enables reliable system operation under extreme conditions, overcoming the technical bottleneck of existing refrigerants' difficulty in balancing low-temperature performance and system compatibility. This makes the self-cascade heat pump system equipped with the mixed refrigerant suitable for hot water supply under extremely low temperature conditions. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 A schematic diagram of a self-cascading heat pump system according to Embodiment 1 of the present invention is shown. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, a system, product, or device that comprises a series of units is not necessarily limited to those units explicitly listed, but may include units not explicitly listed or inherent to such products or devices. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0020] Terminology Explanation:

[0021] R32: Difluoromethane.

[0022] R152a: 1,1-Difluoroethane.

[0023] R1234ze(E): trans-1,3,3,3-tetrafluoropropylene.

[0024] R1234ze(Z): cis-1,3,3,3-tetrafluoropropylene.

[0025] R1233zd(E): trans-1-chloro-3,3,3-trifluoropropene.

[0026] Evaporator evaporation temperature: the arithmetic mean of the evaporator inlet temperature and the dew point temperature at the corresponding pressure.

[0027] Condenser condensing temperature: the arithmetic mean of the dew point and bubble point temperatures in the condenser.

[0028] Relative Qv: Relative unit volume cooling / heating capacity, refers to the ratio of the refrigerant's heat output per unit volume to that of difluoromethane.

[0029] COP: Coefficient of performance for heating.

[0030] As described in the background section of this invention, existing technologies suffer from problems such as high GWP (Gross Potential) of mixed refrigerants used in cascade heat pump systems, high flammability risk, insufficient low-temperature performance, and poor system compatibility. To address these issues, in a typical embodiment of this invention, a mixed refrigerant is provided. The operating temperature of the mixed refrigerant ranges from -60°C to -45°C. The mixed refrigerant comprises a first component, a second component, and a third component. The first component is CO2, the second component is difluoromethane, and the third component is one of 1,1-difluoroethane, trans-1,3,3,3-tetrafluoropropene, cis-1,3,3,3-tetrafluoropropene, or trans-1-chloro-3,3,3-trifluoropropene.

[0031] The mixed refrigerant provided by this invention is applied to a self-cascade heat pump system. It is obtained by compounding carbon dioxide, difluoromethane, and one of the following: 1,1-difluoroethane, trans-1,3,3,3-tetrafluoropropene, cis-1,3,3,3-tetrafluoropropene, or trans-1-chloro-3,3,3-trifluoropropene. This mixed refrigerant utilizes the differences in boiling points of its components to achieve component fractionation through gas-liquid separation. The low-boiling-point carbon dioxide operates on the low-temperature side, the medium-boiling-point difluoromethane operates on the medium-temperature side, and the high-boiling-point 1,1-difluoroethane, trans-1,3,3,3-tetrafluoropropene, cis-1,3,3,3-tetrafluoropropene, or trans-1-chloro-3,3,3-trifluoropropene operates on the high-temperature side. In the aforementioned graded operating mode, the low-boiling-point component ensures that the refrigerant generates effective evaporation pressure at extremely low temperatures (e.g., -50°C), while the high-boiling-point component effectively condenses at high temperatures (e.g., 60°C) and suppresses excessive increases in overall system pressure. This significantly increases the evaporation pressure in low-temperature environments while reducing the pressure ratio, enabling the system to operate normally at -45°C (operating temperatures can include the extremely low temperature range of -60°C to -45°C), providing hot water above 55°C. Furthermore, this mixed refrigerant offers superior environmental and safety performance compared to R32, and its volumetric heating capacity is also better than R32. It expands the operating temperature range of the self-cascade heat pump system, thus overcoming the problem of conventional refrigerants failing to operate normally under extreme conditions.

[0032] The present invention further combines the above-mentioned refrigerants in a specific way, selects appropriate component contents, and achieves further complementary advantages. Specifically, in the mixed refrigerant, the weight percentage of the first component is 10~30%, the weight percentage of the second component is 50~75%, and the weight percentage of the third component is 10~25%.

[0033] By controlling the content of each component within the aforementioned range, the overall performance of the mixed refrigerant under extreme operating conditions can be further improved. Adjusting the content of the first component within this range further enhances the system's ability to achieve sufficient low-temperature evaporation pressure, while simultaneously reducing the risk of system pressure spikes and abnormal exhaust temperatures due to excessive proportions. Combined with the second component's setting within the aforementioned range, it becomes easier to maintain a suitable balance between pressure ratio and volumetric heating capacity, preventing the high-boiling-point third component from negatively impacting the low-temperature evaporation efficiency. Furthermore, the presence of the third component in a specific proportion further promotes the effective fractionation of high and low boiling-point components in the self-cascade heat pump system, concentrating low-boiling-point components on the low-temperature side and high-boiling-point components on the high-temperature side, thereby expanding the system's operating temperature range. This synergistic effect between components is more conducive to optimizing system energy efficiency while maintaining essentially equal environmental and safety performance, enabling the heat pump to stably output high-temperature hot water even in extremely cold environments. This overcomes the operational bottlenecks of single-component or simple mixed refrigerants under low-temperature, high-pressure ratios, achieving a dual improvement in energy efficiency and reliability.

[0034] When the third component is 1,1-difluoroethane, in a preferred embodiment, the weight percentage of the first component in the mixed refrigerant is 10-25%, the weight percentage of the second component is 50-75%, and the third component is 1,1-difluoroethane, with the weight percentage of 1,1-difluoroethane being 10-25%.

[0035] The above component ratio can further improve the volumetric heating capacity of the mixed refrigerant and is more conducive to balancing the pressure distribution on the high-pressure and low-pressure sides of the system. By limiting 1,1-difluoroethane to the above range, it is easier to achieve effective fractionation of high and low boiling point components in the self-cascade cycle, thereby optimizing the matching between low-temperature evaporation pressure and high-temperature condensation performance, and improving the system's operational stability and energy efficiency under extremely cold conditions.

[0036] When the third component is trans-1,3,3,3-tetrafluoropropylene, in order to further promote the effective fractionation of high and low boiling point components in the self-cascade cycle, thereby optimizing the matching of low-temperature evaporation pressure and high-temperature condensation performance, and improving the system's operational stability and energy efficiency under extremely cold conditions, in a preferred embodiment, the weight percentage of the first component is 10-25%, the weight percentage of the second component is 50-75%, and the third component is trans-1,3,3,3-tetrafluoropropylene, with the weight percentage of trans-1,3,3,3-tetrafluoropropylene being 10-25%.

[0037] When the third component is cis-1,3,3,3-tetrafluoropropene or trans-1-chloro-3,3,3-trifluoropropene, the pressure is low because the boiling points of R1234ze(Z) and R1233zd(E) are higher than those of R152a and R1234ze(E). Therefore, more CO2 needs to be added to increase the system pressure and increase the volumetric calorific value.

[0038] Specifically, in a preferred embodiment, when the third component is cis-1,3,3,3-tetrafluoropropylene, the weight percentage of the first component in the mixed refrigerant is 10-30%, the weight percentage of the second component is 50-70%, and the third component is cis-1,3,3,3-tetrafluoropropylene, with the weight percentage of cis-1,3,3,3-tetrafluoropropylene being 10-25%.

[0039] In a preferred embodiment, when the third component is trans-1-chloro-3,3,3-trifluoropropylene, the weight percentage of the first component is 15-30%, the weight percentage of the second component is 50-70%, and the weight percentage of the third component is trans-1-chloro-3,3,3-trifluoropropylene, with the trans-1-chloro-3,3,3-trifluoropropylene weighing 10-25%. This further promotes effective fractionation of high and low boiling point components in the self-cascade cycle, thereby optimizing the matching between low-temperature evaporation pressure and high-temperature condensation performance, and improving the system's operational stability and energy efficiency under extremely cold conditions.

[0040] To further promote effective fractionation of high- and low-boiling-point components in the self-cascade cycle, thereby optimizing the matching between low-temperature evaporation pressure and high-temperature condensation performance, and improving the system's operational stability and energy efficiency under extremely cold conditions, in a preferred embodiment, the mixed refrigerant contains a first component with a weight percentage of 10-25%, a second component with a weight percentage of 60-75%, and 1,1-difluoroethane with a weight percentage of 10-15%; or, the first component with a weight percentage of 10-25%, and the second component with a weight percentage of 10-25%. The content is 60-75%, and the weight percentage of trans-1,3,3,3-tetrafluoropropene is 10-15%; or, the weight percentage of the first component is 15-30%, the weight percentage of the second component is 50-70%, and the weight percentage of cis-1,3,3,3-tetrafluoropropene is 10-20%; or, the weight percentage of the first component is 15-30%, the weight percentage of the second component is 50-70%, and the weight percentage of trans-1-chloro-3,3,3-trifluoropropene is 10-25%.

[0041] For similar reasons, in some embodiments, the weight ratio of the first component to the second component is (0.1~1.7):1.

[0042] For similar reasons, in some embodiments, the weight ratio of the third component to the second component is (0.1~2):1.

[0043] As described above, the mixed refrigerant of the present invention, through the optimization and control of its components and their contents, can optimize the matching between the low-temperature evaporation pressure and high-temperature condensation performance of the refrigerant, thereby improving the operational stability and energy efficiency of the self-cascade heat pump system under extremely cold conditions. Specifically, in a preferred embodiment, the mixed refrigerant has a GWP value ≤ 525, a normal pressure bubble point temperature ≤ -61.6℃, a relative Qv of 1.03~1.58 compared to difluoromethane, and a COP ≥ 1.36.

[0044] In another typical embodiment of the present invention, a method for preparing the mixed refrigerant of the present invention is also provided, comprising the following steps: mixing the components of the mixed refrigerant in a liquid phase state at room temperature and pressure to obtain the mixed refrigerant. This preparation method is simple and easy to apply, wherein the room temperature can be 23~27℃ and the pressure can be 0.1MPa.

[0045] In another typical embodiment of the present invention, a self-cascading heat pump system is also provided, comprising a refrigerant, the refrigerant including the mixed refrigerant of the present invention. The mixed refrigerant of the present invention has excellent cooling / heating performance, high safety level, and good environmental performance, making it more suitable for application in the aforementioned air conditioning systems. Optimizing the refrigerant can effectively balance low-temperature evaporation pressure and high-temperature condensation performance, improving the operational stability and energy efficiency of the self-cascading heat pump system under extremely cold conditions, making it more suitable for application in self-cascading heat pump systems operating at -45℃.

[0046] In some implementations, the self-cascade heat pump system is a three-stage self-cascade heat pump system, such as... Figure 1 As shown. The three-stage self-cascade heat pump system includes a compressor 1, a condenser 2, a regenerator 3, a first-stage gas-liquid separator 4, a first-stage condenser-evaporator 5, a second-stage condenser-evaporator 6, a first-stage electronic expansion valve 7, an evaporator 8, a second-stage electronic expansion valve 9, a third-stage electronic expansion valve 10, and a second-stage gas-liquid separator 11.

[0047] The refrigerant is compressed into a high-temperature, high-pressure gas by compressor 1, then enters condenser 2 where it is cooled by water, outputting hot water above 55°C. The refrigerant is cooled into a gas-liquid two-phase state and further cooled by the low-temperature, low-pressure compressor in regenerator 3. Because the refrigerant contains both high-boiling-point and low-boiling-point substances, the high-boiling-point substances R152a, R1234ze(E), R1234ze(Z), or R1233zd(E) are more easily cooled into liquid, while the low-boiling-point substance CO2 is not easily cooled. In the first-stage gas-liquid separator 4, it separates into gas and liquid phases, with a high concentration of CO2 in the gas phase and a high concentration of R152a, R1234ze(E), R1234ze(Z), and R1233zd(E) in the liquid phase. The liquid phase, after being throttled by a three-stage electronic expansion valve 10, becomes a low-temperature, low-pressure two-phase state and enters the first-stage condenser-evaporator 5 for further cooling of the gas phase with a high CO2 concentration. It is then cooled into a two-phase state and further separated into gas and liquid phases in the second-stage gas-liquid separator 11. The gas phase has a higher proportion of low-boiling-point CO2, while the liquid phase has a higher proportion of boiling-point R32. The liquid phase, after being throttled by a second-stage electronic expansion valve 9, becomes a two-phase state with even lower temperature and pressure. It then enters the second-stage condenser-evaporator 6 for further condensation of the CO2-rich gas phase into a high-pressure liquid phase. After being throttled by the first-stage electronic expansion valve, it becomes a two-phase state with even lower temperature and pressure. It is then evaporated into a gas phase in evaporator 8 at an evaporation temperature of approximately -50°C. Evaporator 8 exchanges heat with the -45°C environment. Due to the low evaporation temperature, conventional substances such as R32 and R134a cannot function properly at this temperature. Low-boiling-point CO2 can function in an environment of -45°C, becoming a CO2-rich working fluid through two component separations.

[0048] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0049] This invention combines the refrigerant components as follows: the first component is CO2, the second component is difluoromethane (R32), and the third component is one of 1,1-difluoroethane (R152a), trans-1,3,3,3-tetrafluoropropene (R1234ze(E)), cis-1,3,3,3-tetrafluoropropene (R1234ze(Z)), or trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)). The basic parameters of each component are shown in Table 1. When the combination method is determined, the components are physically mixed in a liquid phase at room temperature and pressure according to the corresponding weight ratios in Tables 2 and 3. All component ratios are weight percentages, and the sum of the weight percentages of each refrigerant component is 100%.

[0050] Table 1

[0051]

[0052] Table 2

[0053]

[0054] Table 3

[0055]

[0056] Test method:

[0057] The design conditions are: evaporation temperature -50℃, condensation temperature 60℃, compressor 1 adiabatic efficiency of 0.75, heat exchanger 2 efficiency of 1, and suction superheat of 2℃. Theoretical calculations were performed using the cyclic performance parameters of the mixed refrigerants obtained from the above examples and comparative examples in the refrigeration system. All physical property data were taken from REFPROP 10.0. The GWP (calculated linearly by weight percentage), relative volumetric heating capacity Qv (ratio to R32 volumetric heating capacity), atmospheric boiling point (bubble point temperature), safety class, pressure ratio, and evaporation pressure were compared. Because the system pressure ratios of Comparative Examples 1, 3, and 5 were too high, they could not operate normally, and therefore their heating COP was not compared. The results are shown in Table 4.

[0058] Table 4

[0059]

[0060] As shown in the table above, Comparative Example 1, due to the use of only R32, resulted in an excessively high system pressure ratio, rendering it unable to operate normally. Comparative Example 2, being a non-ternary system, contained low-boiling-point, medium-boiling-point, and high-boiling-point components, but its relative volumetric cooling capacity was low. Comparative Example 3, lacking CO2, contained only medium-boiling-point and high-boiling-point components, resulting in a low relative volumetric cooling capacity, a high boiling point, and an excessively high pressure ratio, rendering it unable to operate normally. Comparative Example 4, also lacking R32, contained only low-boiling-point and high-boiling-point components, resulting in a low relative volumetric cooling capacity. Comparative Example 5, lacking both CO2 and R32, contained only high-boiling-point components, resulting in a low relative volumetric cooling capacity, a high boiling point, an excessively high pressure ratio, and poor safety, rendering it unable to operate normally.

[0061] As shown in the table above, the GWP of Examples 1 to 23 are all below 675, achieving a safety level of A2L. Their environmental and safety performance is comparable to or better than Comparative Example 1. The relative volumetric heating capacity of all refrigerant formulations is greater than 1, showing a significant improvement compared to R290. The heating COP is much greater than 1, demonstrating energy-saving effects compared to electric heating. The atmospheric pressure bubble point temperature is below -60℃, allowing normal operation in environments down to -45℃. The compressor pressure ratio is much lower than R32, and the evaporation pressure is much higher than R32. Therefore, this invention provides an environmentally friendly, safe, and operable mixed refrigerant suitable for extreme operating conditions.

[0062] As shown above, a mixed refrigerant is obtained by synergistically combining carbon dioxide, difluoromethane, and one of the following components: 1,1-difluoroethane, trans-1,3,3,3-tetrafluoropropene, cis-1,3,3,3-tetrafluoropropene, or trans-1-chloro-3,3,3-trifluoropropene. This mixed refrigerant significantly improves environmental friendliness and safety while maintaining system operational stability. Its overall performance is superior to that of difluoromethane, effectively avoiding the environmental and usage risks associated with traditional refrigerants due to their high GWP or flammability. Furthermore, the refrigerant exhibits excellent evaporation characteristics at extremely low temperatures (-45℃), meeting the separation and synergistic requirements of high and low boiling point components in a self-cascade cycle. This enables reliable system operation under extreme conditions, overcoming the technical bottleneck of existing refrigerants' inability to balance low-temperature performance and system compatibility. Therefore, the self-cascade heat pump system equipped with the mixed refrigerant is suitable for hot water supply under extremely low temperature conditions.

[0063] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A mixed refrigerant, characterized in that, The operating temperature of the mixed refrigerant includes -60℃ to -45℃; the mixed refrigerant is composed of a first component, a second component, and a third component, wherein the first component is CO2, the second component is difluoromethane, and the third component is one of 1,1-difluoroethane, trans-1,3,3,3-tetrafluoropropene, cis-1,3,3,3-tetrafluoropropene, or trans-1-chloro-3,3,3-trifluoropropene.

2. The mixed refrigerant according to claim 1, characterized in that, In the mixed refrigerant, the weight percentage of the first component is 10-30%, the weight percentage of the second component is 50-75%, and the weight percentage of the third component is 10-25%.

3. The mixed refrigerant according to claim 1 or 2, characterized in that, In the mixed refrigerant, the weight percentage of the first component is 10-25%, the weight percentage of the second component is 50-75%, and the third component is 1,1-difluoroethane, with the weight percentage of 1,1-difluoroethane being 10-25%.

4. The mixed refrigerant according to claim 1 or 2, characterized in that, In the mixed refrigerant, the weight percentage of the first component is 10-25%, the weight percentage of the second component is 50-75%, and the third component is trans-1,3,3,3-tetrafluoropropylene, with the weight percentage of trans-1,3,3,3-tetrafluoropropylene being 10-25%.

5. The mixed refrigerant according to claim 1 or 2, characterized in that, In the mixed refrigerant, the weight percentage of the first component is 10-30%, the weight percentage of the second component is 50-70%, and the third component is cis-1,3,3,3-tetrafluoropropylene, with the weight percentage of cis-1,3,3,3-tetrafluoropropylene being 10-25%.

6. The mixed refrigerant according to claim 1 or 2, characterized in that, In the mixed refrigerant, the weight percentage of the first component is 15-30%, the weight percentage of the second component is 50-70%, and the third component is trans-1-chloro-3,3,3-trifluoropropylene, with the weight percentage of trans-1-chloro-3,3,3-trifluoropropylene being 10-25%.

7. The mixed refrigerant according to claim 1 or 2, characterized in that, In the mixed refrigerant The first component has a weight percentage of 10-25%, the second component has a weight percentage of 60-75%, and the 1,1-difluoroethane has a weight percentage of 10-15%; or, The first component has a weight percentage of 10-25%, the second component has a weight percentage of 60-75%, and the trans-1,3,3,3-tetrafluoropropylene has a weight percentage of 10-15%; or, The first component has a weight percentage of 15-30%, the second component has a weight percentage of 50-70%, and the cis-1,3,3,3-tetrafluoropropylene has a weight percentage of 10-20%; or... The first component has a weight percentage of 15-30%, the second component has a weight percentage of 50-70%, and the trans-1-chloro-3,3,3-trifluoropropene has a weight percentage of 10-25%.

8. The mixed refrigerant according to claim 1 or 2, characterized in that, The mixed refrigerant has a GWP value ≤ 525, a bubble point temperature at normal pressure ≤ -61.6℃, a relative Qv of 1.03~1.58 compared to difluoromethane, and a COP ≥ 1.

36.

9. The method for preparing the mixed refrigerant according to any one of claims 1 to 8, characterized in that, Includes the following steps: The components of the mixed refrigerant are mixed in a liquid phase at room temperature and pressure according to their respective weight percentages to obtain the mixed refrigerant.

10. A self-cascading heat pump system, the self-cascading heat pump system comprising a refrigerant, characterized in that, The refrigerant includes any one of the mixed refrigerants according to claims 1 to 8.

Images