Refrigerant

Abstract

To produce a refrigerant that contains carbon dioxide and can reach temperatures much lower than -57°C in an environmentally controlled laboratory. The refrigerant for a refrigeration device (10) contains a gas mixture containing at least carbon dioxide, 1,1,1,2-tetrafluoroethane, and difluoromethane, and is characterized in that the carbon dioxide content exceeds 50 mass% of the total gas mixture.

Description

[Technical field]

[0001] The present invention relates to refrigerants. In particular, such refrigerants are used in cooling devices operating in environmentally controlled test chambers. Such test chambers have an insulated space in which mechanical bodies can be installed for testing under various conditions of temperature, humidity and pressure. In such an insulated space, it is often necessary to reach very low temperatures, below minus 60°C (-60°C, 213.15K). [Background technology]

[0002] It is well known that according to legal provisions, refrigerants must not significantly contribute to the widening of the hole in the ozone layer in the atmosphere or to global warming. Therefore, halogenated compounds, especially fluorinated and chlorinated gases, can no longer be used as refrigerants. In addition, refrigerants used in refrigeration equipment must be non-flammable in order to make their filling, transportation and operation in the laboratory easier and safer in the light of possible safety regulations that must be observed. Furthermore, when using flammable refrigerants, the production of the circuits through which the refrigerant flows in the refrigeration equipment becomes more expensive due to the technical measures required in that case. Flammable here means that the refrigerant reacts with the surrounding oxygen to generate heat. In particular, a refrigerant is flammable if it falls under fire classes A2L, A2 and A3 C according to the EN 378 or Din 378 regulations.

[0003] Furthermore, it is necessary for the refrigerant to have a relatively low CO2 equivalent value. Essentially, its relative global warming potential (also known in the UK as "Global Warming Power" or "GWP") needs to be as small as possible to avoid indirect damage to the environment if the refrigerant is released. GWP measures a defined mass of a greenhouse gas that contributes to global warming. Such values ​​are set relative to carbon dioxide and therefore act as a reference value. GWP therefore represents the average heating effect of a particular gas or gas mixture over a specific time interval (in this case 100 years). For the definition of the CO2 equivalent or the respective GWP, see this specification and Regulation (EU) No. 517 / 2014 of the European Parliament and of the Council.

[0004] In light of the above considerations, refrigerants have been developed that have a low GWP and are in any case non-flammable. In this regard, refrigerants that use mixtures containing, inter alia, carbon dioxide, 1,1,1,2-tetrafluoroethane (also known as R134a) and difluoromethane (also known as R32) are known.

[0005] In particular, a first embodiment of International Publication WO 2005 / 023332 of Imperial Chemical Industries Ltd. discloses a mixture containing 2-15% by weight of carbon dioxide, 30-96% by weight of R134a, and 2-55% by weight of R32 relative to the total mixture. According to a further embodiment of the same International Publication, the mixture contains 1-20% by weight of carbon dioxide, 5-60% by weight of R134a, and 30-90% by weight of R32 relative to the total mixture.

[0006] Also, Patent Document 2 by Clodic Davis et al. discloses a mixture containing carbon dioxide, R134a and R32. However, in this international publication, the cooling mixture contains 3-7 mass % carbon dioxide, 65-75 mass % R134a and 15-25 mass % R32 based on the total mixture.

[0007] Furthermore, Patent Document 3 to Daikin Industries, Ltd. discloses a refrigerant consisting of a mixture of carbon dioxide, R134a, and R32, with 1-3% by mass of carbon dioxide, 74-62% by mass of R134a, and 25-35% by mass of R32, based on the total. Finally, Patent Document 4 to Showa Denko K.K. discloses another refrigerant containing carbon dioxide, R32, and R134a. In one embodiment described in Patent Document 4, R32, R134a, and carbon dioxide have a mass of 5.70%, 89.47%, and 4.82%, respectively, based on the total mass of the mixture.

[0008] The mixtures described above can be used in conventional refrigeration equipment, have a very low GWP and are non-flammable. However, they cannot expose the insulated space of the test chamber in which the test components are located to temperatures below minus 50°C (-50°C, 223.15K).

[0009] There are also various mixtures of refrigerants consisting of carbon dioxide and pentafluoroethane (R125). For example, patent document 5 of WEISS UMWELTTECHNIK GMBH discloses a refrigerant consisting of carbon dioxide and pentafluoroethane (R125), with the carbon dioxide being 20-80% by mass. However, such solutions are not only technically unable to reach temperatures below minus 57°C (-57°C, 216.15K), but also have a high GWP. In addition, this type of mixture runs the risk of freezing in the circuits of the refrigeration equipment when very low temperatures are required, thus causing major problems for the entire climate-controlled test room in which the refrigeration equipment is installed. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. 1996 / 002606 [Patent Document 2] International Publication No. 2000 / 066678 [Patent Document 3] Japanese Patent Application Publication No. 06-867870 [Patent Document 4] Japanese Patent Application Publication No. 06-220435 [Patent Document 5] US Patent Application Publication No. 2019 / 0093926 Summary of the Invention [Problem to be solved by the invention]

[0011] It is therefore an object of the present invention to produce a refrigerant that, inter alia, contains carbon dioxide and is capable of reaching temperatures much lower than minus 57 degrees Celsius (−57° C., 216.15 K) in an environmentally controlled laboratory.

[0012] A further object of the invention is to produce cooling mixtures which are non-flammable and have the lowest possible GWP value.

[0013] Furthermore, it is an object of the present invention to identify an alternative refrigerant to R23 gas, which has been used so far in refrigeration systems installed in environmentally controlled test chambers, where it is desired to reach temperatures below -55°C, while at the same time achieving a very low GWP.

[0014] Finally, it is an object of the present invention to produce a refrigerant that can be circulated in existing climate-controlled laboratory refrigeration equipment without modification to the refrigeration equipment. [Means for solving the problem]

[0015] These objects are achieved by a refrigeration system refrigerant comprising a gas mixture, the gas mixture comprising at least carbon dioxide, 1,1,1,2-tetrafluoroethane and difluoromethane, the carbon dioxide representing more than 50% by weight of the total mixture.

[0016] It has been proven that such cooling mixtures are capable of functioning in the insulated areas of an environmentally controlled test chamber at temperatures well below minus 57°C. Moreover, such refrigerants have a very low GWP and are non-flammable. This type of cooling mixture, which essentially removes the technical prejudice that more than 50% by mass of carbon dioxide in the total mixture of refrigerant gases can harm the operation of the cooling equipment in which it circulates, has been proven to be able to effectively replace environmentally harmful refrigerant gases and even refrigerant gases that are not environmentally harmful but cannot reach very low temperatures below minus 57°C (-57°C, 216.15K).

[0017] Carbon dioxide accounts for 50% by mass to 75% by mass of the entire mixture. In particular, carbon dioxide accounts for 67% by mass to 70% by mass, and preferably 69% by mass, of the entire mixture.

[0018] Furthermore, 1,1,1,2-tetrafluoroethane (R134a) accounts for 12.5% ​​by mass to 22% by mass, preferably 19% by mass, of the entire mixture.

[0019] Advantageously, difluoromethane represents between 9% and 19% by weight of the total mixture, preferably 12% by weight.

[0020] This final mixture has surprisingly proven to be capable of lowering its own freezing temperature while at the same time rendering itself non-flammable.

[0021] In particular, said mass percentages of carbon dioxide, 1,1,1,2-tetrafluoroethane and difluoromethane are such that said mixture is non-flammable.

[0022] Furthermore, the present invention provides a refrigerator including a refrigeration device having a closed circuit through which a refrigerant circulates, the closed circuit including at least one compressor, a cooling means for the refrigerant, an expansion means for the refrigerant, and at least one evaporator, and the refrigerant according to any one of claims 1 to 6 circulates through the closed circuit.

[0023] Furthermore, such a refrigerator comprises a second refrigeration device having a second closed circuit in which a second refrigerant circulates, said second closed circuit comprising at least one second compressor, a second cooling means for said second refrigerant, a second expansion means for said second refrigerant and at least one second evaporator, said at least one second evaporator being used to cool said refrigerant circulating in said cooling means of said closed circuit, said second refrigerant being different from said refrigerant. In particular, preferably said second refrigerant comprises R404A, or R449A, or R452A, or other refrigerants having similar thermodynamic properties, in particular capable of condensing at a temperature close to the outside air temperature.

[0024] Finally, an environmentally controlled test chamber is also provided, having an insulated space in which a test sample is mounted, in which the test is carried out, and characterized in that it comprises a refrigerator according to any one of claims 7 to 9.

[0025] Some particular embodiments of the present invention will now be described, by way of non-limiting examples, with reference to the accompanying FIG. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic diagram of a refrigerator in an environmentally controlled test chamber with an insulated space inside in which a test sample is placed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Fig. 1 shows in a simplified manner a refrigerator 1 equipped with a refrigeration unit 10 having a closed circuit C in which a refrigerant circulates. The closed circuit C comprises a main compressor 2, at least one cooling device 3 for the refrigerant (also called a condenser if the refrigerant undergoes a phase change), a means of expansion 4 of the refrigerant and an evaporator 5. The expansion means 4 in a particular case comprise a thermostatic type expansion valve, in other embodiments it can comprise a capillary line or other mechanisms without departing from the scope of protection of the present invention.

[0028] The refrigerator 1 further comprises a second refrigeration unit 15 having a second closed circuit C1 in which a second refrigerant circulates. Such second closed circuit C1 comprises a second compressor 21, a second cooling means 31 for the second refrigerant, a second expansion means 41 for the second refrigerant and a second evaporator 51. According to the embodiments described herein, the second evaporator 51 is used to cool and / or condense the refrigerant circulating in the cooling means 3 of the closed circuit C of the refrigerator 10. Essentially, the refrigerator 1 comprises two cascaded refrigeration units 10 and 15.

[0029] Such a refrigerator 1 is used in a known environmentally controlled test chamber (or test chamber) 20, not described in detail here and not shown in detail in Figure 1. Such a test chamber 20 comprises an insulated space 21 in which test specimens 22 are placed, on which tests are carried out under different environmental conditions.

[0030] Advantageously, the second refrigerant is different from the refrigerant circulating in the closed circuit C of the refrigeration device 10 and preferably comprises R404A. As an alternative to R404A, such a second refrigerant may also comprise R449A, or R452A, or other refrigerants having similar thermodynamic properties.

[0031] On the other hand, the refrigerant according to the present invention operating in the refrigeration device 10 of the closed circuit C contains a gas mixture. Such a gas mixture contains at least carbon dioxide, 1,1,1,2-tetrafluoroethane and difluoromethane, with carbon dioxide representing more than 50% by mass of the total gas mixture.

[0032] In particular, according to the embodiment described herein, the carbon dioxide represents 69% by weight of the total mixture, but in any case, refrigerants representing 50% to 75% by weight of the total mixture, preferably 67% to 70% by weight of the total mixture, are still within the scope of the present invention.

[0033] According to the present invention, 1,1,1,2-tetrafluoroethane (or R134a) is 19% by weight, but in another embodiment, the weight percentage of 1,1,1,2-tetrafluoroethane can be between 12.5% ​​and 22% by weight of the total mixture without departing from the scope of the present invention.

[0034] Furthermore, difluoromethane (or R32) is 12% by mass relative to the entire mixture. However, a difluoromethane content of 9% to 19% by mass relative to the entire mixture would fall within the scope of the present invention.

[0035] Basically, according to the preferred embodiment described herein, the cooling mixture that is the object of the present invention therefore comprises 69% by weight, relative to the total mixture, of carbon dioxide, 19% by weight, relative to the total mixture, of 1,1,1,2-tetrafluoroethane (or R134a) and 12% by weight, relative to the total mixture, of difluoromethane (or R32).

[0036] Such compositions have been proven to be non-flammable.

[0037] The inventors have also demonstrated that such refrigerant compositions can reach temperatures much lower than -57°C (216.15K), even down to about -78°C (195.15K), in the insulated space 21 of the environmentally controlled test chamber 20. Moreover, the refrigerants thus obtained have a very low GWP value, i.e. less than 380 for 100 years. Finally, such refrigerants do not contribute to the greenhouse effect. [Explanation of symbols]

[0038] 1. Refrigeration unit 2. Main Compressor 3 Cooling equipment, cooling means 4. Expansion means 5. Evaporator 10 Refrigeration equipment 15 Second Refrigeration Unit 20 Test Room 21 Insulated Space 22 Test Samples 31 Second cooling means 41 Second expansion means 51 Second evaporator C closed circuit C1 2nd closed circuit

Claims

1. A refrigerant for a refrigeration system (10) comprising a gas mixture containing at least carbon dioxide, 1,1,1,2-tetrafluoroethane and difluoromethane, in which carbon dioxide is more than 50 mass% of the entire gas mixture, characterized in that carbon dioxide accounts for more than 50 mass% to 75 mass% of the entire gas mixture.

2. 2. The refrigerant for a refrigeration system (10) according to claim 1, characterized in that carbon dioxide accounts for 67% to 70% by mass of the total gas mixture.

3. The refrigerant for a refrigeration system (10) according to claim 2, characterized in that 1,1,1,2-tetrafluoroethane constitutes 12.5% ​​to 22% by mass of the total gas mixture.

4. The refrigerant for a refrigeration system (10) according to claim 2 or 3, characterized in that difluoromethane accounts for 9% to 19% by mass of the total gas mixture.

5. A refrigerant for a refrigeration system (10) according to any one of claims 1 to 4, characterized in that the mass percentages of carbon dioxide, 1,1,1,2-tetrafluoroethane and difluoromethane are such that the gas mixture is non-flammable.

6. A refrigerator (1) including a refrigeration device (10) having a closed circuit (C) through which a refrigerant circulates, the closed circuit (C) including at least one compressor (2), a cooling means (3) for the refrigerant, an expansion means (4) for the refrigerant, and at least one evaporator (5), wherein the refrigerant according to any one of claims 1 to 5 circulates through the closed circuit (C).

7. The system further includes a second refrigeration device (15) having a second closed circuit (C1) through which a second refrigerant circulates, the second closed circuit (C1) comprises at least one second compressor (21), a second cooling means (31) for the second refrigerant, a second expansion means (41) for the second refrigerant, and at least one second evaporator (51); 7. The refrigerator (1) according to claim 6, characterized in that the at least one second evaporator (51) is used to cool the refrigerant circulating in the cooling means (3) of the closed circuit (C), the second refrigerant being different from the refrigerant.

8. 8. The refrigerator (1) according to claim 7, characterized in that the second refrigerant comprises R404A, or R449A, or R452A, or any other refrigerant having similar thermodynamic properties.

9. An environmentally controlled test chamber (20) having an insulated space (21) in which a test specimen (22) to be tested is mounted, characterized in that it is equipped with a refrigerator (1) as claimed in any one of claims 6 to 8.

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