COMPOSITIONS

Abstract

The invention provides a composition comprising carbon dioxide (CO2, R-744), difluoromethane (R-32) and trifluoroiodomethane (CF.sub.3I) and the use of such a composition as a working fluid in a heat transfer system, such as a refrigeration, heat pump or air-conditioning system.

Claims

1. A composition comprising: (a) carbon dioxide (CO.sub.2, R-744); (b) difluoromethane (R-32); and (c) trifluoroiodomethane (CF.sub.3I).

2. The composition according to claim 1 comprising from about 50 to about 98 weight % CO.sub.2, from about 52 or about 55 to about 95 weight %, from about 59 to about 92 weight %, from about 65 or 70 to about 90 weight %, or from about 75 to about 87 weight %.

3. The composition according to claim 1 comprising from about 1 to about 30 weight % R-32, such as from about 2 to about 25 weight %, from about 3 to about 21 weight %, or from about 3 to about 15 weight %.

4. The composition according to claim 1 comprising from about 1 or about 2 to about 20 weight % CF.sub.3I, from about 3 to about 15, or about 13 weight %.

5. The composition according to claim 1, wherein the composition additionally comprises 1,1-difluoroethylene (R-1132a).

6. The composition according to claim 5 comprising from about 1 or about 2 to about 20 weight % R-1132a, from about 4 to about 17 weight %, from about 7 to about 16 weight %, or from about 10 to about 15 weight %.

7. The composition according to claim 5 comprising R-32 and R-1132a in a combined amount of less than about 37 weight %, or less than about 35 weight %.

8. The composition according to claim 1 comprising R-32 and CF.sub.3I in a weight ratio of R-32 to CF.sub.3I of less than about 2:1, or less than about 1.8:1.

9. The composition according to claim 1, wherein the composition additionally comprises a further component selected from 1,1,1,2-tetrafluoroethane (R-134a), trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)), 2,3,3,3-tetrafluoropropene (R-1234yf) 1,1,1,2,3,3,3-heptafluoropropane (R-227ea) and mixtures thereof, or wherein the further component is R-134a and one or more of R-1234yf and R-1234ze(E).

10. The composition according to claim 9, wherein the composition comprises from about 1 about 15 weight % of the further component(s), from about 3 to about 12 weight %, or from about 4 or about 5 to about 10 weight %.

11. The composition according to claim 1 consisting essentially of the stated components.

12. The composition according to claim 1 wherein the composition is non-flammable as determined in accordance with ASHRAE Standard 34:2019.

13. The composition according to claim 1, wherein the composition has a Global Warming Potential (GWP) of less than about 220, less than about 210, less than about 200, less than about 150, or less than about 140.

14. The composition comprising a lubricant and a composition according to claim 1, preferably wherein the lubricant is selected from mineral oil, silicon oil, polyalkyl benzenes (PABs), polyol esters (POEs), polyalkylene glycols (PAGs), polyalkylene glycol esters (PAG esters), polyvinyl ethers (PVEs), poly (alpha-olefins) and combinations thereof, or wherein the lubricant is selected from PAGs, POEs and combinations thereof.

15. The composition according to claim 1, further comprising a stabiliser, preferably wherein the stabiliser is selected from diene-based compounds, phosphates, phenol compounds and epoxides, and mixtures thereof.

16. The composition according to claim 1 having a coefficient of performance (COP) which is greater than or about equal to that of CO.sub.2.

17. The composition according to claim 1 having a temperature glide in an evaporator of less than about 11K, less than about 9K, or less than about 7K.

18. The composition according to claim 1 having a volumetric refrigeration capacity which is within about 25% of that of CO.sub.2, within about 20%, or within about 15%.

19. The composition according to claim 1 wherein the composition has an operating pressure in a condenser or a gas cooler which is lower than that of CO.sub.2.

20. A method comprising providing a composition according to claim 1 as a working fluid in a heat transfer system comprising a refrigeration, heat pump or air-conditioning system.

21. The method of claim 20, wherein the refrigeration system comprises a commercial refrigeration system, such as a supermarket display refrigeration system, beverage cooler refrigeration system, warehouse refrigeration system or a cold-room refrigeration system.

22. The method of claim 20, wherein the refrigeration system comprises a transportation refrigeration system, such as a refrigeration system fitted to a refrigerating shipping container or a refrigeration system fitted to a vehicle.

23. The method of claim 20, wherein the heat pump system comprises a water heater heat pump system.

24. The method of claim 20, wherein the air-conditioning system comprises a transportation air-conditioning system, such as a bus, car, train or truck air-conditioning system.

25. The method of claim 20, wherein the heat transfer system operates as a transcritical heat transfer system for at least a part of the year.

26. The method comprising providing a composition according to claim 1 as a replacement for an existing working fluid in a heat transfer device, preferably wherein the existing working fluid is R-410A.

27. A heat transfer device comprising a composition as defined in claim 1.

28. A heat transfer device according to claim 27, wherein the heat transfer device is a transcritical heat transfer device comprising a transcritical refrigeration, heat pump or air-conditioning device.

29. The method of producing heating which comprises condensing a composition according to claim 1 in the vicinity of a body to be heated.

30. A method of producing cooling which comprises evaporating a composition according to claim 1 in the vicinity of a body to be cooled.

Description

EXAMPLES

[0062] The vapour liquid equilibrium behaviour of CO.sub.2 with CF.sub.3I and with R-32 is described in the academic literature and the available data was used to generate interaction parameters for use with the NIST REFPROP9.1 software. The vapour liquid equilibrium behaviour of CF.sub.3I with R-32 and R-1132a, and of R-1132a with CO.sub.2 and R-32 was studied experimentally in the temperature range −40° C. to 70° C. using a constant-volume equilibrium apparatus, and the resulting data also used to fit binary interaction parameters for each binary pair. The principle of measurement of this experimental work was the determination of vapour pressure for a series of known compositions over a range of temperatures, followed by regression to the thermodynamic model to minimise the difference between calculated and observed pressure over the data set.

[0063] The interaction parameters thus obtained were used with the NIST REFLEAK5.1 computer program to simulate the fractionation of ternary CO.sub.2/R-32/CF.sub.3I mixtures and quaternary R-744/R-1132a/R-32/CF3I mixtures at −40° C. The compositions studied had 1-30% R-32 and the quaternary compositions had up to 15% by weight R-1132a. The initial fill composition for these simulations was taken as 90% of maximum allowable liquid fill, where the allowable liquid fill was calculated according to the requirements of ASHRAE Standard 34 (2019). The fractionation was run from the initial fill to 95% mass loss for each composition.

[0064] Modelling of a series of compositions led to the following observations [0065] If the total amount of R-1132a+R-32 in the blend is less than about 35% then the initial vapour and liquid compositions are non-flammable. [0066] If the mass ratio of R-32 to CF.sub.3I in the composition is less than or equal to about 2:1 then the final liquid and vapour compositions will be substantially free of CO.sub.2 and R-1132a and will contain less than 58% by weight of R-32, ensuring they will be non-flammable

[0067] Standard refrigeration cycle modelling techniques were then used to estimate the performance of selected compositions of the invention. The performance of R-744 was also calculated as a comparative example. Where the cycle conditions resulted in the high-pressure side of the cycle operating above the fluid critical temperature (a “transcritical” cycle) then the compressor discharge pressure was varied to optimise the cycle efficiency (Coefficient of Performance—COP). The cycle modelled was a transcritical cycle using an internal heat exchanger (IHX) to exchange heat between the gas leaving the gas cooler and the low-pressure vapour leaving the evaporator.

[0068] The following conditions were assumed for the modelling purposes:

TABLE-US-00001 TABLE 1 Model input conditions Air temperature rise over gas cooler 10 K Air on temperature 33 ° C. Air off temperature 43 ° C. Temperature approach in gas cooler 4 K Capacity 6 kW Mean evaporation temperature 7 ° C. Evaporator superheat 0 K Suction line heat gain across IHX 20 K isentropic efficiency 65%

[0069] The performance data for the selected compositions of the invention is shown in Table 2 below.

[0070] It can be seen from the performance data that the compositions of the invention have superior energy efficiency and reduced operating pressures compared to CO.sub.2. In addition, the GWP of the compositions is less than about 210.

[0071] From the performance data, it can be seen that is not desirable to include more than about 30 weight % R-32 in these compositions because the temperature glide in the evaporator becomes greater than 11K. R-32 content of 21% or lower ensures the GWP of the composition will be lower than 150, which is required for some applications under the EU F-Gas Regulation.

[0072] The compositions of the invention can be further augmented by the addition of R-1132a, for example by substitution of a portion of the R-744 content with R-1132a, so that the R-1132a content is between 1% and 15% by weight without generating a flammable composition during fractionation. Addition of R-1132a reduces compressor discharge temperature and reduces the temperature glide in the evaporator. Such compositions also have higher energy efficiency and reduced operating pressures compared to R-744.

TABLE-US-00002 TABLE 2 Compositions comprising CO.sub.2, R-32, CF.sub.3I and, optionally, R-1132a. R744 100% 59% 58% 54% 52% 55% 62% 68% 70% 76% R1132a 0% 10% 10% 15% 10% 0% 0% 0% 0% 0% R32 0% 21% 21% 21% 25% 30% 25% 21% 20% 16% CF3I 0% 10% 11% 10% 13% 15% 13% 11% 10% 8% Coefficient of 2.69 3.12 3.12 3.10 3.21 3.30 3.22 3.16 3.14 3.04 Performance Volumetric kJ/m.sup.3 14497 11646 11591 11333 11288 11364 11852 12208 12312 12497 cooling capacity Compressor ° C. 102.6 105.6 105.9 103.7 107.7 113.5 111.8 109.7 109.0 106.5 discharge temperature Evaporator bar 41.8 28.1 27.8 27.7 25.8 24.2 26.5 28.5 29.2 31.4 pressure Gas cooler bar 90.2 62.8 62.4 61.7 58.9 56.9 61.0 64.4 65.5 68.9 pressure Evaporator glide K 0.0 7.8 8.0 7.7 9.1 10.4 9.4 8.3 7.8 6.4 COP 100.0% 116.1% 116.2% 115.5% 119.4% 122.9% 120.0% 117.5% 116.8% 113.3% Q.sub.vol 100.0% 80.3% 79.9% 78.2% 77.9% 78.4% 81.8% 84.2% 84.9% 86.2% GWP 1 142 142 142 169 203 169 142 136 109