COMPOSITIONS

Abstract

According to the present invention, there is provided a composition carbon dioxide (CO.sub.2, R-744), difluoromethane (R-32) and 1,1-difluoroethylene (R-1132a).

Claims

1. A composition comprising: (a) carbon dioxide (CO.sub.2, R-744); (b) difluoromethane (R-32); and (c) 1,1-difluoroethylene (R-1132a).

2. The composition according to claim 1 comprising from about 1 to about 40 or about 30 weight % R-32, from about 1 to about 25 or about 22 weight %, from about 2 or about 3 to about 20 weight %, optionally or from about 4 to about 18 or about 20 weight %.

3. The composition according to claim 1 comprising at least about 35 weight % CO.sub.2, at least about 37 weight %, at least about 40 weight %, at least about 42 weight % or at least about 45 weight %.

4. The composition according to claim 1 comprising at least about 28 weight % R-1132a, at least about 30 weight %, at least about 32 weight %, at least about 34 weight %, at least about 35 weight %, at least about 37 weight %, at least about 39 weight %, or at least about 40 weight %.

5. The composition according to claim 1 comprising from about 38 to about 70 weight % CO.sub.2, from about 40 to about 65 weight %, from about 42 to about 62 weight %, from about 44 to about 60 weight %, or from about 46 to about 58 weight %.

6. The composition according to claim 1 comprising from about 29 weight % to about 55 weight % R-1132a, from about 31 to about 52 weight %, from about 34 to about 49 weight % or from about 35 to about 47 weight %.

7. The composition according to claim 1 comprising from about 30 to about 70 weight % CO.sub.2, from about 1 to about 25 weight % R-32 and from about 28 to about 50 weight % R-1132a, from about 35 to about 65 weight % CO.sub.2, from about 2 to about 22 weight % R-32 and from about 30 to about 48 weight % R-1132a, or from about 40 to about 60 weight % CO.sub.2, from about 3 to about 20 weight % R-32 and from about 32 to about 46 weight % R-1132a.

8. The composition according to claim 1, wherein the composition additionally comprises a further component selected from monofluoromethane (R-41), pentafluoroethane (R-125), trifluoroethylene (R-1123), 1,1,1,2-tetrafluoroethane (R-134a), 1,1-difluoroethane (R-152a), 2,3,3,3-tetrafluoropropene (R-1234yf), trans-1,3,3,3-tetrafluoropropene (R-1234ze(E)) and mixtures thereof.

9. The composition according to claim 8, wherein the further component is present in the composition in an amount of from about 1 to about 10 weight %, from about 1 to about 8 weight %, from about 2 to about 6 weight % or from about 3 to about 5 weight %.

10. The composition according to claim 8 wherein the further component is selected from R-134a, R-152a, R-1234yf and R-1234ze(E) and mixtures thereof, or wherein the further component is present in an amount of from about 1 to about 5 weight %, optionally wherein the further component is R-134a.

11. The composition according to claim 1, wherein the composition additionally comprises a hydrocarbon.

12. The composition according to claim 11, wherein the hydrocarbon is present in an amount of from about 1 to about 5 weight %, or from about 1 or about 2 to about 4 weight %.

13. The composition according to claim 11, wherein the hydrocarbon is selected from propane (R-290), isobutane (R-600a), ethane (R-170) and mixtures thereof.

14. The composition according to claim 1 comprising the CO.sub.2 and the R-1132a in a weight ratio of from about 1:1 to about 2.5:1, from about 1.05:1 to about 2:1, or from about 1.1:1 to about 1.6:1.

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

16. The composition according to claim 1, wherein the composition is classified as weakly flammable (“class 2L”) as determined in accordance with ASHRAE Standard 34:2019, and/or wherein the composition has a burning velocity of less than about 10 cm/s, less than about 9 cm/s, or less than about 8 cm/s.

17. The composition according to claim 1, wherein the composition has a Global Warming Potential (GWP) of less than about 200, less than about 170, or less than about 150.

18. The composition according to claim 1, wherein the composition has a volumetric cooling capacity which is within about 25% of that of R-23, within about 20%, within about 15%, or within about 10%.

19. The composition according to claim 1, wherein the composition has a coefficient of performance (COP) which is within about 10% of that of R-23, within about 7%, or within about 5%.

20. The composition according to claim 1, wherein the composition has a temperature glide in a condenser or evaporator which is less than about 15K, less than about 12K, less than about 10K, or less than about 8K.

21. The composition according to claim 1, wherein the composition has a compressor discharge temperature which is below about 140° C., below about 130° C., below about 120° C., or below about 110° C.

22. The composition according to claim 1, wherein the composition has an operating pressure in a condenser which is 2 bar±20%, or 2 bar±10%.

23. The composition according to claim 1, wherein the composition has an operating pressure in an evaporator which is 0.5 bar±20%, or 0.5 bar±10%.

24. The composition according to claim 1, wherein the composition does not solidify at a temperature of about −70° C. or higher when in operation, or about −75° C. or higher.

25. The A composition according to claim 1, wherein the composition has a pressure ratio over a compressor which is within about 20% of that of R-23, or within about 10%.

26. A method comprising providing a composition according to claim 1 as a working fluid in a heat transfer system.

27. The method of claim 26, wherein the heat transfer system is a refrigeration system, optionally comprising a cascade refrigeration system.

28. The method of claim 26, wherein the heat transfer system is selected from low-temperature blast freezing systems, climate chamber (e.g. wind tunnel) temperature control systems, biomedical refrigeration systems, food refrigeration systems, or low-temperature refrigerated food transport containers.

29. The method comprising providing a composition as defined in claim 1 as an alternative for an existing working fluid in a heat transfer system, optionally wherein the existing working fluid is R-23 or R-508.

30. A heat transfer system comprising a composition as defined in claim 1.

31. The heat transfer system according to claim 30, wherein the heat transfer is selected from low-temperature blast freezing systems, climate chamber (e.g. wind tunnel) temperature control systems, biomedical refrigeration systems, food refrigeration systems, and low-temperature refrigerated food transport containers.

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

33. A method of producing heating which comprises condensing or cooling a composition according to claim 1 in the vicinity of a body to be heated.

Description

EXAMPLES

[0063] The laminar burning velocity of mixtures of R-1132a with R-744 was tested using the vertical tube method of Jabbour as referenced by ASHRAE Standard 34. The laminar burning velocity of R-32 is 6.7 cm/s and the compositions of the present invention are anticipated to have an overall burning velocity of less than 10 cm/s.

[0064] The binary vapour-liquid equilibrium of R-1132a with R-744 and R-1132a with R-32 was studied in a constant-volume cell in the temperature range −70° C. to 10° C. The general experimental method consisted of the measurement of vapour pressure of known binary mixture compositions over the temperature range to yield a pressure-temperature-composition data set. The data were then regressed to a thermodynamic model capable of representing vapour-liquid equilibrium and also solid-liquid equilibrium. The model used was the Peng-Robinson equation of state using the mixing rules of Wong and Sandler, with liquid phase free energy being correlated to the NRTL model (Referred to hereafter as PRWS/NRTL model). At temperatures below the triple point of R-744, the formation of solid CO.sub.2 was observed at high CO.sub.2 concentrations in the binary R-1132a/CO.sub.2 system. The Schroeder equation was used with the NRTL equation parameters fitted to VLE data to predict the liquid composition in equilibrium with solid CO.sub.2 at these temperatures. It was found to give excellent agreement with experiment with the observed onset of solid formation as shown in FIG. 1.

[0065] The vapour-liquid equilibrium data available in the literature for R-744 with R-32 were fitted to the same PRWS/NRTL model and the resulting NRTL parameters were then used to provide an estimate of the solubility of solid R-744 in the fluorocarbon mixtures at temperatures below the triple point of R-744.

[0066] Next, a thermodynamic cycle model was constructed in the Matlab programming environment using standard cycle modelling techniques. The model used the PRWS/NRTL framework with additional code to estimate the temperature for onset of solid R-744 formation for each composition studied. The compositions were modelled in comparison to R-23 as a reference fluid.

[0067] Table 1 shows the cycle conditions chosen, which are thought to be representative of the operating conditions in the low temperature stage of a very low temperature refrigerated food transportation system.

TABLE-US-00001 TABLE 1 Cycle modelling conditions Parameter Units Value Evaporator temperature ° C. −70 Condenser temperature ° C. −30 Subcooling K. 5 Evaporator superheat K. 5 Suction line superheat K. 30 compressor efficiency % 65% compressor clearance ratio %  3%

[0068] The performance of selected compositions of the invention are shown in Tables 2 and 3 below with R-23 as the reference fluid. Table 4 demonstrates the estimated solid formation temperature of the compositions of the present invention further comprising R-134a.

[0069] From the performance data, it can be seen that the performance of the compositions of the invention is acceptably close to that of R-23. For example, the compositions of the invention preferably exhibit one or more of the following performance properties: [0070] Volumetric cooling capacity from about 90% to 120% of that of R-23 [0071] Coefficient of performance (energy efficiency) within about 5% of that of R-23 [0072] Temperature glide of about 10K or less [0073] Compressor discharge temperatures of below about 130° C. [0074] Similar pressure ratio over compressor as R-23 (which translates into similar volumetric efficiency) [0075] Operating pressures of about 2 bar on condenser and about 0.5 bar on evaporator [0076] Solid formation temperature of below about −70° C. [0077] Global Warming Potential below 150

[0078] It can also be seen from the performance data that reducing the weight ratio of R-744 to R-1132a increases burning velocity but reduces glide, discharge temperature and solid dry ice onset temperature.

TABLE-US-00002 TABLE 2 Compositions shown in mass % - anticipated to have burning velocity similar to that of R-32 R-744 57 56 55 54 53 52 50 49 48 R-1132a 39 38 37 36 35 34 34 33 32 R-32 4 6 8 10 12 14 16 18 20 Parameter Unit Volumetric Cooling Capacity kJ/m.sup.3 1655 1578 1510 1448 1393 1349 1294 1252 1216 Capacity relative to R-23 124.4% 118.6% 113.5% 108.9% 104.8% 101.4% 97.3% 94.1% 91.4% Coefficient of Performance 2.29 2.27 2.25 2.24 2.23 2.23 2.23 2.24 2.24 (COP) COP relative to R-23 96.9% 96.0% 95.4% 95.0% 94.7% 94.4% 94.7% 94.8% 95.0% Average temperature glide K 2.8 3.9 5.0 6.0 7.0 8.0 8.7 9.4 10.1 Compressor exit temperature ° C. 98.7 102.0 105.1 107.8 110.3 114.1 113.6 115.4 116.4 Condenser pressure bar 12.7 12.3 11.9 11.5 11.2 10.9 10.5 10.2 9.9 Evaporator pressure bar 2.46 2.32 2.20 2.09 1.99 1.90 1.81 1.74 1.67 Pressure ratio 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.9 GWP 28 42 55 69 82 96 109 123 136 Estimated solid formation ° C. −70.9 −71.9 −72.8 −73.8 −74.8 −75.7 −77.2 −78.2 −79.2 temperature

TABLE-US-00003 TABLE 3 Compositions shown in mass % - anticipated to have burning velocity of 9 cm/s R744 51 50 49 48 46 45 44 43 41 R1132a 45 44 43 42 42 41 40 39 39 R32 4 6 8 10 12 14 16 18 20 Parameter Unit Volumetric Cooling Capacity kJ/m.sup.3 1631 1558 1491 1430 1372 1323 1278 1236 1194 Capacity relative to R-23 122.6% 117.1% 112.1% 107.5% 103.1% 99.5% 96.0% 92.9% 89.7% Coefficient of Performance 2.30 2.28 2.26 2.25 2.25 2.24 2.24 2.25 2.25 (COP) COP relative to R-23 97.4% 96.5% 95.8% 95.4% 95.3% 95.0% 95.0% 95.2% 95.4% Average temperature glide K 2.8 3.9 4.9 5.8 6.7 7.7 8.5 9.2 9.8 Compressor exit temperature ° C. 94.5 97.9 100.9 103.4 105.1 107.5 109.4 111.1 111.8 Condenser pressure bar 12.4 12.1 11.7 11.3 11.0 10.7 10.4 10.0 9.7 Evaporator pressure bar 2.43 2.30 2.18 2.07 1.97 1.88 1.79 1.72 1.65 Pressure ratio 5.1 5.3 5.4 5.5 5.6 5.7 5.8 5.8 5.9 GWP 28 42 55 69 82 96 109 123 136 Estimated solid formation ° C. −73.3 −74.4 −75.5 −76.6 −78.2 −79.3 −80.4 −81.6 −83.3 temperature

TABLE-US-00004 TABLE 4 effect of adding 10% R-134a to compositions of Table 3 to solid onset temperature Compositions shown in mass % - anticipated to have burning velocity similar to that of R-32 R-744 51 50 50 49 48 47 45 44 43 R-1132a 35 34 33 32 32 31 31 30 29 R-32 4 5 7 9 11 13 14 16 18 R-134a 10 10 10 10 10 10 10 10 10 Parameter Unit Estimated solid formation ° C. −73.0 −73.9 −74.9 −75.8 −76.8 −77.7 −79.2 −80.2 −81.1 temperature