REFRIGERANT

Abstract: A refrigerant which comprises tetrafluoroethane and chlorodifluoromethane or chlorodifluoroethane is disclosed.

Description: This invention relates to the new use of a composition comprising tetrafluoroethane and either chlorodifluoromethane or chlorodifluoroethane as refrigerant. Refrigerants heretofore known include chlorofluoroalkanes, fluoroalkanes, azeotropic compositions thereof and other materials having a similar composition. These are generally called flons or flon refrigerants. Among them, chiefly used at present are dichlorodifluoromethane (hereinafter referred to as "CFC-12"), chlorodifluoromethane (hereinafter called "HCFC-22") and the like. In recent years, however, it has been pointed out that certain kinds of "CFCs or HCFCs" released into the atmosphere would destroy the stratospheric ozone layer, thereby inflicting a serious adverse influence on the ecosystem including humans on the earth. Although said proposition may have yet to be scientifically and completely established, there is a tendency toward the control, under an international agreement, of use and production of CFCs or HCFCs which are likely to destroy the ozone layer. The flons to be controlled include CFC-12. With the spread of refrigerators and air-conditioning systems, the control over the use and production of CFCs or HCFCs which are in greater demand year after year, greatly affects our residential environment and the current social framework as a whole. In consequence, there is an urgent demand for development of novel refrigerants having a high refrigerating performance, particularly a high coefficient of performance, which can substitute for CFC-12. Tetrafluoroethane may be offered as CFCs or HCFCs free of ozone layer-destroying risks but has the defect of being low in coefficient of performance. The term "coefficient of performance" used herein means the ratio of refrigerating capacity to compressing work. The refrigerating capacity is the quantity of heat removed per a unit time from the substances being cooled, and the compressing work is the work volume achieved per a unit time by power for operating the refrigerator. Accordingly the coefficient of performance corresponds to the refrigeration efficiency of the refrigerant. We conducted extensive research to develop novel refrigerants which have a high coefficient of performance and which, when released into the atmosphere, would exert little influence on the ozone layer. Our research revealed that a refrigerant comprising tetrafluoroethane and chlorodifluoromethane or chlorodifluoroethane can exhibit a higher coefficient of performance than tetrafluoroethane. The present invention, therefore, provides the new use of a composition comprising tetrafluoroethane and either chlorodifluoromethane or chlorodifluoroethane as refrigerant. Figs. 1 and 2 show graphs illustrating the refrigerating performance of the refrigerants according to the present invention. The preferably used refrigerant compositions of the invention are those comprising 95 to 5% by weight of tetrafluoroethane and 5 to 95% by weight of either chlorodifluoromethane or chlorodifluoroethane. Refrigerants containing chlorodifluoromethane or chlorodifluoroethane in the foregoing ratio have an improved coefficient of performance compared with tetrafluoroethane singly used. A preferable mixing ratio is as follows. Of refrigerants composed of tetrafluoroethane and chlorodifluoromethane, preferred are those comprising 90 to 5% by weight of the former and 10 to 95% by weight of the latter, and particularly preferred are those comprising 80 to 20% by weight of the former and 20 to 80% by weight of the latter. Of refrigerants composed of tetrafluoroethane and chlorodifluoroethane, preferred are those comprising 80 to 5% by weight of the former and 20 to 95% by weight of the latter. In particular, refrigerants composed of 80 to 20% by weight of tetrafluoroethane and 20 to 80% by weight of chlorodifluoromethane and those composed of 80 to 5% by weight of tetrafluoroethane and 20 to 95% by weight of chlorodifluoroethane can display a higher coefficient of performance than CFC-12. Examples of tetrafluoroethane for use in the invention are 1,1,1,2-tetrafluoroethane ( HFC-134a) and 1,1,2,2-tetrafluoroethane (HFC-134). Examples of chlorodifluoroethane for use herein are 1-chloro-1,1-difluoroethane (HCFC-142b), 1-chloro-1,2-difluoroethane (HCFC-142a) and 2-chloro-1,1-difluoroethane (HCFC-142). Among the compositions of the invention, HFC-134a and HFC-134 can achieve a similar degree of effect and thus can be replaced by each other or mixed with each other in use. This can be done in respect of HCFC-142a, HCFC-142b and HCFC-142. The refrigerants of the invention are smaller in the ratio of specific heat and lower in the temperature of gas discharged from the compressor than HCFC-22 and are consequently suitable for use as a cooling medium for a refrigeration cycle using a relatively high temperature as in an air-conditioning equipment of the heat pump type. The composition of the invention is a non-azeotropic composition. Generally a single compound or an azeotrope is vaporized at a constant temperature in an evaporator because of its evaporation done under constant pressure, whereas a non-azeotropic composition has a low temperature at the inlet of the evaporator and a high temperature at the outlet thereof. On the other hand, a fluid to be cooled is caused to flow in countercurrent to the refrigerant in the evaporator to undergo heat exchange and thus has a temperature gradient along the flow direction even if the refrigerant is vaporized at a constant temperature. In other words, a temperature difference between the refrigerant and the fluid to be cooled diminishes in the evaporator as the fluid flows forwardly. In use, the refrigerant of the non-azeotropic composition according to the invention can be rendered close in temperature to the temperature gradient of the fluid to be cooled in the evaporator, so that the refrigeration efficiency, namely the coefficient of performance, can be enhanced. Examples The features of the present invention will be clarified below with reference to the following Examples and Comparison Example. Examples 1 to 6 and Comparison Example 1 Refrigerants were prepared by mixing together HFC-134a and HCFC-22 in the various proportions shown below in Table 1 (weight ratio). HFC-134a HCFC-22 Comp. Example 1 100 0 Example 1 95 5 Example 2 80 20 Example 3 60 40 Example 4 40 60 Example 5 20 80 Example 6 5 95 A refrigerator was operated with an output of 1 hp. using the refrigerants of the composition shown in Table 1. Each refrigarant started condensation at 50°C in a condenser and had a temperature of 0°C in the inlet of the evaporator with superheat of 5°C. Table 2 below shows (I) the maximum evaporating temperature (°C), (II) refrigerating capacity (kcal/m³) KJ/m³, (III) coefficient of performance and (IV) discharge temperature (°C) at the compressor. Table 2 also shows the results achieved by using HFC-134a alone (Comparison Example 1). Fig. 1 indicates a graph illustrating the relationship between the proportions of HFC-134a and HCFC-22 and the coefficient of performance (curve A). The results shown in Table 2 and Fig. 1 reveal that the refrigerants of the present invention have outstanding properties. Examples 7 to 12 The properties of refrigerants were investigated in the same manner as in Examples 1 to 6 with the exception of using the refrigerants prepared by mixing together HFC-134a and HCFC-142b in the various proportions (weight ratio) shown below in Table 3. HFC-134a HCFC-142b Example 7 95 5 Example 8 80 20 Example 9 60 40 Example 10 40 60 Example 11 20 80 Example 12 5 95 Table 4 shows (I) the maximum evaporating temperature (°C), (II) refrigerating capacity (kcal/m³)KJ/m³ (III) coefficient of performance and (IV) discharge temperature (°C) at the compressor in respect of the refrigerants. Fig. 2 indicates a graph illustrating the relationship between the proportions of HFC-134a and HCFC-142b and the coefficient of performance (curve B).

Claims: Use of a composition comprising tetrafluoroethane and either chlorodifluoromethane or chlorodifluoroethane as refrigerant. Use according to claim 1 wherein the composition comprises 95 to 5% by weight of tetrafluoroethane and 5 to 95% by weight of either chlorodifluoromethane or chlorodifluoroethane as refrigerant. Use according to claim 2 wherein the composition comprises 90 to 5% by weight of tetrafluoroethane and 10 to 95% by weight of chlorodifluoromethane. Use according to claim 3 wherein the composition comprises 80 to 20% by weight of tetrafluoroethane and 20 to 80% by weight of chlorodifluoromethane. Use according to claim 2 wherein the composition comprises 80 to 5% by weight of tetrafluoroethane and 20 to 95% by weight of chlorodifluoroethane as refrigerant.

Inventors: KASHIWAGI HIROSHI, NOGUCHI MASAHIRO, TAMURA KOJI, KASHIWAGI, HIROSHI, NOGUCHI, MASAHIRO, TAMURA, KOJI
Applicants: DAIKIN IND LTD, DAIKIN INDUSTRIES, LIMITED
Application year: 1988
Main classification: C09K5
IPC codes: F25B1, C09K5