| Research Abstract |
Among hydrochlorofluorocarbons, HCFCls, chlorodifluoromethane, CHCIF_2 (HCFC-22, critical temperature, T_c=369.30 K ; critical pressure, p_c=4.988MPa) is widely used today as working fluidsinair-conditioning and refrigeration technology. The ozone depletion potential, ODP, due to the evolution of HCFCs, is presumed to be the comparatively lower compared with those for chlorofluorocarbons, CFCs. However, wity the use in a large quantity of HCFC-22 including chlorine atom, the various harmful influences giving to the earth environmental are anxious in the near future. Suitable replacement compounds for CHCIF_2 may be trifluoromethane, CHF_3 (HFC-23), difluoromethane, CH_2F_2 (HFC-32), pentafluoroethane CHF_2CF_3 (HFC-125) and 1,1,1,2-tetrafluoroethane, CF_3CH_2F (HFC-134a), which those have nearly the same vapor pressures and critical parameters with those for CHCIF_2, and/or their binary mixtures.
In this project, the vapor pressure, ultrasonic speed and density (PVT) in the liquid phase for binary mixtures of CHF_3+CF_3CH_2F and CH_2F_2+CF_3CH_2F were measured along isotherms from 243 to 333 K and at pressures up to about 30MPa. A sing-around technique were used for the measurement of vapor pressure and ultrasonic speed. And the density (PVT) was observed by a direct weighing technique. The temperature, pressure and/or composition variations for these values are found to give a powerful clue to measure the thermophysical properties for each system of binary mixtures. The results obtained in the lower region of CH_2F_2 + CF_3CH_2F system, which indicated the nearly same properties, may be noted as a alternative fluid of chlorodufluoromethane CHCIF_2.
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