MEASUREMENTS OF VAPOR-LIQUID EQUILIBRIUM PROPERTIES FOR THE BINARY REFRIGERANT, CARBON DIOXIDE ＋ DIMETHYL ETHER

摘要

Carbon dioxide is widely used as environmentally friendly refrigerant. In Japan, its major applications are for hot water supply systems. Therefore, some new blends of carbon dioxide with lower condensing pressure are being considered. A binary mixture of carbon dioxide and dimethyl ether is one of the candidates for such purpose. Some retrofit experiments or performance examinations with numerical models have already been reported, however, there are few experimental studies for its fundamental thermo-physical properties. In the present study, therefore, vapor-liquid equilibrium (VLE) of the binary refrigerant carbon dioxide ＋ dimethyl ether are presented. Bubble-point/dew-point pressures and composition are measured by means of a newly developed VLE apparatus. The apparatus consists of a thermo-stated equilibrium cell, high-pressure syringes and gas-chromatograph. The measurement uncertainty of the present apparatus is 0.007 K for temperature, 0.01% F.S. for pressure, and 0.30 mol% for composition, respectively. The present apparatus covers a wide range of temperature from 240 K to 380 K and pressures up to 7 MPa, while it was designed as small as possible, a rapid measurement was realized. As a preliminary result, PTxy data along the saturation boundary at 288.1 K are presented in this paper.