PVT Property Measurements for Difluoromethane

Abstract

Experimental vapor pressure and PVT data of an important alternative refrigerant, difluoromethane (HFC-32), have been measured by means of a constant-volume method coupled with expansion procedures. Sixty-nine PVT data were measured along 10 isochores in a range of temperatures from 322 to 420 K, at pressures from 3.3 to 9.8 MPa, and at densities from 111 to 850 kg[sup 3]. Twenty-one vapor pressures were also measured at temperatures form 320 K to the critical temperature. The uncertainties of the temperature and pressure measurements are within [+-]7 mK and [+-]2 kPa, respectively, while the uncertainty of the density values is within [+-]0.1%. The purity of the sample used is 99.998 mass%. On the basis of the measurements along each isochore, six saturation densities were determined and the critical pressure was determine by correlating the vapor-pressure measurements. The second and third virial coefficients for temperatures form 340 to 420 K have also been determined.