SPEED OF SOUND AND IDEAL-GAS HEAT-CAPACITY AT CONSTANT-PRESSURE OF GASEOUS DIFLUOROMETHANE

The speed of sound of gaseous difluoromethane (HFC-32) was measured fo r temperatures from 273.15 K to 333.15 K and pressures from 48 kPa to 390 kPa with a cylindrical, variable-path acoustic interferometer oper ating at 156.252 kHz. The uncertainty of the speed of sound was less t han +/- 0.1%. The ideal-gas heat capacity at constant pressure and the second acoustic virial coefficients were determined over the temperat ure range from the speed of sound measurements. The ideal-gas heat cap acity at constant pressure results and second virial coefficients calc ulated from these speed of sound measurements were compared with resul ts from the literature determined from PVT measurements and from speed of sound measurements. The uncertainty of the ideal-gas heat capacity at constant pressure was estimated to be less than +/- 1%.