Isochoric Heat Capacity Measurements for Binary Refrigerant Mixtures Containing Difluoromethane (R32), Pentafluoroethane (R125), 1,1,1,2-Tetrafluoroethane (R134a), and Trifluoroethane (R143a) from 200 to 345 K at Pressures to 35 MPa

Molar heat capacities at constant volume Cv were measured for binary refrig- erant mixtures with an adiabatic calorimeter with gravimetric determinations of the amount of substance. Temperatures ranged from 200 to 345 K, while pres- sures extended up to 35 MPa. Measurements were conducted on liquid samples with equimolar compositions for the following binary systems: R32 R134a, R32 R125, R125 R134a, and R125 R143a. The uncertainty is 0.002 K for the temperature rise and is 0.20 for the change-of-volume work, which is the prin- cipal source of uncertainty. The expanded relative uncertainty (with a coverage factor k=2 and thus a two-standard deviation estimate) for Cv is estimated to be 0.70.