A new apparatus applying gas-flow calorimetry has been developed which enables to measure the isobaric specific heat, Cp, of superheated gaseous fluids with high accuracy at temperatures up to 473 K and pressures up to 10 MPa. The experimental uncertainties in temperature, pressure, and Cp measurements are estimated being not greater than ± 5 mK, ± 4 kPa and ± 0.26 %, respectively. Four Cp values of gaseous HCFC-22 have been measured and compared with available data measured by Bier et al. (1974) and Ernst and Busser (1970) for examining the reliability of the apparatus, and four Cp values of the new refrigerant HFC-134a have also been measured and discussed concerning the ideal-gas specific heat by comparing with Cp values derivrd from sound velocity measurements, spectroscopic measurements or existing equation of state for HFC-134a.
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