A new automated adiabatic flow calorimeter was developed which enables one to measure the isobaric heat capacity, Cp, of pure fluids and their mixtures in the liquid phase. The calorimeter has been carefully designed to keep the heat loss from the sample fluid as small as possible being regarded as negligible. The experimental apparatus constitutes a closed circuit of the sample circulation using a combination of two mounted metallic bellows and a metering pump. The present apparatus is designed to measure Cp at temperatures to 500 K and pressures to 15 MPa and is also applicable to measurements in the critical region as well as the region near the saturated liquid state because of its excellent mass flow rate control stability and the high adiabatic efficiency of the calorimeter. The Cp of liquid refrigerant 114 (R114) has been measured at temperatures from 275 to 415 K and pressures up to 3.2 MPa including the critical region with experimental uncertainty of less than ±0.4%. The heat capacity of saturated liquid R114 has also been derived from the data measured in the single phase.
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