Development of an Apparatus for Simultaneous Measurements of Isobaric Specific Heat Capacity and Density for Fluids at High Temperatures and Pressures

We have developed an apparatus for simultaneous measurements of isobaric specific heat capacity and density for fluids at high temperatures and pressures by modified heat relaxation method. Calorimeter in this study is a batch type one and designed for the use in the temperature range from 250K to 473K at pressures up to 20 MPa. Calorimeter is connected with a metal-bellows densimeter which makes possible to keep the sample pressure constant and to measure density of the sample simultaneously. New data processing method applicable to measurement of isobaric specific heat capacity for fluids is proposed in this stydy. After calibration of the apparatus constant by using water, isobaric specific heat capacity of methanol was measured at 323.15 K and 5 MPa. The result was compared with literature values and shows good agreement. Experimental uncertainty in the isobaric specific heat capacity is estimated to be 4.0% with 95% confidence limits.