一种比定容热容测量装置

As one of the most important thermodynamic properties, isochoric specific heat capacity is related to the calculation of internal energy and entropy, is the key parameter of engineering design. What is more, isochoric specific heat capacity is derived by the second derivative of pressure with respect to temperature and is important for verifying the accuracy of equation of state. An adiabatic calorimeter was developed to measure the isochoric specific heat capacity. A spherical bomb with platinum resistance thermometer inserted was used to hold the measured liquid. The cooling capacity was provided by a mixed-refrigerant Joule-Thomson refrigerator. In view of the difficult problem of heat insulation in a wide temperature range, two adiabatic shields were arranged and the PID temperature control method was designed independently to reduce the temperature difference between the bomb and the adiabatic shield. The temperature difference between the bomb and the inner adiabatic shield was less than 0.2 K throughout the experiment. In order to verify the reliability of the experimental setup, the isochoric specific heat capacity data of isobutane were measured over temperatures from 279.10 K to 323.68 K. Satisfactory agreement with published heat capacity data is found and the average absolute relative deviation between this data and the values calculated from REFPROP 9.1 is 0.88%.