Abstract:

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%.

Key words: isochoric specific heat capacity, thermodynamic property, adiabatic calorimeter, radiation, isobutane, compressed liquid, equation of state

摘要：

比定容热容是基础状态方程建立和工程计算的基础热数据。基于绝热量热法研制了一种比定容热容测量装置，使用混合工质节流制冷机实现大温跨制冷并提供稳定的冷量；通过设置双层被动式控温防辐射屏并自主设计PID控温程序，在整个测量过程中样品容器与防辐射内屏的温差小于0.2 K，有效减小了辐射漏热；温度计内置于样品容器，减小了温度梯度，测温更加准确。通过测量异丁烷在279.10～323.68 K温区的压缩液体比定容热容对实验装置的可靠性进行验证。异丁烷的实验数据与文献数据具有较好的一致性，且与REFPROP 9.1的计算值对比最大绝对偏差为1.63%，平均绝对偏差为0.88%。

关键词: 比定容热容, 热力学性质, 绝热量热计, 辐射, 异丁烷, 压缩液体, 状态方程