定容法液相pVT实验系统的研制及初步测试

Design and preliminary test of liquid phase pVT measurement system using constant-volume cell

液相pVT是流体的重要热物理性质之一,定容法是一种可靠、精确的液相pVT测试方法。分析了定容法液相pVT的测量原理,并在此基础上研制了一套液相pVT实验系统,主要包括实验段、温度测量系统、压力测量系统、密度测量系统及真空系统,对可能影响实验测量精度的因素进行了细致分析,探索了液相pVT的实验流程。利用高纯度 R134a标定了294.899 K、21.847 MPa 下的体积,研究了温度与压力的影响,在此基础上开展了温度270～295 K,压力1.7～21.8 MPa下的 R134a液相pVT实验,测量结果与文献结果吻合很好,验证了实验系统的可靠性和精度。

Liquid phase pVT behavior is an important thermodynamic property and can be measured precisely with a constant-volume cell. Based on the fundamental theory of the constant-volume method, a new apparatus for liquid phase pVT measurement was designed, including a constant-volume cell,measurement systems of temperature,pressure,mass and a vacuum system. The volume of the constant-volume cell was calibrated with high purity R134a at a temperature of 294.899 K and a pressure of 21.847 MPa.Then the effect of temperature and pressure on the cell volume was analyzed.The pVT behavior of R134a in liquid phase was measured at a temperature range from 270 K to 295 K and pressure from 1.7 MPa to 21.8 MPa.The experimental results agree well with the reference equation of state,which demonstrates the reliability and accuracy of the apparatus.