氘汽液变化过程的气化热及熵变计算

Calculation on the heat of gasification for the saturated liquid of D_2

计算饱和液体的气化热通常是把该温度下的饱和蒸汽视为理想气体。但是氘的饱和蒸汽在临界温度Tc=38·34K以下作为理想气体计算气化热,得到的结果不符合一般规律。本文采用Clapeyron方程的微分形式和氘的汽液平衡方程,考虑氘由液态转变为气态的体积变化,计算得到20K到38K各温度对应的气化热和熵变,最后绘制出氘的饱和曲线。这种计算方法避免了两个近似:视氘饱和蒸汽为理想气体和忽略氘汽液转变的体积变化,提高了计算的精确度。

In general, the saturated stream is regarded as the ideal gas for calculating the heat of gasification for the saturated liquid. However, the result of calculation wasn＇t consistent with the general law if D2 was treated as the ideal gas under Tc=38.34 K, the critical temperature. Considering the change of the volume from the liquid state to the gas state, this paper implored the Clapeyron differential equation and the equation of vapor-liquid equilibrium, then obtained the heat of gasification and the entropy from 20 K to 38 K and the saturation curve. The method avoided regarding the saturate gas D2 as the ideal gas and ignoring the volume change from the liquid state to the gas state, improving the calculation exactitude.