含相变过程的机械[火用]计算方法

Method for mechanical exergy calculation including phase change process

机械火用作为广泛使用的稳流物系的焓火用的两个组成部分之一,其计算正确与否直接影响到火用分析结果的正确性。通过分析发现,传统的机械火用计算方法没有充分考虑机械火用计算路径下可能存在的相变及其影响。为此,通过对定温变压过程下物态变化及其做功能力的理论分析,提出了适用于含相变过程的完整的机械火用计算方法。应用该方法及传统方法对水的焓火用进行比较计算。结果表明,对存在相变过程的机械火用的计算,传统计算方法的误差较大,而提出的计算方法准确可靠,具有较强的实用价值。

Mechanical exergy is one of the two components of the exergy of steady flow system. Its calculation will influence the accuracy of exergy analysis directly. In the traditional method for mechanical exergy calculation, the possible change in phase and its influence were not taken into account in the calculation of mechanical exergy. A systematical method, which can be applied to calculate the mechanical exergy including a phase change process, was put forward, based on the theoretical analysis of the phase change and the capability of doing work in an isothermal process. The new method and the traditional methods were used to calculate the exergy of water for comparison. The result shows that the traditional method has a great error while the present method is accurate and reliable.