中文摘要：

工质在换热过程中发生相变时,其物性参数将发生剧烈变化,增大了换热系统性能分析和优化的复杂度。本文以顺流、逆流和叉流三种典型换热器为研究对象,在考虑工质发生相变的前提下,构建了与其对应的等效热阻网络图（能量流模型）,获得了换热器的换热量与结构/运行参数以及工质物性间的直接物理联系。以此为基础,对于含相变工质的换热系统,通过构建其整体能量流模型,结合基尔霍夫电压、电流定律明确了系统中各独立设计参数间的整体约束关系,并应用拉格朗日乘子法实现了相变换热系统的性能优化。

英文摘要：

Phase change of working fluids during heat transfer processes leads to drastic variation of fluid properties,which makes the heat transfer analysis and optimization much harder.This study first introduced the equivalent thermal circuit diagrams,i.e.energy flow models,and deduced the mathematical relations among the design requirements,structural and operating parameters and fluid properties for parallel-flow,counter-flow and cross-flow heat exchangers with phase change fluids.On this basis,we constructed the energy flow model for a multi-loop heat exchanger network（HEN） with phase change fluids and then clarify the integral relations among each independent design parameter of the HEN with the aid of Kirchhoff＇s voltage and current laws.Finally,by applying the Lagrange multiplier method,the performance of the multi-loop HEN was analyzed and optimized to show the applications of the newly proposed energy flow model.