管槽内对流换热过程的热力学分析及性能评价

利用热力学第二定律对壁面温度恒定状态下的圆形流道、三角形流道和矩形流道内充分发展区层流对流换热过程进行了研究,得到了熵产数的一般表达式;定义了对流换热过程可用能损率,讨论了入口换热温差、流体温升和流动阻力对可用能损率的影响,并对几种典型流道内对流换热过程的热力学性能进行了比较;同时,从降低可用能损率的角度出发,得到了最小可用能损率所对应的最佳入口换热温差。

THERMODYNAMIC ANALYSIS AND PERFORMANCE EVALUATION OF CONVECTIVE HEAT TRANSFER THROUGH DUCTS

A second law analysis is carried out on convective heat transfer in fully developed region with constant wall temperature through circular, trianglar and rectangular ducts. Besides, the entropy generation rate expression is obtained and the loss rate of available energy in convective heat transfer processes is defined as well. At the same time, the influence of initial temperature difference between fluid and wall as well as the influence of fluid friction on the loss rate of available energy is discussed. Then, the thermodynamic performances of several typical ducts are compared. Finally , the optimum initial temperature difference with the minimum loss rate of available energy is also obtained.