污垢对管内层流换热性能影响的热力学分析和评价

Thermodynamic Analysis and Evaluat ion on Effect of Fouling on Performance of Laminar Convective Heat Transfer Process Through a Duct

采用热力学第二定律,分别在恒壁温和恒热流两种典型工况下分析了污垢对管内层流换热性能的影响;引入单位传热量的熵增率对污垢管道的热力学性能进行了评价;讨论了管内流体雷诺数(无污垢时)、量纲为1的入口换热温差、量纲为1的热流密度和污垢层厚度等参数对单位传热量熵增率的影响;并把结果和紊流时的对应工况进行了比较。结果可为工程上换热设备的优化设计提供依据。

Based on the first and second laws of thermodynamics,the effect of fouling on t he thermodynamic performance of fully developed laminar convective heat transfer process through a duct with constant wall temperature and constant wall heat fl ux respectively has been investigated analytically.The effect of fouling on the thermodynamic performance of laminar convective heat transfer process can be ev aluated by studying the increment rate of entropy generation per unit heat flux due to fouling as compared to that for clean surface ducts.In this study,the R eynolds number(not considering fouling),dimensionless inlet temperature diffe rence,dimensionless wall heat flux and fouling thickness are considered to be t he main parameters.Numerical results of the entropy generation increment rate p er unit heat flux due to both heat transfer(including the conduction of fouling layer)and viscous friction under fouling condition are presented and dis-cuss ed,which are compared with that of turbulent convective heat transfer.The rese arch reported in this paper provides a reference to optimize the design of heat transfer equipment in engineering.