恒热流时污垢对管内对流换热过程热力学性能影响的分析

An Analysis of the Effect of Fouling on the Thermodynamic Performance of Convection Heat Exchange Process in a Tube under Constant Heat Flux Conditions

基于热力学第一、二定律 ,在恒热流工况下分析了污垢对管内对流换热过程热力学性能的影响 ,提出了一项在恒热流工况下反映污垢对管内对流换热过程热力学性能影响的指标———无因次熵产相对增加数 ;讨论了管内流体雷诺数(无污垢时 )和无因次热流密度等参数对无因次熵产相对增加数的影响。研究结果表明 ,该指标不仅能反映污垢对管内传热过程的影响 ,而且能反映污垢对管内流动过程的影响 ,而由污垢层导热所引起的熵产在管内传热过程总的熵产中占有重要的地位。同时 。

On the basis of the first and second laws of thermodynamics and under constant heat flux conditions an analysis was conducted of the influence of fouling on the thermodynamic performance of convection heat exchange process in a tube. A criterion for evaluating such an influence is put forward, the so called relative increment number of dimensionless entropy generation. Also discussed is the effect of parameters such as in tube fluid Reynolds number (in the absence of fouling) and dimensionless heat flux density on the above mentioned increment number. The results of the study indicate that the above criterion reflects not only the effect of fouling on the in tube heat transfer process but also the effect of fouling on the in tube flow process. It is noted that the entropy generation caused by the fouling layer heat conduction plays an important role in the total entropy generation of the in tube heat transfer process. In addition, the study results have been compared with those of a tube with constant wall temperature.