以分析法比较流体的换热性能

A Comparison of the Convective Heat Transfer Performance between Fluids by an Exergy Analysis

基于换热过程中的损失率能定量地反映该过程中流体的传热与流动的综合性能这一特性，借助换热过程的损失率方程，分析比较了几种流体工质在不同换热方式下的综合特性。比较结果表明，液体（如水）有远优于气体（如空气）的流动与传热的综合性能，且随着流体温度的升高其优势更为明显。同时表明分析法在定量评价换热工质性能的突出特点及工程上的应用价值。

Theexergy loss rates of convection for different fluids have been derived by the exergyequation and compared under identical conditions and in identical convective modes for evalu-ating the comprehensive performance of different fulids.The results show that under identi-cal conditions the comprehensive performance of liquids(such as water) is much better thanthat of gases(such as air),For instance,the ratio of the exergy loss rate of water to that ofair is about 0.03 and, with an increase of the fluid temperature,the liquid performance iseven better.