管壁厚度对平行流换热器性能的影响

根据已有的实验数据,建立扁管的（当量直径为0.199~1.923mm）三维数值模型,分析平行流换热器中管壁的轴向导热及扁管的内外壁温差对换热的影响程度。结果表明：Re数较低时（Re=185）,忽略管壁的轴向导热对Nu数的影响很大,使Nu数值偏小,偏差最高达50%以上;Re数较高时（Re=8 166）,用扁管的外壁温度代替内壁温度,同样也会使Nu数值偏小,偏差高达55%以上。故平行流换热器中管壁厚度对换热的影响不能忽略。

Effect of wall thickness of tube on performance of parallel-flow type heat exchanger

Founds three dimensional numerical simulation model（equivatent diameter from 0.199 mm to 1.923 mm） of the flat tube according to existing experiment data.Analyzes the effects of the axial heat conduction on the wall of tube and temperature difference between the inner-wall and out-wall on convective heat transfer in parallel-flow type heat exchanger.The results show that with small Re number（Re=185）,axial heat conduction leads Nu number to decrease apparently and make the maximum error over 50 percent;with large Re number（Re=8 166）,using the out-wall temperature to displace inner-wall temperature leads the Nu number to decrease,and the maximum error over 55 percent.So the wall thickness of tube can not be neglected.