矩形微槽道内对流换热的试验研究

以去离子水为工质,对高为2mm,宽分别为0.3、0.6、2mm的铝制矩形槽中的单相流动阻力、压降以及对流换热努塞尔数进行了试验。结果表明,宽为2mm的微槽道层流向湍流转捩点的Re为2400左右,层流时的fRe为64,Nu为5左右,这与传统常规尺度经典理论相吻合;而宽为0.6和0.3mm的微槽道流动阻力特性与常规尺度槽道相比存在明显的差异,有明显的尺度效应,试验的fRe值均高于传统理论预测值,且层流向湍流的转捩点提前,分别为1500、1200左右;3种矩形槽道随着尺寸的减小,压降Δp增大很快,同时微槽道的对流传热系数曲线转捩点与摩擦阻力因数曲线吻合。这表明微尺度的综合对流传热效果明显优于常规尺寸。

An experimental study of the convective heat transfer within the rectangular micro-channel

With deionized water as the working medium,an experiment was performed on the monophase flow resistance,pressure drop and the Nusselt number of convection heat transfer in the aluminum-made rectangular grooves which are 2 mm high and 0.3,0.6 and 2 mm wide respectively.The results show that the Re of the transitional point of the 2 mm-wide micro-channel from laminar flow to turbulent flow is 2,400 or so,the fRe is 64 and the Nu is about 5,which is in agreement with the traditional classical theory of normal scale.However,the flow resistance properties of the micro-channels with a width of 0.6 mm or 0.3 mm,are remarkably different from those of the normal scale channels,with a noticeable scale effect.The fRe values of the experiment are all higher than the predicted value of the traditional theory.Moreover,the transitional point between the laminar flow and the turbulent flow is changed as about 1,500 and 1,200.The pressure drop labeled Δp of the 3 rectangular channels increases fast with the decrease of the dimensions.Meanwhile,the transitional point of the convective heat coefficient curve of the micro-channels matches the frictional resistance factor curve,which shows that the overall microscale convective heat transfer effect is remarkably better than that of normal scales.