矩形微细通道纳米流体沸腾流动阻力特性研究

Research on boiling flow resistance of nanofluid in rectangular microchannels

以质量分数为0.5%的Fe3O4-H2O磁纳米流体为工质,分别在横截面积宽×高为0.6 mm×2.0 mm,1.0 mm×2.0mm和2.0 mm×2.0 mm 3种微槽内进行磁性纳米流体流动的沸腾流动阻力特性实验,分析不同磁感应强度对纳米流体沸腾传热两相摩擦压降的影响,并将本实验中0.6 mm×2.0 mm微槽道内的两相摩擦压降与现有理论模型及支持向量机预测模型进行比较。研究结果表明:外加磁场对纳米流体的流动特性产生明显的影响,两相摩擦压降在外加磁场作用时增大比较明显,且随着磁感应强度的增大而增大;两相摩擦压降随热流密度和质量通量的增大而增大;尺寸小的微槽两相摩擦压降显著比尺寸大的微槽的大。由于理论预测模型实验条件的差异性,3个理论预测模型均有较大误差,其中效果最好的M-H模型平均相对误差也高达35.7%。支持向量机模型效果很好,平均预测误差小于5%。

The boiling flow characteristics were experimentally investigated through the aluminum-based rectangular microchannels with different sizes of 0.6 mm×2.0 mm, 1.0 mm×2.0 mm and 2.0 mm×2.0 mm, using Fe3O4-H2O magnetic nanofluids with particle of 0.5% （mass fraction） as the working fluids. The effects of the magnetic induction intensity, the heat flux density, the mass flux and the size of the channel on the two-phase frictional pressure drop were investigated, and then the value of the two-phase friction pressure drop was compared with the prediction value of the existing theory models and the support vector machine model. The results show that the magnetic induction influences obviously the flow characteristics of nanofluids. The two-phase frictional pressure drop increases greatly compared with non magnetic field, and it increases significantly with the magnetic induction intensity, the heat flux density and the mass flux. With the decrease of the channel’s size, the frictional pressure drop also markedly increases. The three theory models all have big average error in different experiment conditions, and the M-H model can make the average error at 35.7%. The support vector machine model has better prediction with the average error of 4.68%.