粘度模型对U型封闭腔内Al_2O_3-水纳米流体自然对流的影响

采用四种不同的粘度模型计算纳米流体粘度,对二维U型封闭腔内Al_2O_3-水纳米流体的自然对流换热进行数值模拟,研究分析了不同粘度模型、瑞利数Ra和纳米颗粒体积分数φ对纳米流体自然对流换热的影响。数值模拟时参数变化范围为:Ra=10~3~10~6,φ=0.02~0.08。研究结果表明:采用不同的粘度模型时纳米流体自然对流换热效果相差较大,特别是在瑞利数Ra=10~5和Ra=10~6时,采用粘度模型Ⅱ和粘度模型Ⅲ计算得到的纳米流体平均Nu数变化趋势与采用粘度模型Ⅰ和粘度模型Ⅳ得到的平均Nu数变化趋势完全相反。

Effect of Viscosity Model on Al2 O3-Water Nanofluid Natural Convection in U Type Enclosed Cavity

Four different viscosity models were used to calculate the viscosity of nanofluids,and the numer-ical simulation of natural convection heat transfer of Al2 O 3-water nanofluid in a U type enclosed cavity was carried out,the effects of different viscosity models,Rayleigh number Ra and nanoparticle volume fractionφ on the natural convection heat transfer of nanofluids were researched and analyzed.In the numerical sim-ulation,the range of parameter variation was Ra =103 ~106 ,φ=0.02 ~0.08.The results showed that the natural convection heat transfer effect of nanofluids was much different when using different viscosity mod-els,especially in the Rayleigh number Ra =105 and Ra =106 ,the variation trend of average Nu number of nanofluids obtained by using viscosity model Ⅱ and viscosity model Ⅲ was quite the contrary compared with that of average Nu number of nanofluids obtained by using viscosity model I and viscosity model Ⅳ.