水基纳米流体流动与换热数值模拟

Numerical simulation of flow and heat transfer of water-based nanofluids

采用两步法制备体积分数φ为0.001%、0.01%、0.1%的Al2O3-H2O纳米流体,运用热力学相关式进行计算,并采用Lattice Boltzmann方法模拟圆管内Al2O3-H2O纳米流体的流动与换热,研究分析不同纳米粒子体积分数和粒径对纳米流体平均Nu数的影响。结果表明,不同体积分数的Al2O3-H2O纳米流体,随着纳米颗粒的运动,边界层发生变化,其流动特性和换热特性也受到影响,对于相同位置的纳米流体,当体积浓度为0.9%、0.5%、0.1%时,平均Nu数分别为21、17.8、16,随着纳米颗粒体积分数越大,其平均Nu数越大,即换热强度越大。当纳米颗粒为20 nm,Re数为1000、3000、5000、7000、9000时,平均Nu数分别为11.5、14.5、18、20、21.5,随着Re数的增加,纳米流体的强化换热效果越好。

Al2O3-H2O nanofluids with volume fraction ofφ=0.001%,φ=0.01%andφ=0.1%were prepared by two-step method.The flow and heat transfer of Al2O3-H2O nanofluids were simulated by lattice Boltzmann method,and the influence of the integral number and particle size of different nanoparticles on the average Nusselt number of nanofluids was studied.The results showed that the flow and heat transfer characteristics of Al2O3-H2O nanofluids with different volume fractions change with the movement of nanoparticles.For nanofluids with the same location,when the volume concentration of nanofluids was 0.9%,0.5%and 0.1%,the average Nusselt number was 21,17.8 and 16,respectively.With the increase of the volume fraction of nanoparticles,the average Nusselt number was 21,17.8 and 16,respectively.The larger the number was,the greater the heat transfer intensity was.When the nanoparticle size was 20 nm and the Re number was 1000,3000,5000,7000 and 9000,the average Nu number was 11.5,14.5,18,20 and 21.5 respectively.With the increase of Re number,the enhanced heat transfer effect of nanofluid was better.