纳米流体强化换热特性的LBM模拟

Simulation of nanofluid heat transfer enhancement characteristics with lattice Boltzmann method

采用LBM模拟了封闭方腔内不同体积分数、不同浮升力参数下纳米流体自然对流时速度场与温度场的分布,得出了纳米流体换热强度随各参数的变化情况.结果表明,当Ra较小时换热表现为导热占主导,随着Ra增大,换热表现为对流占主导,两者的换热都会随着纳米颗粒体积分数的增加而增强,且纳米颗粒体积分数在壁面附近对温度分布的影响比在中心区域的明显;在不同Ra下,纳米粒子体积分数增加所引起的X和Y方向速度峰值增大的幅度不同,Ra较大时,随纳米粒子体积分数的增加,X和Y方向的速度峰值大幅增加.

The streamlines and isotherms in a closed cavity are simulated for nanofluid natural convection with lattice Boltzmann method at different nanoparticles volume fractions and different buoyancy obtained. parameters. The heat transfer intensity of nanofluid changing with the parameters is The experimental results show that conduction dominates the heat transfer process when Rayleigh number is smaller, while at larger Rayleigh number convection dominates the process. In either condition the heat transfer will be enhanced with the rise of nanoparticles volume fraction. And near the wall the nanoparticles volume fraction has more obvious effect on the isotherms than in the core region. At different Rayleigh numbers, nanoparticles volume fraction has different effects on the velocity peak values in X and Y directions. When Rayleigh number is larger, the velocity peak values in X and Y directions will increase markedly with rise of nanoparticles volume fraction.