基于格子Boltzmann方法的换热器优化模拟

为优化换热器的结构设计,用格子Boltzmann方法(Lattice Boltzmann Method,LBM)结合多孔介质模型模拟换热器内的换热,研究雷诺数、普朗特数和热扩散率比的变化对温度场和换热性能的影响.模拟结果表明:在小雷诺数范围内,随着雷诺数的增加,努塞尔数先增加后减小,即存在一个使换热性能达到最好的雷诺数;随着普朗特数的增加,努塞尔数减小,换热性能降低;随着热扩散率比的增加,换热性能提高.分析不同管柱排列方式对换热性能的影响,结果表明:叉排的换热效果明显优于顺排,当横向节距等于2时,对于均匀顺排或叉排,努塞尔数均随纵向节距的增加而减小,这与实验结果相符;对于非均匀叉排,采用"前密"或"中间密"的排布方式有利于换热.

Optimization simulation on heat exchanger based on lattice Boltzmann method

To optimize the structure design of heat exchanger, the heat exchange in heat exchanger is simulated by Lattice Bohzmann Method （LBM） combining with porous medium model. The effect of Reynolds number, Prandtl number and thermal diffusivity ratio on temperature field and heat exchange performance is studied. The simulation results indicate that, for small Reynolds number, Nusselt number firstly increases and then decreases with the increase of Reynolds number, i. e. , there exists an optimum value of Reynolds number which yields the best heat exchange performance; Nusselt number decreases with the increase of Prandtl number, i. e. , the heat exchange performance is weakened; the increase of thermal diffusivity ratio strengthens heat exchange. The heat exchange performance under different arrangements of pipes are analyzed, and the results shows that, heat exchange performance of staggered pips bank is much better than that of aligned pipes; if the transversal pitch is set as two, Nusselt number decreases with the increase of longitudinal pitch for both aligned and staggered pipes, which is consistent with experimental results; for non-uniform staggered pipes, the arrangements of ＂intensity in the front＂ or ＂intensity in the middle＂ indicate better heat exchange performance.