【基于格子Boltzmann方法的换热器优化模拟】 ansys拓扑优化实例
摘要： 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.
关键词： 换热器； 格子Blotzmann方法； 传热系数； 多孔介质模型
中图分类号： TK124； TQ.021.3 文献标志码： B
Optimization simulation on heat exchanger based on
lattice Boltzmann method
JIANG Dongdong1, ZHOU Shenggen2
(1. School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240, China;2. School of Science, Kunming University of Science and Technology, Kunming 650500, China)
Abstract： To optimize the structure design of heat exchanger, the heat exchange in heat exchanger is simulated by Lattice Boltzmann 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 nonuniform staggered pipes, the arrangements of “intensity in the front” or “intensity in the middle” indicate better heat exchange performance.
Key words： heat exchanger; lattice Boltzmann method; heat transfer coefficient; porous medium model
换热器性能的好坏直接影响能源利用和转换的效率.对换热器中的流体流动、热量传递和结构尺寸等进行综合性能分析并进行相应的优化设计，具有理论指导意义和工程实用价值.按现有计算机硬件和软件条件，对换热器按照实际管、壳程的流动换热情况进行模拟是不现实的.PATANKAR等［1］最早应用CFD对管壳式换热器进行数值模拟，采用分布阻力和体积多孔度的概念简化换热器复杂几何结构内的流动过程，实现管壳式换热器壳程流场的数值模拟，同时保留用微分方程描述壳程流体流动和换热的特点.本文同样引入多孔介质概念［2］，从宏观上简化换热器管、壳程流动和换热等.
传统的CFD方法是对宏观连续性方程的离散；而格子Boltzmann方法(Lattice Boltzmann Method，LBM)基于统计物理学并以极其简单的形式描述粒子的微观行为，在宏观层次上能正确反映流体的运动.由于计算简单、本质并行和易于边界处理等优点，最近十几年LBM在许多领域(如多孔介质流动［3］、多相流［4］、微尺度流动［5］和电水动力学［6］等)的各种数值问题求解上取得很大成功.