喷雾冷却相变传热的建模与模拟计算

Modeling and Simulation of Phase Change Heat Transfer in Spray Cooling

喷雾冷却是一种高效的热控技术,为了探索形成完善的喷雾冷却技术设计流程,文章开展了喷雾冷却传热过程的建模研究.针对喷雾冷却传热过程的模拟计算,基于喷雾冷却相变传热的4个传热机制液膜对流传热、池沸腾传热、二次气泡沸腾传热、二次气泡高频化机制,利用Monte Carlo方法描述了不同粒径与速率分布的液滴撞击液膜并生成二次气泡的过程,通过液态介质中气泡生长速率的解析计算模型考虑了气泡的生长过程,并结合模化气泡与气泡之间、液滴与气泡之间、气泡与液膜之间的干涉行为描述了气泡的演化过程,通过综合液膜单相对流与气泡相变传热,发展了喷雾冷却相变传热模拟计算方法.基于喷雾冷却实验台开展了稳态喷雾冷却实验,实验校核结果表明,计算方法能够较好地模拟喷雾冷却相变传热性能.另外还分析了影响本方法计算精度的两类因素.

Spray cooling has attracted widespread attention due to its advantages in high heat flux removal and high heat transfer coefficient.Simulation method for spray cooling was studied in this paper to contribute to the design and application of spray cooling.A new simulation method for phase change heat transfer in spray cooling was suggested.It was based on the four heat transfer mechanisms from the literature,including film convection,pool boiling,secondary-bubble boiling,and high frequency mechanism of secondary-bubbles.Monte Carlo method was adopted to describe the impaction of spray droplets on film with different distributions of diameter and velocity and the form of secondary bubbles.Bubble growth rate was modelled with semi-analytical solutions of bubbles in liquid.Bubble evolvement was modelled with the puncture of bubbles by droplets,the collapse of bubbles due to film contaction,and the merge between bubbles.Both wall film convection and bubble phase-change heat transfer were considered,and then spray cooling was simulated.Spray cooling experiment was implemented.The agreement between simulation results and experimental data suggested that the new method could simulate spray cooling quite well.Additionally two groups of factors affecting the prediction accuracy were analyzed.