数值研究“二次成核”在喷雾冷却中的作用

Numerical study on the effect of secondary nucleation on spray cooling

基于喷雾冷却换热原理和气泡-液滴动力学基本知识,对有气泡产生的换热表面进行数值研究,重点考察"二次成核"在整个换热过程中的作用,成核系数α和成核范围系数β变化对换热的影响.研究结果表明,随着成核系数α增大,换热效果增强,当α>6时,增强效果已不明显;成核范围系数β=8为极值位置,增大或者减少都会使换热效果减弱.通过α=6,β=3,5,8,10的各种情况下的换热量计算,并与Cho,Ponzel提出的经验公式结果进行比较,发现在β=8的时,计算结果与经验公式结果符合最好,由此可以得出α,β的最佳值分别为6,8.

Based on the fundamental principle of spray cooling and bubble-droplet dynamics, a numerical method was developed to study the heat transfer characteristics of heated surfaces with bubbles on them, and the effect of secondary nucleation, secondary nucleation coefficient （α） and secondary nuclei range coefficient （β） on spray cooling was specially studied. The results indicate that increasing the secondary nucleation （α） could result in a rise of the heat flux, but the heat flux does not increase obviously any more when a is greater than 6. The extreme point is reached when βequals 8, and increasing or reducing theβ could weaken heat transfer. Compared with the results of Cho, Ponzel, for the cases of α=6, β=3,5,8, 10, it was found that β=8 can achieve the best result. Therefore, the prime α, β are 6 and 8.