垂直微柱蒸发器干涸阈值模型求解及尺寸优化

Model solving and size optimization of dryout threshold for vertical micropillar evaporators

对现有干涸阈值模型进行优化,加入重力的影响,并与毛细作用力和渗透率的求解方法进行组合,得到了平均误差约为7%的表征垂直微柱蒸发器换热性能的最佳组合模型(Darcy_avg(S)+SE)。利用该模型研究了微柱几何结构的影响,发现蒸发器最大换热能力在渗透率与毛细压力间平衡,几何尺寸接近最佳间距比(d/l≈0.35)及高的微柱对应更高的散热能力,具有更小后退接触角的微柱群对应更高的干涸阈值。重力作用下干涸长度的增加导致干涸阈值的显著降低,遗传算法能有效地用于求解不同干涸长度下的最优尺寸。排列方式影响干涸阈值,最佳间距比下叉排布置的微柱阵列较顺排布置换热能力提升近13%。

The existing dryout threshold model was optimized by adding gravity and combining with capillary force and permeability solution methods,so as to obtain the best combined model(Darcy_avg(S)+SE)for characterizing the heat transfer performance of a vertical micropillar evaporator with an average error of about 7%.The effect of micropillar geometry was investigated using this model.Model predictions indicated that the maximum heat transfer capacity of the evaporator was balanced between permeability and capillary pressure;those geometries close to the optimal pitch ratio(d/l≈0.35)and higher micropillars correspond to greater heat dissipation capacity;and that micropillar arrays with smaller receding contact angles correspond to greater dryout thresholds.The increase of the dryout length under gravity led to a significant decrease of the dryout threshold,and the genetic algorithm can be effectively used to solve for the optimal size at different dryout lengths.The arrangement method affected the dryout threshold,the forked-row arrangement of the micropillar arrays increased the heat transfer capacity by nearly 13%compared with the smooth-row arrangement at optimal spacing ratio.