液滴撞击冷铝表面的冻结沉积特性

Freezing Mechanism of Water Droplet Impinging on Cold Aluminum Surface

对单液滴撞击冷表面的动态特性进行试验研究,通过快速可视化观测,分析了直径2.6 mm液滴撞击冷铝表面的冻结行为.结果表明,液滴撞击冷表面动态行为可分为铺展、回缩以及冻结沉积阶段.冻结阶段包括铺展过程冻结以及回缩过程冻结.液滴撞击冷壁面前期(0～3.5 ms),We起主导作用,壁面温度对液滴铺展行为几乎无影响。但壁面温度对液滴回缩及冻结过程影响较大.相同We下,壁面温度T>-20℃,液滴最大铺展因子基本相同,达到冻结的平衡态铺展因子均小于最大铺展因子,且随壁面温度降低而逐渐增加,为回缩过程冻结.壁面温度T≤-20℃时,液滴最大铺展因子与平衡态铺展因子相同,为铺展过程冻结。本文试验条件下壁面温度-20℃可作为区分液滴撞击冷壁面铺展与回缩冻结的临界温度.

Dynamic behavior of a single water droplet investigated and the freezing of water droplet with 2 water droplet impinging process. The result showed impinging on cold surface was experimentally 6 mm in diameter was analyzed during the that the dynamic behavior of water droplet impinging on cold surface can be divided into spreading stage, receding stage and freezing stage. The freezing stage includes freezing in spreading process and freezing in receding process. At initial stage of droplet impacting on cold surface（0~3.5 ms）, We plays a dominant role on spreading behavior of droplet and the effect of cold surface temperature can be ignored. However, it is found that the cold surface temperature has a significant effect on receding and freezing process of droplet impacting. The maximum spreading factors are almost the same with cold surface temperature above -20℃ and the equilibrium spreading factor is less than maximum spreading factor. Moreover, the equilibrium spreading factor will increase with the decrease of cold surface temperature, which is considered as freezing in receding process. In addition, when the cold surface temperature decreases below -20℃, the maximum spreading factor equals to the freezing in spreading. Under the experimental equilibrium spreading factor, which is considered as conditions, the cold surface temperature -20℃ can be considered as the critical temperature to distinguish freezing in spreading or receding process.