Abstract To better understand the droplet impact on the liquid film with vapor bubbles in spray cooling, a two-dimensional symmetric numerical model is set up using the Coupled Level Set and Volume of Fluid method (CLSVOF). Three simulative cases are taken, considering the effects of film thickness and the presence of vapor bubbles or not. The main purposes of this paper are to investigate the evolution of vapor bubbles during droplet impact and to identify the effect of vapor bubbles on convection heat transfer. The results indicate that vapor bubbles will detach from the wall and break up at the surface of the liquid film during droplet impact, for a thinner film, later a “sawtooth” liquid film appears at the non-impact region. However, for a thicker film, no bubbles rupture and the detached bubbles will flow inside the liquid film and then some will merge into larger bubbles. In the presence of vapor bubbles, the crater radius is larger for a thicker liquid film. The presence of vapor bubbles will facilitate the subcooled droplet to spread to the heated wall, leading to a substantial increase in surface heat flux.

中文翻译：

---

液滴撞击内部有气泡的加热液膜后的演化和传热

摘要 为了更好地理解喷雾冷却过程中液滴对带有汽泡的液膜的影响，利用耦合液位集和流体体积法(CLSVOF)建立了二维对称数值模型。考虑了薄膜厚度的影响和是否存在蒸汽气泡，采用了三个模拟案例。本文的主要目的是研究液滴撞击过程中蒸汽气泡的演变，并确定蒸汽气泡对对流热传递的影响。结果表明，在液滴撞击过程中，蒸汽气泡会从壁上脱离并在液膜表面破裂，对于较薄的膜，随后在非撞击区域出现“锯齿状”液膜。但是，对于较厚的薄膜，没有气泡破裂，分离的气泡会在液膜内流动，然后一些会合并成更大的气泡。在存在蒸汽泡的情况下，较厚的液膜的陨石坑半径较大。蒸汽泡的存在将促进过冷液滴扩散到受热壁，导致表面热通量显着增加。