Abstract:

Heater surfaces made of different materials exhibit various thermal response characteristics during boiling process due to differences in thermal properties. To deeply investigate the effect of thermal properties on the interaction between the thermal response of the heater surface and the dynamic behavior of bubbles during single-bubble boiling process, based on the open source software OpenFOAM, a thermofluid coupling numerical model including heat transfer, phase change and flow is developed by analyzing the heat and mass transfer process within the microlayer. Firstly, single-bubble boiling simulations have been realized on different sized pores on copper, aluminum, and silicon surfaces. The results show that with the improvement of thermal conductivity, the superheat of the heater surface decreases and the waiting period of the bubble is shortened, while the effect of thermophysical properties on the waiting period of bubbles gradually decreases with the decrease of vaporization core size. In addition, for the copper surface coated with graphene, the graphene coating enhances the lateral diffusion of heat on the boiling surface. Due to the slow heat transfer rate from the substrate material, a significant amount of heat is carried away from the heating surface by liquid evaporation, this leads to a slower recovery of superheat at the vaporization core, resulting in lower surface superheat and longer waiting periods for bubbles.

Key words: boiling heat transfer, microlayer, OpenFOAM, graphene, bubble departure period

摘要：

不同材质的加热表面因其热物性参数存在差异，在沸腾过程中会表现出不同的热响应特性，对气泡成核、生长脱离也有一定影响。为深入探究加热表面热物性对单气泡沸腾过程中加热表面热响应与气泡动力学行为之间相互作用的影响机理，基于开源软件OpenFOAM，通过对微液层内传热传质过程进行分析，建立了包含传热、相变和流动的流-热耦合模拟框架。首先对铜、铝和硅表面上不同尺寸的汽化核心进行了单气泡沸腾模拟，结果表明，随着导热性能的提升，加热表面过热度下降，气泡等待周期缩短，同时随着汽化核心尺寸的减小，加热表面热物性对气泡等待周期的影响逐渐减弱。另外，对于覆有石墨烯涂层的铜表面，石墨烯涂层的存在增强了沸腾表面热量的横向扩散，由于基底材料向上传递热量的速度慢，同时加热表面因液层蒸发带走热量多，导致汽化核心处过热度恢复较慢，出现了更低的表面过热度和更长的气泡等待周期。

关键词: 沸腾换热, 微液层, OpenFOAM, 石墨烯, 气泡脱离周期