局部微型加热下液滴表面温度分布特性

Surface temperature distribution of droplet heated by local microheater

液滴表面温度分布直接影响液滴内部微流状况,而目前文献对液滴表面温度研究主要基于平板全局加热模式。采用MEMS集成工艺和红外热像分析手段,对基于中心局部微型加热下的液滴表面温度分布特性进行了实验研究。研究发现:局部加热液滴表面温度分布与平板全局加热液滴表面温度分布不同,呈现顶端温度高、边缘温度低的凸形温度分布规律;随着加热功率增加,液滴表面温度和温度梯度都会随之增加,而当加热功率增加到一定值后,液滴表面温度增幅趋于一致,表面温度梯度趋于稳定分布状态。同时对液滴局部沸腾时气泡破裂前后液滴表面温度分布进行了研究。研究结果有助于理解和控制液滴微流分布。

The temperature distribution of droplet surface directly influences the microflow inside the droplet, but most of the papers about droplet surface temperature are based on substrate heating mode. In this study, with the aid of the infrared thermograph and MEMS technology, both the surface temperature and the temperature gradient of the droplet were investigated based on local heating mode. It was found that different from the concave distribution of surface temperature in the substrate heating mode, the surface temperature of the droplet in the local heating mode showed a convex distribution with a higher temperature at the apex but a lower temperature at the edge. With the increase of heating power, both the surface temperature and the temperature gradient were increased. However, as the heating power reached a certain value, the surface temperature gradient increased less and finally tended to a uniform distribution. The surface temperature of the droplet before and after the bubble burst under local boiling was also investigated. The results presented in this paper help to understand the internal microflow of droplets in the local heating mode and manipulate the microflow inside droplets.