孤立气泡生长过程的短时微重力落塔实验研究

利用中国科学院国家微重力实验室北京落塔提供的3.6s微重力时间开展了短时微重力条件下的池沸腾实验研究, 分析了微重力条件下孤立的单个气泡生长过程特征. 实验中采用掺杂磷的N型光滑硅片作为加热面(加热片尺寸10mm×10mm×0.5mm), 以含气率0.0046 (气液摩尔分数比)的FC-72作为工质, 利用恒流源对加热片通电加热. 通过对实验观测到的单个气泡生长图像及相应传热数据分析可知, 经典传热机制控制的气泡生长模型可以描述其早期特征. 相关模型中经验参数的拟合结果在文献报道的数值范围内, 表明重力对气泡生长早期影响较小, 但较大的气泡尺寸可以提供更准确的数值结果. 

Experimental Study on Growth of an Isolated Bubble Utilizing Short-term Microgravity Drop Tower

Pool boiling in short-term microgravity has been studied experimentally utilizing the Drop Tower Beijing of the National Microgravity Laboratory of Chinese Academy of Sciences, which can provide a microgravity period of 3.6s. The growth process of an isolated bubble in microgravity has been presented and analyzed in detail. A P-doped N-type square silicon chip with the dimension of 10mm×10mm×0.5mm with a smooth surface was used for the heater element. Subcooled FC-72 with a concentration of air of 0.0046 moles gas/mole liquid was used as the working fluid. Electric heating with constant current was used to input the heat into the heater element. Analyses on high-speed images of the growth process of an isolated bubble and on the data of heat transfer obtained in the experiments have also been conducted. It is found that the bubble growth model based on classical thermal-controlled mechanism can describe the early period of bubble growth observed in the experiments. The value of the empirical parameter in the relative model is inside the range reported in the literature, which indicates that gravity has a much slight influence during the early period of bubble growth. For large size bubble in microgravity, however, much accurate data can be provided.