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.