Researches on two-phase flow and pool boiling heat transfer in microgravity, which included groundbased
tests, flight experiments, and theoretical analyses, were conducted in the National Microgravity
Laboratory/CAS. A semi-theoretical Weber number model was proposed to predict the slug-to-annular
flow transition of two-phase gas–liquid flows in microgravity, while the influence of the initial bubble
size on the bubble-to-slug flow transition was investigated numerically using the Monte Carlo method.
Two-phase flow pattern maps in microgravity were obtained in the experiments both aboard the Russian
space station Mir and aboard IL-76 reduced gravity airplane. Mini-scale modeling was also used to simulate
the behavior of microgravity two-phase flow on the ground. Pressure drops of two-phase flow in
microgravity were also measured experimentally and correlated successfully based on its characteristics.
Two space experiments on pool boiling phenomena in microgravity were performed aboard the Chinese
recoverable satellites. Steady pool boiling of R113 on a thin wire with a temperature-controlled heating
method was studied aboard RS-22, while quasi-steady pool boiling of FC-72 on a plate was studied
aboard SJ-8. Ground-based experiments were also performed both in normal gravity and in short-term
microgravity in the drop tower Beijing. Only slight enhancement of heat transfer was observed in the
wire case, while enhancement in low heat flux and deterioration in high heat flux were observed in
the plate case. Lateral motions of vapor bubbles were observed before their departure in microgravity.
The relationship between bubble behavior and heat transfer on plate was analyzed. A semi-theoretical
model was also proposed for predicting the bubble departure diameter during pool boiling on wires.
The results obtained here are intended to become a powerful aid for further investigation in the present
discipline and development of two-phase systems for space applications.
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