A Review of Progress in Condensation and Heat Transfer Research in Microgravity

A comprehensive review of experimental and numerical studies of film and droplet condensation in microgravity is presented, covering in-tube and plane condensation as well as enhanced heat transfer mechanisms. For condensing heat transfer in tubes, gravity-independent criterion numbers (Bond number, Froude number, etc.) are used to determine whether gravity affects heat transfer, and the effect of gravity can be attenuated by increasing the mass flow rate of the vapor and reducing the tube diameter. For droplet condensation, continuous droplet condensation in microgravity can be achieved by increasing the vapor velocity, and using surfaces with a wetting gradient or micro/nano structure in combination with airflow purging to remove condensate droplets. Current research on condensation experiments in microgravity is limited, mainly due to the fact that long-term, continuous microgravity experimental are extremely rare. Emphasis should be placed on the Chinese Space Station and the International Space Station to carry out experimental studies of condensation heat transfer over long periods of time, to make up for the large amount of lack of reproducible experimental data, exploring the mechanism of gravity's effect on condensation heat transfer, in order to develop reliable design tools for space station applications.