Gravity Effects on Flow Boiling Heat Transfer Using Temperature Sensitive Paints in Preparation for an ISS Flight Experiment

Understanding the mechanics of flow boiling and heat transfer in space environments will enable the design of more compact and efficient heat e1changers for spaceflight missions and satellites. Testing supported by Flight Opportunities enabled flow boiling data in a zero-gravity environment for samples of different masses and heat fluxes. Results with a 4 mm inner diameter (ID) sapphire tube support the hypothesis that flow becomes gravity independent at significantly lower mass fluxes and that deterioration in heat flux will be less significant in microgravity as compared to data from earlier tests with a 6 mm ID tube. This data offers insight into the dominant heat transfer mechanisms in microgravity and enables prediction of conditions under which boiling is gravity independent. It also supports predicting the magnitude of heat transfer deterioration in zero-gravity environments. Research like this will continue to provide NASA with results and tools required for the design of space-based two-phase heat exchangers, which are lighter, smaller, and higher power than single-phase systems.