Heater Geometry and Heat Flux Effects on Subcooled, Thin Wire, Nucleate Pool Boiling in Microgravity

The purpose of this thesis is to study the effects of microgravity, surface geometry, and heat dissipation per unit area (heat flux) on boiling heat transfer. Boiling is able to move a significant amount of heat for a small area in comparison to other heat transfer methods. Space systems could benefit from the development of thermal management systems that use boiling heat transfer because they would be smaller, more robust, and less expensive. However, boiling is an extremely complicated process which has no comprehensive models to predict its behavior. Multiple correlations have been developed which relate heat transfer efficiencies to various system parameters, but they can only be applied to specific heat transfer systems, lack considerations for the actual mechanisms involved in boiling, and give erroneous results if used beyond their limited applications. This research concluded that twisting thin wire heaters creates crevices that reduce the amount of heat needed to make the system boil. This is particularly beneficial in microgravity because heat transfer prior to boiling is very inefficient. Additionally, this study characterized the observation of a new mode of jet flows, which results in many small bubbles leaving the wire and creates a fluid flow that would not normally exist in microgravity. The results of this study show that sustained boiling can exist in microgravity and in some instances can be more effective than boiling in terrestrial gravity