Two-Phase Fluid Thermal Transport for Spacecraft

Abstract
The research effort described in this report was conducted to begin an analysis of the phase change and flow processes of interest for spacecraft thermal transport loops. Pertinent literature was examined to identify the limits of existing theory and experimental results. It was found that data from low gravity force experiments are very limited, and much of this data is not adequately explained by existing analytical methods. The basic process of bubble growth in a liquid was analyzed, and good correlation was obtained with previous experimental data of other investigators. An expanded explanation of the forces causing bubble separation from a heated surface indicates conditions under which pool bubbling may be possible in a weightless environment. Standard equations for pressure gradients and heat transfer coefficients in boiling and condensing systems were assembled as a starting point for further analysis. Criteria for predicting flow pattern boundaries were also reviewed, and implications for low effective gravity environments are discussed. Finally, initial concepts for two-phase heat transfer loops on a spacecraft are briefly discussed with indications of the need foe continued analytical and experimental work.

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