| Abstract: | Theoretical two phase flow regime transitions under a microgravity environment are analyzed based on physical concepts and validated by KC-135 experimental flight data. The flow regime transitions considered include stratified flow, dispersed flow, slug flow, and annular flow. The principal parameters considered in this analysis are fluid properties, pipe size, void fraction, and flow rates. The basic idea used in this analysis to develop transition boundaries between flow patterns is that a transition from one flow pattern to another will occur when there is a change in the dominant force which controls that flow pattern. The forces considered are body force, surface tension force, inertial force, and the force of eddy turbulent fluctuation. A notable aspect of this analysis is that surface tension effects are included when describing all transition criteria between flow regimes. Three dimensionless parameters A, B, and C are defined and used with the Martinelli parameter as a coordinate. Since this map uses dimensionless parameters and the Martinelli parameter as coordinates and it was developed based on physical concepts, it can be easily applied to predict flow regimes occurring under other design conditions. The two phase heat transfer coefficient and pressure drop were analyzed using the KC-135 experimental data. The two phase condensing heat transfer coefficient was found to be 10 to 100 times greater than the single phase heat transfer coefficient. |
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