Book Description

More effective and efficient thermal transport techniques will be needed for heat rejection from equipment on satellites. Circulating two-phase fluid loops have been suggested and laboratory tested for possible application in the above areas. In comparison to a single-phase loop, the two-phase system operates at considerably smaller flow rates and maintains a tighter temperature control with higher heat transfer coefficients. However, the two-phase fluid flow regimes, pressure gradients and heat transfer coefficients must be evaluated for application in the weightless environment of an orbiting satellite. This projecting studies two-phase flow behavior under zero gravity conditions. The overall objectives of this study were to generate a data base for two-phase pressure drop and the void-quality relationship under simulated zero gravity conditions and to develop analytical models to predict these parameters for bubbly and annular flow. The simulation of zero gravity two-phase flow was achieved by using two immiscible liquids with equal densities to eliminate the buoyancy component. Although this approach does not eliminate the gravity effects, it provides a representation for void distribution in the absence of gravity. The modeling effort is limited to developing relations for the two-phase friction multiplier and void-quality relation under bubbly and annular flow conditions. The bubbly flow model is based on the assumption of local homogeneous conditions between the phases but allows for void distribution in the radial direction. Separated flow conservation equations are used, and single-phase turbulent flow eddy diffusivity relations are employed.