SBIR-STTR Award

The proposed research program is for development of models for two-phase friction multiplier, void fraction-quality relation, and forced connective nucleate boiling heat transfer coefficient under zero gravity conditions. Due to high heat transfer-coefficient, a two-phase gas-liquid medium is expected to be used in the future cooling systems for spacecraft equipment. Design of these cooling systems require a knowledge of two-phase flow and heat transfer under reduced and zero gravities. The objective of the proposed program is to extend the well established two-phase flow models developed at earth gravity to zero gravity conditions. This is achieved by using the reduced gravity pool boiling and bubble dynamic studies to establish the expected void distribution in two-phase flow models in which the gravity component has been neglected or can be easily separated will be used to formulate the models for the above three major engineering parameters.

The proposed program is an experimental and analytical study for the two-phase flow parameters under zero gravity conditions. The objectives of this project are: (1) to perform a series of experiments to simulate zero gravity two-phase flow behavior and to generate data for evaluating the theoretical models; (2) to develop models for the two-phase friction multiplier, void-quality relation, and heat transfer coefficient under flow regimes expected in zero gravity environment. Turbulent mixing length theory will be used to solve the conservation equations for annular and bubbly flow with nucleation at the wall. For the case of bubbly flow, the void fraction at the boundary will be determined from the earth and zero gravity pool boiling data. The approach taken for the analysis of annular flow at earth gravity using a mixing length model will be extended to zero gravity condition. It is planned to simulate zero gravity two-phase flow behavior by producing the desired flow pattern using two liquids with equal densities. Pressure drop and the phase content will be measured along the test section using the instrumentation to be developed in this program.