Effect of flow instability on flow boiling friction pressure drop in parallel micro-channels

Abstract

The relation between flow instability and friction pressure drop of flow boiling in multichannel was investigated by visualization experiments and theoretical analysis. Based on visualization observation, both slug flow and liquid-plug flow were the dominating flow patterns for all operation conditions, and combing with flow instability simultaneous. With theoretical analysis, the vapor slug extension growth velocity would affect the shear force which was the main reason for friction pressure drop. In addition, the channels number and the channel length had significant effects on flow instability. With the simplified vapor growth model and the analysis on the collected database statistically, the modified friction factor, finter, and the structure factor, fstr, were proposed for the revised homogenous friction pressure drop correlation. By comparing with the database, the modified pressure drop correlation predicted the collected experimental data in a good agreement.