Modeling of the minimized two-phase frictional pressure drop in a small tube with different correlations

Abstract

Differences between the predicted and experimental frictional pressure drop of two-phase flow in small tubes have frequently been discussed. Factors that could have contributed to that effect have been attributed to the correlations used to model the flow, some being modified from the originals developed for a macro system. Experimental test-rigs have varied in channel geometry, refrigerant type, and flow conditions. Thousands of data have been collected to find a common point among the differences. This paper reports an investigation of different two-phase friction factor correlations used in the modeling of the frictional pressure drop of refrigerant R22. Laminar and turbulent flow regimes have been considered. Minimum friction factor and minimum frictional pressure drop under a common platform - optimized conditions of the mass flux and vapor quality - are searched for using genetic algorithm. The results show that a larger pressure drop is expected with a smaller channel with a large discrepancy between the correaltion that does not consider surface roughness and that which does, as well as between laminar and turbulent flow condition.