Generalized flow regime map for two-phase mini/micro-channel flows

Abstract

This study concerns the development of a generalized approach for predicting two-phase flow regimes in mini/micro-channel flows. To achieve this, a total of 7391 two-phase flow regime data points for mini/micro-channels are amassed from 25 sources, including the micro-channel experimental data of the authors and data from previous studies on two-phase flow patterns in mini/micro-channels in the literature. The consolidated database encompasses 16 different working fluid data for both single-component and two/multi-component mixtures with hydraulic diameters of 0.2–4.0 mm, superficial liquid Reynolds numbers of 4.6–918,938, superficial gas Reynolds numbers of 0.4–261,017, mass velocities of 2.4–6028 kg/m2·s, flow qualities of 0–0.99, and reduced pressures of 0.036–0.78. Based on the flow regime definition of the present study, the database was classified into two main categories (non-annular and annular flows) and seven subcategories (bubbly, intermittent, transition, multiple, wavy-annular, smooth-annular, and dispersed-annular flows). Predictions of previous generalized flow regime maps are compared to four subsets of the consolidated database, revealing significant deviations in the transition boundaries between the two. Accordingly, a new generalized flow regime map with flow regime boundary correlations was proposed for two-phase mini/micro-channel flows. The new flow regime map was demonstrated to be capable of providing excellent predictions against the entire consolidated database, with evenly good predictions for different flow regimes, working fluids, and over a broad range of hydraulic diameters.