One-dimensional semimechanistic model for flow boiling pressure drop in small to micro passages

Abstract

Accurate predictions of two-phase pressure drop in small to micro diameter passages are necessary for the design of compact and ultra-compact heat exchangers which find wide application in process and refrigeration industries and in cooling of electronics. A semi-mechanistic model of boiling two-phase pressure drop in the confined bubble regime is formulated, following the three-zone approach for heat transfer. The total pressure drop is calculated by time-averaging the pressure drops for single-phase liquid, elongated bubble with a thin liquid film and single-phase vapour. The model results were compared with experimental data collected for a wide range of diameter tubes (4.26, 2.88, 2.02, 1.1 and 0.52 mm) for R134a at pressures of 6 – 12 bar. In its present form, the predictions of the model are close to those of the homogeneous flow model but it provides a platform for further development.