Measurement and theoretical analysis of transient liquid film during micro-channel flow boiling

Abstract

In this paper, three working fluids of deionized water, anhydrous ethanol and FC-72 were used to study the transient variation of liquid film thickness on the bubble's periphery for the flow boiling in micro-channels. The experiments showed that the liquid film declined rapidly under the coupled action of evaporation and shear force of vapor flow until it was dried out. A transition point existed on the curvature of liquid film thickness, and the liquid film thickness at the transition point (initial liquid film thickness) could be predicted by the Taylor flow, which was similar to the liquid film on the bubble's periphery in the adiabatic two-phase flow. Comparisons of the three working fluids showed that the reduction speed of the liquid film thickness depended on many thermophysical properties, including surface tension, liquid viscosity and latent heat. The heat flux also had evident influences on the liquid film behavior. An empirical model was proposed by considering evaporation of the liquid film and shear action on the vapor-liquid interface. The present correlation predicts the transient variation of film thickness within ±15% error and is applicable for all working fluids.