LAUSR

Abstract The present study investigates extensively the capability of computational fluid dynamics (CFD) to predict two-phase fluid flow and heat transfer characteristics of FC-72 flow boiling in vertical upflow. The computational method performs transient analysis to model the entire flow field and bubble behavior for highly subcooled flow boiling in a rectangular channel heated on two opposite walls at high heat flux conditions of about 81% of critical heat flux (CHF). Transient variations of local vapor fraction, thermal energy transfer and concentration, and wall temperature are estimated through the computational methodology based on the Volume of Fluid (VOF) approach combined with shear-lift modeling to overcome a fundamental weakness in modeling multiphase flows. Detailed information about bubble distribution in the vicinity of the heated surface, thermal conduction inside the heating wall, local heat fluxes passing through the solid-fluid interface, and velocity and temperature profiles, which are not easily observed or measured by experiments, is carefully evaluated. Predictions are compared to the experimental data for three sets of operating conditions. Overall, computationally predicted flow pattern, bubble behavior, and heat transfer parameters (such as wall temperature excursion and thermal energy concentration) clearly represent phenomena of premature CHF which take place slightly earlier than actual operating conditions. But, despite these slight differences, the present computational work does demonstrate the ability to effectively predict the severe degradation in heat transfer performance commonly encountered at heat fluxes nearing CHF.