Thermo-Hydrodynamic Study of Subcooled and Critical Heat Flux Flow Boiling

Abstract

In present work high heat and mass flux flow boiling through vertical circular tubes of diameters 24.0 mm, 15.4 mm, 10.0 mm having length 2.0 m, 2.0 m and 7.0 m respectively, subjected to constant wall heat flux was analyzed through CFD approach in order to characterize the boiling heat transfer, pressure drop, variation of vapor fraction in axial direction, wall temperature distribution and vapor velocity. Subcooled flow boiling up to critical heat flux (CHF) and past dry out were investigated to predict the heat transfer phenomena. For this purpose a detailed mathematical model of wall boiling has been discussed which includes modeling of wall heat flux partition, bubble departure diameter, frequency of bubble departure, nucleate site density, interfacial heat, mass and momentum transfer and other interactions. Commercially available ANSYS FLUENT 15.0 with user defined functions was used to solve the numerical model and analyze the results.