| A transient, three-dimensional, two-phase computational model for simulating boiling-enhanced mixed convection in free-surface flow is developed. General discrete-element analysis is used and equations of balance of momentum, conservation of energy, mass and vapor mass fraction are solved. The associated constitutive models for the kinetic (nonequilibrium) phase transport, thermophysical and transport properties are described. The computational model is first applied to study the three-dimensional hydrodynamic flow field around a protruding block in a channel filled with water. The numerical results show that the three-dimensional leading-edge horseshoe vortex and the downstream three-dimensional vortex are capable of strongly perturbing the flow structure and possibly modifying the heat transfer characteristics. The computational model is then applied to the simulation of transient, two- and three-dimensional, two-phase flow around a computer chip in a test tank filled with Freon-(R113) in both natural convection and boiling heat transfer regimes. While three-dimensional simulation results agree qualitatively with two-dimensional ones in both the natural convection and boiling heat transfer regimes, the flow is essentially three-dimensional and a two-dimensional model can not correctly capture the features of the flow. The outward heat flux in the boiling heat transfer regime is increased by ten-fold over the outward heat flux in the natural convection regime. The simulated heat fluxes are in good agreement with the available experimental data. |
