Numerical study of flow and heat transfer in a molten flux layer

Numerical simulations are performed to study coupled fluid flow and heat transfer in a thin liquid slag or flux layer. The steady state Navier-Stokes equations are solved using the commercial finite volume code FLUENT. The combined effects of natural convection, bottom shear velocity and strongly temperature dependent viscosity are investigated. It is found that the variation of Nu with Ra for fluxes with strongly temperature dependent viscosities is analogous to correlations for fluids with constant viscosity, but the critical Ra number for the onset of natural convection is larger. For thin layers of realistic fluxes, natural convection is suppressed, and Nu increases linearly with increase of bottom shear velocity. The increase is greater for decreasing average viscosity. The increase of Nu is slight and is only due to end effects for the flat interface shape studied here.