Effect of Prandtl number on buoyancy-induced transport processes with and without solidification

In studying the transport processes with solidification, various materials such as aqueous solutions, which are of high Prandtl number (Pr), have been used to help understand the solidification characteristics of silicon or metal based materials, which are of low Pr. Influences of Pr on the buoyancy-induced transport phenomena are investigated through two-dimensional steady-state computations for flow in a square enclosure at two different vertical wall temperatures, both with and without solidification. With a constant Rayleigh number (Ra), the momentum and heat transport characteristics are very insensitive to Pr if Pr > 1, regardless of whether phase change appears or not. The Pr effect becomes more noticeable as it is progressively reduced from one. With respect to phase change, for cases with no solidification, Pr effects on all aspects of the transport process increase with Ra. With solidification, more vigorous convection induced by higher Ra, which coupled with the Stefan number effects, result in stronger Pr influence on maximum streamfunction and Nusselt number, but not on global enthalpy patterns. It is also found that features such as morphology of phase boundaries may be more sensitive to Pr variations than momentum and heat transport are.