A NUMERICAL STUDY ON NATURAL CONVECTIVE HEAT TRANSFER OF PSEUDOPLASTIC FLUIDS IN A SQUARE CAVITY

Abstract

The natural convective heat transfer of pseudoplastic fluids in a square cavity with a heated bottom and cooled top walls was examined by a direct numerical analysis using the Sutterby model. Consequently, it could be verified that the heat transfer rate of pseudoplastic fluids became larger than that of a Newtonian fluid under thermal conditions where stable vortex flows were formed. The reason is that fluid flows are easy to further develop particularly near the walls due to the decrease in the apparent viscosity by the shear-thinning effect. On the other hand, it was found that the locally larger change in viscosity had the potential of causing the formation of a complicated flow field when the non-Newtonian fluid was highly pseudoplastic and the Rayleigh number increased. The contribution of the shear-thinning effect depending on the non-Newtonian property and the thermal condition was clearly revealed.