HEAT TRANSFER IN FLOWS OF NON-NEWTONIAN BINGHAM FLUIDS THROUGH AXISYMMETRIC SUDDEN EXPANSIONS AND CONTRACTIONS

The heat transfer phenomena associated with the laminar, constant properties flow of non-Newtonian Bingham fluids over sudden expansions and through contractions in circular pipes are studied by numerically solving the fully elliptic governing continuity, momentum, and energy equations for a wide range of the governing Reynolds, yield, and Prandtl numbers. The influence of the yield number on the thermal field is more pronounced at high Reynolds and Prandtl numbers. In the sudden expansion case this influence takes the form of a localized peak in the Nusselt number distribution downstream of the reattachement point. The magnitude of the peak Nusselt number increases with the Reynolds, yield, and Prandtl numbers. A sharp reduction in the Nusselt number values right before the contraction plane is found to be more significant at high Reynolds and Prandtl numbers.