Search

This work reports results on the drag and heat transfer from an in-line array of three isothermal spheres falling in a cylindrical confinement filled with Bingham plastic fluids. The effects of dimensionless parameters, such as the Reynolds number (1 ≤ Re ≤ 100), Prandtl number (1 ≤ Pr ≤ 100), Bingham number (0 ≤ Bn ≤ 100), blockage ratio (2 ≤ β ≤ 4) and sphere-to-sphere distance (1.5 ≤ t ≤ 6) have been elucidated. The flow and heat transfer characteristics were analysed in terms of yielded/unyielded regions, streamline and isotherm contours, drag coefficient, pressure coefficient, and local and average Nusselt number. Broadly, the drag coefficient shows a positive dependence on Bn and sphere-to-sphere distance (t) while it exhibits an inverse dependence on Re and β. On the other hand, the Nusselt number shows a positive dependence on Re, Pr, Bn and β; and a complex dependence on t for each sphere. Simple predictive expressions for the average Nusselt number for each sphere are formulated, thereby enabling its prediction in a new application. [ABSTRACT FROM AUTHOR]

Forced convection heat transfer from an isothermal heated cone (apex up and down) in Bingham plastic fluids has been studied numerically. Extensive results are presented here in terms of isotherm and Nusselt number over ranges of conditions as: Reynolds number, 1 ≤  Re  ≤ 100, Prandtl number, 10 ≤  Pr  ≤ 100, Bingham number, 0 ≤  Bn  ≤ 100 and cone angle, 20 °  ≤  α  ≤ 150 ° . The rate of heat transfer is influenced mainly by the values of Re , Pr and Bn and to a lesser extent by the cone angle and orientation. The present results are consolidated in terms of the modified Reynolds ( Re ⁎ ) and Prandtl numbers ( Pr ⁎ ) incorporating the role of Bingham number. [ABSTRACT FROM AUTHOR]

The laminar forced convection momentum and heat transfer aspects of a circular disk oriented normal to the flow and maintained at a constant flux or a constant temperature condition in a stream of a Bingham plastic fluid are studied over wide ranges of parameters as follows: Reynolds number,Re ≤ 150; Prandtl number, 1 ≤Pr ≤ 100; Bingham number,Bn ≤ 100, and thickness-to-diameter ratio, 0.01 ≤ (t/d) ≤ 0.075. The new results on hydrodynamics are analyzed in terms of streamline plots, recirculation length, morphology of yielded/unyielded regions, and drag coefficient, and on heat transfer aspects in terms of isotherm contours, local and average Nusselt number. The flow domain is spanned by the simultaneous existence of the yielded and unyielded sub-regions, depending upon the relative strengths of the fluid inertia (Re) and yield stress (Bn). All else being equal, the rate of heat transfer is higher for an isothermal disk than that for the isoflux condition. Both the drag and average Nusselt number bear a positive dependence on the Bingham number. The drag is influenced only slightly (∼5%) by thickness (t/d); however, the heat transfer can increase on this count by up to 15% under appropriate conditions. Finally, the present numerical results on drag and Nusselt number (in terms ofjH-factor) have been correlated via simple empirical equations using the modified definitions of the Reynolds (Re*) and Prandtl number (Pr*), thereby enablinga prioriestimation of drag and heat transfer in a new application. [ABSTRACT FROM PUBLISHER]