Mixed convection heat transfer from a spheroid to a Newtonian fluid

Abstract

In this paper the flow of an incompressible Newtonian fluid past a stationary unconfined spheroid under the mixed convective heat transfer regime is studied numerically. The spheroid is assumed to be maintained at a constant wall temperature. The effect of Reynolds number (Re), Prandtl number (Pr), aspect ratio (E) and Richardson number (Ri) on the average drag coefficient and Nusselt number is investigated. The range of parameters considered in this study is: 10 ≤ Re ≤ 100; 0 < Ri < 2 and 0.5 ≤ E ≤ 1.5 and for two Prandtl numbers of 1 and 5. The drag coefficient increases monotonically with the increase of surface temperature for all Reynolds number. Prolate spheroids have higher drag coefficient and Nusselt numbers compared to oblate spheroids. The variation of Nusselt number with Ri at a fixed Re is non monotonic at large Re and this effect is stronger for prolate spheroids when compared to oblates. For aspect ratios greater than unity and for Re > 60, Nusselt numbers for small Ri (∼0.5) are lower compared to Nusselt numbers for Ri = 0. This difference in Nusselt numbers becomes appreciable for larger Prandtl numbers. A correlation for average Nusselt number was developed using least squares regression analysis.