Purpose This study aims to elucidate the role of curved walls in the presence of identical mass of porous bed with identical heating at a wall for two heating objectives: enhancement of heat transfer to fluid saturated porous beds and reduction of entropy production for thermal and flow irreversibilities. Design/methodology/approach Two heating configurations have been proposed: Case 1: isothermal heating at bottom straight wall with cold side curved walls and Case 2: isothermal heating at left straight wall with cold horizontal curved walls. Galerkin finite element method is used to obtain the streamfunctions and heatfunctions associated with local entropy generation terms. Findings The flow and thermal maps show significant variation from Case 1 to Case 2 arrangements. Case 1 configuration may be the optimal strategy as it offers larger heat transfer rates at larger values of Darcy number, Dam. However, Case 2 may be the optimal strategy as it provides moderate heat transfer rates involving savings on entropy production at larger values of Dam. On the other hand, at lower values of Dam (Dam ≤ 10−3), Case 1 or 2 exhibits almost similar heat transfer rates, while Case 1 is preferred for savings of entropy production. Originality/value The concave wall is found to be effective to enhance heat transfer rates to promote convection, while convex wall exhibits reduction of entropy production rate. Comparison between Case 1 and Case 2 heating strategies enlightens efficient heating strategies involving concave or convex walls for various values of Dam.

No abstract

This article presents a detail analysis of heatlines and entropy generation during natural convection in various enclosures with curve (concave and convex) walls. The dimensions of enclosures are fixed in such a way that thedimensionless area of the cavity is one and the dimensionless length of the wall is one. Two heating strategies are considered such as (a) type 1: hot bottom wall, cold side walls in the presence of adiabatic top wall and (b)type 2: hot left, cold top and bottom walls in the presence of adiabatic right wall. Numerical simulations have been carried out for fluid with Prandtl number Pr = 0. 7 at different Rayleigh number (10 3 ≤ Ra ≤10 5). The distributions of isotherms, streamlines, heatlines and entropy generation due to heat transfer and fluid friction are compared for curved walled enclosures with those of square enclosure. The effect of Ra on the total entropy generation, average Bejan number and average Nusselt number is illustrated for considered enclosures involving both the heating strategies. The optimal configuration and optimal heating strategy is chosen based on the less entropy generation rate and higher heat transfer rate.

No abstract