Role of various concave/convex walls exposed to solar heating on entropy generation during natural convection within porous right angled triangular enclosures

The solar heating of the inclined wall has the direct application for the processing of various porous materials. Analysis of natural convection is carried out for the built structure where the right wall is exposed to the sun and the left wall is exposed to the cold ambience in the presence of the bottom adiabatic wall. The current work also involves with the study of the entropy generation for natural convection in porous right angled triangular enclosures with the concave/convex right wall. The finite element simulations are performed for a wide range of Darcy number (10(-5) <= Da(m) <= 10) at a representative high Rayleigh number (Ra-m = 10(6)) for various fluids of industrial importance (Pr-m = 7.2: saline water, 0.7: air and 0.01: molten metal). An extensive investigation on the effect of Da(m) for the entropy generation due to heat transfer (S-theta) and fluid friction (S-psi) is carried out for various cases of wall curvatures. In addition, the total entropy generation rate (S-total), average Bejan number (Be-av) and average Nusselt number ((Nu(l)) over bar) are presented for various Da(m) and Pr-m. Overall, the built structure with the concave right wall (case 1) may be recommended for the thermal processing of fluids of all Pr-m, at all Da(m) via the solar heating on the curved wall. (C) 2016 Elsevier Ltd. All rights reserved.