Numerical analysis of the performance improvement of a flat-plate solar collector using conjugated porous blocks

Performance enhancement of a flat-plate solar collector (FPSC) of direct absorption has been studied using porous insertions. The FPSC channel includes three conjugated porous blocks with various levels of permeability near the bottom insulator wall. Both the length and width of the blocks are altered near the inlet and outlet sections. The size of the middle trapezoidal block is aligned with reference to the gap available between the blocks near inlet and outlet. The parametric study focuses on finding the optimum design and arrangement of porous insertion. The height and width of the inlet sections are varied between 0 - H (step of 0.2) and 0-L (step of 0.2), respectively. The permeability of the porous blocks is varied between Da = 10(-3) - 10(-1). The opensource tool OpenFOAM (R) is used, and a generic steady-state thermal transport code is modified by the extended Darcy-Brinkman-Forchheimer model for realising porous medium. Numerical results indicate that the overall performance of the flat plate collector channel is improved by using the conjugated arrangement of porous bodies. The approach of placing the bodies near the bottom insulator plate improves heat transfer by promoting thermal mixing. Also, it is seen that more flow deviates towards the top absorber plate, and hence better thermal contact is established with the working fluid. The optimum performance is noticed for lower values of height of the block near the inlet and higher values near the outlet. (c) 2021 Elsevier Ltd. All rights reserved.