Enhanced thermal performance of a flat-plate solar collector inserted with porous media: A numerical simulation study

This study proposes a novel design scheme of the flat plate solar collector (FPSC) with porous metal blocks on the inner wall of absorber. The enhanced thermal performance of FPSC is numerically investigated using the extended Darcy-Brinkman-Forchheimer model and the local thermal equilibrium condition in porous regions. Concerning the factors of the shape (rectangular, trapezoidal, and triangular), number of porous blocks (N = 2, 4, 6), permeability (corresponding Da = 10- 5-10- 2), material type (stainless steel, alumina, aluminum, copper), and Reynolds number (Re = 234, 351, and 468) on its thermal performance of FPSC, the results reveal that the global Nusselt number is definitely improved, but the friction factor undesirably rises as well. By comparative analysis of all cases, inserting rectangular porous blocks performs better heat transfer in the FPSC channel, and the best heat transfer performance is achieved at N = 6 under the condition of high permeability (Da = 10-2), while the friction factor is the highest at N = 4. For the effect of Reynolds number, the heat transfer enhancement is significantly improved with increase of Reynolds number. Also, a maximum value of Nug by inserting REC porous copper material in the channel can reach 7.17 at N = 6, Da = 10-2, Re = 468. But, considering the balance of heat transfer enhancement and pressure drop in the channel, the performance evaluation criteria (PEC) is used to comprehensively analyze the thermal performance of FPSC. The results show that for the case of inserted REC porous blocks at N = 6, Da = 10-2 and Re = 234, PEC can reach a maximum value of 1.8 compared with the empty channel.