Heat Transfer Studies in Matrix-Type Solar Air Heaters

The effectiveness of a matrix-type solar air heater with a thick, porous absorber and a double-glass cover is analyzed theoretically and experimentally. The theory presents an exact formulation of simultaneous radiation, conduction, and convection heat transfer for quasi-steady, one-dimensional, isotropic, homogeneous, absorbing, emitting, scattering gray porous slab along with the energy conservations for the cover and floor plates of the collector. This set of the nonlinear coupled equations governing the transfer of energy in the collector is solved numerically by employing several iterative schemes. The effects of air flow rate, scattering, optical thickness, thickness, and conductivity of porous materials on the collector performance are discussed. Experimental results are found to partially support numerical predictions.