A study of a solar air collector with a mixed “porous” and “non-porous” composite absorber

In this work, a solar air collector with a composite absorber is designed and experimented. Its composite absorber results from the coupling of a non-porous absorber made of a corrugated iron sheet and a porous absorber made of a mesh of aluminum. The prototype collector was modeled in unsteady-state by considering heat capacity effects in its components. The temperatures were simulated by solving energy balance equations relating to each component. Solutions to these equations gave temperatures variation according to time of the day and distance from collector inlet. Results show that the collector overall thermal efficiency approximates 61% at solar midday with maximum temperatures of 77, 142, 107 and 73 °C respectively for glass cover, non-porous and porous absorbers and airstream. Compared to quasi-steady state studies, unsteady state studies lead to results in better agreement with experiment. Experimental and unsteady state simulated temperatures were very close and unsteady state model therefore allowed predicting suitably collector performances.