Designing and Evaluating an Innovative Solar Air Collector with Transpired Absorber and Cover

Applying solar collectors is a popular tool for harnessing solar energy. In this work, a flat plate solar air collector was investigated under direct solar radiation in an endeavor to enhance the thermal efficiency of solar air collector with a slatted glass cover, perforated absorber aluminum sheets (porosity 0.0177, 0.0314 and absorber thickness of 1.25, 2.5 mm) which is the most suitable for a solar dryer. The effects of porosity and thickness on absorber performance of collector were evaluated. Six levels of air mass flow rates (0.0056 to 0.0385 kg m−2 s−1) were adopted. The tests were conducted in three replications on very clear sky days in September and October. The experimental results showed that thermal efficiency of collector was increased by an increase in the porosity of the absorber. The absorber with lower porosity showed a better thermal efficiency at lower air mass flux. In the minimum air flow rate, absorber efficiency with porosity 0.0177 and 0.0314 was 0.31 and 0.29, respectively, whereas at the maximum flow, efficiency showed an enormous change of 0.83 and 0.88, respectively. This solar air heater can be used for drying agricultural products, heating the space of greenhouse, and so forth.