Experimental study on the thermal performance of a solar air heater integrated with multi-geometry arrangements over the absorber plate

A solar air heater (SAH) is investigated experimentally by employing multi-geometry arrangements over the absorber plate. In the current work, the absorber plate is designed with rectangular ribs, slits, and cylinders. For the proposed system, this multi-geometry arrangement serves as an artificial roughness (baffles). Different airflow rates of 0.01, 0.02, 0.03, and 0.04 kg/s are used in the experiment. The results of this experiment are compared to those of a conventional SAH to assess the improvement. Compared to a conventional SAH, the proposed system has higher thermal efficiency, energy gain, and minimal top loss. The highest thermal efficiency and energy gain are observed at a mass flow rate of 0.04 kg/s. Increasing the mass flow rate increases the system's performance. For the analyzed flow rates, the average thermal efficiency of a SAH with multi-geometry baffle is 40.8%, 58.2%, 68.2%, and 77.4%. For the same flow rates, it is 12.8%, 10.2%, 12.3%, and 13.5% higher than a conventional SAH. For the same examined air flow rates, the suggested air heater gains 31.9%, 21%, 19.2%, and 20.8% more energy than conventional SAH. Significant decreases in top losses are reported up to 8.1%, 7.3%, 7.2%, and 6.5%, respectively for the specified flow rates.