Experimental Study of a Solar Air Heater With New Arrangement of Transverse Longitudinal Baffles and Wire Mesh Layers

In this study, experiments were conducted on single- and double-pass solar air heaters (SAHs) with baffles and sixteen wire mesh layers inserted between the baffles. The baffles and mesh layers were inserted in the collector and tested to observe their effects on the thermal performance of the SAHs. Three cases of single- and double-pass SAHs were considered with bed heights of 3, 5, and 7.5 cm. The different bed heights were considered to improve the thermal efficiency and outlet temperature. For all cases, the airflow rate was varied between 0.011 and 0.032 kg/s, and the height of the upper channel for the double-pass SAH was fixed at 2.5 cm. The effects of the airflow rate and number of baffles in each case on the thermal efficiency and outlet temperature of the SAHs were experimentally investigated. The results showed that the efficiency could be improved by increasing the airflow rate, increasing the number of baffles, and decreasing the bed height. However, the temperature difference (ΔT) increased when the airflow rate was decreased, number of baffles was increased, and bed height was decreased. In all cases, the double-pass SAHs showed a greater thermal efficiency and outlet temperature than the single-pass SAHs. A maximum efficiency of 68.1% was obtained using a double-pass SAH with seven baffles, an airflow of 0.032 kg/s, and a bed height of 3 cm. The maximum average temperature difference between the ambient and outlet air temperatures of 54 °C was achieved using a double-pass SAH with seven baffles, airflow of 0.011 kg/s, and bed height of 3 cm. The pressure drop increased with the number of baffles and airflow rate. When the airflow was kept the same, the pressure drop decreased as the bed height was increased. A comparison of the pressure drops for the single- and double-pass SAHs showed that the latter had a higher pressure drop than the former, as expected. Keywords: Solar air heater, single- and double-pass, mesh layers, thermal efficiency, airflow.