Influence of bladed and glazed entrance on the performance of solar air heater

The performance of a flat plate single-pass solar air heater (SAH) modified at the entrance region of the heater was experimentally investigated. The entrance region was covered with glass cover instead of steel cover. The aim of using glass at the entrance region is increasing the heating area exposed to solar irradiation. In addition, replacing the steel cover with glass reduces the shading effect occurred due to steel which decreases the temperature of the surface of the absorber and hence the outlet temperature of the air. Also, guide blades were placed in the entry region to ensure well air distribution on the absorber surface and hence enhancing the thermal performance of SAH. The modified SAH was compared with another one without air blades and without glass cover at the entrance. The experiments were performed at four air flow rates ranged from 0.013 kg/sec to 0.04 kg/sec. The modifications led to good enhancement in both the air temperature difference and the efficiency. The glazed-bladed SAH showed a good improvement in the daily thermal efficiency by 6.72 % to 10.5 % over the conventional heater and by 2.16 % to 3.25 % over the glazed SAH.