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 in the entrance region, was experimentally investigated. This entrance region was covered with glass instead of steel. Using glass cover in the entrance region increases the exposure of the heating area to solar radiation; however, using steel cover prevents solar radiation from reaching this area. In addition, guide blades were placed in the entrance region to ensure well air distribution on the absorber surface and, hence, enhancement of the thermal performance of SAH. The modified SAH was compared with that at the conventional entrance. The experiments were performed at four airflow rates, which ranged from 0.013 to 0.04 kg/s. The modifications led to good improvement in both the air temperature difference and the efficiency. For the daily efficiency, the maximum values include 43.43, 40.48, and 32.92% for the glazed-bladed entrance SAH, glazed entrance SAH, and conventional SAH, respectively, at a rate of 0.04 kg/s. The glazed-bladed SAH showed 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.