Tubular solar air heater using finned semi-cylindrical absorber plate with swirl flow: Experimental investigation

Abstract

In this research, a tubular swirl-flow solar air heater (SF-SAH) with a find semi- cylindrical absorber plate is adopted to enhance its thermohydraulic performance. The proposed SF-SAH is tested with two types of fins: radial and longitudinal. Three sets of fins; 3, 4, and 5number of fins are tested. Data obtained from the proposed SF-SAH are compared with the plain duct conventional SF-SAH without fins under a typical air flow rate range 0.01–0.050 kg/s and Reynolds number (Re) from 7078 to 35190. Results obtained from this study reveal that radial fins enhance SF-SAH performance parameters when compared with the plain heater or heater with longitudinal fins. Also, increasing the number of radial fins and air flow rate enhances SF-SAH efficiency and Nusselt number and reduce the production cost. SF-SAH with five radial fins and air flow rate of 0.050 kg/s results maximum values for thermal and thermohydraulic efficiencies of 76.79%, 72.40%, respectively, Nusselt number of 223.64, and a minimum estimated production cost of 0.0105 $/kW.hr. The maximum effectiveness and exergy efficiency of SF-SAH are obtained with five radial fins and reached about 0.6 and 1.3 % respectively.