Performance Analysis of Double Pass Solar Air Heater with Bottom Extended Surface

A model of solar air heater with selective absorber coating with longitudinal fins at the bottom of absorber has been prepared to produce hot gases by consuming solar energy in day time. It is kept in position in such a way that air will flow due to forced convection and the entire setup placed at an angle of 15° to 17° inclination as per the considered global position (20.2961° N, 85.8245° E). Air flow rate is increased by applying a DC suction fan at outlet which sucks the air to flow over extended surfaces which are present at bottom inlet channel. Special selective coating applied over the entire Aluminum absorber plate to increase the heat absorbing capacity. Average ambient, inlet and plate temperatures are recorded daily along with solar flux. It is found that the instantaneous efficiency and air outlet temperature increased up to 69% and 94 °C respectively. Theoretical analysis has been made as well for the present set up. The difference between the theoretical and experimental values lies within 1.23-9.75%.