Experimental investigation on Counter Flow Double-Pass Solar Air heater with absorber attached with perforated C-shaped Fins.

A solar air heater with double-pass and counter flow featuring a perforated C-shaped finned absorber, considering mass flows of 0.041, 0.045 and 0.049 kg/s was investigated experimentally in an outdoor environment. The results of the experiments indicate that solar irradiance, ambient temperature, and the mass flow of air have a noteworthy impact on the efficiency, air temperature rise, and thermal effectiveness of the solar air heater. A noticeable trend indicates a reduction in the efficiency of the heater as the mass flow of air decreases. The mean thermal efficiencies at air mass flows of 0.041, 0.043 and 0.049 kg/s were found to be 77.46, 79.81 and 82.79%, respectively. The temperature rise per unit solar irradiance for the air mass flows of 0.041, 0.043 and 0.049 kg/s were 0.027, 0.026, and 0.025 °C/W-m 2 , respectively. The thermal effectiveness of the heater was 73.34 72.28 and 70.31% at 0.043, 0.045, 0.049 kg/s air mass flows, respectively. It is noteworthy that the thermal effectiveness declines as the mass flow rates of air decreases.