Appraising the performance of a baffled solar air heater with external recycle

• Thermal performance for a baffled solar air heater with external recycle is studied.
• Applying external recycle boosts the energy efficiency of the air heater remarkably.
• Applying fins and baffles under external recycle enhances energy efficiency.
• Utilizing baffles at high recycle ratios and mass flow rates declines ηeff.
• Utilizing only fins at high mass flow rates and recycle ratios is well-organized.

This study aims at appraising the possibility of enhancing thermal performance of an upward-type single pass solar air heater by utilizing fins and baffles over the absorber plate as well as applying external recycle device simultaneously under various parametric conditions. The energy and effective efficiencies analysis is used as criteria to evaluate the performance. The investigation is carried out for three cases: simple absorber plate, absorber plate with fins and absorber plate with fins and baffles. The achieved results disclose that attaching both fins and baffles to the absorber plate under external recycling operation is an effective method to boost the energy efficiency notably. In contrast, the effective efficiency analysis reveals that attaching both fins and baffles at high mass flow rates and recycle ratios leads to considerable decline in effective efficiency. Parametric studies on variation of baffle parameters illustrate that increasing the baffles width as well as declining the distance between baffles under turbulent flow regime are not economically feasible owing to extremely increase of the pressure drop and required pump work. In a nutshell, it is found that utilizing only fins under external recycle application at high mass flow rates and recycle ratios is an attractive option.