The thermal performance of a double pass solar air heater with 2, 4, and 6 fins attached was investigated experimentally. Wire mesh layers were used between the fins instead of an absorber plate. The effects of mass flow rate of air on the outlet temperature and thermal efficiency were studied. The indicated results show that the efficiency increases with increasing the mass flow rate for the range of the flow rate used in this work between 0.0121-0.042 kg/s. Moreover, the maximum efficiency was obtained by using 6 fins at the same mass flow rate. The maximum efficiency obtained for the 2, 4, 6 fins of SAH were 75.0%, 82.1% and 85.9% respectively for the mass flow rate of 0.042 kg/s. In addition, the maximum average temperature difference between the inlet and the outlet, Delta T, for the SAH with 6 fins was the highest for the same mass flow rates compared to 2 and 4 fins SAHs. The maximum average and instantaneous peak of Delta T obtained were 43.1 degrees C and 62.1 degrees C respectively for the 6 fins SAH when the mass flow rate was 0.0121 kg/s. Comparison of the results of a counter flow packed bed collector with those of a conventional collector shows a substantial enhancement in the thermal efficiency. Published by Elsevier Ltd.