Solar air heaters are used for drying applications for different agricultural products. Selecting the proper type dryer needs a correct picture about its performance. The performance assessment of solar collectors is done generally based on the first law efficiency. The second law efficiency or the efficiency based on exergy would be a more accurate method of assessment. This is because, as in the case of drying, both air flow rate and temperature play a key role in exergy analysis methodology. In this paper the standard method of "DT over I? is used to determine the parameters of a solar collector. The heat removal factor and the loss coefficient thus obtained can be used to forecast the performance of the system for different solar radiation data. The output of this calculation gives the air outlet temperature for different mass flow rates of air. Exergy or available energy from hot air is simulated under two different types of solar radiation and ambient air conditions and the results are compared with the drying results. Thus the available energy analysis is found to be an ideal method for comparison of performance of driers.