Unglazed transpired collector (UTC) is a kind of solar air heater is used for different applications such as air ventilation, preheating, and crop drying. Passing air through the perforated plate, which acts as an absorber, is the main mechanism of heat transfer and air preheating in UTCs. In order to design UTCs and determine the effective parameters, energy and exergy analyses are performed. A mathematical model which is solved using an iterative method by a computer code has been developed. In order to validate the present model, this solution is compared with numerical and experimental results available in the literature, where a good agreement is obtained. After verifying the model, the code has been used to study the influence of the effective parameters on the performance of the system. The results show that the exergetic analysis is very important to design.