Fabrication and Thermal Modeling of Unglazed Transpired Solar Air Heater Collectors with metallic (Steel) and non-metallic absorber plates

Unglazed transpired solar air heater collectors are relatively new solar technologies that can be used for air heating or pre-heating ventilation air and drying agricultural and industrial products. Passing air through the perforated plate, which is usually metallic is the main mechanism of heat transfer. The cost of buying and preparing the absorber plate is the dominant share of costs allocated to this type of collector. In the present study, performance of non-metallic absorber plates available in the Iranian market, as an alternative to metal absorber plates are examined experimentally and theoretically. Therefore, three collectors with Metallic, Polycarbonate and Compressed-Plastic are designed, fobricated and tested in real conditions. In addition, a thermal modelbased on the first law of thermodynamic is developed for these collectors. In this model, all mood of heat transfer (including conduction, convection and radiation) are considered. Results show that there is a good agreement between experimental and theorical results (For most test condition, average relative error in estimation of the outlet temperature of the collectors is less than 5%). The results showed that the performance of three collector’s, espisially for low mass flow rates, was not too different. However, for considered condition Steel (metallic) collector has the best performance and the polycarbonate collector the worse performance. The performance of the Compress plastic was close to the Steel collector and given the low cost of non-metallic collectors, it can be used as a convenient alternative to metal collectors.