Thermal performance study of a solar air heater with packed flow passage

A solar air heater with the air flow channel underneath the absorber plate has been designed and tested. The performance tests have been carried out when the flow channel is empty (type I) and packed with Raschig rings made of hard plastic (type II). The packing causes a considerable increase in the efficiency. The theoretical analysis of the systems has been performed using a heat transfer model based on the quasi-steady state condition. The energy balance equations of the systems with one and two glass covers have been solved explicitly for various design and operating variables. The agreement between the measured and predicted performances is satisfactory for the type I, while it is relatively poor for the type II. © 1987