Heat Transfer Characteristics of a Back-Corrugated Absorber Surface for Solar Air Collectors

Current literature on solar air collectors emphasizes satisfactory heat transfer between the absorber and the flowing air as a major factor in overall performance. Heat transfer in the airflow passages, usually in or near the transitional flow range, is also influenced by entrance effects. The present study experimentally examines a back-corrugated absorber-convector composed of a rectangularly corrugated plate attached to the back side of a flat absorber plate with a high-temperature, high-strength adhesive. The upper surface is subjected to a heat flux from a blanket-type electric heater which simulates solar irradiation. The corrugated-plate configuration creates two parallel airflow channel types. The two channels have different geometries and, therefore, may have different heat transfer characteristics. An apparatus was designed to determine the local convective heat transfer coefficients along each of the channels. The results show that the back-corrugated absorber-convector has much better thermal performance than the simple flat-plate absorber-convector, primarily because of the increased convective heat transfer area.