Design And Performance Evaluation Of Solar Air Heaters For Industrial Thermal Applications

Abstract

Solar air heaters (SAHs) provide a technically simple route for converting incident solar radiation into useful hot air for low- and medium-temperature industrial duties such as product drying, process-air preheating, curing, timber seasoning, and ventilation-air heating. Their principal limitation is the relatively low convective heat-transfer coefficient between a flat absorber and the flowing air. This methodology paper develops a design and performance-evaluation framework for a single-pass, roughened-duct solar air heater intended for industrial thermal applications. The proposed configuration combines a blackened metal absorber, single transparent cover, insulated casing, forced air circulation, and controlled rib roughness on the air-side absorber surface. Performance is evaluated from measured solar irradiance, inlet and outlet air temperatures, absorber temperatures, airflow rate, ambient temperature, and pressure drop. The principal response variables are useful heat gain, outlet-air temperature rise, thermal efficiency, Nusselt number, friction factor, pumping-power requirement, and a thermo-hydraulic performance parameter. A literature-constrained design window is adopted from work published up to 2017. An illustrative calculation set shows the expected trade-off between higher airflow, rising thermal efficiency, declining temperature lift, and increasing pressure drop. The proposed procedure is suitable for laboratory validation and subsequent scale-up to industrial preheating or drying systems while avoiding the misleading use of thermal efficiency as the only design criterion.