Solar Thermal Performance: Using Perforated, Corrugated, Waved and Punched Absorber Plates
Abstract
The heat transfer and thermal efficiency of a solar air heater are diminished due to the low thermal conductivity of air. Using various artificial roughness geometries has proven effective in increasing the heat contact surface area. In this study, two double-pass glazed solar heaters, equipped with perforated and corrugated absorber plates, are then changed to wavy and punched absorber plates. Experimental and numerical modeling are conducted to assess the effects of inlet temperature, solar intensity, and airflow rate on the outlet temperature and thermal efficiency. Thermal efficiencies significantly increase at higher flow rates, but heat loss from the absorber plate to the surroundings also becomes more pronounced at an airflow rate of 0.035 kg/s, for perforated, wavy, corrugated, and punched collectors are 0.76, 0.62, 0.52, and 0.394% respectively. However, the highest outlet temperatures are recorded at a minimum airflow rate of 0.017 kg/s, with perforated and corrugate heaters reaching 66.7 and 60.6 °C, wave and punched heaters reaching 59.9 and 51.8 °C. Additionally, the findings reveal a notable enhancement in outlet temperature when using a perforated absorber plate, compared to corrugated, wavy, and punched absorber plates. Additionally, empirical formulas for thermal efficiencies and outlet temperatures are developed based on the theoretical model.