Thermal Performance Enhancement of Solar Air Heaters Using Multi-V-Shaped Perforated Ribs With Different Directions

This experimental study investigates the thermal performance of three solar air heater (SAH) configurations: a conventional flat plate, a V-up perforated ribs absorber plate, and a V-down perforated ribs absorber plate. The studies were conducted in real outdoor conditions at the University of Zakho, Zakho, Iraq, on 15, 18, and 25 February 2025. Each SAH was tested at three different air mass flow rates: 0.00882 kg/s, 0.01323 kg/s, and 0.01764 kg/s. The findings demonstrated that the V-down SAH consistently outperformed the others in terms of daily thermal efficiency and heat gain. At the maximum flow rate (0.01764 kg/s), the V-down configuration achieved a maximum daily thermal efficiency of 84% and a peak useful heat transfer rate of 529 W. The V-up SAH followed with 77% efficiency and 492 W, while the flat plate SAH reached 69% efficiency and 470 W. The enhanced performance of the V-down design is attributed to improved turbulence and convective heat transfer induced by its downward-facing perforated ribs. These findings confirm the effectiveness of using V-shaped perforated ribs, particularly the V-down orientation, in enhancing the thermal performance of solar air heaters.