<p>Passive heat transfer enhancement techniques play a crucial role in improving the thermal performance of heat exchangers. Among these techniques, vortex generators are widely used due to their ability to induce secondary flows that disrupt the thermal boundary layer and promote fluid mixing. In this study, the heat transfer augmentation characteristics of a solar air heater equipped with trapezoidal winglet-type vortex generators are experimentally investigated. The winglets are mounted on the absorber plate in multiple configurations and arranged at different angles of attack. Both solid winglets and winglets with punched holes are considered to evaluate their relative performance. Experiments are conducted over a Reynolds number range of 9,000 to 22,000. The results indicate that an increase in the number of winglets leads to a significant improvement in heat transfer rate and overall thermal performance. Additionally, winglets with punched holes exhibit marginally better performance compared to solid winglets, attributed to enhanced flow mixing and reduced pressure losses. The findings demonstrate that trapezoidal winglet vortex generators are an effective passive technique for improving the thermal efficiency of solar air heaters.</p>