Energy and exergy analysis of solar air heater utilizing noble half conical ribs of various designs: an experimental study

The heat transfer performance of the solar air heater (SAH) is improved by employing an artificially roughened plate, which effectively disrupts the viscous layer and increases turbulent intensity near the absorber plate. This research assesses the energy and exergy analysis of three noble half conical rib designs SAHs examined alongside a smooth plate Type-1 SAH across a range of mass flow rates (0.013, 0.021, 0.033, 0.051, and 0.061 \(\text{kg}/\text{s}\) $\text{kg}/\text{s}$ ). The case of roughened Type-4 SAH shows significantly enhancements in average comparative energy efficiency of 25.5%, 18.9%, 25.1%, 29.5%, and 30.5%, as compared to Type-1 SAH for varying mass flow rate. Moreover, the average comparative percentage increase in exergy efficiency for Type-4 is found to be 71.3%, 61.3%, 56.9%, 55.6%, and 53.1% as compared to Type-1 SAH. Energy efficiencies increase as mass flow rates rise, whereas exergy efficiencies decrease with increasing mass flow rates. The Type-4 SAH effectively minimizes pressure drops along the ribs due to improved airflow along the cone's slant surface and promotes proper air mixing, thereby reducing dead surfaces within the duct and enhancing the heat transfer coefficient significantly.