Abstract
Conventional natural convection flat plate solar air heater (SAH) suffers from low heat transfer characteristics. Putting extended surfaces in the air flow channel to augment thermal performance actually hinders the buoyancy driven flow, and thereby reducing the hydraulic performance due to high frictional losses. The objective of the present study is to enhance thermo-hydraulic performance by incorporating convex and concave flow channel with chimney effect. The curved SAH has been investigated using an experimentally validated computational fluid dynamic model for different curvature angles in the range of 25–50°. The results show significant increase in Nusselt number per unit pressure drop (NuP), heat transfer enhancement factor, temperature enhancement ratio and effectiveness, in comparison to conventional flat SAH. The convex and concave designs are respectively 43% and 31% thermally, and 7% and 6% by NuP, higher than conventional flat natural convection SAH. Two different independent correlations derived for Nusselt number for different geometries were found to be in excellent agreement with the data. The designs and data presented in the study would help scientific community and solar based industries in developing efficient natural convection SAH.
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