Performance characteristics of a new curved double-pass counter flow solar air heater

Abstract

In this paper, a novel design of counter flow curved double-pass solar air heater (DPSAH) is proposed, and its performance characteristics are numerically investigated and compared with various parallel designs under different flow and geometric conditions. The developed model is first experimentally validated. The hydraulic and thermal performance of various DPSAH designs (smooth curved single pass, smooth parallel curved double-pass, smooth counter curved double-pass, roughened parallel curved double-pass, and roughened counter curved double-pass) show that counter flow curved DPSAH with asymmetrically placed turbulators is thermally better compared to other designs. A maximum of 23% augmentation in thermal performance was observed. To predict the performance of the best design, new correlations for Nusselt number (Nu) and friction factor (f) are developed in terms of Reynolds number (Re) and relative roughness height (d/H). The data estimated from these correlations are in good agreement with the values of f and Nu predicted from the model. © 2021 Elsevier Ltd