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Computational fluid dynamics (CFD) and exergy analysis are conducted to investigate the impact of secondary flow produced by V-ribs on the overall performance of a triangular solar air heater (SAH) duct. For a fixed relative rib pitch (R p = 10) and relative rib height (R h = 0.05), the effect of rib inclination (α) is studied using CFD technique for varying Reynolds number (5000 ≤ Re ≤ 20000). Based on the CFD simulation results, empirical correlations capable of predicting Nu and f with an absolute variance of 8.7%, and 4.7%, respectively, are developed. Employing these correlations, exergetic performance analysis is carried out. Maximum effectiveness parameter (ε) of 2.01 is obtained for α = 45° at Re = 7500. The exergy analysis reveals that the entropy generated is lower for the ribbed triangular duct compared to the smooth duct with maximum enhancement in exergetic efficiency (η ex) as 23% for α = 45°. The study is extended for the rectangular duct to compare the performance with the ribbed triangular duct SAH (α = 45°). Results show that ribbed triangular duct SAH (α = 45°) is superior over various configurations of the ribbed rectangular duct SAH at higher mass flow rates. • CFD and exergy analysis of a triangular duct solar air heater with V-rib is proposed. • Secondary flow in triangular duct significantly enhances the Nusselt number. • A significant enhancement in the effectiveness parameter of 2.01 is obtained. • Empirical correlations are developed for Nusselt number and friction factor. • The proposed design exhibits superior performance at high mass flow rates. [ABSTRACT FROM AUTHOR]