In this study, a triangular guide rib (TGR) is designed with the aim of enhancing the heat transfer rate by accelerating a jet impinging downward on an asymmetric concave surface with curvature radii of 8 cm (Cr = 0.15) and 12 cm (Cr = 0.1). An infrared thermometer camera is employed to measure the temperature distribution in the steady-state condition. Predicted Nusselt number profiles by the renormalization group k-ϵ turbulent model go well with the experimental data. An equilateral triangular rib with each side measuring 12 mm (D/2) is placed in the stagnation region to investigate the effects of the TGR on flow and heat transfer of the asymmetric concave surface. This investigation is carried out for three different Reynolds numbers: 23 000, 35 000, and 50 000. The acceleration of the impinging jet due to the TGR creates a horseshoe-shape in the zone of high Nusselt number values. Numerical results show that the TGR provides higher averaged Nusselt numbers compared to a smooth concave surface.