This paper presents numerical and experimental studies on the heat transfer characteristics around a radial heat sink with a horizontal circular base, concentric ring, and rectangular fins that are subject to natural convection. An FVM (Finite Volume Method) numerical model was used to analyze the temperature and natural convection heat transfer on the surfaces of the radial heat sink for a wide range of geometric parameters. The effects of dimensionless fin length (0.40 <= l* <= 0.53), dimensionless spacing between fins (0.127 <= s* <= 0.288), and the Elenbaas number (0.5 < El < 50) on the Nusselt number of the heat sink were investigated. In order to support the numerical results, experimental study is performed. The experimental result indicates that the present numerical model predicts the Nusselt number well within a maximum error of 4%. Based on the numerical results, a generalized correlation for predicting the Nusselt number was developed as a function of the three aforementioned nondimensional parameters. This correlation can be widely utilized for predicting the thermal performance of radial heat sinks with concentric rings subject to natural convection. (C) 2015 Elsevier Ltd. All rights reserved.