This paper reports the numerical study of two-dimensional, steady, incompressible, conjugate, laminar, natural convection with surface radiation in open top cavity having air as the intervening medium for different locations of uniform volumetric heat generating source at the left wall. For surface radiation calculations, radiosity-irradiation formulation has been used, while the view factors required therein, are calculated using the Hottel's Crossed-string method. The analysis has been done for a constant property of fluid, with the Boussinesq approximation assumed to be valid. The effects of the magnitude of heat source, location, the material and surface properties of the heat source on both heat transfer and fluid flow have been studied and discussed. An important contribution from the present work is to find the location of heat source for efficient cooling and it is found at the top of the left wall. Based on a large set of numerical data, correlations have been developed for maximum non-dimensional temperature of heat source for three different locations at the left wall. (C) 2015 Elsevier Ltd. All rights reserved.