This present investigation deals with experimental and numerical analysis of natural convection in a right-angled triangular cavity heated from below and cooled on sidewall while its other wall, the hypotenuse, is kept adiabatic. The enclosure is filled with water and heat transfer surfaces are maintained at constant temperature. Experimental study covers flow visualization studies involving the use of the particle tracing method. Numerical solutions are obtained using a commercial CFD package, FLUENT, using the finite volume method. Contradictory results existing in the open literature for the Nusselt number resulting from the singularity at the corners of heated surfaces and from the definition of the Nusselt number are discussed in detail. A new approach is used to overcome the singularity at the corner joining the differentially heated isothermal walls when determining Nu. Effects of Rayleigh number, Ra on the Nusselt number, Nu as well as velocity and temperature fields are investigated for the range of Ra from 10(3) to 10(7). It is shown that the experimental and numerical results agree fairly well. Finally, a correlation for Nu is developed. (C) 2013 Elsevier Ltd. All rights reserved.