Numerical and experimental analyses of velocity and temperature fields inside a tank submitted to internal natural and mixed convection are presented in this paper. The numerical analyses were performed with two approaches: one using a two-dimensional model in cylindrical coordinates through the finite volume method and another using a one-dimensional model. A turbulence model for low Reynolds numbers was added to the two-dimensional model in mixed convection regime. The two-dimensional model was experimentally validated and then adopted as reference. Its results were compared to those obtained with one-dimensional models (combined with certain computational artifices described in this work) with a good agreement. (C) 2003 Elsevier Ltd. All rights reserved.