This paper deals with the CFD predictions of the three dimensional incompressible flow over a wall mounted cubic obstacle placed in fully developed turbulent flow along with the heat transfer calculations. Reynolds number considered in this study is 1870 based on cube height, h and bulk velocity U-b. Our main objective is to find out the appropriate two equation turbulence model for the complex flow structure which involves recirculation, separation and reattachment. We have used standard kappa-epsilon, low-Reynolds number kappa-epsilon, non-linear kappa-epsilon model, standard kappa-omega and improved kappa-omega models to solve the closure problem. The non-linear kappa-epsilon model and improved models kappa-omega along with standard models are validated with bench mark problem - flow through a backward facing step (BFS). Results showed that the improved kappa-omega model is giving overall better predictions of the flow field especially recirculation zone, mean streamwise velocity, and turbulent characteristics when compared to those by standard eddy viscosity models. The non-linear kappa-epsilon model is giving better prediction when compared to standard kappa-epsilon and low Reynolds number kappa-epsilon models. The complex vortex structure around the cube causes large variation in the local convective heat transfer coefficient. The maximum of the heat transfer coefficient occurred in the proximity of the reattachment points and the minimum is found at the recirculation zone. (c) 2007 Elsevier Ltd. All rights reserved.