The present paper reports numerical results of mixed convection and surface radiation within a horizontal ventilated cavity heated from below and provided with an adiabatic thin partition on the heated surface. Air, a radiatively transparent medium, is considered to be the cooling fluid. The effect of the governing parameters, which are the Reynolds number, 200 <= Re <= 5000, the baffle position from the inlet, 0.25 <= L-b <= 1.75, and the emissivity of the walls, 0 <= epsilon <= 0.85, on the fluid flow and heat transfer characteristics is studied in detail. The maximum and mean temperatures, the ratio, Q(E)/Q(L), of the heat quantities leaving the cavity through the exit, Q(E) and through the vertical cold left side, Q(L) are also presented versus the above controlling parameters. (c) 2008 Elsevier Ltd. All rights reserved.