Material processing involving natural convection within a trapezoidal enclosure for uniformly and nonuniformly heated bottom wall, insulated top wall, and isothermal sidewalls with inclination angle φ have been investigated. The penalty finite element method is used to obtain isotherm and streamline profiles for model liquids e.g. molten metal, salt water and olive oil. Parametric study for the wide range of Rayleigh number (Ra), 103 ≤ Ra ≤ 105 and Prandtl number (Pr) for model fluids with various tilt angles φ = 45°, 30°, and 0° have been obtained. Secondary circulations were observed during molten metal processing. Streamlines show that the strength of convection is larger for φ = 45° and flow intensities are also found to be larger for olive oil compared to molten metal and salt water. Heat transfer rates are shown via local and average Nusselt number plots. Local heat transfer rates are found to be relatively more for φ = 0° than those with φ = 45° and φ = 30°. Average Nusselt number plots show higher heat transfer rates for φ= 0° except for the nonuniform heating of the bottom wall with Pr = 0.015 (molten metal). Overall, less heat transfer rates are observed for molten metal processing. © 2008 American Chemical Society.