Transient temperature and fluid flow during natural convection heating of a cylindrical can containing large food particles is simulated. The three dimensional equations of mass, momentum and energy conservation are solved using the finite volume method. A can (11 cm high and 10 cm in diameter) containing nine spherical particles (45 mm in diameter) is considered. Two meshes are tested. The first uses 1,650,000 tetrahedral cells. The second uses only 95,000 cells but with smaller prismatic cells near the can walls in order to better take into account the boundary layer phenomena. The simulated temperature evolutions in the liquid and at the centre of the particles obtained with the second grid are in good agreement with the experimental results. The liquid flows upwards in a thin boundary layer (about 2 mm thick) and flows downwards in the interstice between the particles. Due to thermal stratification, the slowest heating is for the particles at the bottom of the can. (C) 2007 Elsevier Ltd. All rights reserved.