The magnitude of surface heat and mass transfer coefficients in microwave ovens is important to control food surface temperature and moisture and are a result of the faint airflow present in the oven cavity and of surface radiation. Magnitude and patterns of airflow inside a microwave oven and the resulting surface heat transfer coefficients were studied using a computational fluid dynamics model of the process. The governing Navier-Stokes and energy equations were solved for both natural, forced and combined convection. The magnitude and distribution of surface heat transfer coefficients on the food surface were computed for a 3-D oven cavity with one inlet and one outlet and a cylindrical food placed inside the oven. Calculated convective heat transfer coefficient values were found to be in the same range as has been used in the literature. A combined convection regime proves beneficial for heat transfer uniformity and the reduction of moisture accumulation inside the oven. Radiation heat transfer coefficients for energy exchange between food surface and oven interior were calculated and shown to be of the same order of magnitude as the convection heat transfer coefficients. (C) 2003 Elsevier Science Ltd. All rights reserved.