Microwave heating and mass transfer in white beans

A thermodynamic equation consistent with the features of microwave (polarised) heating systems is presented. The basic difference between microwave (polarised) and conventional (non-polarised) heating systems is shown. The influence of a polarising electric field on system properties, parameters, and behaviour are derived. It is revealed that an additional thermodynamic force due to an electric field gradient exist in materials during microwave heating. The force may increase microwave drying rates over that of conventional drying at the same temperature and pressure. A new mass transport phenomenological equation that accounts for the effect of all electric field gradient on microwave drying rates is derived.;Heat and mass transfer data for a thin layer of white beans at microwave absorbed power ranging from 0.28-0.44 W/g dry basis is collected using a experimental microwave heating apparatus operating in the TE;A microwave heating model based on the macroscopic application of the energy conservation equation to a hygroscopic granular solid is derived. The derived equation is used with the series solution of Fick's diffusion equation and a modified Gallaher's equation to predict the heat and mass transfer characteristics of a typical granular solid. Method for determining the effective heat transfer coefficient, and the heat of desorption during microwave heating are presented. The microwave heating model provided good predictions of the microwave heating characteristics of the white bean.