COMPARISON OF EXPERIMENTAL AND MODELLING STUDIES FOR THE MICROWAVE DRYING OF IRONBARK TIMBER

Abstract

Temperature profiles through boards during the microwave-assisted drying of Australian Ironbark timber have been investigated in this work in order to explore evidence for timber degrade via “charring” at internal temperatures below those required for pyrolysis (Brooke et al., 1998). A previously published model (Turner and Jolly, 1990a) describing one-dimensional microwave power absorption, based on the solution of Maxwell's equations, has been reviewed and significant limitations identified and overcome. Improvements included the use of a linear-mixing approach for the dielectric constants, the incorporation of temperature and moisture dependencies for these dielectric properties and the inclusion of diffusion within an overall system model. A control-volume technique has been used for predicting both moisture and temperature distributions within the timber, with a second-order finite-difference method being used to solve Maxwell's equations. The final model showed