Numerical modelling of microwave heating of frozen wood

Abstract

The heating process of frozen wood exposed to plane microwaves is numerically investigated. The nonlinear heat conduction problem involving phase change such as wood freezing is solved by a specific 3D volumetric enthalpy‐based finite element method. Dielectric and thermal properties are a function of temperature and moisture content. The numerical model is validated by experimental and analytical means. As an application, we studied the effect of moisture content and frequency on microwave heating of trembling aspen wood.

Numerical investigation on phytosanitary treatment of frozen wood using microwave energy

“…[13] To this end, four eastern Canadian wood species are used: trembling aspen (Populus tremuloides Michx. [13] To this end, four eastern Canadian wood species are used: trembling aspen (Populus tremuloides Michx.…”

“…The coupling is taken into account through the dissipated power density per unit volume in medium, which, in the case of propagation of a uniform electric plane wave in a semi-infinite medium, is given by [13] Q wave ¼ 1 2 v 0 k 00 jtE 0 j 2 expðÀ2a zÞ: ð4Þ The coupling is taken into account through the dissipated power density per unit volume in medium, which, in the case of propagation of a uniform electric plane wave in a semi-infinite medium, is given by [13] Q wave ¼ 1 2 v 0 k 00 jtE 0 j 2 expðÀ2a zÞ: ð4Þ…”

“…It is therefore essential to crosscheck that the treatment method does not negatively affect the wood's properties. [13] In order to abide with the abovementioned IPPC's regulations, comparative analysis of the heating time will be conducted on four wood species. However, there are several approaches for modelling of high frequency heating of wood.…”

“…[13] It is assumed that thermophysical and dieletrical properties of the materials are both temperature and moisture dependent. [13] An experimental validation of the radiation transfer has been made by simulating the heating of a tridimensional wood structure from À20 8C to 808C. In this analysis, we will specifically consider the effects of the microwave frequency, the wood sample geometry and its intrinsic properties, such as the moisture content and the thermophysical properties, on the heating time.…”

“…[11,12] From a modelling view of wood treatment by microwave heating, we consider a 3D finite element method (FEM), with a formulation based on volumetric enthalpy. [13] It is assumed that thermophysical and dieletrical properties of the materials are both temperature and moisture dependent. [13] In order to abide with the abovementioned IPPC's regulations, comparative analysis of the heating time will be conducted on four wood species.…”