Investigation of the radiofrequency heating of anisotropic dielectric materials with a phase change: application to frozen Douglas-fir and white oak woods

Autor: M. Diagne, Z. Annasabi, Fouad Erchiqui
Rok vydání: 2021
Předmět:
Zdroj: Wood Science and Technology. 56:259-283
ISSN: 1432-5225
0043-7719
DOI: 10.1007/s00226-021-01345-y
Popis: Dielectric heating is a promising process for the uniform sterilization of food products as well as for the drying of products. However, radio frequency heating of wood-based materials (a highly anisotropic material with temperature, moisture and structural orientation dependent properties) does not seem to be elucidated in the literature. It is within this framework that this study is carried out and concerns the modeling of anisotropic dielectric heating by radio frequency (RF) and its application to the thawing of frozen wood. The nonlinear heat conduction problem involving phase changes is formulated in terms of volume enthalpy. For the numerical resolution of the thermal conduction equation, the finite element method is considered. Thermophysical and dielectric properties are expressed as a function of temperature, moisture content (MC), and structural orientation. The numerical approach is further validated by a combination of the analytical, numerical and experimental analyses. Finally, the effect of RF on the thawing of the Douglas-fir (Pseudotsuga menziesii) and the white oak (Quercus alba), which are two North American wood species, was studied based on an initial temperature of − 20 °C and a frequency of 50 MHz. In this regard, two MC of 65% and 90% are considered. For the two species of the studied wood, it is observed that the RF induce a uniform temperature profile.
Databáze: OpenAIRE
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