| Summary: | The purpose of this study was to evaluate the dielectric properties (loss factor) of two
British Columbian softwoods (western hemlock [Tsuga heterophylla (Raf.) Sarg.] and western
red cedar [Thuja plicata Donn]) at different moisture content, temperature, and electric field
strength levels. This study is expected to provide useful information for the development of a
mathematical model to describe heat and moisture transfer mechanisms in wood during radio
frequency/vacuum (RF/V) drying. Such a model would predict and optimise the RF/V drying
behaviour of wood on a commercial scale without the requirement of experimentation.
In this study, the radial direction loss factor of full-sized western hemlock sapwood and
heartwood, and western red cedar heartwood timbers was measured using the direct calorimetric
data method with a laboratory-scale RF/V dryer at the frequency of 13.56 MHz, moisture content
range between 10 and 80%, temperature range between 25 and 55 °C, and root mean square
(rms) electrode voltages 0.8 and 1.1 kV, respectively.
The results indicated that the moisture content, temperature, electric field strength and
species significantly affected the loss factor. Empirical regression equations were derived based on
the experimental data, that made possible the calculation of the loss factor and power density
within the wood mass during RF heating. === Forestry, Faculty of === Graduate
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