The radial direction loss factor of full-size western hemlock sapwood and h
eartwood, as well as western red cedar heartwood timbers was measured using
the direct calorimetric method with a laboratory-scale radio frequency/ va
cuum dryer at the frequency of 13.56 MHz, moisture content range between 10
and 80%, temperature range between 25 and 55 degrees C, and root mean squa
re (rms) electrode voltages of 0.8 and 1.1 kV, respectively.
The results indicated that the moisture content, temperature, electric fiel
d strength and wood type 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 wood d
uring RF heating.