Heating characteristics of western hemlock (Tsuga heterophylla) in a high frequency fieldVerhalten von Western Hemlock (Tsuga heterophylla) bei Hochfrequenzerhitzung

The research aimed to establish whether dielectric heating of wood at high frequency could be accomplished fast, without excessive temperature fluctuations and no wood degrade. The intention was to develop optimized dielectric heating schedules in order to effectively pasteurize green timbers and logs for export—an eco-friendly substitute to currently used toxic chemical method. Data analysis revealed that the electric field distribution within the specimen was a strong function of its dielectric properties. Specifically, homogeneous moisture contents generated constant electric field values while heterogeneous distributions generated sudden drops and raises of the electric field strength with heating uniformly dispersed due to a fast redistribution from hot to colder areas. Convection losses through air contact may reduce the average heating rate of the timber shell by about 50%.