Preliminary researching the heating intensity of wood as an effect of microwave radiation

Microwave treatment is a technology also used in wood protection, including treating deciduous and pine wood. Wood boring insects and wood boring mould can be eliminated by treating the wood with microwave. In our experiment we examine the heating of different types of wood (beech, oak, pine and spruce) using a MWG-1000-A-1 type generator, with a pyramid shaped applicator. First we heated up lamella made of pine (Pinus sylvestris) sapwood and measured the heating intensity of the lamellas in relation of the cross section of the wood. For our experiment we modelled a 150mm thick solid wood, placing on each other 6 pieces of lamella, each conditioned in normal climate and measuring 25mm in width. In the blind holes, of 5mm in diametre and 15mm in length, made in the middle of five lamella, experimentally we placed a live fly larvae in each, that resembled the larvae of House Longhorn Beetle (Hylotrupes bajulus), monitoring the eliminating effects of the heating treatment to the larvae. We used a heat camera to check the temperature of the lamellas prior to the treatment and after the 15 minutes long irradiation. Depending on the irradiated material thickness, the degree of heating up decreased and along the length of the lamella there were two focal points observed.10 seconds after the treatment, we measured degrees between 35,4 - 111 degrees C in the edges, and 36,3 - 69 degrees C in the middle of the impactors. During penetration time we observed thermal degradation of the wood touching directly the applicator, what suggests that the temperature of the wood locally may have exceeded 200 degrees C during the treatment. It proves the efficiency of the treatment eliminating the larvae, that during the time of our experiment, the larvae placed in the wood up to 75 + 10 mm material thickness - that is in the 4 lamellas closest to the applicator - all larvae were destroyed. In case the material thickness exceeded 100mms, the applied treatment didn't prove to be efficient, leaving the larva alive in the 5th lamella.