Wood drying is essential for preparation of this natural resource for practical applications.Most drying models confirm that the tortuosity of the moisture transport path, associated with high wood density or low moisture permeability, is an important control parameter during the diffusion-controlled drying process. Drying systems, such as kilns, control the external environment in order to manipulate moisture diffusion and transport mechanisms; however they are powerless to manipulate wood density or permeability. Controlled application of microwave energy has been shown to selectively rupture the wood structure creating radial pathways in the wood through which moisture may readily move. New analytical equations that describe simultaneous heat and moisture transport during microwave heating have been derived and validated. These new equations assume that the microwave fields decay exponentially with distance inside the irradiated material and enforce a boundary condition, which allows convective heat transfer at the inter-facial boundary between the moist dielectric material and the air. They demonstrate the importance of applying the theory of simultaneous heat and moisture movement to microwave heating. In this theory a set of synchronised heat and moisture waves propagate through the material with velocities that are vastly different from those predicted by the constant vapour concentration thermal diffusivity of the material. They also correctly predict the “S” shaped temperature versus electric field strength curves discussed by other authors.(For complete abstract open document)
| Identifer | oai:union.ndltd.org:ADTP/245094 |
| Creators | Brodie, Graham |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
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