Presented by Tim Langrish, University of Sydney, Wednesday 23 October 2013.
There is a lot of experimental evidence for solar kilns being good at drying timber [1-8], but the fundamental scientific reasons for this have not always been clear. However, the mathematical modelling study here shows that the evidence has a good reason, due to the stress relaxation that occurs during the simultaneous changes in stress and moisture content in timber that occur during cyclic drying, called the mechanosorptive effect.
This webinar will explain the scientific basis for the stress-strain analysis in timber during drying, as used in this study. This work has compared a conventional continuous drying schedule with a solar cyclic drying schedule for the seasoning of an Australian hardwood timber, Eucalyptus grandis, focussing on the simulated stresses and strains developed during drying as a measure of timber quality. The cycling of the drying conditions, particularly the relative humidity, in solar drying, are effective (in combination with the mechanosorptive effect) in relaxing the drying-induced stresses and strains. The more gentle initial drying conditions during cyclic drying are also beneficial compared with the harsher and unmodulated nature of conventional drying schedules. In conventional drying, without the modulation of the external drying conditions, the mechanosorptive strains are unable to relax or mitigate the stresses that are caused naturally by timber drying.
Presenter:
Tim Langrish is Head of School and Professor at the University of Sydney, where his research interests are in the areas of process technology, particularly drying technology and particle processing and production. He has done research in the application of Computational Fluid Dynamics to drying problems involving spray drying and timber processing, and he has also produced optimized drying schedules for softwood and hardwood timber, in collaboration with timber processing companies and organizations. He graduated with honours in Chemical and Process Engineering from the University of Canterbury in 1985 and with a D.Phil. from Balliol College, Oxford, in 1989.
