Use of a combined constant rate and diffusion model to simulate kiln-drying of Pinus radiata timber

This paper presents the use of a combined constant drying-rate and diffusio n model to simulate the drying of Pinus radiata timber under kiln-drying co nditions. The constant drying-rate and diffusion coefficients of the model, which control the drying rate of individual pieces of timber, were determi ned from calibrating the model against the experimental drying curves obtai ned under the kiln-drying conditions. The experimental drying curves were o btained from the gravimetric measurements of the moisture content of timber during kiln drying. Statistical relationships were developed for the const ant drying-rate and the diffusion coefficients of the model as functions of kiln temperature and the dry basis density of timber. To determine the eff ects of variability of timber, a simulation scheme was developed based on t he model, the probability distribution of the density of timber, the equati ons for the constant drying-rate coefficient and the diffusion coefficient. The model and the associated simulation method provides a simple way to es timate the drying time of a stack of timber using parameters determined fro m experimental results for the specific timber kiln.