Mathematical modelling and experimental investigation of dehumidifier drying of radiata pine timber

Abstract

A dynamic kiln-wide wood drying model was developed previously to solve the integral form of the unsteady-state mass, momentum and energy balance equations in the air side. For the wood side, an empirical model, characteristic drying curve, for the internal moisture movement is used, which was obtained for low and medium temperature drying of Pinus radiata, with a medium velocity of 1.4- 4.1 m s–1. As part of the research programme to improve the design and control of dehumidifier wood drying kilns, the wood drying model has been assessed using the experimental data measured under drying conditions similar to those in dehumidifier kiln. It is noted that close agreement between the modelled results and the experimental data can be obtained for Pinus radiata drying processes with a medium air velocity (< 5 m s–1). However, larger discrepancy between the modelled results and the measured data has been observed with a higher velocity (8 m s–1). To solve this problem a new characteristic drying curve, based on a two-zone diffusion model, has been used in the kiln-wide wood drying model and more accurate results have been obtained.