A SIMULATION MODEL FOR TIMBER DRYING CHECKED BY MEASUREMENTS AT TECHNICAL KILNS

ABSTRACT

A physically based simulation program for timber drying, which predicts the integral drying course, the profiles of moisture content, and internal stress during drying, was checked by data from technical drying runs. A data logging system served to record the data sets from several drying runs at diverse kilns. The comparison of model predictions and measured data led to the following conclusions: The integral drying course, i.e. time dependence of the average moisture content, can be well precalculated in quantity. Calculations of the moisture profiles were found to be right in tendency, but not in accuracy. Stress calculation by means of a visco-elastic Burger model leads to results correct in tendency, but to high in comparison with measured data.

To improve the stress calculation mechano-sorptive creep by models of Salin and Ranta-Maunus were tested. The calculation of these models corresponded with measurements from laboratory experiments. The simulation program is estimated to be applicable for further calculations of energy demand and costs in drying.