A Semi-Empirical Moisture Transport Model for On-Line Optimal Lumber Drying Control

Green lumber is often dried in climatically controlled kilns to prepare it for commercial use. Optimization of the kiln drying schedule (air temperature and humidity) to minimize drying costs requires a mathematical model of the drying lumber. A model that will predict moisture content distribution within the lumber when drying from 80 percent to 6 percent adequately enough for control purposes does not exist at this time. Graphical results from this study have demonstrated that a non-linear regression method for on-line optimizing of the model diffusion coefficient function provides an effective predicting model. Thus a simplified version of an available diffusion model can function in an optimal process control system.