Dynamic Modelling of the Wood Stack in a Wood Drying Kiln

Abstract

For the design of energy efficient dryers employing heat pump systems, the dynamic response of the product to the kiln conditions must be taken into account. In this paper, the formulation of a dynamic, kiln-wide drying model is described. The model solves the unsteady-state mass, momentum and energy balance equations for both the air flow and the wood boards in drying three types of stack: normal stack, aligned stack and staggered stack. In order to represent the dynamical response of the system, the model equations provide more complete energy and mass balances than those presented in recent publications. The transient profiles of the air humidity, temperature, pressure, and velocity, and the wood temperature and moisture content along the air flow direction within the stack are obtained using this model. To illustrate the use of the model, the drying processes of sapwood boards of Pinus radiata under typical dehumidifier kiln conditions have been calculated, and the modelled results have been discussed in detail. In addition, the model has been tested by using the performance data for a commercial scale kiln. The agreement between the modelled and measured performance results shows that the model is suitable for the design and analysis of dehumidifier wood dryers.