A Mathematical Model of the Thermal Decomposition of Wood

Abstract

A mathematical model developed for computer solution of heat transfer problems involving change of phase heat effects was applied to the prediction of transient temperature distributions and volatile product evolution rates in decomposing wood specimens. The required data input for the model was obtained directly from differential scanning calorimetric and thermal gravimetric measurements along with measured values of thermal conductivity

A fast response electrical heater was designed to allow accurate specification of a constant heat flux boundary condition at the surface of a wood test specimen. Wood specimens were heated and partially decomposed while temperature profiles in the test specimen were measured with fine wire thermocouples. The measured temperature profiles, along with measurements of the weight loss of the heated specimen, were in good agreement with results predicted by the mathematical model.

The model has several advantages over previous models, in that constancy of thermal properties, including heat of decomposition, is not assumed. Furthermore, no explicit kinetic model need be assumed since the energy effects associated with internal chemical reaction are measured directly by differential scanning calorimetry.

Additional information

Notes on contributors

J. A. HAVENS

Dr. Havens is Assistant Professor of Chemical Engineering, University of Arkansas, Fayetteville, Arkansas 72701