Fire Safety Science Digital Archive

A three-dimensional mathematical model for the pyrolysis of wet wood including a detailed consideration of the evaporation of moisture, anisotropic and variable properties, and pressure driven internal convection of gases in wood has been developed. A computational code has been formulated modeling multiple competing reactions for up to six constituents, although a single first order Arrhenius reaction is adopted in the results presented. The pyrolysis of a beech wood cube with different initial moisture contents has been computed for a range of furnace temperatures. The Arrhenius kinetic parameters have been determined by a method of best fit to the experimental results of Bonnefoy et a1 [16]. The values agree very we1 with the range of kinetic data reported by Tinney [4]. The computed results giving a full 3-D description of the transient chemical and physical processes of the pyrolysis of a wet wooden cube heated in a furnace are presented. The influences of the anisotropic properties due to the grain structure on heat and mass transfers in pyrolysing wood are discussed.