Quasi-steady shrinking core analysis of wood combustion
A shrinking core model of the combustion of individual chunkwood and particle wood elements is developed and validated by comparison with literature data. The model is formulated on the physical evidence that large wood specimens inserted into a hot convective environment lose weight mostly over a relatively thin outside layer, while the interior (core) remains relatively undisturbed. The modeling of the complete process requires a correlation of the turbulent heat and mass transfer coefficients which include explicitly the effects of transpiration of volatilized organic compounds and moisture, along with geometry, and equivalent radius. The fuel element burnout time is shown to be a function of fuel properties, moisture content, and size. Drier and smaller elements burn faster while moisture is shown to slow the shrinking rate due to the cooling effects of transpiration and the latent heat of evaporation.