The Surface Emission Coefficient of Wood
Keywords:Diffusion, drying, heat convection, laminar boundary layer, Lewis relation, mass convection, Newman's solution, non-Fickian diffusion, surface resistance, turbulent boundary layer
AbstractConsiderable research has been undertaken to measure and characterize the mass convective surface resistance of wood, with particular emphasis on conditions below the fiber saturation point. While the effects of air velocity and wood moisture content have been demonstrated, the influence of other critical factors such as wood specific gravity, surface condition, and specimen size have not been evaluated. Results obtained by several investigators indicate little agreement between them with a wide range of coellicients whose values are a small fraction of those calculated from the classical equations that have been successfully applied to drying from moist surfaces. The low coefficients in the hygroscopic range indicate that surface resistance can add significantly to the energy consumption during drying. Therefore, a better understanding of the convection losses of dry hygroscopic materials such as wood may offer the opportunity of more effective optimisation of drying conditions.
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