Geometric Model for Softwood Transverse Thermal Conductivity. Part I

Hong-mei Gu, Audrey Zink-Sharp

Abstract


Thermal conductivity is a very important parameter in determining heat transfer rate and is required for development of drying models and in industrial operations such as adhesive cure rate. Geometric models for predicting softwood thermal conductivity in the radial and tangential directions were generated in this study based on observation and measurements of wood structure. Modeling effective thermal conductivity in the radial and tangential directions is helpful in understanding the heat transfer mechanism in the two directions and predicting the values for a wide range of moisture contents (MC) when practical experiments for obtaining those values are unrealistic. Theoretical estimations indicate that radial thermal conductivity of softwood species is greater than tangential thermal conductivity when the MC is below the fiber saturation point (FSP) due to structure differences in the two directions. A linear relationship was found between MC and radial thermal conductivity in the range of 0%-30%. Both radial and tangential thermal conductivity increases with an increase in latewood percentage. When MC is above the FSP, tangential and radial thermal conductivity increases dramatically and nonlinearly with moisture content. However, no significant difference was found between radial and tangential thermal conductivity above the FSP. Geometric differences in the two directions had little effect on the model-estimated thermal conductivity when free water occupied a portion of the cell lumen.

Keywords


Transverse thermal conductivity;heat transfer;geometric thermal conductivity model

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