Geometric model for softwood transverse thermal conductivity. Part I

Abstract

Thermal conductivity is a very important parameter in determining heat transfer rate and is required for developing 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 obervation 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 greather than tangenial 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 FSP, tangential and radial thermal conductivity inceases dramatically and nolinearly 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 occupoed a portion of the cell lumen.

Citation

Gu, Hong-mei; Zink-Sharp, Audrey. 2005. Geometric model for softwood transverse thermal conductivity. Part I. Wood and fiber science. Vol. 37, no. 4 (2005): pages 699-711