Theoretical thermal conductivity equation for uniform density wood cells

Abstract

The anisotropy of wood creates a complex problem requiring that analyses be based on fundamental material properties and characteristics of the wood structure to solve heat transfer problems. A two-dimensional finite element model that evaluates the effective thermal conductivity of a wood cell over the full range of moisture contents and porosities was previously developed, but its dependence on software limits its use. A statistical curve-fit to finite-element results would provide a simplified expression of the model’s results without the need for software to interpolate values. This paper develops an explicit equation for the values from the finite-element thermal conductivity analysis. The equation is derived from a fundamental equivalent resistive-circuit model for general thermal conductivity problems. Constants were added to the equation to improve the regression-fit for the resistive model. The equation determines thermal conductivity values for the full range of densities and moisture contents. This new equation provides thermal conductivity values for uniform-density wood material using inputs of only oven-dry density and moisture content. An explicit method for determining thermal conductivity of uniform density wood cells has potential uses for many wood applications.

Citation

Hunt, John F.; Gu, Hongmei; Lebow, Patricia. 2008. Theoretical thermal conductivity equation for uniform density wood cells. Wood and Fiber Science 40(2): 167-180