Determining surface emission coefficient of wood using theoretical methods and near-infrared spectroscopy

Abstract

Emission of surface water on wood should be controlled because moisture movement on the wood surface initiates changes in its morphological, physical, chemical, and biological properties. In this study, surface moisture content (SMC) of yellow poplar (Liriodendron tulipifera L.) wood was measured by a near-infrared spectroscopy (NIRS) technique, nondestructively and continuously, during unsteadystate desorption conditions. With these SMC data, surface emission coefficients (SECs) were determined continuously while the wood was being dried. These experimentally determined coefficients were compared with values that were converted from the theoretically determined mass transfer coefficients. The conversion method, which was developed to facilitate a comparison among the mass transfer coefficients, indicated that the boundary layer theory was useful in evaluating the degree of external moisture resistance while the wood dried. Also, the NIRS technique can be used for determining SEC at each specific point of wood, experimentally, in real time.