Thermal characterization of pine wood by photoacoustic and photothermal techniques

Leon, Gustavo Adolfo; Cruz-de-Leon, J.; Villaseñor, L.

doi:10.1007/s001070050418

Cited by 21 publications

(8 citation statements)

References 3 publications

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“…The thermal conductivity of wood in the longitudinal direction is approximately two times greater than that in the transversal or radial directions as reported in the literature 16, 21. The thermal conductivities in different directions are …”

Section: Mathematical Modelsupporting

confidence: 53%

Transient multiphase model for the high‐temperature thermal treatment of wood

et al. 2006

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in Wiley InterScience (www.interscience.wiley.com). The hygrothermal behavior of wood at high temperature is analyzed, taking into account all the phases present such as wood, liquid water in free and bound forms, and water vapor. The moisture transport phenomenon includes water vapor convection and diffusion along with capillary water convection in the pores of the particle as well as bound water diffusion in the solid wood. Local thermodynamic equilibrium is assumed, which is represented by a sorption isotherm that relates the moisture contents in the solid and gas phases. The equations of the model were solved numerically using the commercial IntroductionWood continues to be the principal raw material for a large number of products in construction and furniture industries, although other competitive materials such as metals and plastics are also available. To ensure a suitable and usable end product and to prevent undesirable biochemical reactions and microbiological growth, most of the moisture present in wood must be removed. In most industrial drying operations, heat is supplied externally to wood by air or superheated steam to evaporate the moisture. During these conventional heat treatment processes (drying), the wood is heated to about 120°C and the water is removed by evaporation. Full descriptions of the moist air and superheated steam drying models are given elsewhere. [1][2][3][4] The high-temperature treatment of wood is different from that of conventional drying. This technique offers an alternative to the chemical treatment of wood, which uses traditional oil (creosote and pentachloro-phenol) and chromated copper arsenate (CCA). These chemicals are toxic and, thus, harmful when they are released into the environment. During the hightemperature treatment process, the wood species with different moisture contents are heated slowly up to 200 -230°C in a hot inert gas atmosphere. This treatment reduces the hydrophilic behavior of wood by modifying the chemical structure of some of its components.Several physical mechanisms contribute to the migration of moisture in wood during its removal. In a porous solid medium containing free water, bound water, vapor, and air or any other gas, the moisture transport through the medium can be in the form of either diffusion or capillary flow driven by individual or combined effects of the moisture, temperature, and pressure gradients. The predominant mechanisms that control the moisture transfer depend on the hygroscopic nature and properties of the materials as well as the heating conditions.In the literature, a number of investigations have been undertaken by various researchers [5][6][7] to study the heat and moisture transfer in porous materials. Luikov 5 developed a set of Correspondence concerning this article should be addressed to R. Younsi at ryounsi@uqac.ca. © 2006 American Institute of Chemical Engineers 2340AIChE Journal July 2006 Vol. 52, No. 7 coupled partial differential equations (PDEs) to describe the heat and mass transport in capillary porous ...

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Section: Mathematical Modelsupporting

confidence: 53%

Transient multiphase model for the high‐temperature thermal treatment of wood

et al. 2006

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“…The thermophysical properties of birch given by Simpson and Tenwold (1999) were used in the simulations and were assumed to be constant. The thermal conductivity in the axial direction was taken as twice the ones in the radial and tangential directions as reported in the literature (Leon et al, 2000). Mass transfer coefficient h m and heat transfer coefficient h q are determined from the following expressions for laminar flow (Incropera and DeWitt, 2002), respectively,…”

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confidence: 99%

“…A Reynolds number which is lower than 5 Â 10 5 indicates a laminar flow. Table I shows all the model parameters used during the simulations (Simpson and Tenwold, 1999;Siau, 1984;Leon et al, 2000).…”

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Thermal modelling of the high temperature treatment of wood based on Luikov's approach

Younsi¹,

Kocaefe²,

Poncsák³

et al. 2006

Int. J. Energy Res.

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SUMMARYA 3D, unsteady-state mathematical model was used to simulate the behaviour of wood during high temperature treatment. The model is based on Luikov's approach and solves a set of coupled heat and mass transfer equations. Using the model, the temperature and moisture content profiles of wood were predicted as a function of time for different heating rates. Parallel to the modelling study, an experimental study was carried out using small birch samples. The samples were subjected to high temperature treatment in a thermogravimetric system under different operating conditions. The experimental results and the model predictions were found to be in good agreement. The results show that the distributions of temperature and moisture content are influenced appreciably by the heating rate and the initial moisture content.

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“…The thermal conductivity in the axial direction is taken as twice the radial and tangential thermal conductivities [13]. The heat transfer and mass transfer coefficients are calculated using the empirical relations reported in the literature [14,15]:…”

Section: Initial Conditionsmentioning

confidence: 99%