A proposed theory for nonisothermal unsteady-state transport of moisture in wood

Siau, J. F.

doi:10.1007/bf00351834

Cited by 18 publications

(15 citation statements)

References 2 publications

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“…Luikov (1966Luikov ( , 1975 developed a set of coupled partial differential equations for this purpose. The wood properties as a function of moisture content have to be considered in mathematical models (MacLean 1941;Siau 1983;Skaar 1988;Trcala 2012;Zhang et al 2014). Recent developments in this field confirmed that the experimental results and model predictions are in good agreement, while the thermo-physical properties of wood influence the accuracy (Kocaefe et al 2006;Younsi et al 2007Younsi et al , 2008Zhu and Kaliske 2011).…”

Section: Introductionmentioning

confidence: 78%

Numerical analysis of temperature profiles during thermal modification of wood: chemical reactions and experimental verification

Trcala

Čermák

2014

Holzforschung

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Numerical analysis of temperature profiles during thermal modification of wood was carried out. The numerical solution -based on finite element analysis, FEA -of the 3D problem of transient nonlinear heat transfer model is presented for wood as a typical anisotropic material. The numerical model was enhanced for describing chemical reactions of cellulose, hemicelluloses and lignin (pyrolysis model), which takes into account the exothermic reactions as an internal source of heat energy. Experimental as well as theoretical process schedules were applied and the influence of sample dimensions (sample geometry) and wood species was studied. The influence of wood species was negligible on heating time to reach the highest temperature, i.e., the temperature differences were about 2°C during the drying phase. A expected, the sample size played an important role in the heating duration and in terms of the exothermic reactions of wood. The experimental and numerical data are generally in good agreement. The numerical error increased in the range of higher temperatures. The results can be improved by consideration of wood species (mass of wood compounds) and boundary conditions in the pyrolysis model, thus, better insight into details of thermal modification of wood could be reached.

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Section: Introductionmentioning

confidence: 78%

Numerical analysis of temperature profiles during thermal modification of wood: chemical reactions and experimental verification

Trcala

Čermák

2014

Holzforschung

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“…Average moisture content was determined by weighing samples collected from the fresh section and drying the samples at 380±2 K [37]. Oven-dry density (oven dry mass/fresh sample volume) was calculated by weighing another set of samples and coating them in molten paraffin before weighing them again.…”

Section: Methodsmentioning

confidence: 99%

FireStem2D – A Two-Dimensional Heat Transfer Model for Simulating Tree Stem Injury in Fires

et al. 2013

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FireStem2D, a software tool for predicting tree stem heating and injury in forest fires, is a physically-based, two-dimensional model of stem thermodynamics that results from heating at the bark surface. It builds on an earlier one-dimensional model (FireStem) and provides improved capabilities for predicting fire-induced mortality and injury before a fire occurs by resolving stem moisture loss, temperatures through the stem, degree of bark charring, and necrotic depth around the stem. We present the results of numerical parameterization and model evaluation experiments for FireStem2D that simulate laboratory stem-heating experiments of 52 tree sections from 25 trees. We also conducted a set of virtual sensitivity analysis experiments to test the effects of unevenness of heating around the stem and with aboveground height using data from two studies: a low-intensity surface fire and a more intense crown fire. The model allows for improved understanding and prediction of the effects of wildland fire on injury and mortality of trees of different species and sizes.

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“…The species were analyzed at different times to eliminate systematic errors. The first MC analysis was performed already after 3.5 h (spruce) and 4.5 h (beech), and the Soret effect was confirmed (Siau 1983;Avramidis et al 1994). The Soret effect decreases with time, and disappears after 10-15 h.…”

Section: Moisture Fieldmentioning

confidence: 99%

“…Heat transfer occurs through conduction (Fourier law), phase change, and moisture transfer (Dufour effect). Similarly, the mass transfer (i.e., moisture transfer) is governed by diffusion (Fick's law), temperature gradient (Soret effect), and convectional flow (Siau 1983(Siau , 1984Avramidis et al 1994;Avramidis and Hatzikiriakos 1995;Horáček 2003;Čermák and Trcala 2012;Trcala 2012). The literature dealing with temperature distribution during heat treatments is scare.…”

Section: Introductionmentioning

confidence: 99%

Measured temperature and moisture profiles during thermal modification of beech (Fagus sylvatica L.) and spruce (Picea abies L. Karst.) wood

2013

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Measured temperature and moisture profiles during thermal modification of beech (Fagus sylvatica L.) and spruce (Picea abies L. Karst.) wood Abstract: The temperature and moisture profiles during thermal modification of beech (Fagus sylvatica L.) and spruce (Picea abies L. Karst.) wood have been investigated. Specimens with dimensions of 80 × 80 × 200 mm 3 were heat treated based on ThermoWood technology. Heat transfer was continuously measured by several thermocouples placed into various positions of the samples. In the course of the treatment, samples were removed from the chamber at different times, and their moisture content (MC) was measured by the so-called slicing technique. The complete data of heat and moisture movement during the heat treatment process are presented. Significant temperature gradients occur in the initial and modification stages of the process. In the latter, the chamber temperature was 200°C for 3 h, but exothermic reaction increased the sample temperatures to 240°C (beech) and 215°C (spruce). Thermodiffusion (Soret effect) at the beginning of the process was observed. Therefore, the MC under surfaces (in transverse and in longitudinal direction) was increasing ∼0.5%-3% for 5 h. The results provide a better insight into details of thermal modification of wood.

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A proposed theory for nonisothermal unsteady-state transport of moisture in wood

Cited by 18 publications

References 2 publications

Numerical analysis of temperature profiles during thermal modification of wood: chemical reactions and experimental verification

Numerical analysis of temperature profiles during thermal modification of wood: chemical reactions and experimental verification

FireStem2D – A Two-Dimensional Heat Transfer Model for Simulating Tree Stem Injury in Fires

Measured temperature and moisture profiles during thermal modification of beech (Fagus sylvatica L.) and spruce (Picea abies L. Karst.) wood

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