Geometric Model for Softwood Transverse Thermal Conductivity. Part I
Keywords:Transverse thermal conductivity, heat transfer, geometric thermal conductivity model
AbstractThermal conductivity is a very important parameter in determining heat transfer rate and is required for development 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 observation 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 greater than tangential 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 the FSP, tangential and radial thermal conductivity increases dramatically and nonlinearly 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 occupied a portion of the cell lumen.
Couturier, M. F., K. George, M. H. Schneider. 1996. Thermophysical properties of wood-polymer composites. Wood Sci. Tech.30:179-196.nGong, L. 1992. A theoretical numerical and experimental study of heat and mass transfer in wood during drying. Ph.D. Thesis, Dept. of Mechanical and Material Engineering, Washington State University, Pullman, WA.nGriffiths, E. and G. W. C. Kaye. 1923. Proc. Roy. Soc. Lond. Ser. A104:71.nGu, H. M. 2001. Structure-based, two-dimensional anisotropic, transient heat conduction model for wood. Ph.D. Dissertation, Virginia Polytechnic Institute and State University, Blacksburg, VA.nHaygreen, J. G., and J. L. Bowyer. 1982. Forest products and wood science: An introduction. 3rd Ed. Iowa State University Press, Ames, IA.nHendricks, L. 1962. Thermal conductivity of wood as a function of temperature and moisture content. Thesis, State University College of Forestry at Syracuse University, Syracuse, NY.nHoadley, B. R. 1980. Identifying wood: Accurate results with simple tools. The Taunton Press, Newtown, CT.nKellogg, R. M. and F. F. Wangaard. 1969. Variation in the cell density of wood. Wood Fiber1:180-204.nKollmann, F., and L. Malmquist. 1956. Uber die Waimeleitzahl von Holz und Holzwerkstoffen. Holz Roh-Werkst.14:201-204.nPanshin, A. J. and C. de Zeeuw. 1980. Textbook of wood technology. 4th ed. McGraw-Hill Book Company, New York, NY.nMacLean, J. D. 1941. Thermal conductivity of wood. Heating, Piping and Air Conditioning13:380-391.nMaku, T. 1954. Studies on the heat conduction in wood. Wood Res. Bull.13:1-80. Kyoto University, Kyoto, Japan.nRowley, F. B. 1933. The heat conductivity of wood at climatic temperature differences. Heating, Piping, and Air Conditioning5:313-323.nSiau, J. F. 1995. Wood: Influence of moisture on physical properties. Department of Wood Science and Forest Products, Virginia Tech., Blacksburg, VA.nSiau, J. F., R. W. Davidson, J. A. Meyer, and C. Skaar. 1968. A geometrical model for wood-polymer composites. Wood Science1(2):116-128.nSteinhagen, H. P. 1977. Thermal properties of wood, green or dry, from -40°C to +100°C: A literature review. USDA Forest Service General Tech. Rept. FPL-9, Forest Products Laboratory, Madison, WI.nSuleiman, B. M., J. B. Largeldt, and M. Gustavsson. 1999. Thermal conductivity and diffusivity of wood. Wood Sci. Technol.33:465-473.nUrakami, H. and M. Kuyuyama. 1981. The influence of specific gravity on thermal conductivity of wood. Bull. Kyoto Prefect Univ. For.25:38-45.nVan Dusen, M. S. 1920. The thermal conductivity of heat insulators. J. Am. Soc. Heat. Vent. Eng.26:625-656.nWangaard, F. F. 1940. Transverse heat conductivity of wood. Heating, Piping and Air Conditioning.12:459-464.nWangaard, F. F. 1943. The effect of wood structure upon heat conductivity. Transactions of the A.S.M.E. February, 1943: 127-135.nWard, R. J. 1960. A dynamic method for determining specific heat and thermal conductivity of wood based materials as a function of temperature. Thesis, State University College of Forestry at Syracuse University, Syracuse, NY.n
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