Heat and Mass Transfer in Wood Composite Panels During Hot-Pressing: Part I. A Physical-Mathematical Model
Keywords:Wood composites, hot pressing, heat and mass transfer, modeling
AbstractA theoretical model for heat and moisture transfer in wood composite mats during hot-pressing is developed based on the basic principles of mass conservation, momentum of gas flow, energy conservation, and resin curing kinetics. The model provides a mathematical description of the coupled physical phenomenon in hot-pressing process as a closure problem in which fifteen governing equations are rigorously derived to solve fifteen unknown variables of mat environmental conditions. These variables, including mat temperature, gas pressure, and moisture content are linked to basic material properties such as mat density, thermal conductivity, and permeability. Initial and boundary conditions for solving the governing equations are also discussed.
Bolton, A. J., and P. E. Humphrey. 1988. The hotpressing of dry-formed wood-based composites. Part I. A review of the literature, identifying the primary physical process and the nature of their interaction. Holzforshung42(6):403-406.nBolton, A. J., P. E. Humphrey., and P. K. Kavvouras. 1989a. The hot pressing of dry-formed wood-based composites. Part III Predicted pressure and temperature variation with time, and compared with experimental data for laboratory board. Holzforschung43(4):265-674.nBolton, A. J., P. E. Humphrey., and P. K. Kavvouras. 1989b. The hot pressing of dry-formed wood-based composites. Part IV. Predicted variation of mattress moisture content with time. Holzforschung43(5):345-349.nCarvalho L. A. M., and C. A. V. Costa. 1998. Modeling and simulation of the hot-pressing process in the production of medium density fiberboard (MDF). Chem. Eng. Comm.170:1-21.nDai, C. 2001. Viscoelastic behaviour of wood composite mats during consolidation. Wood Fiber Sci.33(3): 353-363.nDai, C., and P. R. Steiner. 1993. Compression behaviour of randomly-formed wood flake mats. Wood Fiber Sci.25(4):349-358.nDai, C., C. Yu, and P. Hubert. 2000. Modeling vertical density in wood composites during hot pressing. Proc. 5th Pacific Rim Bio-based Composites Symposium, 10-13 Dec. 2000, Canberra, Australia.nHarless, T. E. G., F. G. Wagner, P. H. Short, R. Dan Seale, P. H. Mitchell, and D. S. Ladd. 1987. A model to predict the density profile of particleboard. Wood Fiber Sci.19(1):81-92.nHaselein, C. R. 1998. Numerical simulation of pressing wood-fiber composites. Ph.D. Thesis, Oregon State University, Corvallis, OR.nHata, T. 1993. Heat flow in particle mat and properties of particleboard under steam-injection pressing. Wood Research, Bull. Wood Research Inst., Kyoto University.80: 1-47.nHata, T., R. Kawai, Ebihara, and H. Sasaki. 1993. Production of particleboard with steam injection. Part V. Effect of particle geometry on temperature behaviors in particle mats and air permeabilities of boards. Mokuzai Gakkaish.39(2):161-168.nHumphrey, P. E., and A. J. Bolton. 1989. The hot pressing of dry-formed wood-based composites. Part II A simulation model for heat and moisture transfer, and typical results. Holzforschung43(3):199-206.nKauman, W. G. 1956. Equilibrium moisture content relations and drying control in superheated steam drying, Forest Prod. J.6(9):328-332.nKellogg, R. M. 1981 Physical properties of wood Pages 195-218 in F. F. Wangaard Wood: Its structure and properties. The Pennsylvania State University, University Park, PA.nLang, E. M., and M. P. Wolcott. 1996. A model for viscoelastic consolidation of wood strand mats: Part II. Static stress-strain behavior of the mat. Wood Fiber Sci.28(3):369-379.nLenth, C. A., and F. A. Kamke. 2001. Equilibrium moisture content of wood in high-temperature pressurized environment. Wood Fiber Sci.33(1):104-118.nNelson, R. M. 1983. Jr. Amodel for sorption of water vapor by cellulosic materials. Wood Fiber Sci.15(1): 104-118.nSiau, J. F. 1984. Transport process in wood. Springer-Verlag, New York, N.Y.nSimpson, W. T. 1973. Predicting equilibrium moisture content of wood by mathematical models, Wood Fiber5(1): 41-49.nThomen, H. 2000. Modeling the physical processes in natural fiber composites during batch and continuous pressing. Ph.D. Thesis, Oregon State University, Corvallis, OR.nThomen, H., and P. E. Humphrey. 2003. Modeling the continuous pressing process for wood-based composites. Wood Fiber Sci.35(3):456-468.nVon Haas, G. 1998. Investigations of the hot pressing of wood-composite-mats under special consideration of the compression-behaviour, the permeability, the temperature-conductivity and he sorption-speed (in German). Hamburg, Germany. Pp. 127-146.nWinistorfer, P. M., W. W. Moschler, S. Wang, E. De-Paula, and B. L. Bledsoe. 1999. Fundamentals of vertical density profile formation in wood composites. Part I. In-situ density measurement of the consolidation process. Wood Fiber Sci.32(2):209-219nWu, Q. 1999. Application of Nelson's sorption isotherm to wood composites and overlays. Wood Fiber Sci.31(2): 187-191.nZombori, G. B., F. A. Kamke, and L. T. Watson. 2003. Simulation of the internal conditions during the hotpressing process. Wood Fiber Sci.35(1):2-23.n
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