Drying Douglas-fir Lumber: a Computer Simulation


  • Helmuth Resch
  • Hoyang Kang
  • Michael L. Hoag


Drying, computer simulation, moisture measurement, Douglas-fir lumber


Three experimental kiln runs were designed to investigate how well the drying rate of 2-inch-thick lumber from Douglas-fir heartwood can be simulated by Hart's computer model. Simulated data were compared with gravimetric records and with electrical measurements obtained using the moisture-monitoring system designed by Forrer. This thermomoisture meter proved useful in continuously measuring moisture gradients and temperatures in boards. The first step of the computer simulation showed how diffusion coefficients varied with moisture content; however, two adjustments of the computer inputs were needed to arrive at good agreement between simulated and observed drying rates.

It was concluded that Hart's computer simulation programs and Forrer's thermomoisture meter are excellent tools for future lumber drying research and improvement of kiln schedules.


Bramhall, G. 1979a. Mathematical model for lumber drying. I. Principles involved. Wood Sci. 12(1):14-21.nBramhall, G. 1979b. Mathematical model for lumber drying. II. The model. Wood Sci. 12(1):22-31.nBrown, H. P., A. J. Panshin, and C. C. Forsaith. 1952. Textbook of wood technology. Vol. 2. P. 159. McGraw-Hill, New York. 783 pp.nClark, J. D., and J. W. Williams 1933. The electrical conductivity of commercial dielectrics and its variation with temperature. J. Phys. Chem. 17(1):119-131.nClaxton, H. D. 1966. Computer simulation of kiln drying. Western Dry Kiln Clubs Proc. 18:55-61.nDavidson, R. W. 1958. The effect of temperature on the electrical resistance of wood. For. Prod. J. 8:160-164.nForrer, J. 1984. An electronic system for monitoring gradients of drying wood. For. Prod. J. 34(778):34-38.nHart, C. A. 1965. The drying of wood. Ext. Cir. 471, The North Carolina Agricultural Extension Service, Raleigh.nHart, C. A. 1977. Effective surface moisture content of wood during sorption. Wood Sci. 9(4):194-210.nHart, C. A. 1981. SIMSOR: A computer simulation of water in wood. Wood Fiber 13(1):46-71.nHart, C. A. 1983. A user's manual for a family of simulations of moisture sorption in wood. Dept. of Wood and Paper Science, North Carolina State University, Raleigh.nJames, W. L. 1963. Electric moisture meters for wood. USDA For. Serv. Res. Note FPL-08. For. Prod. Lab., Madison, WI.nKawai, S., K. Makato, and T. Sadoh. 1978. Prediction of moisture distribution in wood during drying. Mokuzai Gakkaishi 24(8):120-125.nKeylwerth, R., and D. Noack. 1956. [The influence of higher temperatures when electrically measuring wood moisture content using the resistance method.] Holz als Roh u. Werkst. 14(5): 162-172.nLin, R. T. 1965. A study of the electrical conduction in wood. For. Prod. J. 15(11):506-514.nMcNamara, W. S., and C. A. Hart. 1971. An analysis of interval and average diffusion coefficients for unsteady-state movement of moisture in wood. Wood Sci. 4(1):37-45.nMoschler, W. W., Jr., and R. E. Martin. 1968. Diffusion equation solution in experimental wood drying. Wood Sci. 1(1):47-57.nRasmussen, E. F. 1961. Dry kiln operator's manual. USDA For. Serv. Agric. Handbook No. 188. For. Prod. Lab., Madison, WI.nSiau, J. F. 1984. Transport processes in wood. Pp. 151-171. Springer, New York. 245 pp.nSkaar, C. 1948. The dielectric properties of wood at several radio frequencies. Tech. Publ. 691. New York State College, Forestry, Syracuse.nSkaar, C. 1964. Some factors involved in the electrical determination of moisture gradients in wood. For. Prod. J. 14(6):239-243.nStamm, A. J. 1927. The electrical resistance of wood as a measure of its moisture content. Ind. Eng. Chem. 19(9):1021-1025.n






Research Contributions