Summary
Round wood wafers, 4 mm thick along the grain and 2 cm in cross-sectional diameter, of green basswood (Tilia americana L.), yellow birch (Betula alleghaniensis Britton), and black cherry (Prunus serotina Ehrh.), were dried to equilibrium in air of 77% relative humidity and 25°C. Weight, and radial and tangential dimensions were recorded during the drying using a mean air velocity of 212 feet/minute.
Two drying stages were observed, a constant rate period during the early stages, followed by a falling rate period. The convective heat transfer coefficient h calculated from the constant drying rate period and based on an energy — mass balance equation was about 6.1×10-4 cal/cm2-sec-C° (4.5 BTU/ft2-hour-F°). It was independent of wood species and was within the range found by other workers. The calculated emission coefficient σ ranged from 0.50 to 0.58×10-4 cm/s.
From the dimensional change measurements, it was noted that radial shrinkage began later than tangential shrinkage in each specimen tested. This may be due to structural differences between ray and longitudinal tissues.
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This paper is based on a Ph.D. dissertation of the senior author in the Wood Products Engineering Department of the SUNY College of Environmental Science and Forestry, Syracuse, NY 13210, U.S.A. The authors are indebted to Dr. C. H. de Zeeuw for his contribution to the dissertation as co-advisor
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Chomcharm, A., Skaar, C. Moisture and transverse dimensional changes during air-drying of small green hardwood wafers. Wood Sci. Technol. 17, 227–240 (1983). https://doi.org/10.1007/BF00372321
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DOI: https://doi.org/10.1007/BF00372321