Analysis of Heat and Mass Transfer during High-Temperature Drying of Pinus radiata

Abstract

This article describes the analysis of heat and mass transfer coefficients for a single board of Pinus radiata (D. Don) timber over a range of high temperature and superheated steam drying conditions. The calculated heat transfer coefficients were in the range 20 to 60 W m⁻² K⁻¹. The mass transfer coefficients were of the order of 2 × 10⁻⁸ to 3 × 10⁻⁷ kg m⁻² s⁻¹, based on the vapor pressure difference, and of the order of 0.002 to 0.04 m s⁻¹ (expressed in terms of mass transfer velocity) based on vapor concentration difference between the surface of the board and the bulk drying medium.

Keywords:

• Pine
• Schedule
• Single-board
• Superheated steam
• Wood processing

ACKNOLEDGEMENTS

This work has been conducted under the Research for Industry contract scheme between the NZ Foundation for Research Science and Technology and NZ Forest Research Institute Ltd. The author thanks Mr. John Sole and other members of the Wood Drying Group, Ensis JV, of CSIRO & Scion, Rotorua, New Zealand, for their help at various stages of this work. The author thanks Dr. Jamie Hague and Mr. Richard Northway, Ensis, Clayton, Australia, and Dr. Pratish Bandopadhayay, CSIRO MIT, Highett, Australia, for their comments on this manuscript. Thanks are also due to Associate Professor Tim Langrish, University of Sydney, Sydney, Australia; Dr. Jarl-Gunnar Salin, Tratek, Stockholm, Sweden; and Dr. Mike Milota, Oregon State University, Corvallis, Oregon, USA, for valuable discussion.

Notes

∗The relative saturation in the superheated steam is the ratio of working pressure to saturation pressure at the given dry-bulb temperature. ^[7]