EXPERIMENTAL-MEASUREMENT AND NUMERICAL-SIMULATION OF LOCAL MASS-TRANSFER COEFFICIENTS IN TIMBER KILNS

A comparison has been made between measurements of mass transfer coefficients inside a timber drying kiln and a numerical simulation of the air flow pattern in an array of boards. This solved the two-dimensional Navier-Stokes equations on a finite difference grid. The experimental results showed that the small gaps between boards, which are inevitable in practice, caused large enhancements in the mass transfer coefficients near the leading edge of the boards. The asymptotic values of these coefficients were always greater than those predicted from flat plate correlations. The simulation also predicted enhancements in the mass transfer coefficients at the leading edge, but of smaller magnitude than those measured. The asymptotic values were predicted within 15%. The simulation predicted that the increase over the flat plate correlations was due to the generation of turbulence by the gaps between boards.