Moisture Diffusion Coefficient in Wood as Calculated from Adsorption, Desorption, and Steady State Data

The relationships between the diffusion coefficient and moisture content were analyzed from data obtained by each in adsorption, desorption, and steady state in the range of 6 to 16 percent moisture content. The shapes of the two steady state regressions were about the same. However, the relationship obtained from steady state following adsorption was different. At low moisture contents there was little difference between diffusion coefficients calculated from the adsorption and desorption data, but at high moisture contents diffusion coefficients from both were well below those obtained from the steady state. It is suggested that the anomalous behavior at high moisture contents was due to a failure of the wood to meet one of the boundary conditions for the solution of Fick’s second law; namely, that the surface of the specimens did not reach the equilibrium value immediately.

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