Non-steady state water adsorption of wood

Summary

The validity of the following equation of water adsorption into wood substance which was derived in the previous report, is examined: d(δW)/dt = k₀(1 − exp(-k₁/t))δW(l − δW), which can approximately be written as: d(δW)/d(logt) = rδW(l − δW), where δW is moisture content; t is time (t > 0); k₀, k₁ and r are constants. After measuring dimensional change with change in time under various relative humidities, the change of moisture content was indirectly calculated from the proportional relationship between dimensional change and moisture content. It was found that the theoretical equation satisfactorily agreed with the experimental results. These results lead to the conclusion that the equation was valid. Furthermore, the properties of the equation, whose constants are determined from experimental results, is discussed. The rate of water adsorption of wood shows interesting and systematical properties, especially near relative humidities corresponding to the fiber-saturation point.