Adsorption rate of wood during moisture sorption processes.

Moisture sorption processes carried out in successive steps in seven relative humidity environments between 11% and 92% at 20°C for Chinese fi r ( Cunninghamia lanceolata Hook.) and Sitka spruce ( Picea sitchensis Carr.) were studied. A theoretical equation was developed to describe wood adsorption processes, either started from oven-dry condition or certain initial moisture content. Th e relation between adsorption rate constant in the equation and relative humidity was clarifi ed as follows: with an increase in relative humidity, the adsorption rate constants for both species fi rst decreased and then increased slightly with the minimum values falling into the relative humidity range between 60% and 70%. Further, an attempt was made to model the observed relation between the rate constant and relative humidity by applying the Hailwood-Horrobin sorption theory.