Kinetic Water Vapour Sorption of Sitka Spruce at Variable Temperature Using the Parallel Exponential Kinetics Model

IRG/WP 10-40512

Yanjun Xie, C Hill

In this study the water vapour sorption of Sitka spruce (Picea sitchensis (Bongard) Carr.) was measured using a Dynamic Vapour Sorption (DVS) apparatus and then analysed using the parallel exponential kinetics (PEK) model. The water vapour sorption rate of wood quickly increased when the relative humidity was changed. With the elapse of time, the sorption rate gradually decreased within any specific relative humidity range. The sorption hysteresis of wood reduced with increasing isotherm temperature. The equilibrium moisture contents obtained from DVS measurements were comparable to these derived from PEK model in the full relative humidity range. The PEK model deconvolutes the sorption kinetics curve into two exponential kinetics processes (fast and slow) which have characteristic times and moisture contents associated with them. The slow adsorption and desorption processes exhibited important differences in their characteristic times, although hysteresis in the moisture contents was found to be variably distributed between the fast and slow processes depending on isotherm temperature.

Keywords: water vapour sorption, sorption rate, kinetics, parallel exponential kinetics, Sitka spruce

Conference: 10-05-09/13 Biarritz, France

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