Moisture sorption isotherms and thermodynamic properties of Jack pine and palm wood: Comparative study

• Isotherms desorption for two type of wood was established.
• Net heat of desorption was deduced through Clausius–Clapeyron equation.
• Differential heat of desorption was calculated from Gibbs–Helmholtz relationship.
• Isokinetic temperature was determined and compared to the harmonic mean of temperatures.
• Results comparison for two wood species in term of thermodynamic properties was established.

Currently, the impact of the controlled climate on moisture sorption isotherms of Jack pine and palm wood still remains unclear. The aim of this paper was to determine and compare the moisture sorption isotherms and thermodynamic properties of Jack pine and palm wood. The equilibrium moisture content of wood samples was measured within the range of 5 to 90% relative humidity at 50 °C, 60 °C, 70 °C and 80 °C. For both wood varieties, the equilibrium moisture content decreased with increasing temperature, however the effect of temperature is very remarkable for palm wood. The isosteric heat of desorption, the enthalpy and the entropy decreased with the increase of the moisture content. A good straight line correlated differential enthalpy and entropy, according to the enthalpy–entropy compensation theory. The spreading pressure decreased with increasing temperature at a given water activity, and increased with increasing water activity at a constant temperature. Predictive correlations of the two wood properties, based on experimental methods and physical laws, were established and compared.