Applications of the capillary isotherm

The effect of temperature on the capillary isotherm is accounted for in a modified derivation. Some new equilibrium moisture content data for E. regnans are presented and fitted by the capillary isotherm. Some earlier data for Klinki pine are also fitted. It is shown precisely how reductions in the shear modulus of the cell wall material with increasing temperature give rise to reductions in equilibrium moisture content for a given relative humidity.Symbols A G₀/R, K - a₁ external radius of annulus, m - a₂ internal radius of annulus, m - a_f a₂ at fibre saturation, m - a a constant length, m - B a constant of integration - b₁, b₂ temperature parameters, K^1- - G rigidity of wood substance, Pa - G₀ G for dry wood, Pa - G_f G at fibre saturation, Pa - h isosteric heat, J/kg - latent heat, J/kg - p capillary pressure, Pa - P_s pressure of water vapour at saturation, Pa - R specific gas constant for water, J/kg K - r relative humidity - r_i inflection intercept - r_t tangent intercept - T temperature, K - t temperature, °C - X see equation (18) - x see equation (28) - , , ₁, ₁ coefficients, equations (27), (37) - y₁, y₂ see equations (25), (26), K - parameter, equation (9) - parameter, equation (33) - density of water, kg/m³ - _W density of wood substance, kg/m³ - equilibrium moisture content - _0.2 at r = 0.2 - _0.5 at r = 0.5 - _0.9 at r = 0.9 - _f at fibre saturation