Wood-Water Relations

1 Wood Moisture and the Environment.- 1.1 Humidity and Vapor Pressure of Water.- 1.2 Measurement of Wood Moisture Content and Humidity.- 1.2.1 Measurement of Wood Moisture Content.- 1.2.1.1 Gravimetric Method.- 1.2.1.2 Distillation Method.- 1.2.1.3 Karl Fischer Titration Method.- 1.2.1.4 Nuclear Magnetic Resonance.- 1.2.1.5 Electrical Moisture Meters.- 1.2.1.6 Miscellaneous Methods.- 1.2.2 Measurement of Relative Humidity.- 1.2.2.1 Hygrometers.- 1.2.2.2 Dew-Point Sensors.- 1.2.2.3 Psychrometers.- 1.2.2.4 Humidity Probes in Wood.- 1.3. Moisture Content of Green Wood.- 1.4. Equilibrium Moisture Content of Wood.- 1.4.1 Effect of Relative Humidity.- 1.4.2 Effect of History (Sorption Hysteresis).- 1.4.3 Effect of Temperature.- 1.4.4 Miscellaneous Factors.- 1.5 Moisture Content of Wood in Use.- 1.6 Fiber-Saturation Point.- 1.7 Moisture Content and Strength of Wood.- 2 Moisture Sorption Thermodynamics.- 2.1 Introduction.- 2.2 Thermodynamic Properties of Water.- 2.3 Enthalpy Changes During Moisture Sorption.- 2.3.1 Differential Heat of Sorption.- 2.3.2 Heat of Wetting and Integral Heat of Sorption.- 2.3.3 Significance of Heats of Wetting and of Sorption.- 2.3.3.1 Heat of Sorption.- 2.3.3.2 Heat of Wetting.- 2.4 Free-Energy and Entropy Changes During Moisture Sorption.- 2.5 Moisture Sorption and Specific Heat of Wood.- 2.6 Swelling Pressure of Wood.- 2.7 Mechanical Stress and Sorption (Hygroelastic Effect).- 2.8 Mechanical Stress and Sorption Hysteresis.- 3 Theories of Water Sorption by Wood.- 3.1 Introduction.- 3.2 Moisture Sorption Theories and Equations.- 3.2.1 Dent Sorption Theory.- 3.2.2 BET Sorption Theory.- 3.2.3 Hailwood-Horrobin Sorption Theory.- 3.2.4 Peirce Sorption Theory.- 3.2.5 Enderby-King Sorption Equations.- 3.2.6 Bradley and Related Sorption Equations.- 3.2.7 Capillary Condensation and Sorption.- 3.2.8 Malmquist’s Sorption Model.- 3.2.9 Additional Sorption Isotherm Equations.- 4 Hygroexpansion in Wood.- 4.1 Introduction.- 4.2 Definition of Terms.- 4.3 Volumetric Hygroexpansion of the Wood Cell Wall.- 4.4 Volumetric Hygroexpansion of Wood.- 4.4.1 Maximum Volumetric Shrinkage and Swelling.- 4.4.2 Volumetric Hygroexpansion Coefficients.- 4.5 Directional Hygroexpansion in Wood.- 4.5.1 Longitudinal Hygroexpansion.- 4.5.2 Radial and Tangential Hygroexpansion.- 4.6 Hygroexpansion and Mechanical Stress.- 4.7 Reducing Hygroexpansion in Wood.- 5 Moisture Movement in the Wood Cell Wall.- 5.1 Introduction.- 5.2 Isothermal Moisture Diffusion.- 5.2.1 General Mechanism of Bound-Water Diffusion.- 5.2.2 Eyring’s Absolute Reaction Rate Theory.- 5.2.3 Moisture Content as a Driving Force.- 5.2.4 Vapor Pressure as a Driving Force.- 5.2.5 Chemical Potential as a Driving Force.- 5.2.6 Osmotic Pressure as a Driving Force.- 5.2.7 Spreading Pressure as a Driving Force.- 5.3 Irreversible Thermodynamics and Nonisothermal Diffusion.- 5.3.1 Introduction.- 5.3.2 Derivation of Coupled Flow Equations.- 6 Electrical Properties of Wood.- 6.1 Introduction.- 6.2 Electrical Resistance.- 6.2.1 Introduction.- 6.2.2 Inherent Variables Affecting Resistivity.- 6.2.2.1 Effect of Moisture Content and Species.- 6.2.2.2 Effect of Temperature on Resistivity.- 6.2.2.3 Effect of Structural Orientation.- 6.2.2.4 Effect of Chemical Constituents.- 6.2.2.5 Effect of Wood Density.- 6.2.3 External Variables Affecting Resistivity.- 6.2.3.1 Electrode Configuration.- 6.2.3.2 Contact Pressure.- 6.2.3.3 Sample Shape and Dimensions.- 6.2.3.4 Electrolytic Effects.- 6.2.3.5 Voltage Magnitude and Duration of Application.- 6.2.4 Theory of Electrical Conduction in Wood.- 6.3 Dielectric Properties.- 6.3.1 Dielectric Principles.- 6.3.1.1 Dipole Polarization (Debye Effect).- 6.3.1.2 Interfacial Polarization (Maxwell-Wagner Effect).- 6.3.2 Dielectric Properties of Water.- 6.3.3 Dielectric Properties of Dry Wood.- 6.3.4 Dielectric Properties of Moist Wood.- 6.3.4.1 Primary Dispersion in Moist Wood.- 6.3.4.2 Secondary Dispersion in Moist Wood.- 6.4 Electrical Moisture Meters.- 6.4.1 Resistance Moisture Meters.- 6.4.2 Dielectric Moisture Meters.- References.- List of Symbols.- List of Subscripts.