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Full Description
At present, no single book adequately covers a basic understanding of wood book satisfies the need for such a work. It describes drying in practice. This the fundamental basis of kiln-drying technology, to enable forest companies to imFrove their drying operations as high-quality timbers become scarcer and of yesteryear can no longer be tolerated. Adaptive the wasteful practices is no longer good enough. Innovations change based on past experience of the material being dried and the processes require a sound understanding of drying. Newer techniques, such as the use of ultrahigh temperature sea soning and superheated steam under vacuum, require an even greater depth of physical understanding for these methods to be used effectively and economically. book provides a description of modern ideas about wood structure, This moisture movement and stress development, from which models of the drying process are developed to give the kiln operator important information about the course of drying under specified conditions, and thus a means is compared with practice wherever for rational process improvement. Theory possible.
Contents
1 The Structure of Wood.- 1.1 The Structure of Softwoods.- 1.2 The Structure of Hardwoods.- 1.3 Cell-Wall Structure and Composition.- 2 Wood-Water Relationships.- 2.1 Water in Wood.- 2.2 Moisture Sorption.- 2.3 Fibre Saturation and Maximum Hygroscopic MoistureContent.- 2.4 Theories of Sorption.- 2.5 Heat of Sorption.- 2.6 Response to Environmental Changes.- 3 Evaporation and Humidification.- 3.1 Moisture in Air.- 3.2 Enthalpy of Moist Air.- 3.3 Adiabatic Saturation and Wet-Bulb Temperatures.- 3.4 Humidity Charts.- 3.5 Ideal Heat Demand.- 3.6 Evaporation from a Wood Surface.- 3.7. Subsurface Evaporation.- 3.8 Mass-Transfer Coefficient Measurements.- 4 Wood-Drying Kinetics.- 4.1 Empirical Observations.- 4.2 Normalisation of Drying-Rate Curves.- 4.3 Pathways for Moisture Movement in Wood.- 4.4 Selection of Drying Models.- 5 Moisture Diffusion.- 5.1 Driving Forces for Diffusion.- 5.2 Penetration Periods and Regular-Regime Drying.- 5.3 Theoretical Modelling of Diffusion Coefficients.- 5.4 Experimental Measurements of Diffusion Coefficients.- 5.5 Conclusions.- 6 Multiple-Mechanism Models.- 6.1 Fundamental Equations.- 6.2 Experimental Observations.- 6.3 The Physical Process of Drying for a Softwood, Pinus radiata.- 6.4 Mixed-Wood Boards.- 6.5 Conclusions.- 7 Lumber Quality.- 7.1 Gross Features of Wood.- 7.2 Intrinsic Features of Wood.- 7.3 Processing Implications.- 8 Stress and Strain Behaviour.- 8.1 Mechanical Analogues.- 8.2 Shrinkage.- 8.3 Instantaneous Strain.- 8.4 Viscoelastic Strain.- 8.5 Mechanosorptive Strain.- 8.6 Relative Magnitude of Strain Components.- 8.7 Solution Procedures.- 8.8 Experimental Apparatus.- 8.9 Applications.- 9 Airflow and Convection.- 9.1 Airflow in a Batch Kiln.- 9.2 Flow between Boards.- 9.3 Convection in Kilns.- 9.4 Bypassing.- 9.5 Kiln Economics.- 10 Kiln Operation.- 10.1 Drying under Constant External Conditions.- 10.2 Drying under Variable External Conditions.- 10.3 Practical Kiln Schedules.- 10.4 General Practical Considerations.- 10.5 End-Moisture Specification.- 10.6 Handling Kiln-Dried Lumber.- 11 Pretreatments of Green Lumber.- 11.1 Protecting Wood Prior to Drying.- 11.2 Physical Methods to Improve Permeability.- 11.3 Low-Temperature Predrying.- 11.4 Heat Treatment.- 11.5 Prefreezing.- 11.6 Antishrink Chemicals.- 11.7 Presurfacing.- 11.8 Green Finger-Jointing and Cutting Blanks.- 11.9 Precoating.- 11.10 Presorting.- 12 Less-Common Drying Methods.- 12.1 Solar Kilns.- 12.2 Dielectric Drying.- 12.3 Superheated Steam Drying.- 12.4 Vacuum Drying.- 12.5 Dehumidifier Kilns.- References.- Species Index.
