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air circulation air flow air movement average moisture content BAFFLE blower calibrated capillary case-hardening coils cold zone condensate constantan control bulbs cubic foot determine Douglas-fir drain header dried dry air dry kiln dry-bulb temperature drying aircraft lumber drying rate drying stresses entering-air equilibrium moisture content fans feet fiber-saturation point flue green heartwood heat hot zone hygroscopic inches indicated instrument kiln charge kiln conditions kiln drying kiln operator kiln samples kiln temperatures length located longitudinal temperature maximum mois moisture content sections moisture content values moisture distribution obtained oven-dry weight perature percent piling pipe potentiometer pounds prongs readings record relative humidity return-air ducts sapwood schedule shown in figure shrinkage Sitka spruce specific gravity Specification AN-W-2 stages of drying steam pressure sticker surface fibers tempera THERMOCOUPLE thermometer thermostat thickness tion transverse trap ture content uniform usually valve vapor pressure vents volume wet-bulb wet-bulb temperature wood
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Página 146 - ... the ratio of the ovendry weight of a sample to the weight of a volume of water equal to the volume of the sample at some specific moisture content, as green, air-dry, or ovendry.
Página 134 - The total heat in steam includes the heat required to raise the temperature of the water from 32° F. to the temperature of the steam plus the heat required to evaporate the water at that temperature.
Página 147 - Moisture content of wood. Weight of the water contained in the wood, usually expressed as a percentage of the weight of the ovendry wood.
Página 146 - HEARTWOOD. The wood, extending from the pith to the sapwood, the cells of which no longer participate in the life processes of the tree. Heartwood may be infiltrated with gums, resins, and other materials which usually make it darker and more decay-resistant than sapwood.
Página 149 - The layers of wood next to the bark, usually lighter in color than the heartwood, one-half inch to 3 or more inches wide that are actively involved in the life processes of the tree. Under most conditions sapwood is more susceptible to decay than heartwood ; as a rule, it is more permeable to liquids than heartwood.
Página 6 - ... point. Wood shrinks most in the direction of the annual growth rings (tangentially) , about one-half to two-thirds as much across these rings (radially), and very little, as a rule, along the grain (longitudinally). The...
Página 7 - GENERAL. Among the important classes of properties that affect the general utility of any wood are its machining properties, which embrace all woodworking operations. In these, as in other classes of properties, different woods vary widely and a given wood may give good results in some operations, fair in others, and poor in still others. The "workability...
Página 11 - In a progressive kiln, a number of truckloads of lumber at different stages of drying extend through the kiln in an unbroken line. Truckloads of green stock are periodically fed into the kiln and truckloads of dried stock removed at the same time from the other end of the line. The stock thus moves progressively through the kiln until it emerges, supposedly dry, after a specified time of exposure to the various conditions along the length of the kiln. The temperature and relative humidity at any...
Página 145 - Defects, drying: Any irregularity occurring in or on wood, as a result of drying, that may lower its strength, durability, or utility value. Degrade: A drop in lumber grade that results from kiln drying.
Página 147 - A lumber dry kiln is composed of one or more chambers, rooms, or tunnels in which temperatures and relative humidities can be controlled and maintained at any desired level by means of either manual or automatic control.