2 edition of Drying rates of thin sections of wood at high temperatures. found in the catalog.
Drying rates of thin sections of wood at high temperatures.
Herbert Oswald Fleischer
|LC Classifications||TS837 .F55|
|The Physical Object|
|Number of Pages||86|
|LC Control Number||a 54005613|
The articles cover a range of topics, only a few of which deal with drying lumber on the scale of a beginning-to-mid amateur. A lot of the topics are of interest: spalted wood, a bit of the theory behind wood's material properties, essays on a few favored species, turning a trunk into lumber, and even logging with a s: The convective drying of pine wood cylinders (40 mm diameter) in hot air has been investigated experimentally for conditions reproducing those encountered in the drying section of fixed-bed updraft gasifiers (nominal velocities of – m / s and maximum air temperatures of – K).Temperature profiles show a drying zone slowly propagating from the heat exposed surfaces .
Drying wood at high temperatures ( to °C) is an effective method to improve the dimensional stability and biological durability of wood (Perré and Degiovanni , ). Based on the cited work, it is reasonable to expect that in the high temperature drying of beech the loss of moisture will be directly proportional to the drying time. Hardwood lumber may be dried for many reasons. First, drying increases dimensional stability. Wood shrinks considerably more across the grain than along the grain when it dries. Because wood shrinks during drying, if it is cut to size before properly dried, it will be undersized in its final form. Second, drying can reduce, or even eliminate, decay or stain. Wood dried below 20 percent.
the breakdown of the particles dried at high temperatures. KEYWORDS Particleboard, drying temperature, internal bond strength. From this, it can be seen that drying wood chips at C resulted in % improvement in internal bond strength of . The high-temperature drying of beech wood was carried out by means of hot air in a laboratory drier for maximum 33 hours at maximum temperatures of and °C. The initial moisture content of samples was approximately 70%. The resulting drying times were short in comparison to conventional warm-air drying, which is caused by the high.
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Detailed fundamental information is lacking about the drying of wood in thin sections and the effects of high temperatures commonly used in drying such material. This study was intended to investigate the drying of small, thin wood sections at high temperatures, with particular emphasis on the drying by: 6.
Get this from a library. Drying rates of thin sections of wood at high temperatures. [Herbert Oswald Fleischer]. the literature on high-temperature kiln-drying of hardwoods and to evalu-ate the advantages, problems, and prob-able cost of this type of drying in the United States.
High-temperature drying in current literature refers to drying wood at temperatures above ° F. ( ° C.). The drying may take place in the absence of air, but more common.
Overdrying or drying at excessively high temperatures can have deleterious effects. Nylon 6,6 dried at °F (93 °C) for ≥4 h can cause thermal oxidative degradation, leading to yellowing.
PC is typically dried at °F ( °C) for four to 6 h; drying ABS at the same temperature results in a large solid ball because this is above the. Therefore, this paper includes the theoretical study of changes of the moisture content in wood in response to the high temperature of the drying air.
The aim of this research was to investigate the theoretical background of wood drying by high temperatures and determination of the drying coefficients.
DOI: /ERDevNAuthor: Aivars Aboltins, Jan Papez, Pavel Kic. The convectional kilns are designed to dry wood in the air and steam fusion, at the temperature of 40 °C (low-temperature seasoning and pre-drying) or temperatures of 40 to °C (common hot.
Freeze-drying is an extreme form of vacuum drying in which the water or other solvent is frozen and drying takes place by subliming the solid phase.
Freeze-drying is extensively used in two situations: (1) when high rates of decomposition occur during normal drying; and (2) with substances that can be dried at higher temperatures, and that are.
by Eric Meier. Allowing lumber to passively sit at a given humidity level in order to obtain a desired EMC (air-drying) may be the simplest and least expensive method of seasoning wood, but it is also the very slowest. Drying times can vary significantly depending upon wood species, initial moisture level, lumber thickness, density, ambient conditions, and processing techniques.
ing rates were reported. Some green 1-inch softwoods were dried to 10 per-cent moisture content in 24 hours, at drying temperatures as high as ° F. in an atmosphere of steam. The rela-tive humidity of the steam was regu-lated by controlling the dry-bulb tem-perature and maintaining a wet-bulb temperature at the boiling temperature.
• Drying times range from sec (drying of tissue paper) to five months (for certain hardwood species) • Production capacities may range from kg/h to t/h • Product speeds range from zero (stationary) to m/s (tissue paper) • Drying temperatures range from below the triple point to above the critical point of the liquid.
The fast drying is accompanied with a high risk that the wood may crack. To its advantage, microwave drying is a quick way to dry a piece of wood that just can’t wait for some of the better methods. Accepting that this method is an extended process goes a long way to aiding in its success.
Don’t try to dry a blank in just one or two cycles. kiln-dried at high temperatures is higher than that of air-dried or conventionally dried wood. Booker and Evans () reported that the higher radial permeability of Pinus radiata D. Don dried at a high temperature is caused by the movement and modification of resin in the canals.
Terziev () also compared the effect of drying methods on the. Drying has a number of close synonyms. Dehydration is the process of depriving a material of its water or the loss of water as a constituent.
The term is often used in food-drying operations to describe processes which strive to expel moisture but retain other volatile constituents in the original material, and which are responsible for valuable aromatic and flavoring properties.
Dried wood’s tensile strength reaches its peak when the moisture content is from %. Wood doesn’t like excessive moisture and high humidity levels. Wood prefers dry conditions. When the temperature is between C and the wood moisture content remains above 20% for an extended period of time, wood will start to get moldy.
Keylwerth, R., and Kübler, H., () Maximum operating temperatures and corresponding surface and interior temperatures in thin softwood lumber during drying. Deutsche Holzwirtschaft 8:. There are seven special methods listed for drying wood, i.e.
Vacuum drying 2. Infrared radiation 3. High frequency dielectric heating 4. Chemical seasoning 5. Boiling in oil 6. Vapor drying 7. Solvent seasoning Each of these will be discussed briefly. Vacuum drying. Many different processes have been proposed for using a vacuum to dry wood.
CHEMICAL ENGINEERING At equilibrium, the rates of heat transfer given by equations and must be equal, and hence: H −H w=− h h Dρ Aλ (θ−θ w)() In this way, it is seen that the wet bulb temperature θ wdepends only on the temperature and humidity of the drying air.
Major consideration was directed toward establishing relationships to describe the individual parameters in a thin-layer drying model as a function of dry bulb and dew point temperatures. Thin.
exposed the wood to high temperatures longer than necessary for normal high- temperature drying (Hartley ). OBJECTIVE The objective of this study was to demonstrate the effects of high temperatures and air velocities on drying time for pine dimension lumber.
Experimental studies have indicated that drying time can be reduced by using either. Over drying of corn should be kept to a minimum by utilizing proper storage techniques. If corn is dried from 24% to 13% rather than % it will require 40% more fuel plus up to a 30% reduction in drying capacity.
Utilizing a high as possible drying temperature is the best way to increase fuel efficiency as long as grain quality is not negated.
Wood drying (also seasoning lumber or wood seasoning) reduces the moisture content of wood before its use. When the drying is done in a kiln, the product is known as kiln-dried timber or lumber, whereas air drying is the more traditional method. There are two main reasons for drying wood: Woodworking When wood is used as a construction material, whether as a structural support in a building.Thus, exit gas temperatures are still higher (by ∼10°C) than exiting wood temperatures.
However, many individ-ual chips in the dryer see relatively high surface tempera-tures (∼70°C) (O’Hagan and Smith ); these high lo-cal surface temperatures cause oxidation/thermal degrada-tion of the volatile compounds, increasing oxygenated VOC.S.
Srivaro et al. / Songklanakarin J. Sci. Technol. 30 (4),water are removed from 1 m3 of lumber during the drying process (Hong, ). Kiln drying can be categorized into 4 regimes accord-ing to the operating temperatures (dry bulb): low temper.