Humidity Of Wood Research Articles

Improvement of methods for strengthening wooden beams in support zones using clamps

The article addresses the issues of deformation in wooden beams in support zones and proposes methods to resolve them using metal clamps. Special attention is given to the fact that when wood humidity changes, it expands, creating high compressive stresses in the clamp zones, potentially leading to material failure. As shown in the article, even a relatively small change in humidity (within 2 %) is enough to compress the wood and stop the clamp from functioning. This limitation significantly restricts the current use of clamps to reinforce wooden structures. To prevent such issues, adjustable clamps are proposed, which compensate for changes in wood dimensions due to humidity fluctuations. It is recommended that the adjustment of the clamps be done using a wrench. The article presents research results on the deformations of wooden beams reinforced with metal clamps and provides recommendations for calculating the forces required to compensate for wood swelling due to humidity. Parameters for adjusting the clamps are calculated using special formulas, including determining the angle of rotation of the adjustment nut depending on time and humidity changes in the environment. The article also discusses conditions where clamp use is most effective, especially for tall wooden beams in support zones. This work may be useful for engineers and specialists in wooden construction, offering practical recommendations to improve the strength and durability of structures exposed to external factors.

Kiln-Furnace System: Validation of a Technology for Producing Charcoal with Less Environmental Impact in Brazil

Brazil is the world’s largest producer of charcoal. Therefore, there is need for improvement in the gravimetric yield of conversion and the reduction of gas emissions, including greenhouse gases (GHGs), released during carbonization. The objective was to apply the methodology of Measurement, Reporting and Verification (MRV) to evaluate the emission of GHG, mainly CO2 and CH4. The charcoal production kiln-furnace system used was composed of 4 kilns with a capacity of ~6 t of wood, each. The MRV cluster of coal gravimetric yield and gas burners were used to determine the gravimetric yield and burner efficiency and thus evaluate the emission of GHGs generated in the carbonization system. The carbonization was performed in an isolated way producing, in total, 3.34 t of charcoal, with an average gravimetric yield of 25.82%. The MRV methodology was effective for evaluating the GHG emissions. The wood burner reduced by 50% the methane burning and provided a reduction of 0.392 tCO2 eq (23.91%). The humidity of wood and high precipitation were the main limiting factors in this research, and responsible for the decrease in the gravimetric yield. The kiln-furnace system was effective for a sustainable production with the use of non-continuous carbonization gas burners.

ЕКСПЕРИМЕНТАЛЬНІ ДОСЛІДЖЕННЯ СУЦІЛЬНОЇ ДЕРЕВИНИ КОНСТРУКЦІЙНИХ РОЗМІРІВ З ВРАХУВАННЯМ ФАКТОРА ВОЛОГОСТІ

2National University of Water and Environmental Engineering, Rivne Materials, elements and structures made of wood can be operated in environments with different humidity. Humidity of wood directly affects its strength and deformable properties. The works of domestic and foreign authors who studied the effect of moisture on the strength and deformability of wood of different species were analyzed in detail. It turned out that there are very few such works. According to these works, it is difficult to detect the effect of moisty on the basic physical and mechanical properties of wood. And they usually concerned the testing of wood under a soft load regime, which does not fully reflect their real stress-strain state. We have developed a method of experimental studies of various deciduous (birch, alder, ash) and coniferous (larch, pine, spruce) compression along the fibers with a single short-term load under a rigid test mode (by increasing the displacement of the press plate) with different moisture (30%, 21% , 12%). The age of all wood samples was 60 years. Section of prisms 30x30x120mm and grades of wood without defects and damages. The total number of tested samples - 126 pcs. After conducting experimental research and processing the results, complete diagrams of deformation of wood σ-u deciduous (birch, alder, ash) and coniferous (larch, pine, spruce) wood species from the beginning of loading and to the point of ultimate deformation, respectively, at a moisty of 30% , 21%, 12%. For the first time, critical deformations of different wood species at the corresponding maximum stress at different moisty were obtained experimentally. It was found that with a decrease in moisty from 30% to 12%, the strength of wood of all species increases. The critical deformations herewith are reduced.

Дослідження січних модулів листяних та хвойних порід деревини з різним показником вологості

Most wood-based materials, elements, products and structures work in both non-aggressive and aggressive environments. Aggressive also include environments with high humidity. Humidity of wood in such conditions is higher than standard (in an unprotected condition), that is more than 12 %. The humidity content of wood directly affects its physical and mechanical properties, in particular the initial modulus of elasticity and the modulus of deformation. The method of experimental researches of wooden prisms in the size of 30´30´120 mm on compression along fibers at a rigid mode of loadings (on increase of movements of a press of the testing machine) is in detail given. The following species of wood were tested: coniferous species — larch, pine, spruce; deciduous — birch, alder, ash. The trees from which the samples were made were grown, in particular, pine, spruce — in the forests of Rivne region; birch, alder, ash — in the forests of Volyn region; larch — in the forests of Ivano-Frankivsk region. The tested wood had a humidity content of 30 %, 21 %, 12 % at the age of 60 years and grade without defects and damage. Wood blanks were pre-dried in the laboratory to an average humidity of 30 % and in special drying chambers to a humidity of 21 % and 12 %. The humidity of the wood was controlled using a humidity meter MD-814. Experimental studies were performed on a servo-hydraulic testing machine STM-100 with an automated control and data recording system. On the basis of experimental researches diagrams (secant modulus—stress level) of continuous deciduous (birch, alder, ash-tree) and coniferous (larch, pine, spruce) breeds of wood were constructed. The initial modulus of elasticity and modulus of deformation of different types of wood in the range from 30 % to 12 % of humidity were obtained experimentally and theoretically. It is established that with a decrease in humidity from 30 % to 12 %, the strength of wood of all species increases the initial modulus of elasticity and the modulus of deformation increases significantly

Зміни анатомо-морфологічних показників рослин роду Аcer L. в умовах м. Дніпро

Вивчено видоспецифічні особливості анатомо-морфологічних показників одно-річних пагонів представників роду Acer L. Показано різницю параметрів гістологіч-них елементів пагонів дерев, що зростають на узбіччі автострад, та дерев з умовночистої зони. Виявлено пряму залежність між розмірами короку, первинної і вторин-ної кори та здатністю дерев протидіяти антропогенному впливу. Встановлено, що заанатомічною будовою найбільш толерантним до впливу техногенних емісій виявив-ся A. pseudoplatanus L., найбільш чутливим – A. negundo L.

The Analysis of Experimental Research of Gasification Process of Low-Grade Fuel

There are many ways of recycling wood and its waste into energy. But one of the most perspective is gasification. Therefore, the technology of thermal recycling of wood fuel in gaseous fuel is an urgent problem to be solved. Consequently, our objective is to find the dependence of net calorific value of synthesis gas from the amount of air, humidity and particle size of chopped wood, which is fed into the gasifier. For the experimental research and development process of gasification of wood in gaseous fuel a gasifier with a continuous layer is designed. In the process of of experimental research the author used a mix of wood (willow (Salix alba L.) in the amount of 1/3 of the total weight of the mixture, Pine (Pinus sylvestris) – 1/3 of the total weight of the mixture, birch (Betula pendula Roth.) – 1 / 3 of the total weight of the mixture). From experimental data we have evaluated the most optimal parameters gasification process of mixes wood, when net calorific value of synthesis gas reaches its maximum. We also obtained mathematical description of the object in a second order polynomial. To conclude, completed rationalization derived dependence to determine the values of the factors that ensure the maximum Q = 10.4 MJ / nm3, namely the size of the particles of wood l = 36 mm, the amount of air G = 68 nm3 / h, a mixture of wood humidity W = 34 %. The experimental data show that the experimental gasifier enables gasifying wood, at low and high humidity (50 %); while the gas generators for the industrial impact of humidity on the process of gasification is significant. Therefore, the results of theoretical and experimental researches should determine the technical parameters of the gas generator installation with the definition of rational parameters of the process: particle size and humidity of chopped wood, the amount of air that is fed into the gasification chamber and to develop practical recommendations for thermal recycling of wood.

Estimating the humidity of wood by terahertz infrared thermography

The usage of terahertz infrared thermography for assessing the humidity of wooden samples is described. Terahertz radiation transmitted through a sample is imaged by means of a tera-thermoconverter. The temperature field of the converter is analyzed with an infrared imager. The possibility of using the technique for testing the nonuniformity of drying of timber is illustrated.

The Cause of Whitening by Flame Retardants Treatment on Korean Wooden Cultural Heritage

Korean wooden cultural heritages are treated by flame retardants to protect fire hazards. Two types of flame retardants are used to treat wooden cultural heritage. These flame retardants cause some problems such as surface whitening, discoloration, and cracks due to the chemical reaction caused by Korean traditional wood painting (Dancheong), flame retardant and wood humidity. The Korean government is trying to cut down on the amount of flame retardants for the wooden cultural heritage because of these problems. This study was carried out to find the cause of whitening by flame retardants treatment. The reaction between pigment and flame retardant chemicals was analyzed by infrared spectroscopy.

Emissions of Nanoparticles from Small Combustion Equipment with Regard to the Combustion Mode and Wood Humidity

Contamination of air by solid particles is serious problem for human health and also environment, especially in certain regions of the Czech Republic and Poland. Small particles in nano-sizes are more dangerous than same weight of larger size. Negative effect namely of the solid particles depends on number, specific surface area, respirability and bonding of others substances (e.g. PAH, As, Cd, Zn, Cu etc.) which are higher for smaller (nano-sizes) particles compared to larger one. With the approaching winter, yearly problems with distribution of particles from small combustion equipments arise. The annual emission balance indicate that the proportion of small sources to total air pollution (PAH, dust) is surprisingly expressive [1]. For this reason mentioned above this contribution deals with measuring of amount, and distribution of nanoparticles produced form combustion of wood in small combustion unit. <br />For combustion test in grave-free stoves were used three samples of wood (wet spruce, dry spruce and raw spruce) and two combustion modes. Nanoparticles from flue gas were characterized by the aperture low-pressure cascade impactor DLPI (separation and weighing of particles in sizes 30 ηm ÷ 10 µm). Wood were combusted in the form of ¼ logs.

Effect of ozonation on the reactivity of lignocellulose substrates in enzymatic hydrolyses to sugars

The efficiency of pre-treatment of aspen wood with ozone for subsequent enzymatic hydrolysis into sugars is determined by the amount of absorbed ozone. The ozone absorption rate depended on the water content in the sample being ozonized and was maximum at a relative humidity of wood of ∼40%. As a result of ozone pre-treatment, the initial rate of the enzymatic hydrolysis of wood under the action of a cellulase complex increased eightfold, and the maximum yield of sugars increased tenfold depending on the ozone dose. The ozonation at ozone doses of more than 3 mol/PPU (phenylpropane structural unit of lignin) led to a decrease in the yield of sugars because of the oxidative destruction of cellulose and hemicellulose. The alkaline ozonation in 2 and 12% NaOH was inefficient because of the accompanying oxidation of carbohydrates and considerably decreased the yield of sugars.

Influence humidity of wood on the process gasification of wood in a continuous layer

This paper presents the results of research of the influence humidity of wood on the process thermal recycling of wood in a continuous layer to the gaseous fuel. We obtain the regression equation, which can be the basis for the process under investigation and rational control

Schnellbestimmung des Wassergehalts von Holzscheiten

For a rapid determination of the moisture content of wood logs numerous test devices in a price range between 10 and 800 Euros are available on the market. Comparative measurements with 12 wood samples in the usual moisture range show, that only few devices can fulfil the requirements concerning accuracy and repeatability when compared to moisture results from a drying cabinet determination. Moisture content readings higher than 30 % (i.e. 43 % wood humidity as based to the dry matter) should in most cases be interpreted carefully. The true moisture content is also almost consistently underestimated by the rapid test devices. The correct use of the terms „moisture content“ (wet basis) and the term „wood humidity“ (dry basis) as common in wood industry is sometimes questionable in the technical documents of the devices.

Factors affecting relative humidity during wood vacuum drying

Effects of pressure and temperature in the chamber during vacuum drying on the relative humidity and evaporation of wood surface were investigated by using the vacuum chamber. The setting temperature during vacuum drying included dry-bulb temperature td, the wet-bulb temperature tw and the temperature difference between the air in the vacuum chamber and the cooling water in the condenser. Results indicated that relative humidity during vacuum drying was affected by the dry-bulb temperature td, the wet-bulb temperature tw and the temperature difference between the air in the vacuum chamber and the water in the condenser. Relative humidity of wood decreased with the increase in temperature at the given temperature of the water in the condenser. The relative humidity was affected slightly by pressure in the vacuum chamber pA, and it decreased from 70% to 65% with pA increased from 50 kPa to 101 kPa. Moreover, there was nearly no evaporation under the vacuum without external heating.

Evaluation of the humidity state of glued wooden constructions during monitoring

The work presents the research method for determining the humidity of wood in glued structures during their exploitation. The conductometric method serves a basis for the above-mentioned technique, but instead of regular sensors of humidity meter, we suggest the use of special sensors with electrodes of different lengths. It has been shown that the developed method has a number of advantages compared to the gravimetric method for determining wood humidity and can be used to monitor wooden structures during their exploitation with minimal time and labor inputs.

Untersuchungen zu ausgewählten mechanischen Eigenschaften von Eschenholz | Investigation into certain mechanical properties of ash

Ash originating from two locations in Switzerland was investigated for certain selected mechanical properties. Values were determined for raw density, sorption, swelling, tensile strength,MOE and work on bending strength as well as annual rings. In addition the influence of wood humidity on the tensile strength was investigated as well as the correlation between humidity/tensile strength and annual rings density. The samples, as expected,were generally tough as far as breakage is concerned and the breakage energy required was higher than that of spruce. In view of its relative robustness and strong mechanical properties, there is a potential for the use of ash for the production of layered boards, but also for other wood parts for construction purposes with high requirements.

Trials of wood carbonization of some forest and fruit-bearing species

We have tried wood carbonization of eighth species from forest and fruit-trees found in Tunisia. The wood humidity of the different types has varied from 16 to 20% and the density is in the order of 0,8 to 1,1%. The duration of carbonization was from 110 to 130 hours. The temperatures of combustion were between 600 and 700°C during the carbonization. The technical efficiency of the carbonization from species wood was between 6 and 25%. The best yield obtained of different species studied were of olea europea and citus aurantium.

Investigation of the wetting characteristics of medium density fibreboards (MDF) by means of contact angle measurements

The influence of some parameters (wood species, binder content, water repellent finish, wood humidity and roughness) on the wetting of MDF was investigated by means of contact angle measurements with selected test liquids (water, glycerol, ethylene glycol and diiodmethane) using the sessile drop method. The investigations show that contact angle measurements are mainly disturbed by the penetration of the liquids into the MDF and by the high roughness of the surface. Therefore, the results have principally qualitative character. They represent the following tendency for the five parameters: the use of water repellent finish, increased wood humidity and increased roughness made wetting less effective with water repellent finish showing by far the biggest effect. MDF made of beech showed predominantly better wetting behaviour than that made of spruce. The influence of the binder content could not be unambiguously ascertained.

The influence of certain factors on thickness loss after the hot gluing of cut lamellas into solid wood layered boards

An experimental laboratory investigation has been carried out into the hot gluing of solid wood layered boards made out of 5.3 mm thick solid-wood lamellas, the latter being produced by the lengthwise veneer cutting technique, the object of the research being to determine some of the reasons (humidity of wood before heating, temperature of wood before cutting into lamellas, and temperature and pressure during the gluing of boards) for the permanent thickness loss which occurs during gluing. Spruce wood (Picea abies (L.) Karst.) was used in the experimental tests. Before cutting into lamellas, this wood was classified into two humidity groups, and heated to three different temperatures. The dried lamellas were used, after suitable preparation, for the two outer layers, which were glued, together with a middle layer of sawn lamellas, by the hot gluing process. A total of 162 laboratory boards, of length 500 mm, width 475 mm and thickness from 24 to 25 mm, were hot glued, using melamin-urea-formaldehyde glue, at three different gluing temperatures and three different gluing pressures. Regression analysis of the measured results of thickness loss showed that the influence of the studied factors on thickness loss was linear, and that thickness loss depends the most on gluing pressure, followed by gluing temperature. It was also found that a higher wood humidity results in a slightly greater thickness loss than the wood’s temperature before cutting into lamellas.

Density, humidity, and nitrogen content of dominant wood species of floodplain forests (várzea) in Amazonia

The bulk density in the wood of 15 dominant tree species of white-water floodplain forests (varzea) of Amazonia varies between 0.235 and 0.716 g/cm3 (average 0.495±0.002 g/cm3). The mean wood humidity is 115.1% dry weight (variation ≈50−260%). Nitrogen concentrations vary between 0.03 and 0.50% (average 0.20±0.002). Ecological and technical consequences of the results (implications for wood decay in this ecosystem, and potentialities for commercial use of varzea wood) are pointed out.