Yasar Kocaefe

Changes in wettability of heat-treated wood due to artificial weathering

Effect of artificial weathering on the wettability of three heat-treated North American wood species (jack pine, aspen, and birch) is studied from the point of view of the structural and chemical changes taking place on the wood surface. Weathering increases wettability of all three heat-treated woods by water. Changes in wettability during artificial weathering differ according to heat treatment procedure and wood species and are likely due to combination of structural and chemical changes of the surfaces. Scanning electron microscopic analysis indicates that cracks form due to degradation taking place during weathering. As a result, water has easier entry into the cell wall, which consequently increases wettability. IR spectra suggest that the OH/CH2 ratio for heat-treated specimens is inversely proportional to the contact angle regardless of the type of wood species. The presence of cellulose-rich layer on wood surface and increasing amount of amorphous cellulose transformed from crystallized cellulose due to weathering result in increase in hydroxyl; consequently, it increases heat-treated wood wettability.

Effect of surface preparation on the wettability of heat-treated jack pine wood surface by different liquids

The objectives of this study are to quantitatively evaluate, using a wetting model, the wettability of three probe liquids with different properties on heat-treated jack pine surfaces prepared by three different types of machining (sanding, planing and sawing) and to compare with those of untreated wood surfaces. The results indicate that the heat-treated wood is wetted less than the untreated wood due to degradation of wood components (hemicelluloses, lignin and cellulose) during heat treatment and it absorbs less liquid. The heat-treated wood becomes most hydrophobic when wood surfaces are sanded by 180-grit paper compared to those prepared by other machining process. Heat-treated wood surfaces are strongly acidic similar to those of untreated wood. Consequently, the basic probe liquid, formamide, shows the highest spreading and penetration rate (K-value) on wood surfaces.ZusammenfassungZiel dieser Studie war es, die Benetzbarkeit mit drei Versuchsflüssigkeiten mit unterschiedlichen Eigenschaften von thermisch behandeltem Jack Pine Holz, dessen Oberflächen unterschiedlich bearbeitet worden waren (schleifen, hobeln, sägen) quantitativ anhand eines Modells zu bestimmen und mit unbehandelten Holzoberflächen zu vergleichen. Die Ergebnisse zeigen, dass thermisch behandeltes Holz aufgrund des Abbaus von Holzbestandteilen (Hemicellulose, Lignin und Cellulose) bei der thermischen Behandlung weniger stark benetzt wurde als unbehandeltes Holz und dass es weniger Flüssigkeit aufnimmt. Thermisch behandeltes Holz, dessen Oberfläche mit Schleifpapier der Körnung 180 bearbeitet wurde, ist im Vergleich zu anders bearbeitetem Holz am hydrophobsten. Thermisch behandelte Holzoberflächen sind stark acidisch, ähnlich wie unbehandeltes Holz. Folglich weist die basische Testflüssigkeit Formamid die höchste Ausbreitungs- und Eindringrate (K-Wert) auf Holzoberflächen auf.

Application of the imaginary planes method to three-dimensional systems

Abstract Three-dimensional (3-D) mathematical formulation of the imaginary planes method (IPM) for the calculation of radiative transfer in rectangular furnaces is presented. In this method, radiative transfer is modelled in terms of chain interaction from zone to zone as opposed to direct interaction in the classical zone method. A number of tests are carried out for gray and real gases as well as different enclosure geometries. The results compare well with those of the zone method. Moreover, considerable reduction in computer time (reduction factor up to 24) has been obtained with respect to the zone method. This feature will allow the IPM to be more easily incorporated into an overall simulation involving the equations of motion, combustion kinetics and transfer of heat and mass.

Dimensional Stabilization of Wood

This paper comprehensively reviews the relevant literature and presents the methods and processes used to investigate the dimensional stabilization of wood using various modification techniques, including (a) hydrophobization of wood surfaces to block the entrance and exit of water; (b) impregnation treatment with bulking agents, such as resin and wax, to maintain wood in a swollen state and diminish dimensional changes caused by moisture; (c) chemical treatment with different chemical agents to reduce the hygroscopicity of the wood; and (d) high temperature heat treatment, which modifies wood components, reducing accessible hydroxyl groups and decreasing the possibility of water absorption. The results of dimensionally stabilizing wood via different treatments are interpreted and compared, and the effects of treating conditions and parameters on the dimensional changes of wood are analyzed.

3D-simulation of the thermal performance of a coke calcining kiln

This is the first time ever a fully three-dimensional model of the rotary coke calcining kiln is built, to include all the important phenomena occurring therein. The overall kiln model consists of two separate models, one for the freeboard gas and one for the coke bed, coupled together with intermittent information exchange. The phenomena treated by the model include heat transfer, fluid flow, turbulence, volatiles combustion, third air, effect of kiln rotation. The model, based on the general equations of conservation is solved with the help of the CFD general-purpose code PHOENICS. Due to the huge dimensions of the real kiln, the model is validated on a laboratory size pilot kiln. Results are presented and the potential use of the model is discussed.

Mathematical modeling of an aluminum casting furnace combustion chamber

A mathematical model has been developed for the combustion chambers of aluminum casting furnaces by combining the fluid flow code PHOENICS with a zone model for the radiative heat transfer analysis and a simplified flame model. It offers flexibility in specifying the size and the combustion and heat transfer characteristics of the furnace. Thus, the model can be used to study a combustion chamber under different operating conditions and for different design op-tions. This paper presents the model and describes the coupling mechanism between PHOENICS and the zone method. Various case studies have been carried out for a 72-ton melter-holder. Results are presented which show the negative effect of ambient air inleakage on furnace per-formance as an application example.

Combined effect of acetylation and heat treatment on the physical, mechanical and biological behavior of jack pine ( Pinus banksiana ) wood

A comparative study on the combined effect of heat treatment and acetylation on jack pine wood properties was undertaken and the results were compared with those of each treatment carried out individually. The dimensional stability and mechanical property of wood with different treatments were examined and statistically analyzed. The results demonstrated that combined acetylation of jack pine wood with acetic anhydride and heat treatment at 190xa0°C has a positive effect on the dimensional stability. Results also suggested that the dimensional stability was affected more than the modulus of rupture (MOR) and modulus of elasticity (MOE) by both heat and acetylation treatments under the experimental conditions used. In addition, the hardness increases after high temperature modification but decreases slightly after acetylation. A comprehensive investigation of the effects of heat treatment and acetylation separately and together (combination treatment) on the fungal durability of jack pine wood against a brown rot fungus, Poria placenta (pp), and a white rot fungus, Trametes versicolor (tv) has also been performed. The results indicated that the weight loss caused by fungi is reduced by both modifications. It was also found that combination of heat treatment and acetylation offers additional bioprotection. FTIR results indicated that the heat and acetylation treatments have a significant influence on the chemical properties, but less influence on their structures.

Performance prediction of the aluminum casting furnace

ABSTRACT A comprehensive three-dimensional overall transient model has been built for the aluminum casting furnace. It results from the coupling of two models, representing the combustion chamber and the metal respectively. The chamber model takes account of gas flow, combustion and heat transfer, mainly radiative. The metal model includes the melting of a solid charge. The overall model can readily accommodate the various operational procedures and can be used to study furnace performance as well as solve design problems.