Kinetics of drying beech wood contain red false heartwood

Patrik Halčin, Ivan Klement, Tatiana Vilkovská, Peter Vilkovský

Abstract


The article was focused on analysing the differences in the drying of beech wood (Fagus sylvatica L.) containing red false heartwood. The woodworking industry and, gradually, the construction sector in Slovakia have been increasingly oriented toward the greater utilization of beech wood as a primary raw material. The occurrence of false heartwood in beech significantly affected the quality of logs and sawn timber. It was necessary to determine the differences in drying between beech with red false heartwood and mature beech wood. The differences in drying kinetics during a two-stage convective drying process, moisture loss, moisture gradients, and density were analysed. From the measured values, differences in drying intensity between red false heartwood and mature beech wood were identified, which were caused by the altered structure of red false heartwood and changes in permeability to liquids and vapours. The moisture loss was higher in red false heartwood samples (0.187-0.189%/h) at moisture levels above the fiber saturation point (> 30%) compared to mature wood samples (0.135-0.145%/h). Below the fiber saturation point ( 30%), the moisture loss was lower (0.148-0.177%/h) in red false heartwood samples, while in mature wood samples, it either remained unchanged or increased (0.171-0.145%/h). Red false heartwood lost moisture faster and had lower final moisture content at the end of drying.

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Analysis of shape changes during different stages of air drying at the hornbeam (Carpinus Betulus L.)

Hugo M. Uličný, Peter Vilkovský, Ivan Klement

Abstract


This study focuses on the analysis of shape changes at the hornbeam timber (Carpinus betulus L.) during different phases of air drying. The main objective was to identify and quantify warp bow, warp crook, warp cup, and warp twist at various drying stages. The research was conducted on hornbeam timber samples that were subjected to air drying. Measurements were carried out at regular intervals throughout the drying process, with the influence of moisture on the development of different types of warp being observed. The results showed that warps increased exponentially at the beginning of air drying, with twist- warp being most pronounced in radial-type timber. Significant changes were observed when the relative humidity of the air was reduced from 80.2% to 40.3%, and the temperature was lowered from 11.1°C to 3.3°C. The greatest shape change increase was recorded in November. The warp of some samples was found to have increased up to 25 mm. The observed variability in warp was closely linked to the original position of the samples within the log and the spiral grain structure. This study provides essential insights for optimizing the drying process of hornbeam timber to minimize shape changes.

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Effect of grain direction on particle size distribution during sanding of spruce, beech and oak wood

Martin Kučerka, Alena Očkajová

Abstract


This paper focusses on the impact of the grain direction of the sanding of selected wood types on the particle size distribution. In the experiment, a hand-held GBS 100 AE belt sander was used, with particles obtained through two grain directions of the sanding models: at angles of 0° and 90° with respect to the wood structure. The study examined the effects of grain direction on the particle size distribution in beech, oak and spruce wood sawdust. Statistical analysis was used to characterize the particle size distribution, and a combination of grain direction was compared for each type of wood. Statistical analysis revealed significant differences in the particle size distribution between the two cutting grain directions, with p-values of 0,018 and 0,0002 for beech and spruce, respectively. On the contrary, oak did not show minimal statistically significant differences between grain directions (p = 0,912). The results highlight the crucial role of the wood microstructure in determining the effect of grain direction on particle morphology. Specifically, spruce showed the highest sensitivity to grain direction changes, while oak remained relatively stable in different cutting directions.

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Contact drying of birch wood using different drying pressures

Ivan Klement, Tatiana Vilkovská, Peter Vilkovský, Jacek Barański, Aleksandra Suchta

Abstract


Research on the drying conditions of birch wood reveals that different drying methods can have a significant impact on its properties and overall quality. Birch, a wood species valued for its unique characteristics, including strength, flexibility, and aesthetic appeal, is highly suitable for a wide range of applications in industry. However, the drying process plays a critical role in determining the final quality, dimensional stability, and usability of the wood. As such, understanding the drying behaviour of birch wood is necessary for optimizing drying techniques, preserving its desirable properties, and ensuring its suitability for various products. One particularly interesting drying method is contact drying, which offers reduced drying times and lower heat consumption compared to traditional drying techniques. In this study, experimental samples were prepared from birch logs. The moisture content, moisture gradient, residual stresses, and density were measured, and drying was conducted under various pressures of 1.0 MPa, 1.4 MPa, and 1.8 MPa, with a drying temperature of 170°C. The results indicated that higher pressures led to an increased final moisture content, and substantial dimensional changes were observed during the drying process. Remarkably, the density of the wood increased by 13.03% to 19.55%, depending on the applied pressure. The study concluded that the optimal pressure for contact drying of birch wood is between 1.4 MPa and 1.8 MPa.

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