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  • 1.
    Ananías, Rubén A.
    et al.
    Department of Wood Engineering, Faculty of Engineering, University of Bío-Bío, Concepcion.
    Mena, Marcelo
    Department of Wood Engineering, Faculty of Engineering, University of Bío-Bío, Concepcion.
    Elustondo, Diego
    Díaz-vaz, Juan Eduardo
    ITPF, Faculty of Forest Sciences, Austral University.
    Valenzuela, Luis
    Faculty of Forest Sciences, University of Concepción.
    Salinas, Carlos T S
    Department of Mechanical Engineering, Faculty of Engineering, University of Bío-Bío, Concepción.
    Testing New In-Kiln Meter for Monitoring Lumber Moisture Content during Drying2013In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 31, no 3, p. 277-281Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to test a new in-kiln sensor for monitoring lumber moisture content during industrial drying. The theoretical foundation of the technology was already known, because it is based on electrical conductivity, but the mechanism of implementation was new and required validation. For this reason, the technology was compared with two other widely used methods for assessing lumber moisture content, namely, the oven-drying and electrical capacitance methods. The tests were performed in a 120-m3 industrial kiln operated by a sawmill in the eighth region of Chile, and the results showed that the average moisture content at the end of drying was satisfactorily determined by the new in-line sensor. As predicted by theory, the sensor was not able to accurately measure moisture content above 25%, but it was still able to provide the equivalent of a drying curve for monitoring of the drying process

  • 2.
    Ananías, Rubén A.
    et al.
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Perez, Patricio
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Salinas, Carlos
    Department of Mechanical Engineering, University of Bío-Bío, Concepción.
    Elustondo, Diego
    Drying Schedules for Canelo Wood2013In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 31, no 3, p. 282-285Article in journal (Refereed)
    Abstract [en]

    Canelo wood is a highly valued native species in Chile that shows delicate marbling patterns with a pinkish soft silver luster. Due to its decorative qualities, canelo wood is dried for the manufacture of furniture and musical instruments. However, canelo wood lacks vessels cells that typically transport the water in hardwoods. Per its drying behavior, canelo wood is considered a transition species between hardwoods and softwoods. Therefore, this article reports drying schedules that were developed for drying 25-mm and 50-mm canelo lumber. In addition, this article reports experimental overall mass transfer coefficients, so that drying times for each of the drying stages can be easily estimated

  • 3.
    Ananías, Rubén A.
    et al.
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Sepúlveda-Villarroel, Victor
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Perez-Peña, Natalia
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Leandro-Zuñiga, Laura
    Instituto Costarricense de la Madera, San Pedro, San José.
    Salvo-Sepúlveda, Linette
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Salinas-Lira, Carlos
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Cloutier, Alain
    Society of Wood Science & Technology Member, Centre de Recherche sur le Bois, Université Laval, Québec.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Collapse of Eucalyptus nitens Wood after Drying Depending on the Radial Location Within the Stem2014In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 32, no 14, p. 1699-1705Article in journal (Refereed)
    Abstract [en]

    Collapse is almost certain to occur in the industrial drying of Eucalyptus nitens, and as such this prevents the lumber manufacturing industry in Chile from producing commercial solid wood products from this species. This problem is still unsolved, and different studies to reduce collapse are currently underway. In this exploratory study, shrinkage and collapse after drying of Eucalyptus nitens was measured for boards cut from different radial locations within the stem (core, transition and outer wood from pith to bark) and having different annual ring orientation (flat-sawn and quarter-sawn). Even though exploratory, the results appear to confirm that pieces that were cut from the center of the trees were less susceptible to collapse than the pieces cut from the transition zone between the center and the periphery. On average, collapse in transition wood was approximately 50% higher than the collapse observed in wood cut from the central zone of the trees.

  • 4.
    Ananías, Rubén A.
    et al.
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Ulloa, J.
    Aserraderos Arauco S.A., Arauco.
    Elustondo, Diego
    Salinas, Carlos T S
    Mechanical Engineering Department, University of Bío-Bío, Concepción.
    Rebolledo, Pamela
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Fuentes, C.
    Aserraderos Arauco S.A., Arauco.
    Energy Consumption in Industrial Drying of Radiata Pine2012In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 30, no 7, p. 774-779Article in journal (Refereed)
    Abstract [en]

    This article reports the results of an exploratory study designed to reduce heat and electricity consumption in industrial drying of radiata pine. The experiments were performed with slight modifications of the standard drying schedules used by the sawmill to dry radiata pine in 100-m 3 industrial kilns. The heat and electricity consumption were determined with data collected during the drying runs and calculations based on mathematical models. The results showed that depending on the case, heat and power consumption were respectively reduced by up to 14 and 35%.

  • 5.
    Antti, Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Zhao, H.
    Turner, I.
    Investigation of the heating of wood in an industrial microwave applicator: theory and practice2000In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 18, no 8, p. 1665-1676Article in journal (Refereed)
    Abstract [en]

    In this work a comprehensive set of experimental results are used as an excellent means to understand the coupling that exists between the material and the electromagnetic fields in a specific industrial microwave applicator. The analysis of the infrared images allows an accurate map of the power and temperature distributions within the wood sample to be determined. This map, together with the simulation results of a previously developed computational electromagnetic model, can provide a detailed understanding of the design features of the microwave applicator. In particular, it is possible to locate the occurrence of localised hot spots and to examine the uniformity of the heat distribution throughout the sample. The simulation results provide the evolution of the electromagnetic fields inside the entire applicator and the sample. The coupling of theory and practice is the best way to proceed in optimising the design and for proposing new applicator geometry that can heat the material more effectively.

  • 6.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Guest Editorial: R&D Needs in Wood Drying Technology2014In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 32, no 6, p. 629-630Article in journal (Other academic)
  • 7.
    Elustondo, Diego
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ahmed, Sheikh Ali
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Oliveira, Luiz
    Department of Lumber Manufacturing, FPInnovations, Vancouver.
    Drying Western Red Cedar with Superheated Steam2014In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 32, no 5, p. 550-556Article in journal (Refereed)
    Abstract [en]

    This exploratory study evaluated the possibility of drying 50-mm-thick western red cedar with superheated steam. Since there are no industrial facilities in Canada drying western red cedar with superheated steam, the study was designed to explore the potential of this technology in terms of lumber quality, moisture content distribution, and drying time. The experiments showed that the 50-mm-thick product can be dried in less than three days without jeopardizing lumber quality (in comparison with the two weeks that is currently required in conventional kilns), and the percentage of pieces that remained wet after drying was within the 10% to 15% range that is typically tolerated in industry.

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  • 8. Elustondo, Diego
    et al.
    Avramidis, Stavros H.
    Department of Wood Science, University of British Columbia, Vancouver.
    Comparative analysis of three methods for stochastic lumber drying simulation2005In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 23, no 1-2 Spec. issue, p. 131-142Article in journal (Refereed)
    Abstract [en]

    This article describes a novel stochastic model designed to simulate systems that cannot be analyzed as a unit, but as a collection of a large number of similar components. In order to state advantages and disadvantages, the proposed method is compared with two other published models. The first is a symbolic mathematical relationship designed to predict average moisture content and standard deviation after conventional drying of lumber. Since this model is exact, it was used as reference to evaluate the accuracy of the other approximate numerical methods. The second model is entirely random, and it emulates a real system behavior in which the parameters and conditions randomly change from one component to the other. The proposed method is based on numerical integration of the parameter's frequency distribution curves, which always produce the same and most probable result for the same parameters and conditions. The three methods were applied for simulation of conventional lumber drying, and the results were compared both qualitatively and numerically

  • 9.
    Elustondo, Diego
    et al.
    Department of Wood Science, University of British Columbia, Vancouver.
    Avramidis, Stavros H.
    Department of Wood Science, University of British Columbia, Vancouver.
    Stochastic numerical model for radio frequency vacuum drying of timbers2002In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 20, no 9, p. 1827-1842Article in journal (Refereed)
    Abstract [en]

    A new numeric method to simulate stochastic dispersion (a natural phenomenon that occurs when a magnitude cannot be associated to a specific value, but to the probability of being within a range of values) is proposed and applied to predict Radio Frequency Vacuum (RFV) drying of timber. A theoretical formulation of the method is described and complemented to take into account the frequency distribution of the timber initial moisture content, so that it can be applied to industrial runs. Experimental data obtained from mixed western hemlock and amabilis fir dried in a commercial RFV kiln are used to validate the stochastic model, and the results are compared through moisture content histograms and probability charts. A numerical example is shown in order to provide an idea of the movement of the moisture profiles during RFV drying.

  • 10.
    Elustondo, Diego
    et al.
    Department of Wood Science, University of British Columbia, Vancouver.
    Avrimidis, Stavros H.
    Department of Wood Science, University of British Columbia, Vancouver.
    Shida, Satoshi
    Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo.
    Predicting thermal efficiency in timber radio frequency vacuum drying2004In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 22, no 4, p. 795-807Article in journal (Refereed)
    Abstract [en]

    In this work, the efficiency of transforming dielectric energy into evaporated water is analyzed for the case of timber radio frequency vacuum drying. Based on well-known heat and mass transfer equations, a simplified mathematical model is proposed that estimates the drying efficacy in regards to the thermo-physical properties of wood. Although not exact, the theoretical results are close to the experimental observations and elucidate some phenomena like the tendency of the timber to dry from inside to outside, and the drying rate increase with the rise of the timber gas permeability. The theoretical efficiency model also predicts a range of wood permeability values for which the drying efficiency changes from 100 to 0%, thus providing a quantitative scale for classifying the spectrum of "difficult-to-dry" all the way to "easy-to-dry" wood species when using radio frequency vacuum technology

  • 11.
    Elustondo, Diego
    et al.
    PLAPIQUI (UNS-CONICET), Camino La Carrindanga Km 7.
    Mujumdar, Arun Sadashiv
    PLAPIQUI (UNS-CONICET), Camino La Carrindanga Km 7.
    Urbicain, Martin J.
    Department of Mechanical Engineering, National University of Singapore.
    Optimum operating conditions in drying foodstuffs with superheated steam2002In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 20, no 2, p. 381-402Article in journal (Refereed)
    Abstract [en]

    It is inferred from experimental data that in drying foodstuffs with superheated steam, the initial drying rate has a direct effect on the rate at which the overall drying takes place. That is, the faster the initial drying rate, the shorter the overall drying time. This criterion is very convenient because at the beginning, water moistens the sample external surface so evaporation does not depend on internal sample characteristics, but only on external convective heat and mass transfer rates. Mass and energy balance equations are solved and the result converted into a general initial drying rate equation, in which all dryer characteristics are grouped into one dimensionless parameter. The initial drying rate equation is mathematically maximized and the optimum working conditions determined. The result shows that initial drying rate always increase with increases of either the superheated steam temperature or velocity, but once these two variables are fixed, there exists at least one "optimum" pressure at which the initial drying rate is a maximum. Finally, the initial drying rate and optimum condition equations are applied to three model dryers, a dryer for a flat sheet, a fixed bed dryer and a rotary dryer. In each case, numeric values are computed and plotted as drying rate versus pressure curves, in which the optimum drying rate is also included. Also presented is a chart to compare the optimum pressures as functions of temperature and steam velocity for the three dryers.

  • 12. Elustondo, Diego
    et al.
    Oliveira, Luiz C De S
    FPInnovations, Canada, Pointe-Claire.
    Opportunities to reduce energy consumption in softwood lumber drying2006In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 24, no 5, p. 653-662Article in journal (Refereed)
    Abstract [en]

    While a few years ago the cost and availability of energy was not an important issue for the Canadian lumber industry, this situation has recently changed. Today, companies that have operated trouble-free for many years using the same technologies and practices may now have to adapt to the rising cost of fossil fuels and concerns about greenhouse gas emissions. This article addresses this problem for the particular case of the softwood lumber industry. The study describes the most important sources of energy losses in conventional drying and proposes a number of strategies and technologies to reduce kiln energy demand

  • 13. Elustondo, Diego
    et al.
    Oliveira, Luiz C De S
    FPInnovations, 2665 East Mall, Vancouver.
    Ananías, Rubén A.
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Visual Method to Assess Lumber Sorting Before Drying2013In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 31, no 1, p. 32-39Article in journal (Refereed)
    Abstract [en]

    This article explores the possibility of using a simplified but intuitive method to quickly assess the potential benefits of sorting lumber before industrial kiln drying. The method consists of using scatter plots to visualize the probability of obtaining a certain drying result, such as final moisture content, as a function of a property of the green lumber that can be measured in practice. The method was first validated with four drying runs of 116 mm × 52 mm hemlock lumber: one run contained unsorted lumber and the others contained the same type of lumber but sorted into low, medium, and high groups depending on the electrical capacitance of the green wood. After validation, the scatter plots were used to assess the benefits of two typical industrial sorting strategies, namely, sorting by electric capacitance and sorting by weight. It was found that both methods have the potential to increase lumber production and reduce over dried lumber in approximately the same magnitude. For a typical industrial schedule, sorting into three groups reduced the drying time by approximately 10% and over dried lumber to practically zero

  • 14.
    Elustondo, Diego
    et al.
    Department of Wood Science, University of British Columbia, Vancouver.
    Oliveira, Luiz C De S
    Forintek Canada Corporation, Western Laboratory, Vancouver, BC.
    Avramidis, Stavros H.
    University of British Columbia, Department of Wood Science.
    Evaluation of three semi-empirical models for superheated steam vacuum drying of timbers2003In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 21, no 5, p. 875-893Article in journal (Refereed)
    Abstract [en]

    Superheated steam drying at sub-atmospheric pressure (SSV) has been successfully employed in Europe and Asia for drying some types of timbers, showing that drying time could be reduced by 50% with respect to conventional drying without significant losses in the quality of the final product. This reduction is the consequence of a different heat and mass transfer control mechanism. Since SSV drying is carried out in absence of gaseous air, diffusion of the generated vapor is not a limiting factor and drying rate becomes more dependent on heat transference. Therefore, classical interpretation of timber drying as a process based on moisture migration control is not applicable to SSV. This work is targeting the development and validation of a simplified semi-empirical model for SSV drying of timbers. Mathematical representation of the proposed model is uncomplicated and straightforward to apply, and the comparison between model predicted and experimental data showed a high degree of agreement under variable drying conditions.

  • 15.
    Hansson, Lars
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Antti, Lena
    Modeling microwave heating and moisture redistribution in wood2008In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 26, no 5, p. 552-559Article in journal (Refereed)
    Abstract [en]

    A finite element model was developed to describe and explain microwave heating of wood and the following moisture redistribution in wood. Dielectric and thermal properties are of great importance, since they are continuously affected during the process by moisture content, density, grain direction, temperature, and more. Computer tomography was used to detect wood density and moisture content. Heat distribution was verified by fiber-optic temperature sensors. The tests were performed in a designed microwave dryer based on 1-kW generators, 2.45GHz. The results show that finite element modeling is a powerful tool to simulate heat and mass transfer in wood, providing the material is well described.

  • 16.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Frishfelds, Vilnis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    Discrete and continuous modelling of heat and mass transport in drying of a bed of iron ore pellets2012In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 30, no 7, p. 760-773Article in journal (Refereed)
    Abstract [en]

    Drying of a porous bed of iron ore pellets is here considered by modeling a discrete two-dimensional system of round pellets. As a complement to the two-dimensional model, a continuous one-dimensional model enabling fast calculations is developed. Results from the discrete model show that the temperature front advances faster in areas with large distances between the pellets. In areas with low flow speed, the temperature of the pellets increases with a relatively slow rate. The water inside these pellets will therefore remain for a long time. The continuous model fits the discrete model very well for a regular distribution of equal-sized particles. A discrete model with irregular packing will, compared to the continuous model, show a larger variation in the distribution of temperature and moisture content in the final phase of drying.

  • 17.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lindmark, Elianne M.
    AB Electrolux.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Influence of plate size on the evaporation rate of a heated droplet2015In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 33, no 15-16, p. 1963-1970Article in journal (Refereed)
    Abstract [en]

    The purpose of this study is to numerically investigate how the width of a plate influences natural convection around a droplet. Droplets evaporating on hot surfaces has many applications including drying of dishes and paint. Evaporation rate and deposition of particles withheld in the fluid is of great importance in both cases. As a first step to investigate how the drying rate and deposition mechanisms can be controlled, this work aims to investigate how the external flow around a water droplet influences the evaporation rate. Natural convection caused by the hot plate on which the droplet rests is considered and the effect of different widths is examined. Results show that an extension of the plate past the droplet will increase the maximum velocity in the domain due to natural convection while the flow close to the surface is decreased due to the no slip condition and temperature gradient. A decrease of the evaporation rate is therefore observed when the plate is extended past the droplet as compared to the case when the plate and droplet have the same diameter. Simulations furthermore show that the results from the heat and mass transfer analogy only compare well to the results of Fick's law when the droplet and plate has the same width.

  • 18.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, Staffan T.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Evaporation of a sessile water droplet subjected to forced convection in humid environment2019In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 37, no 1, p. 129-138Article in journal (Refereed)
    Abstract [en]

    The evaporation of a sessile droplet is here investigated numerically with a design of experiment approach. Boundary conditions are chosen based on forced convection in humid air, i.e., mimicking the conditions inside a dishwasher. Computational fluid dynamic simulations of an axisymmetrical droplet placed on a heated plate show that relative humidity, initial contact angle, plate temperature, and temperature difference between plate and air all have significant effect on the initial evaporation rate. For the studied conditions, relative humidity is the most significant factor while the magnitude of the velocity and type of internal flow are insignificant within a 95% confidence interval.

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  • 19.
    Ljung, Anna-Lena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lundström, T. Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Marjavaara, Daniel
    LKAB.
    Tano, Kent
    Influence of air humidity on drying of individual iron ore pellets2011In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 29, no 9, p. 1101-1111Article in journal (Refereed)
    Abstract [en]

    The influence of air humidity on drying is investigated at four inlet air dew points; T dp = 273, 292, 313, and 333 K. A numerical model taking into account capillary transport of liquid and internal evaporation is applied to a spherical geometry representative for an individual iron ore pellet. Drying simulations are carried out with commercial computational fluid dynamic (CFD) software and the boundary conditions are calculated from the surrounding fluid flow. The results indicate that the effect of air humidity arises from the start of the first drying period, that is, the surface evaporation period, whereas the difference is reduced at the end of the period due to a prolonged stage of constant rate drying attained at high saturations. At low saturations, there is no constant drying stage because the surface becomes locally dry before the pellet temperature has stabilized at the wet bulb temperature. The magnitudes of the drying rates and moisture contents are rather similar at the time when internal drying becomes dominating (i.e., when the total surface evaporation rate is zero) for the respective dew points, yet the drying time is increased at high saturations. It was also found that the moisture gradients at the surface and inside the pellet increased with drying rate.

  • 20.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Infrared thermography in the analysis of moisture flux from drying wooden surfaces1992In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 10, no 5, p. 1219-1230Article in journal (Refereed)
  • 21.
    Oliveira, Luiz C De S
    et al.
    FPInnovations-Wood Products, Vancouver, British Columbia.
    Elustondo, Diego
    Mujundar, Arun
    Department of Mechanical Engineering, National University of Singapore.
    Ananías, Rubén A.
    Department of Wood Engineering, University of Bío-Bío, Concepción.
    Canadian Developments in Kiln Drying2012In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 30, no 15, p. 1792-1799Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to summarize recent trends related to industrial kiln drying with especial emphasis on the drying of softwood dimension lumber in Canada. The paper explores future trends by analyzing the current market condition and wood products requirements. The paper also summarizes current research developments in the area of kiln lumber drying that was published by Canadian universities and research institutes. This includes basic research, such as wood physics and computer simulation, and applied research, such as non-conventional drying strategies and new technologies and sensors. A last note is also included to mention a kiln supervisor tool that was developed in Canada to analyze information related to kiln performance indicators. The kiln supervisor provides important trends for mills aiming to optimize their drying processes and realize gains without substantial investments in capital and other resources

  • 22.
    Salinas, Carlos T S
    et al.
    Department of Mechanical Engineering, Faculty of Engineering, University of Bío-Bío, Concepción.
    Chavez, Cristian
    Mechanical Engineering Department, University of São Paulo, São Carlos.
    Ananías, Rubén A.
    Department of Wood Engineering, Faculty of Engineering, University of Bío-Bío, Concepcion.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Unidimensional Simulation of Drying Stress in Radiata Pine Wood2015In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 33, no 8, p. 996-1005Article in journal (Refereed)
    Abstract [en]

    This article reports an experimental and numeric methodology for studying the development of internal stresses during drying of solid wood. For validation purposes, tests were performed for drying of radiata pine at the equivalent of constant air-drying conditions at 44°C dry-bulb and 36°C wet-bulb temperatures. The methodology involves the simulation of drying stresses caused by the development of internal moisture content gradients during drying, where the moisture content gradients are also simulated numerically based on the theory of effective diffusion coefficient. The resulting mathematical model is a second-order non-linear set of partial differential equations with variable coefficients, which are integrated numerically through the Control Volume Finite Element Method (CVFEM). The results showed consistency between simulated values and the experimental strain and moisture content data both in the radial and tangential directions. It was concluded that the proposed method could be a valuable tool for studying general trends in the development of stress during drying, which are difficult to evaluate by measuring only due to the limited amount of data points and high experimental error associated to destructive strain tests.

  • 23.
    Sepúlveda-Villarroel, Victor
    et al.
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Perez-Peña, Natalia
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Salinas-Lira, Carlos
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Salvo-Sepúlveda, Linette
    Departamento de Ingenieria en Maderas, Universidad del Bio Bio, Avenida Collao 1202, Casilla 5-C-CP: 4081112, Concepción.
    Elustondo, Diego
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ananías, Rubén A.
    Department of Wood Engineering, Faculty of Engineering, University of Bío-Bío, Concepcion.
    The Development of Moisture and Strain Profiles During Pre-Drying of Eucalyptus nitens2016In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 34, no 4, p. 428-436Article in journal (Refereed)
    Abstract [en]

    This paper describes one of a series of studies carried out at the University of Bio-Bio in Chile with the objective of characterizing the response of Eucalyptus nitens to drying. The ultimate goal is to minimize collapse and internal intra-ring checking in the industrial drying of Eucalyptus nitens, which currently prevents the lumber manufacturing industry in Chile from producing a large number of commercial solid wood products from this species. This study focuses, however, on the drying conditions that have been shown in previous studies and are known in the industry to minimize collapse and internal intra-ring checking. For these conditions, this study reports the development of moisture content and internal strain profiles during drying. In addition, a simple diffusion model based on the concept of the effective diffusion coefficient was proposed to compare the drying rates in the radial and tangential directions. The results showed that the diffusion coefficient in the radial direction was approximately 50% higher than that in the tangential direction. Internal strains, on the other hand, developed approximately at the same time, regardless of the annual ring orientation. This indicates that it would be feasible to apply strain relief strategies simultaneously to all boards regardless of their annual ring orientation in order avoid internal intra-ring checking during pre-drying. This finding could be used as a benchmarking tool in the industrial drying for solid wood products of Eucalyptus nitens.

  • 24. Wiberg, P.
    et al.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Heat and mass transfer during sapwood drying above the fibre saturation point2000In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 18, no 8, p. 1647-1664Article in journal (Refereed)
    Abstract [en]

    Pine sapwood was dried in an air convection kiln at temperatures between 60-80 °C. Temperature and weight measurements were used to calculate the position of the evaporation front beneath the surface. It was assumed that the drying during a first regime is controlled by the heat transfer to the evaporation front until irreducible saturation occurs. Comparisons were made with CT-scanned density pictures of the dry shell formation during initial stages of drying of boards. The results indicate a receding evaporation front behaviour for sapwood above approximately 40-50% MC when the moisture flux is heat transfer controlled. After that we finally reach a period where bound water diffusion is assumed to control the drying rate. The heat transfer from the circulating air to the evaporation front controls the migration flux. In many industrial kilns the heating coils therefore have too small heat transfer rates for batches of thin boards and boards with high sapwood content.

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