| 1. |
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| 2. |
- Elustondo, Diego, et al.
(författare)
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Drying with superheated steam : Maximum drying rate as a linear function of pressure
- 2002
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Ingår i: Chemical Engineering Journal. - 1385-8947 .- 1873-3212. ; 86:1-2, s. 69-74
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Tidskriftsartikel (refereegranskat)abstract
- Drying with superheated steam (SS) as heating agent is controlled through three operative variables, the steam temperature, the recycle velocity, and the system pressure. Once the other conditions are fixed, there is an optimum pressure at which drying rate reaches its maximum value. The exact optimum conditions can be found through a differential mass and energy balance over the heat exchange area, resulting in two equations. The first one to calculate the drying rate as function of the operating conditions and the second one to find the values of those conditions which make the operation optimum. Then, using these equations, this paper shows that the relationship between maximum drying rate and pressure can be rewritten in a unique linear equation. Experiments were performed in a model system to obtain a family of drying rates versus pressure curves, and in accordance with the predicted behaviour, it was observed that all maximum drying rates lay on a straight line
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| 3. |
- Elustondo, Diego, et al.
(författare)
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Mathematical modeling of moisture evaporation from foodstuffs exposed to subatmospheric pressure superheated steam
- 2001
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 49:1, s. 15-24
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a reduced expression to calculate the drying rate of foodstuffs being dried with low pressure superheated steam is developed. It is based on a theoretical drying mechanism which assumes that water removal is carried out by evaporation in a moving boundary making the vapor to flow through the dry layer built as drying proceeds. The theoretical model can be applied to any form and features dimensionless parameters to allow for the influence of form, shrinking effect and boiling point rise. To make the application easier, a simplified expression was derived, which has only two experimentally determined parameters and allows the calculation of the drying rate of a given product. Different foodstuffs were dried with this technique and the empirical parameters were calculated from the experimental data fitting equation. Interestingly, those parameters can be considered constant within the 10000-20000 Pa pressure range and the 60-90°C temperature range
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| 4. |
- Elustondo, Diego, et al.
(författare)
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New thermal conductivity probe design based on the analysis of error sources
- 2001
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Ingår i: Journal of Food Engineering. - 0260-8774 .- 1873-5770. ; 48:4, s. 325-333
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity determination by means of the thermal probe is a classical non-stationary method, suitable for foodstuffs because of the relatively short period of time and the small temperature rise required during experimental measurements. Even though its simplicity, this method has theoretical and practical implicit errors, their main sources being evaluated in this paper. The theoretical analysis shows that experimental errors can be kept within acceptable values, if the testing time period is within certain limits, out of which the errors grow quite rapidly. The error arising from the calculation of the thermal conductivity by means of an approximate equation is studied and a new way to express it is presented. Also, testing times were calculated for different probe dimensions. Finally, on the basis of two former probe which exhibits some advantages upon each other, a new probe design is proposed which recoveries those features.
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| 5. |
- Vasco, Diego A., et al.
(författare)
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Kinematic characterization of the pressure-dependent PCM impregnation process for radiata pine wood samples
- 2018
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Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 76:5, s. 1461-1469
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on the properties of Pinus radiata wood impregnated with an organic phase change material (O-PCM). The tests are aimed at characterizing the kinetics of impregnation (rates, flows, and fronts) and the thermophysical properties (thermal conductivity and specific heat). In particular, a paraffin type O-PCM (octadecane) is used to impregnate dry radiata pine wood in the tangential flow direction at four manometric pressures (0, 1, 2, and 3 bar) and constant temperature of 50 °C. The wood is sapwood from 12-year old P. radiata growing in the Bío-Bío region and dimensioned according to Chilean standard for treated wood sample extraction. The results show that it is viable to impregnate P. radiata wood with O-PCM to improve its thermophysical properties with the purpose of passive conditioning.
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| 6. |
- Ahmed, Sheikh Ali, et al.
(författare)
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Anatomical properties and process parameters affecting blister/blow formation in densified European aspen and downy birch sapwood boards by thermo-hygro-mechanical compression
- 2013
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 48:24, s. 8571-8579
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Tidskriftsartikel (refereegranskat)abstract
- Approximately, 13.5 % of the standing volume of productive forest land in Sweden is covered by birch and aspen, which provides the vast potential to produce value-added products such as densified wood. This study shows whether it is possible to densify those species with a thermo-hygro-mechanical (THM) process using heat, steam, and pressure. In this process, transverse compression on thin European aspen (Populus tremula) and downy birch (Betula pubescens) boards was performed at 200 ºC with a maximum steam pressure of 550 kPa. To obtain a theoretical 50 % compression set, the press’s maximum hydraulic pressure ranged from 1.5 to 7.3 MPa. Preliminary tests showed that ~75 % of the birch boards produced defects (blisters/blows) while only 25 % of the aspen boards did. Mainly, radial delamination associated with internal checks in intrawall and transwall fractures caused small cracks (termed blisters) while blows are characterized by relatively larger areas of delamination visible as a bumpy surface on the panel. Anatomical investigations revealed that birch was more prone to those defects than aspen. However, those defects could be minimized by increasing the pre-treatment time during the THM processing.
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| 7. |
- Ananías, Rubén A., et al.
(författare)
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Collapse of Eucalyptus nitens Wood after Drying Depending on the Radial Location Within the Stem
- 2014
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Ingår i: Drying Technology. - : Informa UK Limited. - 0737-3937 .- 1532-2300. ; 32:14, s. 1699-1705
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Ananías, Rubén A., et al.
(författare)
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Drying Schedules for Canelo Wood
- 2013
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Ingår i: Drying Technology. - : Informa UK Limited. - 0737-3937 .- 1532-2300. ; 31:3, s. 282-285
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 9. |
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| 10. |
- Ananías, Rubén A., et al.
(författare)
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Energy Consumption in Industrial Drying of Radiata Pine
- 2012
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Ingår i: Drying Technology. - : Informa UK Limited. - 0737-3937 .- 1532-2300. ; 30:7, s. 774-779
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Tidskriftsartikel (refereegranskat)abstract
- 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%.
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| 11. |
- Ananías, Rubén A., et al.
(författare)
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Kiln schedule certification for industrial drying of radiata pine
- 2013
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Ingår i: Wood and Fiber Science. - 0735-6161. ; 45:1, s. 98-104
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Tidskriftsartikel (refereegranskat)abstract
- This is a summary of a study carried out in Chile to certify industrial kiln drying of radiata pine to comply with the international phytosanitary standard ISPM 15. The drying tests were performed in 100-m3 industrial kilns located at four different sawmills of the VIII region in Chile. The objective was to develop a standard protocol to certify industrial drying of radiata pine depending on the drying schedule and wood thickness. In part, the results were used to develop a multiple regression equation that permits sawmills to select their drying schedules in such a way that the lumber can be officially stamped as both kiln-dried and heat-treated for international trade.
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| 12. |
- Ananías, Rubén A., et al.
(författare)
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Testing New In-Kiln Meter for Monitoring Lumber Moisture Content during Drying
- 2013
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Ingår i: Drying Technology. - : Informa UK Limited. - 0737-3937 .- 1532-2300. ; 31:3, s. 277-281
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 13. |
- Bajraktari, Agron, et al.
(författare)
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Weathering protection for beech wood in Kosovo
- 2013
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Ingår i: International Journal of Current Engineering and Technology. - 2277-4106. ; 3:2, s. 331-333
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Tidskriftsartikel (refereegranskat)abstract
- Beech wood (Fagus sylvatica L.) is one of the most important timber species produced in Kosovo. About 33% of the trees in our country are beech and most of the wood products are from this kind of timber. The color difference between red heart wood and white wood of the beech is significant. Adequate protection against weathering (snow, rain and low temperature) and leaching of preservative components into the environment are the main problems faced by wood companies in Kosovo as coatings defects may become apparent after only one year of outside exposure. The aim of this study was to assess the best way to protect beech wood products from weathering with available types of commercial wood coatings: film forming, non film forming, transparent stain and semi transparent penetrating stain. We concluded that the film forming and semitransparent penetrating stain are the best painting methods for beech woodproducts protection, according to weathering performance and coating properties.
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| 14. |
- Couceiro, José, et al.
(författare)
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Implementation of Computer Aided Tool for Non-Destructive X-Ray Measurement of Moisture Content Distribution in Wood
- 2015
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Ingår i: Pro Ligno. - 1841-4737 .- 2069-7430. ; 11:4, s. 330-336
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports recent attempts for implementing non-destructive measuring of moisture contentin wood based on computed tomography technology. The study focus onan image analysis method that has been already proposed and validated in the literature, but ithas not been tested for measuring low moisture content variations below fibre saturation point.The computed tomography method was tested against the oven-dry method.The results show thatit is possible to apply this technology to measure low levels of moisture content based on a regression model, where therootmean square error of the modelwas 1,4percentage points of moisture content. The method can still be improved because the density differences between samples are relatively small in relation to the experimental error and the computed tomography precision.
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| 15. |
- Elustondo, Diego, et al.
(författare)
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A method for optimizing lumber sorting before kiln-drying
- 2009
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Ingår i: Forest Products Journal. - 0015-7473. ; 59:9, s. 45-50
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Tidskriftsartikel (refereegranskat)abstract
- Drying lumber can be quite challenging when uniformity and consistency are required. Over-drying and under-drying are common causes for lower grade recovery and dimensional stability problems. It is known that both over-drying and underdrying can be reduced by sorting green lumber into different moisture content groups. Additionally, sorting also offers the opportunity to redesign drying schedules. In this study, a new methodology was designed and tested to optimize kiln-drying of lumber by implementing green sorting coupled with modified drying schedules. The methodology was applied to optimize the drying of 114 by 114 mm2 hem-fir lumber sorted with an NMI capacitance type meter. It was found that in comparison to unsorted lumber, sorting into three groups reduced the drying time by approximately 7 percent and recovered around threequarters of the under-dried lumber
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| 16. |
- Elustondo, Diego, et al.
(författare)
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Comparative analysis of three methods for stochastic lumber drying simulation
- 2005
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Ingår i: Drying Technology. - 0737-3937 .- 1532-2300. ; 23:1-2 Spec. issue, s. 131-142
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Tidskriftsartikel (refereegranskat)abstract
- 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
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| 17. |
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| 18. |
- Elustondo, Diego, et al.
(författare)
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Development of method for surface modification of wood
- 2015
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Ingår i: Proceedings of the Eighth European Conference on Wood Modification. - Helsinki : Aalto University, School of Chemical Engineering. ; , s. 137-140
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Konferensbidrag (refereegranskat)abstract
- This study concerns the development of a method for surface modification based on the hot-and-cold bath process. In the experiments the wooden boards were first heated in an oven and after that they were immediately soaked in a cold chemical solution. This procedure allowed the chemicals to penetrate partially into the wood without using pressure equipment. In this study copper, furfuryl alcohol and phenol formaldehyde based solutions were used. The impregnation resulted in modified layers below the wood surfaces representing a trade- off between the full-bulk modification and surface coating of wood. It is concluded that the method can be developed further for potential industrial use to produce e.g. flooring, cladding or decking.
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| 19. |
- Elustondo, Diego, et al.
(författare)
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Drying Western Red Cedar with Superheated Steam
- 2014
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Ingår i: Drying Technology. - : Informa UK Limited. - 0737-3937 .- 1532-2300. ; 32:5, s. 550-556
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 20. |
- Elustondo, Diego, et al.
(författare)
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Estimation of green moisture content distribution in hemfir timber by stochastic simulation
- 2004
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:4, s. 413-417
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes an improved stochastic model designed to simulate systems, such as green timbers, that cannot be analyzed as a unit but as a collection of a large number of similar components. The stochastic model provides a piecewise green moisture content frequency distribution curve by using nondestructive measurements such as of timber weight. A new, relatively simple two-parameter function was designed to describe the log-normal moisture concentration distribution above the fiber saturation point, and the parameters of this function were determined by fitting the experimental timber weights with the results of the stochastic model. The simulated green moisture content distributions showed good agreement with the experimental data for Pacific coast hemlock (hemfir) timbers, thus providing a piece of information that is indispensable for applying stochastic simulation to industrial drying of timbers.
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| 21. |
- Elustondo, Diego, et al.
(författare)
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Evaluation of three semi-empirical models for superheated steam vacuum drying of timbers
- 2003
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Ingår i: Drying Technology. - 0737-3937 .- 1532-2300. ; 21:5, s. 875-893
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 22. |
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| 23. |
- Elustondo, Diego, et al.
(författare)
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Industrial evaluation of re-dry stragegy for softwood lumber
- 2005
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Ingår i: MADERAS. - 0717-3644 .- 0718-221X. ; 7:2, s. 65-78
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an experimental evaluation of the first commercial scale dry-sort-redry (DSRD) strategy for drying of 2x4 Pacific coast hemlock (PCH) lumber. The DSRD strategy is a methodology designed to reduce final moisture content variability in kiln dried lumber by complementing conventional drying with radio frequency vacuum (RFV) drying technology. The strategy′s objective is to avoid producing over-dried lumber in conventional drying by setting the target moisture content to a value much higher than those usually used in industry. Then, RFV drying technology is implemented to quickly and efficiently re-dry the lumber that remains wet (under-dried) after the first conventional pass. Six experimental tests were performed in an industrial sawmill with the intention of studying the effect of target moisture content on the properties and quality of the dried lumber. In all cases, the first drying pass was performed in a 260m3 industrial heat-and-vent conventional kiln, and the re-drying of wets was performed in a 75m3 RFV kiln. Additionally, a mathematical model developed for prediction of data dispersion in lumber drying was calibrated with experimental data, and used to simulate the DSRD strategy under other hypothetical conditions. The results of the study demonstrate that the DSRD strategy reduces drying time, shrinkage and kiln drying degrade in comparison with a single conventional pass.
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| 24. |
- Elustondo, Diego, et al.
(författare)
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Localized wood surface modification, Part I : Method characterization
- 2017
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Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 12:1, s. 283-295
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Tidskriftsartikel (refereegranskat)abstract
- This study assesses the potential of an open process for treatment of European Scots pine (Pinus sylvestris) with chemicals that could potentially make the surfaces stronger, more dimensionally stable, or more durable, depending on the treatment solution. The method provides an intermediate solution between full volume impregnation by pressure treatment and superficial surface treatment by dipping. Figuratively speaking, the process creates the equivalent of a layer of coating applied below the wood surfaces rather than above. Two different techniques were compared, namely, heating-and-cooling (H & C) and compression-and-expansion (C & E). Taking into account that commercial suppliers recommend 0.15 to 0.25 L/m2 of coating in sawn wood and 0.1 to 0.15 L/m2 in planed wood surfaces, then this study demonstrates that the H & C method can impregnate an equivalent amount of solution under the surfaces in less than 15 min using treatment temperatures below 150 °C. © 2017 North Carolina State University.
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| 25. |
- Elustondo, Diego
(författare)
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Lumber quality model : The theory
- 2010
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Ingår i: Wood Material Science & Engineering. - : Informa UK Limited. - 1748-0272 .- 1748-0280. ; 5:3-4, s. 162-172
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Tidskriftsartikel (refereegranskat)abstract
- A new model for predicting moisture content, distortion and shrinkage distribution after lumber drying has been designed, implemented and tested. The model was implemented using Monte Carlo simulation, and it involves three empirical equations that were developed on the basis of experimental data. The model is referred as the Lumber Quality Model, and it is designed to be calibrated by knowing the initial and final moisture content, distortion and shrinkage distribution for a reference drying run. After calibration, the model can be used to predict the same information for other hypothetical drying scenarios. The present study explains the theoretical aspects of the model and the methodology for implementation. The model was validated with experimental data measured in a laboratory kiln. A full-scale industrial validation will be reported in a future paper.
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