HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES

Among the many interesting topics in the field of Wood Science and Technology is a fascinating story about research and development on drying wood products with high-frequency electric current. Historically, it can be traced back over decades. Heat transfer to and evaporation of moisture from wood m...

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Autor principal:	Resch,Helmuth
Lenguaje:	English
Publicado:	Universidad del Bío-Bío 2006
Materias:	Wood drying Hf-current
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2006000200001
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spelling	oai:scielo:S0718-221X20060002000012006-09-11HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVESResch,Helmuth Wood drying Hf-current Among the many interesting topics in the field of Wood Science and Technology is a fascinating story about research and development on drying wood products with high-frequency electric current. Historically, it can be traced back over decades. Heat transfer to and evaporation of moisture from wood may be accomplished with high frequency current depending on its dielectric properties. Because wood is generally heterogeneous, these properties vary not only with the frequency of the current and the field orientation, but also with the moisture content, temperature, and density of wood. Considering these parameters and the specific heat of the material, estimates of power absorption can be made. In an attempt to develop this technology, research covered many products from paper and veneer to lumber and heavy timbers. Much emphasis, however, has been placed on wood species and/or products with larger dimensions that are difficult or impossible to dry when using conventional drying methods. The advantages of employing dielectric heating were found to be rapid and fairly uniform heat transfer often to solidly stacked timbers, very high drying rates, and avoidance of various drying defects including any significant case-hardening and oxidative discoloration of the wood. During the last two decades, the development focused mainly on drying lumber in vacuum kilns using dielectric heating, often termed high-frequency/vacuum drying. It has been justified economically on the basis of increased throughput and higher quality. Existing industrial installations provide a positive picture for higher value products. The economics should improve with advances in available equipment, better basic understanding and more practical experience with industrial units now operating. Also, the combination of high-frequency/vacuum drying with other systems, such as moisture leveling after primary drying or pre-heating prior to the high-frequency/vacuum step, hold promise for further technical improvementinfo:eu-repo/semantics/openAccessUniversidad del Bío-BíoMaderas. Ciencia y tecnología v.8 n.2 20062006-01-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2006000200001en10.4067/S0718-221X2006000200001
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Wood drying Hf-current
spellingShingle	Wood drying Hf-current Resch,Helmuth HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES
description	Among the many interesting topics in the field of Wood Science and Technology is a fascinating story about research and development on drying wood products with high-frequency electric current. Historically, it can be traced back over decades. Heat transfer to and evaporation of moisture from wood may be accomplished with high frequency current depending on its dielectric properties. Because wood is generally heterogeneous, these properties vary not only with the frequency of the current and the field orientation, but also with the moisture content, temperature, and density of wood. Considering these parameters and the specific heat of the material, estimates of power absorption can be made. In an attempt to develop this technology, research covered many products from paper and veneer to lumber and heavy timbers. Much emphasis, however, has been placed on wood species and/or products with larger dimensions that are difficult or impossible to dry when using conventional drying methods. The advantages of employing dielectric heating were found to be rapid and fairly uniform heat transfer often to solidly stacked timbers, very high drying rates, and avoidance of various drying defects including any significant case-hardening and oxidative discoloration of the wood. During the last two decades, the development focused mainly on drying lumber in vacuum kilns using dielectric heating, often termed high-frequency/vacuum drying. It has been justified economically on the basis of increased throughput and higher quality. Existing industrial installations provide a positive picture for higher value products. The economics should improve with advances in available equipment, better basic understanding and more practical experience with industrial units now operating. Also, the combination of high-frequency/vacuum drying with other systems, such as moisture leveling after primary drying or pre-heating prior to the high-frequency/vacuum step, hold promise for further technical improvement
author	Resch,Helmuth
author_facet	Resch,Helmuth
author_sort	Resch,Helmuth
title	HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES
title_short	HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES
title_full	HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES
title_fullStr	HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES
title_full_unstemmed	HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES
title_sort	high-frequency electric current for drying of wood - historical perspectives
publisher	Universidad del Bío-Bío
publishDate	2006
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-221X2006000200001
work_keys_str_mv	AT reschhelmuth highfrequencyelectriccurrentfordryingofwoodhistoricalperspectives
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HIGH-FREQUENCY ELECTRIC CURRENT FOR DRYING OF WOOD - HISTORICAL PERSPECTIVES

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