High-frequency electric current for drying of wood - historical perspectives
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| Format: | Artículo científico |
| Sprache: | en |
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Universidad del Bío Bío
2006
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| _version_ | 1876436424603992064 |
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| author | Helmuth Resch |
| author_facet | Helmuth Resch |
| contents | High-frequency electric current for drying of wood - historical perspectives Helmuth Resch Agrociencias Hf current Wood drying Among the many interesting topics in the field of Wood Science and Technology is a fascinatingstory 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 frequencycurrent depending on its dielectric properties. Because wood is generally heterogeneous, these propertiesvary not only with the frequency of the current and the field orientation, but also with the moisturecontent, temperature, and density of wood. Considering these parameters and the specific heat of thematerial, estimates of power absorption can be made.In an attempt to develop this technology, research covered many products from paper and veneer tolumber and heavy timbers. Much emphasis, however, has been placed on wood species and/or productswith 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 transferoften to solidly stacked timbers, very high drying rates, and avoidance of various drying defects includingany significant case-hardening and oxidative discoloration of the wood.During the last two decades, the development focused mainly on drying lumber in vacuum kilnsusing dielectric heating, often termed high-frequency/vacuum drying. It has been justified economicallyon the basis of increased throughput and higher quality. Existing industrial installations provide a positivepicture 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, thecombination of high-frequency/vacuum drying with other systems, such as moisture leveling after primarydrying or pre-heating prior to the high-frequency/vacuum step, hold promise for further technicalimprovement. 2006 artículo científico 0717-3644 https://www.redalyc.org/articulo.oa?id=48580201 en http://www.redalyc.org/revista.oa?id=485 Maderas. Ciencia y Tecnología application/pdf Universidad del Bío Bío Maderas. Ciencia y Tecnología (Chile) Num.2 Vol.8 |
| format | Artículo científico |
| id | redalyc_48580201 |
| institution | Redalyc |
| language | en |
| publishDate | 2006 |
| publisher | Universidad del Bío Bío |
| spellingShingle | High-frequency electric current for drying of wood - historical perspectives Helmuth Resch Agrociencias Hf current Wood drying High-frequency electric current for drying of wood - historical perspectives Helmuth Resch Agrociencias Hf current Wood drying Among the many interesting topics in the field of Wood Science and Technology is a fascinatingstory 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 frequencycurrent depending on its dielectric properties. Because wood is generally heterogeneous, these propertiesvary not only with the frequency of the current and the field orientation, but also with the moisturecontent, temperature, and density of wood. Considering these parameters and the specific heat of thematerial, estimates of power absorption can be made.In an attempt to develop this technology, research covered many products from paper and veneer tolumber and heavy timbers. Much emphasis, however, has been placed on wood species and/or productswith 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 transferoften to solidly stacked timbers, very high drying rates, and avoidance of various drying defects includingany significant case-hardening and oxidative discoloration of the wood.During the last two decades, the development focused mainly on drying lumber in vacuum kilnsusing dielectric heating, often termed high-frequency/vacuum drying. It has been justified economicallyon the basis of increased throughput and higher quality. Existing industrial installations provide a positivepicture 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, thecombination of high-frequency/vacuum drying with other systems, such as moisture leveling after primarydrying or pre-heating prior to the high-frequency/vacuum step, hold promise for further technicalimprovement. 2006 artículo científico 0717-3644 https://www.redalyc.org/articulo.oa?id=48580201 en http://www.redalyc.org/revista.oa?id=485 Maderas. Ciencia y Tecnología application/pdf Universidad del Bío Bío Maderas. Ciencia y Tecnología (Chile) Num.2 Vol.8 |
| title | High-frequency electric current for drying of wood - historical perspectives |
| topic | Agrociencias Hf current Wood drying |
| url | https://www.redalyc.org/articulo.oa?id=48580201 |