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Impact of radio frequency heating pre-treatment on the kiln drying characteristics of sub-alpine fir

Einfluss einer Vorbehandlung mittels Hochfrequenzerhitzung auf den Verlauf der technischen Trocknung von Tannenholz

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Abstract

This study examined the impact of dielectric heating at radio frequencies (RF) as a pre-treatment on the kiln drying characteristics and end-quality of sub-alpine fir that is difficult to dry due to significant amount of wet pockets. Five plus a control group of 51×102 mm sub-alpine fir were RF heated at fixed power density (72 kW/m3), to the same core temperature (100°C) and at five time spans (15, 60, 75, 90, and 120 minutes) before conventional kiln drying was carried out. Air permeability tests were also performed on selected specimens. Results showed relatively higher permeability in almost all treatments. Drying rates above and below the fiber saturation point increased by 18–30% and 21–55%, respectively. All treatments resulted in improved lumber moisture gradients after kiln drying.

Zusammenfassung

Untersucht wurde in dieser Studie der Einfluss einer Vorbehandlung mittels Hochfrequenzerhitzung auf den Verlauf der technischen Trocknung und die Qualität des getrockneten Tannenholzes, das aufgrund hoher Nasskernanteile als schwierig zu trocknen gilt. Vor Durchführung der technischen Trocknung wurden fünf von sechs Gruppen (außer einer Kontrollgruppe) von Tannenschnittholz mit den Abmessungen 51×102 mm2 bei konstanter Leistungsdichte (72 kW/m3) mittels Hochfrequenz auf dieselbe Kerntemperatur (100°C) erhitzt. Diese wurde über fünf Zeitspannen (15, 60, 75, 90 und 120 Minuten) beibehalten. Des Weiteren wurden an ausgewählten Prüfkörpern Luftdurchlässigkeitsprüfungen durchgeführt. Die Ergebnisse ergaben bei nahezu allen Behandlungen eine relativ höhere Durchlässigkeit. Die Trocknungsgeschwindigkeiten über und unter Fasersättigung nahmen um 18–30 % bzw. 21–55 % zu. Alle Behandlungen ergaben nach der technischen Trocknung eine Verbesserung der Feuchtegradienten im Schnittholz.

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Authors and Affiliations

  1. Department of Wood Science, University of British Columbia, Vancouver, BC, Canada

    Alhassan Abubakari & Stavros Avramidis

  2. Forintek Division, FP Innovations, Vancouver, BC, Canada

    Luiz C. Oliveira

Authors
  1. Alhassan Abubakari
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  2. Stavros Avramidis
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  3. Luiz C. Oliveira
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Correspondence to Stavros Avramidis.

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Abubakari, A., Avramidis, S. & Oliveira, L.C. Impact of radio frequency heating pre-treatment on the kiln drying characteristics of sub-alpine fir. Eur. J. Wood Prod. 70, 245–251 (2012). https://doi.org/10.1007/s00107-011-0546-y

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  • DOI: https://doi.org/10.1007/s00107-011-0546-y

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