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Material parameters of suspended wood fibre networks: II. Measurements
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
(engelsk)Manuskript (Annet vitenskapelig)
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-5214OAI: oai:DiVA.org:kth-5214DiVA, id: diva2:8032
Merknad
QC 20100901Tilgjengelig fra: 2005-05-31 Laget: 2005-05-31 Sist oppdatert: 2022-06-23bibliografisk kontrollert
Inngår i avhandling
1. Fibre flow mechanisms
Åpne denne publikasjonen i ny fane eller vindu >>Fibre flow mechanisms
2005 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The flow behaviour, and primarily the floc-floc interaction, of pulp paper suspensions have been studied visually. Analogy models based on these observations have been developed as well as the identification of important parameters of floc break-up in low shear rate flow fields. Floc compressions and the locations of voids (areas of lower fibre concentration) where found to influence the floc splitting mechanism. Based on this investigation an equipment for measuring the load carrying ability of fibre flocs and networks was designed, and the effect of measurement geometry, network structure and fibre suspension concentration was investigated. The load carrying ability with concentration increases rapidly when going from 1% to 2% in initial suspension concentration.

A model handling the fibre floc behaviour during extension and compression has been developed, and some basic flocculated flow mechanisms are discussed on an analogy basis. A modified Voigt element is use, describing mainly the compressional behaviour and plastic behaviour of loose fibre network structures. Further the pos- sibility of stress chain formation is discussed on a fibre level as well as on a floc level.

The effect of fibre flow (shear field) occurring in the forming zone of a roll former has been studied in detail. Basic forming mechanisms on floc scale has been investi- gated, and the effect of running parameters like dewatering pressure and jet-to-wire speed difference as well as the fibre type and concentration of the pulp suspension has been evaluated. It is evident that floc elongation increases with shear rate (jet-to-wire speed difference) and lower dewatering rate. The latter is because the fibre floc is subjected to the shear field longer due to slower immobilisation. Shorter fibre tends to create weaker networks, which promotes a higher elongation of the flocs.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2005. s. 15
Serie
Trita-FPT-Report, ISSN 1652-2443 ; 2006:17
Emneord
Fibre flow, floc, shear, compression, fibre network, stress chain
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-240 (URN)
Disputas
2005-06-17, Hörsal D2, Kungliga Tekniska Högskolan, Lindstedtsvägen 5, Stockholm, 14:00
Opponent
Veileder
Merknad
QC 20100901Tilgjengelig fra: 2005-05-31 Laget: 2005-05-31 Sist oppdatert: 2022-06-23bibliografisk kontrollert

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