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Melting in single screw extruders models, calculations, screw design
Melting in single screw extruders : models, calculations, screw design, by
H.E.H. Meijer,
PhD. Thesis, 1980,Enschede : Technische Hogeschool Twente
Advisors: J.F.Ingen Housz,
Abstract
In this work three main aspects are distinguished. The theory of melting is represented by an evaluation of various models which have been proposed over the years. The models of Tadmor and Lindt are recognised as two extremes, intermediates between these two are possible. All improvements reported in literature are based on Tadmor's model. As a further improvement the in- fluence of convective heat transport in the upper layer of this model is taken into account and investigated. The original Lindt model is extended to include a non linear viscosity and convection in the meltlayers and inside the solid bed. The relation between channel tapering, solid bed velocity and calculated down channel pressure gradient is investigated as well as the influence of the heating of the solids on calculated melting lengt! hs.
The second aspect is encountered in calculations comparing the different screw designs which have been proposed to increase melting capacity: compression and multichannel screws, screws by Maillefer, Barr, Dray & Lawrence and Kim. The comparison is mainly based on analytical calculations and only the important screws are compared on the basis of a more elaborate numerical calculation.
The third part contains the calculation, design, testing and development of a new screw concept which is superior in theory and practice to all others, at least when combined with a cooled, grooved feed section.
These three aspects are not contained in distinct parts. A different division into chapters has been preferred. After the introduction and a description of the assumptions, which have to be made, all aspects of the melting process are treated in a comprehensive, analytical approach. Thereafter a numerical treatment is given. Finally the results of exp! eriments are presented and a discussion follows.
