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The influence of power‐law rheology on flow distribution in coathanger manifolds
Author(s) -
Reid J. D.,
Campanella O. H.,
Corvalan C. M.,
Okos M. R.
Publication year - 2003
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.10057
Subject(s) - flow (mathematics) , manifold (fluid mechanics) , rheology , function (biology) , materials science , index (typography) , power law , mechanics , distribution (mathematics) , mathematics , thermodynamics , mathematical analysis , physics , mechanical engineering , computer science , statistics , composite material , engineering , evolutionary biology , world wide web , biology
Coathanger dies are effective in delivering uniform flow if a polymer melt; however, when the fluid flow index varies from the design values, the flow is not uniform. Although mechanisms such as die lip adjustments have been effective tools for adjusting flow profiles, the issue of a variable flow index has not been fully addressed at the design stage. An analytical solution, based on the assumptions present in the 1‐D design equation, has been developed for the flow distribution in a coathanger manifold. This solution determines the flow distribution for a power‐law fluid with a flow index n * in a manifold designed for a separate flow index n *. From this solution, a uniformity index and a critical design angle are defined. The critical design angle is the angle at which the local derivative of the uniformity index with respect to n * approaches a maximum (for n * < n ) or a minimum (for n * > n ) as a function of the design angle. The critical design angle is independent of n and is presented as a function of the manifold aspect ratio.