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Journal of Rheology / Volume 43 / Issue 5

J. Rheol. 43, 1099 (1999); http://dx.doi.org/10.1122/1.551043 (18 pages)

Pressure and temperature effects in slit rheometry

Grant Hay and M. E. Mackay

Materials Characterisation and Processing Centre, Department of Chemical Engineering and The Cooperative Research Centre for International Food Manufacture and Packaging Science, The University of Queensland, Queensland 4072, Australia

K. M. Awati and Y. Park

Materials Characterisation and Processing Centre,

Department of Chemical Engineering, The University of Queensland, Queensland 4072, Australia

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We present an approximate theoretical treatment of pressure and viscous heating effects on the flow of a power law fluid through a slit die. It is assumed that the flow remains one dimensional, and the accuracy of this approximation is checked via finite element simulations of the complete momentum and energy equations. For pressures typically achieved in the laboratory it is seen that the one dimensional approximation compares well with the simulations. The model therefore offers a method of including pressure and viscous heating effects in the analysis of experiments and is used to rationalize experimentally obtained pressure profiles for the flow of polymer melts through a slit die. Data for the flow of a linear low density polyethylene and a polystyrene melt in a slit die show these two effects are significant under normal laboratory conditions. Thus, the shear stress–shear rate curves will be affected to the point of being inaccurate at high shear rates. In addition, it is found that the typical technique to correct for a pressure dependent viscosity is also inaccurate being affected by the viscous heating and heat transfer from the melt to the die. © 1999 Society of Rheology.  

© 1999 Society of Rheology

KEYWORDS and PACS

Keywords

polymer melts, rheology, confined flow, finite element analysis, viscosity, flow measurement, Pressure, effect on viscosity, Viscometry, Slit rheometry

PACS

  • 47.60.-i

    Flow phenomena in quasi-one-dimensional systems

  • 83.80.Rs

    Polymer solutions

  • 83.80.Sg

    Polymer melts

  • 47.80.-v

    Instrumentation and measurement methods in fluid dynamics

  • 66.20.-d

    Viscosity of liquids; diffusive momentum transport

  • 47.50.-d

    Non-Newtonian fluid flows

  • 02.70.Dh

    Finite-element and Galerkin methods

PUBLICATION DATA

ISSN

0148-6055 (print)  

Publisher

Society of Rheology

RELATED DATABASES

Web of Science

View this record in Web of Science

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ARTICLE DATA

History
Received 18 May 98
Revised 02 Jun 99
Digital Object Identifier
http://dx.doi.org/10.1122/1.551043

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