Prediction of temperature profiles in twin screw extruders

Ibrahim O. Mohamed, Robert Y. Ofoli

Research output: Contribution to journalArticle

  • 4 Citations

Abstract

A model incorporating viscous dissipation effects and a heat transfer coefficient based on the Brinkman and Graetz numbers is presented for predicting the temperature profiles of non-Newtonian food doughs in a twin-screw extruder, assuming uniform product temperatures in the direction normal to the screw shafts. Experimental measurements were obtained to evaluate the model for three screw configurations: 30° forwarding paddles (30F), feed (two-start or double-flighted) screws and single-start (single-flighted or single-lead) screws. Model predictions were well within engineering accuracy for 30F paddles and feed screws under all experimental conditions. Predictions for single-start screws were inaccurate, with deviations of up to 50%. In general, results indicate that the one-dimensional energy equation is sufficient for heat transfer analysis of extruder sections configured with mixing paddles and feed screws, particularly at high flow rates, high RPM, or combinations of the two variables. However, the level of mixing provided by single-start screws over the RPM and flow rates used in this study does not justify the assumption of uniform temperatures in the transverse direction. For these screws, at least a two-dimensional formulation of the energy equation must be used.

LanguageEnglish (US)
Pages145-164
Number of pages20
JournalJournal of Food Engineering
Volume12
Issue number2
DOIs
StatePublished - 1990

Profile

extruders
screws
temperature profiles
Temperature
prediction
Hot Temperature
Food
heat transfer coefficient
energy
heat transfer
Direction compound
dough
engineering
temperature

ASJC Scopus subject areas

  • Food Science

Cite this

Prediction of temperature profiles in twin screw extruders. / Mohamed, Ibrahim O.; Ofoli, Robert Y.

In: Journal of Food Engineering, Vol. 12, No. 2, 1990, p. 145-164.

Research output: Contribution to journalArticle

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abstract = "A model incorporating viscous dissipation effects and a heat transfer coefficient based on the Brinkman and Graetz numbers is presented for predicting the temperature profiles of non-Newtonian food doughs in a twin-screw extruder, assuming uniform product temperatures in the direction normal to the screw shafts. Experimental measurements were obtained to evaluate the model for three screw configurations: 30° forwarding paddles (30F), feed (two-start or double-flighted) screws and single-start (single-flighted or single-lead) screws. Model predictions were well within engineering accuracy for 30F paddles and feed screws under all experimental conditions. Predictions for single-start screws were inaccurate, with deviations of up to 50{\%}. In general, results indicate that the one-dimensional energy equation is sufficient for heat transfer analysis of extruder sections configured with mixing paddles and feed screws, particularly at high flow rates, high RPM, or combinations of the two variables. However, the level of mixing provided by single-start screws over the RPM and flow rates used in this study does not justify the assumption of uniform temperatures in the transverse direction. For these screws, at least a two-dimensional formulation of the energy equation must be used.",
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