Viscous dissipation in die flows

Howard W. Cox, Chris Macosko

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

The flow of polymer melts in cylindrical, annular, and slit dies has been examined. Large temperature rises at the outer surface of the extrudate were measured with an infrared pyrometer. Calculations show that severe radial temperature gradients exist in these flow geometries under conditions similar to those encontered in polymer processing and in viscometry measurements. A common method of estimating the average temperature rise from the total mechanical energy input seriously underestimates the maximum temperature rise. A numerical solution of the flow and energy equations models the flow in all three geometries. A very simple Nusselt number correlation allowed an estimate of the temperature rises possible if heat transfer with the die wall occurrs. Good agreement was obtained between predicted and infrared measured melt surface temperature rises. The pressure drop gives only an indication that nonisothermal flow is occuring and is not sensitive enough to distinguish the type of heat transfer boundary condition present. The mathematical model presented could be helpful in die design and in process modeling, allowing the designer to obtain some knowledge of the kind of flow situations which might be encountered.

Original languageEnglish (US)
Pages (from-to)785-795
Number of pages11
JournalAICHE Journal
Volume20
Issue number4
DOIs
StatePublished - Jan 1 1974

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Temperature
Polymers
Heat transfer
Infrared radiation
Pyrometers
Hot Temperature
Geometry
Polymer melts
Viscosity measurement
Nusselt number
Thermal gradients
Pressure drop
Boundary conditions
Mathematical models
Theoretical Models
Pressure
Processing

Cite this

Viscous dissipation in die flows. / Cox, Howard W.; Macosko, Chris.

In: AICHE Journal, Vol. 20, No. 4, 01.01.1974, p. 785-795.

Research output: Contribution to journalArticle

Cox, HW & Macosko, C 1974, 'Viscous dissipation in die flows' AICHE Journal, vol. 20, no. 4, pp. 785-795. https://doi.org/10.1002/aic.690200421
Cox, Howard W. ; Macosko, Chris. / Viscous dissipation in die flows. In: AICHE Journal. 1974 ; Vol. 20, No. 4. pp. 785-795.
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