ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The exit flow from a capillary is analyzed with the help of macroscopic mechanical energy and momentum balances. The analysis shows that primary normal stress differences cannot be determined from the exit pressures under the assumption that the flow is viscometric down to the exit. This assumption and the second one (made by Han [9]) that both slit and capillary exit pressures are the same would lead to unacceptable results. Published exit pressure data for polyethylene melts are shown to be unreliable because of large hole-pressure errors in the pressure measurements. Pressure profiles obtained with a thin tube technique for the flow of a poly(isobutylene) solution indicate that the flow does not remain fully developed near the exit. Moreover, it is shown that for this polymer solution the excess viscous dissipation at the exit contributes to approximately 90 percent of the exit pressure.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760251105
