Rheometry SLIT RHEOMETER
Rheometry SLIT RHEOMETER
Rheometry SLIT RHEOMETER
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<strong>Rheometry</strong><br />
<strong>SLIT</strong> <strong>RHEOMETER</strong><br />
NON-NEWTONIAN CASE<br />
Correction for the real wall shear rate is analogous to the Rabinowitch<br />
correction.<br />
( ) ( )<br />
6Q 2 + β<br />
Wall Shear Rate ˙γ w =<br />
(8-34a)<br />
h 2 w 3<br />
β = d [log(6Q/h2 w)]<br />
d [log(σ w )]<br />
(8-34b)<br />
Apparent Viscosity<br />
η = σ w<br />
= −∆P<br />
˙γ w L<br />
h 3 w<br />
4Q(2 + β)<br />
NORMAL STRESS DIFFERENCE<br />
The normal stress difference N 1 can be determined from the exit pressure<br />
P e .<br />
( ) dPe<br />
N 1 ( ˙γ w ) = P e + σ w (8-45)<br />
dσ w<br />
(<br />
N 1 ( ˙γ w ) = P e 1 + d(log P )<br />
e)<br />
(8-46)<br />
d(log σ w )<br />
These relations were calculated assuming straight parallel streamlines<br />
right up to the exit of the die. This assumption is not found to be valid<br />
in either experiment or computer simulation.
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