CHEMICAL ENGINEERING

FLOW IN PIPES AND CHANNELS 47

PROBLEM 3.34

Data obtained with a cone and plate viscometer, cone half-angle 89°cone radius 50 mm,
were:

cone speed (Hz) measured torque (Nm)

0.1 4. 6 ð 10 ^1

0.5 7 ð 10 ^1

11.0

53.4

10 6.4

50 3. 0 ð 10

Suggest a suitable model to describe thefluid properties.

r 0

r 0

r

r

dr

θ

ω

Figure 3f. Cone and plate viscometer

Solution

A cone and plate viscometer, such as the Ferranti–Shirley or the Weissenberg instru-
ments, shears afluid sample in the small angle (usually 4°or less) between aflat surface
and a rotating cone whose apex just touches the surface. Figure 3f illustrates one such
arrangement. This geometry has the advantage that the shear rate is everywhere uniform
and equal toω/sin 4 , since the local cone velocity isωrand the separation between the