1. Capillary and Cone & Plate Viscometers
Viscosity
Capillary and Cone & Plate Viscometers
Brydger Cauch
November 27, 2006

2. Importance Classifies fluid flow Motor Oil: 5W30
Newtonian or non-Newtonian
Motor Oil: 5W30
Higher Number=Thicker

3. What is viscosity? Rheology Viscosity
Deformation and flow of matter under the influence of applied stress
Viscosity, elasticity, and plasticity
Viscosity
Measure of the resistance to deformation of a fluid under shear stress

4. Overview Theory Operation of capillary and cone & plate viscometers
Shear Stress
Molecular Origins
Newtonian and non-Newtonian fluids
Operation of capillary and cone & plate viscometers
Calibrations
Parameter for Capillary Viscometer
Calibration Curve for Cone and Plate Viscometer
Viscosity of an unknown fluid
Conclusions
Questions

5. Theory

6. Shear Stress Experiment
Internal friction between layers of flow
(Wikipedia 2006)

7. Molecular Origins Gases Molecular diffusion between layers of flow
Independent of pressure
Increases with increasing temperature
Newtonian
Liquids
Additional forces between molecules but exact mechanics unknown
Independent of pressure except at very high pressure
Decrease with increasing temperature
Newtonian and non-Newtonian

8. Characterization of Fluids
Newtonian Fluid
Non-Newtonian Fluids are usually complex mixtures
(de Nevers 2005)

9. Operation of Capillary and Cone & Plate Viscometers

10. Capillary Viscometer
Select appropriate capillary size to give reasonable times
Keep constant temperature
Time fluid falling between two fiducial marks (a) and (b)
Avoid parallax

11. Brookfield Cone & Plate Viscometer
Shallow angled cone in very close proximity with a flat plate
Important features
Circulating bath to keep constant temperature
Different cone sizes
Level on the instrument
Adjusting ring
Motor speed in RPM
Operation
Adjust cup so pins barely not making contact
Measure torque needed to overcome viscous resistance

12. Calibrations

13. Calibration Capillary Viscometer
Second term neglected for sufficiently long times (>60 sec)
Fluid of known viscosity used to determine parameter B

14. Calibration
Cannon-Fenske Routine Capillary Viscometer: Size 400 with T=25°C
Brookfield Standard
Density
(g/mL)
Viscosity 25°C)
Average time (sec)
Parameter B (cP*mL/g*sec)
Fluid 100
0.974± (2)
96.6
89.84±
0.22 (1)
1.104±
0.006 (2)
Fluid 50
0.971± (2)
47.9
44.74±
0.14 (1)
1.102±
(1) Standard deviation (2) Propagated error

15. Calibration
Brookfield cone and plate viscometer with cone size CP-41 and T=28.5°C

16. Viscosity of an Unknown Fluid

17. Unknown Fluid Capillary Viscometer Accuracy: 0.7% vs ±0.2% reported
Reproducibility: 0.19% vs ±0.1%
Average Time (sec)
Density
(g/mL)
Viscosity
(cP)
89.89±0.17 (1)
0.974±0.005 (2)
96.7±0.7 (2)
(1) Standard deviation (2) Propagated error

18. Viscosity Reading (cP)
Unknown Fluid
Brookfield Cone and Plate Viscometer
Average viscosity=95.5±1.5 cP (st dev)
Accuracy: 1.6% vs ±1%
Motor speed (RPM)
Viscosity Reading (cP)
Viscosity (cP) 6
85.8
94.5 12
86.0
96.6

19. Results
Unknown fluid determined to be Brookfield Fluid 100 (μ=96.6 cP)
Capillary Viscometer (25°C)
96.7±0.7 cP
Error of 0.10%
Cone and Plate Viscometer (28.5°C)
95.5±1.5 cP
Error of 1.1%
Student’s T Test
84.4% Probability they are the same

20. Conclusions Both viscometers straightforward once set up
Capillary viscometer simpler and more accurate
Cone and plate viscometer showed a larger deviation from the known viscosity
Higher temperature creates error
Lower viscosity at a higher temperature follows the expected trend

21. Review Theory Operation of capillary and cone & plate viscometers
Calibrations
Determining the viscosity of an unknown fluid
Results
Conclusions

22. References “Viscosity.” Wikipedia. 2006. 24 August 2006.
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de Nevers, Noel. Fluid Mechanics. McGraw-Hill, New York, 2005.
Shoemaker, D.P., C.W. Garland, and J.W. Nibler. Experiments in Physical Chemistry, 6th ed. Mc-Graw-Hill, New York, 1996.
“Measuring Viscosity with a Digital Viscometer.” 21 June University of Utah. 24 August 2006.
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23. Questions?