The second lecture in the module Particle Technology, delivered to second year students who have already studied basic fluid mechanics. Dilute particle systems is mainly about sedimentation of single particles and dilute suspensions. The Particle Reynolds number determines the degree of turbulence in the fluid and techniques are provided for settling in laminar and turbulent systems. Industrial clarification is included.

1. Dilute Particulate Systems Chapter 5 in Fundamentals Watch this lecture at http://www.vimeo.com/10200970 Visit http://www.midlandit.co.uk/particletechnology.htm for further resources. Professor Richard Holdich R.G.Holdich@Lboro.ac.uk

3. Stokes’s settling equation

4. Particle Reynolds number

5. Drag coefficient/Friction factor plot

6. what to do when Re'>0.2

7. (Heywood tables)

9. Discovered in his bath?

12. The centrifugal force is:where r is radial position and omega is the angular speed (s-1).

14. Mainly applicable to small particles (less than 10 microns) is gases

17. Significant with particles 1 micron in diameter and less.

19. Stokes’s settling equation The Stokes settling equation: Stokes law valid for no inertia present AND a low concentration/single particle. Note that bigger particles settle faster - Galileo and that tower in Pisa?

22. Often assessed by the Zeta potential

24. Particle Reynolds number

25. Drag coefficient/Friction factor plot

26. What to do when Re'>0.2 Drag force = RAp cf Friction factor: shear stress over density and velocity2 Weight = Drag force =

27. What to do when Re'>0.2 Drag force = RAp Weight = Drag force = …check that this reduces to Stokes law in laminar region.

29. Above can be used to give settling velocity =f(diameter) or vice-versa.

31. Stokes’s settling equation

32. Particle Reynolds number

33. Drag coefficient/Friction factor plot

34. what to do when Re'>0.2

35. (Heywood tables)

37. Industrial Clarification - long tube test

39. Stokes’s settling equation

40. Particle Reynolds number

41. Drag coefficient/Friction factor plot

42. what to do when Re'>0.2