Mixer Impeller Speed & Particle Velocity Discussion

[thegeant]

I would like to ask question and open a discussion about the relation between the impeller speed (RPM) of a mixer and particles velocity (bubbles). Thanks

 

[CWatters]

If you think of an impeller/propeller as being like a wood screw screwed into some wood then you can calculate how far it should move for each revolution. From that and the rpm you can work out how fast it should move through the material...or how fast the material should move through it.

The above give a rough estimate of the maximium speed that an impeller/propeller can move material, however it could be less than that due to "slip".

If you think of a propeller blade as being like a wing then without slip the pitch of the blades would have zero angle of attack relative to the material they are moving through. Wings are generally more efficient at a slightly positive angle of attack.

I'm sure there are people out there who know more then me but that's my take on the issues.

 

[Bobbywhy]

I would like to ask question and open a discussion about the relation between the impeller speed (RPM) of a mixer and particles velocity (bubbles). Thanks

thegeant, Welcome to Physics Forums!

Will you please be more specific? Are you referring to gas bubbles induced by cavitation of the impeller blades? Or are you referring to gas bubbles entrained from the surroundings by the impeller? The hydrodynamics literature normally contains studies of the terminal velocity of rising bubbles. Is this what you are asking about?

Cheers,
Bobbywhy