Lecture 40: Equipment, flow patterns, power requirement
Power requirement
Dimensional analysis is used to determine the power requirement. Variables are
Relatively larger viscous fluid requires high power for mixing. Similarly, high density fluid–mixture also require large power for mixing:
From Buckingham theorem, no of independent dimensionless groups can be formed. For (6+m) variables, there will be (3 + m) groups:
Power number, ,
Reynolds number, , where
is the tangential velocity of the tip of the impeller or
Froude number
The other groups are
(Power number is analogous to friction factor and equals drag force on an unit area of impeller per KE of unit-fluid-volume )
Or,
(Here, Reynolds number is based on peripheral speed and diameter of impeller)
theorem, no of independent dimensionless groups can be formed. For (6+m) variables, there will be (3 + m) groups: 
,
, where
is the tangential velocity of the tip of the impeller or 
