Power number 2

[Vishal Kumar]

Hello all ,
Power number of commonly used agitator are available in literature
Please help me out to understand how to calculate the power number for an agitator with more than one stage with different combinations of PBT,hydrofoil,anchor with each other etc.
Data (number of stages, imp stage dia , etc) will be available with me but the procedure is not known to me.

 

[Latexman]

The conservative approach is calculate the power draw for each impeller independent of others, and sum the power draw of all.

There are correlations that correct for close proximity which will reduce power draw due to interference.

Good Luck,
Latexman

 

[Vishal Kumar]

Thanks for quick revert , if possible please share me reference link to the correlation although I will also try googling about it.

 

[pierreick]

Hi,
Try to find a copy of FMP 028, design guide for Impeller Power Numbers. This is a document published in April 1987.

https://www.eng-tips.com/viewthread.cfm?qid=498704

FMP stands for fluid mixing processes.

https://fmp.framatomebhr.com/

Pierre

 

[geesaman.d]

As Latexman correctly pointed out, each impeller is a power consumer. When used in most arrangements, each one consumes power independently. FMP is a good resource for impeller behavior.

The power draw should follow published power numbers provided that:
1) You are mixing product in the turbulent regime
2) You aren't attempting to crank through a settled bed of solids
3) Your vessel is properly baffled
4) Your lowest impeller is appropriately spaced off-bottom for its intended flow pattern.
5) You aren't gassing under the impeller (thus lowering local density)
6) Your mixing product is Newtonian