Eductor/Diffuser sizing

[johnta]

I am an EE working on a project that needs a small eductor pump. I understand the basic theory from Air Ejectors and eductor pumps for jet fuel tanks; however I have not been able to locate a ratioing formula for the effect that the length of the diffueser has on the suction force applied to the entrained fluid. Is there a text or technical paper that provides a ratio, or am I stuck writing bernoulli equations?

Terry Johnson EE

 

[katmar]

As far as I am aware the length of the diffuser is determined empirically, rather than by analysis. You can determine the area ratio by energy and momentum analysis, but even there you would apply an empirical correction or efficiency factor.

It is very difficult to design an eductor from first principles. It is best left to the suppliers of proprietary devices. An estimate of the size can be made from the nomograph in Perry's Chemical Engineers Handbook.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[mechprocess]

I use Schutte & Koerting

Eductors

Go here and you can get your data sheets. Most of the sizing is vendor specifide. Just tell em what you want.

http://www.s-k.com/