Vacuum

[gatz]

Is there a way to estimate cfm through an opening
vs (peak?) hp rating on a vacuum ?
For instance, a 4.5 peak hp shop vacuum connected via a standard 2" hose to a chamber that has a 6" opening at one end.
How is this measured?

The hp rating on a vacuum is theoretical at best (and most likely exaggerated); is there any other way to rate it?

Are there any charts or Excel templates that might cover this subject?
Thanks,
Gatz

 

[MintJulep]

Short answer, no.

 

[RossABQ]

I think you can get a decent ESTIMATE of CFM using pretty much standard flow equations, but not with the shortcut methods used for pressurized air flows. You've got a dP, a known area, but you'll have to make assumptions for hose friction. I'm not sure why you say HP ratings are "theoretical"; vacuums are a fan and have P-V curves like any other. If you are truly dealing with a ShopVac and not a commercial blower, I can imagine the curve isn't "pretty".

I have done some piping work on process vacuum systems and a rigorous analysis of pressure drops and flows in a system gets pretty complicated.

 

[MintJulep]

You could MEASURE the flow reasonably easily.

Some water, a length of clear hose, a shoe box, tape and some card board would be all you need.

 

[MintJulep]

Thinking further, I don't think you would need the card board.