Pressure drop through sand (Ergun equation?)
Pressure drop through sand (Ergun equation?)
(OP)
I’d need to estimate the pressure drop of an air stream through a cylinder of sand.
After a brief research I’ve bumped into Ergun equation (new stuff to me) and I’ve thought it could be fine for my needs.
The Ergun equation gives the pressure drop for unit length of a fluid flowing through granular media. Pressure drop depends on a series of factors such as void fraction, media particles diameter, Reynolds number, fluid density and velocity. If the fluid were a liquid I think Ergun equation would be the right way to go. Now since I’m dealing with a gas (air specifically), I was wondering if this could affect in any way Ergun equation. In particular I’m thinking of density and velocity variations due to pressure changes as air flows through the sand.
Any input from those already familiar with Ergun equation and its application would be appreciated. If by chance anyone had approached a similar problem in a different way, his/her comments would be welcome as well.
After a brief research I’ve bumped into Ergun equation (new stuff to me) and I’ve thought it could be fine for my needs.
The Ergun equation gives the pressure drop for unit length of a fluid flowing through granular media. Pressure drop depends on a series of factors such as void fraction, media particles diameter, Reynolds number, fluid density and velocity. If the fluid were a liquid I think Ergun equation would be the right way to go. Now since I’m dealing with a gas (air specifically), I was wondering if this could affect in any way Ergun equation. In particular I’m thinking of density and velocity variations due to pressure changes as air flows through the sand.
Any input from those already familiar with Ergun equation and its application would be appreciated. If by chance anyone had approached a similar problem in a different way, his/her comments would be welcome as well.





RE: Pressure drop through sand (Ergun equation?)
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RE: Pressure drop through sand (Ergun equation?)
http://www.scielo.org.za/img/revistas/jsaimm/v113n...
From memory (it's been a couple of years since those courses) there is no real great way of predicting the pressure drop without knowing specific material data for the type of sand you're using, by which you'd need to do testing to determine anyway. They really drilled into us at uni how different all material samples are, and that to work stuff like this out properly each sample needs to be tested.
Is there any kind of direct messaging function on this site? If you could somehow get me an email address I'd be happy to email a copy of my course notes, which has (one of) Erguns equations for the pressure gradient through a packed bed, in which case you might find you could knock together some kind of estimate before testing. There's an example of a test rig that has been used as well which might help. If you don't want to email thats fine, I'll dig up the rest of my notes and attach them in this thread.
RE: Pressure drop through sand (Ergun equation?)
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RE: Pressure drop through sand (Ergun equation?)
dP/L = aμV + bρV2
Easy to curve fit with just a few test runs. Try to run the tests to span the actual operating range.
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Pressure drop through sand (Ergun equation?)
Good luck,
Latexman
Technically, the glass is always full - 1/2 air and 1/2 water.
RE: Pressure drop through sand (Ergun equation?)