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Anonymous Poster

Cooling Tower Pump and Submergence Level

02/25/2009 12:48 AM

Hello,

I have a cooling Tower basin of 1.7m Ht and a axial split cooling water pump.Note that the pump is located below the tank and the outlet from the tank is located sideways.

The reqd flowrate is 15300 US GPM.

Consider Center line of the pump as datum/ref line.

Let H1 be the ht from the datum till level of the water inside tank = 1.78m.

Let H2 be the ht from the datum till the centerline of the tank outlet nozzle = 1.06m.

Now applying bernoullis thm, we get velocity at the tank outlet nozzle as 3.75 m/s and this is very high considering that suction of the pump should be maintained with 1.8 m/s velocity.

Now what should be the submergence level i.e H1?

Thanks
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Anonymous Poster
#1

Re: Submergence

02/25/2009 2:23 AM

Can't Help you on the calculation I am afraid.

But if you want to use a totally environment friendly treatment for hard water scale prevention in your cooling tower you might consider our Colloid-A-Tron product. Simple to install, simple to use . Clients include Kelloggs, Ford, Coca Cola and many thousands more;

This is the link: http://www.treatwater.com/colloid1.html
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The Prof
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Engineering Fields - Mechanical Engineering - New Member Hobbies - CNC - New Member

Join Date: Aug 2006
Location: Western Australia
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#2

Re: Submergence

02/25/2009 3:15 AM

I am confused, how will the level affect the velocity in the suction pipe?

Reduce flow or increase pipe diameter will work, but the level will have no effect.

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Codemaster
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Join Date: Jul 2005
Location: Stoke-on-Trent, UK
Posts: 4496
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#3

Re: Submergence

02/25/2009 4:46 AM

Hello Guest

Shouldn't be a problem if you design it right. Depending on the suction pipe details, at 3.75m/s the ΔP is likely to be ~ 3m (you need to do the calcs to be sure). So NPSH available is ~ 1.78 + 10 - 3 = 8.78m. This should be more than enough for the pump. If not try another pump!

But I make pipe dia 24" OD. This is pretty big compared with 0.72m from pipe C/L to water surface. You need to be careful to avoid vortexing etc. Bellmouth exit with vortex breaker would improve things.

Cheers......Codey

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