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Old Jul 29th 2016, 02:03 AM   #1
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Bernoulli Equation

Dear Sirs

By Bernoulli equation, and a pipe reduction from 20" to 52 mm, with an initial static internal pressure of 18 Bar, and 200 cubic metrs per hour (sea water), I found a static internal pressure in the second pipe, of -18 bar!

Is that possible?!

I have sent my data sheet attached.

Best Regards

Luis Fernando
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Old Jul 29th 2016, 02:14 AM   #2
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Try the attachment again.
Use the paperclip icon in the top toolbar.
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Old Jul 29th 2016, 02:52 AM   #3
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Bernoulli Equation

Dear Sirs

I think now the attachment has been sent.

Best Regards

Luis Fernando
Attached Files
File Type: xls Cópia de Livro1-20 in-6 in.xls (147.0 KB, 10 views)
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Old Jul 29th 2016, 03:45 AM   #4
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I agree your velocity calculations are close enough.

Using continuity I make the inlet velocity 0.2829 m/s and the pipe velocity 26.16 m/s.

But there must be some physical agent to cause this velocity, such as a pump or sloping pipe.
Both these have a term in Bernoulli that you have not included.

Include these and you will have a possible flow with sensible pressures.
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Old Jul 29th 2016, 04:11 AM   #5
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Bernoulli Equation

Thank you very mach, Studiot!

But I did not quite understood what new terms I must includ in Bernoulli, refered to pump or any other device.

Do you think it is correct to have an outlet pressure of -18 bar?!

Best Regards

Luis
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Old Jul 29th 2016, 04:59 AM   #6
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How does the water at the inlet get to be at 18 bar pressure?
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Old Jul 29th 2016, 06:04 AM   #7
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Bernoulli Equation

Dear Studiot

By means of a diesel pump.

It is a fire water system, feeded by sea water, as the instalation is an oil terminal.

Best Regards

Luis
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Old Aug 1st 2016, 04:26 AM   #8
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hydrodynamica

The increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy: (v^2)/2 + gz + p/d = const
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