In my application I have a very long horizontal water pipe moving water at very high pressure. I want to keep the velocity low so as to reduce the viscosity/frictional losses to the pressure. But when I apply Bernoulli's(adsbygoogle = window.adsbygoogle || []).push({});

principle to the find the exit velocity, I seem to get the same high speed irregardless of the pipes diameter. Is this correct?

Here's the calculation:

Pi + 1/2(density)(Vi)^2 = Pe + 1/2(density)(Ve)^2 , where P and V are the pressure and velocity and the i and e subscripts indicate initial and exit values.

There is no height term since the pipe is horizontal.

For my application, I have Pi = 6000psi = 4*10^7Pa, Vi = 1m/s, and density of water = 1000kg/m^3. Pe is the ambient pressure of the air, Pe = 1bar = 100,000Pa . Solving this for Ve I get 282m/s . This is too high for me as a speed moving through the pipe because of the frictional losses in the pressure that would result over the long distance involved. But because water is incompressible if it is leaving the pipe at this speed it must be moving through the pipe at this speed. Note that the diameter of the pipe is immaterial.

Is this correct?

Bob Clark

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# Exit velocity of a water pipe.

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