Pressure Drop in Tubes

Pressure Drop in Tubes
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Posted by: NC ^®

01/11/2006, 15:55:10

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Can someone help me verify the following:

I'm trying to get some basic numbers on an oil cooler. If tube dimensions, flow, and pressure drop across tube(s) are given, can I assume laminar incompressible flow situation if Reynold number is less than 2300? How do I find a friction factor without using Moody Chart? How is pressure drop related to temperature (we got various pressure data when varying temperatures)? What I'm trying to get is to estimate a friction factor that accounts for the turbulators inside each tube, similar to a big fudge factor. Can it be done non-empirically? If yes, what is the basic starting principle/formula? Or is this a turbulent flow problem?

P.S. I'm using h(head loss) = f(L/d)(v^2)/2g

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Re: Pressure Drop in Tubes

Re: Pressure Drop in Tubes -- NC Post Reply Top of thread Forum

Posted by: zekeman ^®

01/12/2006, 09:13:46

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If the Reynold's number is less than 2000, then you can use the Hagen-Poiseuille law for fully developed laminer flow in circular pipes,namely
f=64/N. However, you must be sure that it is under 2000.; otherwise you must note that there is a transition period from 2000- 3000 where it is wildly different.
Temperature changes affect pressure drop only inthat the viscosity changes with it and it appears in the denominator of the Reynolds equation.

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