# Gas flow through a 90 deg Elbow

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 June 29, 2004, 16:08 Gas flow through a 90 deg Elbow #1 Novice Guest   Posts: n/a I am a mechanical engineer, who does flow calculations occasionally. I have been asked to estimate the loss of pressure of a gas flowing through a 90 deg. elbow. Is there any ready formala for doing this, and is there any references somebody can help me. Thanks a lot for your assistance.

 June 29, 2004, 19:59 Re: Gas flow through a 90 deg Elbow #2 abhi Guest   Posts: n/a The Diffrence Between pressure inlet and pressure outlet will be total pressure loss.

 June 29, 2004, 21:12 Re: Gas flow through a 90 deg Elbow #3 Novice Guest   Posts: n/a My problem is I only know the inlet pressure, and may not have an oppurtunity to plug a pressure gauge after the outlet. I have to predict the pressure loss before the equipment is built. Any input is greatly appreciated.

 June 30, 2004, 07:36 Re: Gas flow through a 90 deg Elbow #4 Tim Guest   Posts: n/a Hi yes you can use an approximate loss coefficient approach. The pressure head loss (h) can be approximated as... h = (k*u*u)/(2g) as h = dp/(rho*g) you can re-arrange to get dp = k. 0.5*rho*u*u I assume you know or can calculate the density and average flow velocity. The value of k can be found listed in tables for differend bends/valve/etc. a 90 degree elbow has a k coefficient of 0.9 i.e. loss of pressure = 0.9 * dynamic pressure dp = 0.9 * 0.5* density * velocity squared This is described fully in the book 'mechanics of fluids' by B.S. Massey . ISBN 0-412-34280-4 alternatively you can calculate the friction factor from a moody chart and use a l/d approximation to find the pressure loss hf = f . (l/d) (vel squared/2g) Darcy weisbach equation try http://www.engineering.uiowa.edu/~fl...Chapter_10.pdf Good luck Tim,

 June 30, 2004, 10:43 Re: Gas flow through a 90 deg Elbow #5 Novice Guest   Posts: n/a Tim, Thanks a lot, appreciate your help.

 July 4, 2004, 08:29 Re: Gas flow through a 90 deg Elbow #6 James Date Guest   Posts: n/a Have a look in: Fluid Flow - Internal Flow Systems 2nd Edition by D.S. Miller This has pretty much everything you need to know about doing pipe flow calculations. Regards James

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