frictional loss calculations

From: <adolphus.o.omodu@exxonmobil.com>
Date: Mon Jan 05 2004 - 02:29:00 EST

Hi kamil,

Flow is always accompanied by friction. This friction results in a loss of energy available for work. A general equation of pressure drop due to friction is the Darcy-Weisbach (often called simply Darcy's equation or formula ).This equation is expresed in meters of fluid as:

h(subscript: L) = f(subscript: m)LV(superscript: 2)/2gD

Where ;

h(subscript: L) = frictional head loss

L = Pipe length
V = Velocity of the fluid under consideration
D = Internal diameter of pipe

f(subscript: m) = The moody friction factor which is expressed as ( f (subscript: m) = 4.0f(subscript: f)) where f(subscript: f) is the fanning friction factor.
g = The accelaration due to gravity

The Darcy-Weisbach equation is valid for both laminar and turbulent flows of any liquid, and may also be applied for gases with certain restrictions. When using this equation, changes in elevation, velocity, and density must be accounted for by applying Bernoullis's theorem. The Darcy-Weisbach equation must be applied to line segments sufficiently short such that fluid density is essentially constant over that segment.

Adolphus O Omodu
Projects Department/Design Engg.
Exxonmobil
E-mail: adolphus.o.omodu@exxonmobil.com
Telephone: 234(01)-2621640 Ext. 2524
Telephone: 1-713-431-8500 Ext. 2524

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Received on Mon Jan 05 02:29:00 2004