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Q: pipeing flow loss ( Answered 5 out of 5 stars,   1 Comment )
Subject: pipeing flow loss
Category: Miscellaneous
Asked by: hutch03-ga
List Price: $2.00
Posted: 04 Aug 2005 06:35 PDT
Expires: 03 Sep 2005 06:35 PDT
Question ID: 551594
formula for estimating flow loss in pipeing installations due to
fittings such as elbows
Subject: Re: pipeing flow loss
Answered By: landog-ga on 04 Aug 2005 08:37 PDT
Rated:5 out of 5 stars
Thanks for the question.
I believe you are looking for something utilizing The Darcy equation/law.
"Darcy's Law is a phenomologically derived constituative equation that
describes the flow of a fluid through a porous medium (typically water
through an aquifer). The law was formulated by Henry Darcy based on
the results of 1855 and 1856 experiments on the flow of water through
beds of sand. It, along with the conservation of mass, comprises the
groundwater flow equation, which is one the basic building
relationships of hydrogeology."

This equation may help you:

hL = f(L/D)v2/2g

hL  -  pressure
f   -  friction factor 
L/D -  the ratio of pipe length to internal diameter
v   -  velocity of flow 
g   -  the acceleration of gravity

Fittings and valves & bends also affect the pressure drop.  The above
equation  requires a modification:

hL =K v2/2g

K is the resistance coefficient, which is defined as the number of
velocity heads (or pressure) lost due to the valve or fitting.  If
desired, one can relate this resistance coefficient to equivalent pipe
length by using the Darcy equation:

K = f(L/D) 

f is the friction factor and L and D are the length and diameter of
the pipe, in feet.

Fitting			K coefficient
90 degree Mitre(elbow)	  60f
90 degree Sweep	          30f
45 degree sweep		  10f

More details can be found here:

Crane Technical Paper No. 410 (TP-410) is the ultimate guide to
understanding the flow of fluid through valves, pipe and fittings,
assisting you to select the correct equipment for your piping system:

A very nice document that details other factors that affect flow rates
through pipes (velocity, friction, viscosity and  density:
hutch03-ga rated this answer:5 out of 5 stars
Wow that was fast,the equation or law that you quoted apears to be
over my head but I may be able to muddle through thanks

Subject: Re: pipeing flow loss
From: landog-ga on 04 Aug 2005 10:28 PDT
Please let me know if you need help.

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