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To PI or not to PI
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Leslie Chaim
Ranch Hand
Joined: May 22, 2002
Posts: 336
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You had a 10" water line that broke down. Unfortunately, there's only 1" pipe available for replacement.
How many 1" pipes is needed (and why/how) to replace the one 10"?
Cheers,
Leslie
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Normal is in the eye of the beholder
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Sonny Pondrom
Ranch Hand
Joined: Jun 05, 2001
Posts: 128
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Does a 10" line have an inside diameter of 10 inches?
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Arjun Shastry
Ranch Hand
Joined: Mar 13, 2003
Posts: 1861
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100
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MH
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fred rosenberger
lowercase baba
Bartender
Joined: Oct 02, 2003
Posts: 10043
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100. assuming that the flow isn't restricted by surface area of the pipe...
a 10" (i'm assuming this is the inside diameter) pipe has an area of PI * r^2. if our diam. is 10, our radius is 5. so the 10" pipe has a cross-section area of 25PI.
Each 1" pipe has a radius of 1/2", or an area of (1/4)PI. so, we need 100 pipes.
However, the first pipe has a surface area equal to 10PI (times the length, which we can ignore). the 100 pipes have a surface area of 100PI.
I am not a fluids engineer, but i would imagine that more surface area would result in more friction, slowing down the flow, but i have no idea how to calculate that.
[ July 02, 2004: Message edited by: fred rosenberger ]
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Never ascribe to malice that which can be adequately explained by stupidity.
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Arjun Shastry
Ranch Hand
Joined: Mar 13, 2003
Posts: 1861
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Yes, I think so.Factor that determines is I think Reynold's numebr.Ratio of inertial force to viscous force.Bigger pipe will have more intertia.
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SJ Adnams
Ranch Hand
Joined: Sep 28, 2001
Posts: 925
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I think Poiseuille's Law applies here.
which means that the flow is proportional to r^4
which means 100million 1" tubes!! 
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SJ Adnams
Ranch Hand
Joined: Sep 28, 2001
Posts: 925
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strike that - 10,000 is the answer
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subject: To PI or not to PI
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