Pressure drop and dirty tubing

gone_fishin · 11-12-2002, 04:47 PM

A quote from the study page,

"If all other variables are held constant, the pressure drop is proportional to 1/D5. This means that the
pressure drop at a given flow rate is very sensitive to the diameter. A diameter chance in our tube of 1/100
in. (at the limit of our measurability) would increase the pressure drop by about 14%." end quote

read the pdf here

This should be a factor in keeping a rad as clean as possible. Any more comments, I thought this could make an interesting discussion.

bigben2k · 11-12-2002, 05:02 PM

(re-post)

The surface roughness adds to the flow restriction, as per this formula:

f=0.2083 (100 / C) ^ 1.812 * (Q^1.852 / d^4.8655)

Where
f = friction loss per 100 feet in feet of water
C=roughness coefficient (Hazen-Williams factor)
Q=flow rate (gpm)
d=inside diameter of pipe (inches)

Source: http://www.ppfahome.org/pdf/pvcpipewaterspec.pdf

For PVC piping, a value of 150 is used for C. A steel pipe would have a C value of about 100, and a rusty one about 80.

[addition]
Smooth copper piping is calculated with a value of 140.

bigben2k · 11-12-2002, 05:42 PM

Well, I didn't mean to stop the conversation!

Dirty tubing will reduce flow. We could compare say, a 120 gph rig, with 1/2 inch ID tubing, using a factor of 150 (clean) and a factor of 80 (~dirty).

11-12-2002, 04:47 PM	#1
gone_fishin Cooling Savant Join Date: May 2002 Location: Da UP Posts: 517	Pressure drop and dirty tubing A quote from the study page, "If all other variables are held constant, the pressure drop is proportional to 1/D5. This means that the pressure drop at a given flow rate is very sensitive to the diameter. A diameter chance in our tube of 1/100 in. (at the limit of our measurability) would increase the pressure drop by about 14%." end quote read the pdf here This should be a factor in keeping a rad as clean as possible. Any more comments, I thought this could make an interesting discussion.

11-12-2002, 05:02 PM	#2
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	(re-post) The surface roughness adds to the flow restriction, as per this formula: f=0.2083 (100 / C) ^ 1.812 * (Q^1.852 / d^4.8655) Where f = friction loss per 100 feet in feet of water C=roughness coefficient (Hazen-Williams factor) Q=flow rate (gpm) d=inside diameter of pipe (inches) Source: http://www.ppfahome.org/pdf/pvcpipewaterspec.pdf For PVC piping, a value of 150 is used for C. A steel pipe would have a C value of about 100, and a rusty one about 80. [addition] Smooth copper piping is calculated with a value of 140. __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

11-12-2002, 05:42 PM	#3
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	Well, I didn't mean to stop the conversation! Dirty tubing will reduce flow. We could compare say, a 120 gph rig, with 1/2 inch ID tubing, using a factor of 150 (clean) and a factor of 80 (~dirty). __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

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