head loss in pipe/hose???

[Blackeagle]

I need a link to charts or graphs for figureing the flow rate head loss in pipe/hose lines vs. velocity of water. I'm not having any luck with search engines, can anyone offer a link? And a source for fitings head loss?

Thanks

[Sebastian]

Try searching for Bernoulli's equation and Fluid dynamics. Sorry not to post just the equation, but there are a lot things involved in actual head loss. Unless there is a long run of pipe and it has higher roughness coefficient headloss isn't that great. Connections actually have a greater effect on headloss.

[pHaestus]

Crane Technical Paper 410. Or wait a few days on a lil writeup I am planning.

[Blackeagle]

Thanks guys, will give my searching more focus.

Look forward to your paper pHaestus.

[bigben2k]

I've got an Excel file that'll do just that, using the Hazen-Williams formulae. PM me your e-mail add.

[pHaestus]

Ooops I didnt read the first post carefully enough. Writeup (at present time) discusses fittings and connectors and impact they have on water loop. I can add a comment or two regarding the tubing choice I suppose if I can find the relevant coefficients.

Ben: If you are using a spreadsheet anyway why not use relevant Darcy eqn? Also do you have C coeff or friction factor values for silicone or tygon tubing? I haven't really dug around for such, but the book I have just has materials commonly used by civil engineers (and that didn't include any hoses).

[bigben2k]

That would be a problem: I only have a correction factor for: rusty steel pipe, new steel pipe, new copper pipe, and PVC piping. I can only guesstimate tubing as an in-between.

Darcy, Hazen-Williams... potato, potAto...

[pHaestus]

Was just thinking that the Hezen-Williams sacrifices some accuracy to be independent of diameter (if my recollection on reading up on such is correct). If going to the trouble of calculation on computer, might as well use full eqn...

Could be that my bias for Darcy is I was taught Darcy's law and am somewhat familiar with him from school.

[bigben2k]

Darcy versus Hazen-W

Hum... I'll have to give Darcy a shot!

[bigben2k]

On-line Darcy calculator

[pHaestus]

I am not personally sure how useful (in a quantitative sense) that this exercise would be (the calculator). Was just interjecting a comment about Darcy

[bigben2k]

Ok, but if the following is true... :

Note that the Manning and Hazen-Williams formulas are valid for turbulent flow only and even for turbulent flow for "reasonable" velocities. The Darcy-Weisbach equation on the other hand is valid for all types of flow. The Darcy-Weisbach roughness should give correct results for any pipe diameter or Reynolds number.

(from first link above)

...then I'd be WAY off, with Hazen.

[BillA]

I've seen roughness values ("e") for pvc and pe (and glass) - somewhere
extrapolate from the chart in #410

I have some data on 14" 90^ 'ells' from silicone hose of different dia.s, I'll try to get it written up

[bigben2k]

Thanks Bill.


Googling, and back-tracking...

"...computed using the Darcy-Weisbach friction loss equation (which utilizes the Moody friction factor). "
from http://sweb.uky.edu/~gvrajp2/jose/bpayne3.html

"Moody Friction Factor Calculator"
http://www.lmnoeng.com/moody.htm
in which:
"Calculation uses an equation that simulates the Moody Diagram"

So from
http://www.cam.org/~jacobie/faqonp~1.htm#q34
"3.5 What is the Moody diagram?"

A: A graphical representation of the Colebrook and the laminar flow equation.

and

3.8 What is the effect of pipe roughness on Friction Head?

The Colebrook equation gives the value of the friction parameter f with respect to the Reynolds number and the pipe roughness. When the Reynolds number is small, below 2,000 (laminar flow region), pipe roughness has no effect at all. When the Reynolds number is between 4,000 and 50,000, that is low velocity and/or high viscosity, then the influence of pipe roughness is as equally important as the effect of velocity. When the Reynolds number is large, above 50,000, that is high velocity and/or low viscosity, then the friction is entirely dependent on pipe roughness.


WTF am I looking at? Need coffee...

[Sebastian]

The Colebrook equation gives the value of the friction parameter f with respect to the Reynolds number and the pipe roughness. When the Reynolds number is small, below 2,000 (laminar flow region), pipe roughness has no effect at all. When the Reynolds number is between 4,000 and 50,000, that is low velocity and/or high viscosity, then the influence of pipe roughness is as equally important as the effect of velocity. When the Reynolds number is large, above 50,000, that is high velocity and/or low viscosity, then the friction is entirely dependent on pipe roughness.


WTF am I looking at? Need coffee...

hehe what I said before

[Sebastian]

When I get into work tomorrow i'll post the formulas to use. I'll see if we any detail info on rounghness numbers for that smooth of material. Tygon usually has good spec sheets.

Off the top my head, I think will take about 5-10 feet to equal the same amount as one connection.

[Blackeagle]

I didn't relize the amount or complexity of the math formulas involved.

Looking forward to your article pHaestus, hope you can translate for me.

:shrug:

[pHaestus]

Easy to get boggled down on all these equations without need. The proposed calculations in this thread are for the most part noodling by people who would rather spend time doing this than their gainful employment. I don't have the time or the will to run all the calcs; would just make a crude manometer and measure flow rate like that. Much easier to just crudely measure flow rate through the entire loop and then look back at pump's P-Q curve to determine the head that corresponds to that flow rate.

My article is more of a guide to choosing loop layout and design. Some mention of Darcy eqn and (more importantly) K coefficient for valves, elbows, and Ts. Not math heavy at all, just uses some available numbers to illustrate points.

[BillA]

just the hose, bent to 90°, no end connection/fitting

EDIT:
corrected length of hose

r = ~8", a short straight on both ends

[pHaestus]

for the 5/8" those numbers look like hell to measure...

[Sebastian]

Concerning the graphs, what is the radius of your bends?


Head loss in pipe bends:

is defined by hl=Kb[(V^2)/2g]

Kb is a function of the inverse of the bend radius versus the diameter.

I know there is a formula some where for the above, but I usually get that information from a big book of nomagraghs I have on my desk.

[pHaestus]

18" it says

your eqn is roughly same as Darcy-Weisman eqn:

hL = f(L/D)v^2/g

where f is the friction factor and L/D is the ratio of length to inside diameter.

It is not possible to calculate a friction factor from Bill's data using ONLY that eqn, because there is also a 90 degree turn so I assume you can set the eqn for calculating head loss in long bend 90 to the above eqn and then solve for friction factor. I find myself getting a bit confused by various subscripts associated with K at the moment.

For example, Crane lists K coefficients in tables as #*ft where ft is the fully turbulent friction factor but I would have expected K to = f(L/D) so if expressed as L/D then K/f would be equivalent not K*f). Gotta reread a bit...

[pHaestus]

eh just loked over it again in daytime and their K = 60f is just another way to say L/D = 60. ok carry on...

[BillA]

yea pHaestus, I know I said 14", but I meant 18"
(can't be doing this stuff at midnight !)

I pulled the pieces out (I keep everything just for these questions) and remeasured, 18" net

r = ~8"

Thanks Sebastian

[pHaestus]

so is this then enough info to estimate a friction factor for silicone hose then Bill?