hi Steve McKenzie !
thanks alot about your answer!!!!!!
do you know that (k) is absolute roughness or hydrolic roughness because there
is some different between absolute roughness and hydrolic roughness.
best regards.
babak rad.
Steve McKenzie wrote:Hi babak rad
If you are talking about the friction factor, I normally use the Swamee Jain Equation:
f = 0.25/(log(k/(3.7*d)+5.74/(Re^0.9))^2
k is surface roughness in mm
d is pipe internal diameter in mm
Re is Reynolds number
and f is of course the friction factor as used in the Darcy equation Hf=
f*L/d*(V^2)/(2*g)
I find the Swamee Jain equation easier to use than the Colebrook White equation because no iteration is necessary.
For surface roughness, k, you will find these in books.
For starters, the standard ISO 5167-1 Appendix E gives some, a few of which are:
Brass, copper, aluminium, plastics, glass, new seamless cold drawn steel
pipe: k<0.03mm
Other new steel pipe: k= 0.05 to 0.1mm
Rusty steel pipe: k= 0.1 - 0.3mm
Encrusted steel pipe: 0.5 - 2 mm and upwards for heavy deposits
Galvanized pipe: 0.13mm
New Cast Iron: 0.25mm
etc
If you search the web, you are sure to find more. There appears to be more "roughness" information for the civil engineering head loss formulae such as the Hazen William and Chezy equations. With a little patience you can work backwards to calculate k from the coefficients that these equations use.
cheers
Steve Mckenzie
-----Original Message-----
From: Jacques Chaurette [mailto:jchaurette@fluidedesign.com]
Sent: Saturday, September 07, 2002 12:16 AM
To: <a href="/group/PipingDesign/post?postID=JZQkPtAqyEaAh68T6dAX8aAUXhmJE9N-nOC3RlUF-Od7osJz83GhSw3NWhGoFu5sNPMwE1K858d786SlrGBqTFt_CAE">PipingDesign@yahoogroups.com</a>
Subject: Re: [PipingDesign] hydrolic roughness
You cannnot calculate roughness, this is something that must be measured.
Jacques
Jacques Chaurette
Fluide Design Inc.
<a href="http://www.fluidedesign.com">http://www.fluidedesign.com</a>
tel (514) 484-PUMP (7867)
fax (514) 484-2294
----- Original Message -----
From: BABAK RAD
To: <a href="/group/PipingDesign/post?postID=JZQkPtAqyEaAh68T6dAX8aAUXhmJE9N-nOC3RlUF-Od7osJz83GhSw3NWhGoFu5sNPMwE1K858d786SlrGBqTFt_CAE">PipingDesign@yahoogroups.com</a>
Sent: Friday, September 06, 2002 1:56 AM
Subject: [PipingDesign] hydrolic roughness
hi!
i want to know that how can i calculate hydrolic roughness in a circular pipes?
best regards.
babak rad.
[Non-text portions of this message have been removed]
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