Pressure loss pipe fittings during a laminary flow

[Yobbo]

Hi,
I have got the following question. With turbulent flow fittings have got an almost constant loss factor. It can be found in the literature and internet. Now I am confronted with the question to calculate pressure loss over a fitting with laminary flow. I know that turbulent flow results in a quadratic function ( dP = K*1/2*rho*v^2 ). This goes for the piping itself and the fittings. With laminary flow though the relationship between pressure loss and flow velocity is linear. I assume that the fittings in this case will also behave as a linear resistance. Where can I find the bygoing constants?

 

[SNORGY]

I would just take f=64/Re, use Darcy-Wiesbach and call it a day.

Regards,

SNORGY.

 

[katmar]

If you search here for the 2-K and 3-K methods by Hooper and Darby respectively you will find what you need. You are correct that while the K factors for fittings can be regarded as constant for turbulent flow with reasonable accuracy, the K factors are very different for laminar flow. However, the equivalent length values (i.e. L_e/D) obtained for fittings in turbulent flow can be used for laminar flow. Using L_e/D values will generally estimate slightly higher pressure drops than the 2-K and 3-K methods.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[Latexman]

K factors of fittings in laminar flow usually take the form of a constant divided by the Reynolds number, i.e. K = A/N_Re. The slower the flow the larger the K.

Good luck,
Latexman

 

[ione]

As already pointed out by Katmar the 2-K (Hooper) and 3-K (Darby) methods are what you are looking for.

You can find useful info at the link below (table 7-3 at page 210 is useful)

http://books.google.it/books?id=hoX...&resnum=4&ved=0CDEQ6AEwAw#v=onepage&q&f=false

 

[Yobbo]

L.S.,

Thank you for your swift reactions to my questions. I will dig in deeper along the suggestions being made.