Resistance coefficient for pipe fittings 1

[KZ001]

I need to determine a resistance coefficient for pipe fittings. The data I found in the web shows different values for resistance coefficient (K). What is the best source providing the most accurate data? Sending a link would be very helpful. Also, do PVC fittings and Steel fittings have different resistance coefficient? If so, then the friction losses in PVC pipe and Steel pipe would be different. Is that correct? Finally, does resistance coefficient depend on pipe schedule? Thank you!

 

[rconner]

Actual head loss through any particular fitting is dependent on a great many parameters. Included are the actual internal cross-sectional diameter and many different aspects of configuration of the fitting (e.g. is it a tee, bend etc., and if it is a bend or tee etc. what is the specific geometry of same, including bend radii and laying length etc?), characteristics of the flow contact surface (very small effects here), and also any actual effects of transition in the application (e.g. expansion/contraction, differences in internal diameter etc.) between the mainline pipe and fitting (incl. joints etc.)
All that being said, I believe in general there may be little practical effect of even many minor variations of fitting styles, as actual head losses through common fittings are typically quite small numbers, and of course differences between very small numbers are even smaller numbers. Tables of minor loss coefficients have been available for many decades in many references, and I suspect due to their survival most of these coefficients have probably proven adequate for most design purposes (see e.g. contemporary reference

http://www.haestad.com/library/books/awdm/online/wwhelp/wwhimpl/java/html/wwhelp.htm

in “Section 2.5 Minor Losses”).
If you have interest in even more depth, you may also wish to check fitting manufacturers with specific questions, some of whom I know have made some detailed calculations and also ran some tests over the years (of specific configurations) for various purposes.