RK1:
I pulled out my fluid mechanics book (how I hated that class!!).....and the formula for head loss is:
head loss = K(V^2/2g)
The factor K = 1.5 for a typical 90 degree fitting and .4 for a typical 45 degree fitting.
The V^2 portion of the formula means that the head loss is proportional to the square of the velocity of the fluid through the pipe, therefore, the higher the velocity of the fluid in the pipe, the higher the head loss will be due to the fitting by the square of the velocity....
Because of this formula, I would say there is no real rule of thumb for equating types of fittings to a certain head loss in the pipe. I can tell you to use the largest diameter pipe possible when plumbing -- this will allow for the lowest velocity in the pipe which, in turn, means the lowest head losses due to friction and turbulence...
I hope this helps....I know it doesn't clear things up for you, but hopefully it will help you with the concepts.
[ April 05, 2002: Message edited by: dobish ]</p>