Otter said:
I never have been able to make heads or tails out of the equations in that article.
Number of velocity heads?
i'll try to explain this to you.
Head loss in the energy equation is defined by
((k1+k2+k3+kn...)+f(L/d))*v^2/2g
Friction factor f which is determined using Ks/d, reynolds number, and a moody diagram. You can probably search and find a good tutorial on this somewhere.
K is a factor of restriction for a 90° Miter bend it is 1.1 without vanes or .2 with internal vanes.
For swept bends it bcomes a factor of the bend radius divided by the diameter of the pipe.
For fittings they are considered constants for each general type of fittings.
L/d is the length of piping divided by the diameter of the piping.
V^2/2g is called your velocity head. It is your velocity(ussualy dtm from flow rate) divided by 2*your gravitional accleration constant (32.2 Ft/s)
That V^2 /2g is almost nothing at 2gpm though so I would be much more worried about WB restrictions rather than 90° bends personally.
Also I repeat my question whats so bad about having a 90° fitting right before you inlet. It should only be as bad as a 90° fitting anywhere else.
I don't think the DDC with a modded top is a good reason though becuase under restriction you have barely any higher flow rate with a modded top VS the stock top(about .1 GPM) and that could be attributed to the modded tops being 1/2" rather than anything I can think of.