calculating water pressure drop in cooling tower piping system
When calculating water pressure drop in chilled water pipisystem (closed circuit) we always use Hazen Williams equation as follow:-
h100ft = 0.2083 x (100 / c)^1.852 x q^1.852 / dh^4.8655
where h100ft = friction head loss in feet of water per 100 feet of pipe (ft.w/100 ft pipe)
c = Hazen-Williams roughness constant q = volume flow (gal/min)
dh = inside hydraulic diameter (inches)
but in case of calculating water pressure drop in cooling tower piping system (open circuit), shall we modify something in Hazen Williams equation or shall we use another equation?
Pump intake conditions are atmospheric pressure plus water column (consider pump NPSH to avoid cavitation).
At the end of the hydraulic circuit, you have the sprayers discharging at atmospheric pressure.
Consider also changes of temperature of the water through the pipes circuit.