How to calculate water pressure drop in cooling tower piping system?

[HVAC Master]

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???

 

[bimr]

If your piping is an open channel, then refer to the Mannings equations.

Mannings

 

[LittleInch]

Can you sketch which bit you mean?

If it's the open vertical flow through the cooling tower then there is no pressure drop.

Is its flow in a pipe which is full of water then your equation should work.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[pierreick]

Hi,
Let you consider this document where you can find hints.
Good luck
Pierre

 

[MortenA]

@OP, you can use Hazen Williams, but remember that if you discharge elevation is different than your suction point then you will have a hydrostatic head - something that you dont (really) need to take into account in your closed loop circuit. dP=dH*9.81*den/100000 (in bar, m, kg and m³)

Best regards, Morten

--- Best regards, Morten Andersen