quantity of chilled water required?

[gladstone]

hi friends ,
how can calculate quantity of chilled water required for 102 ton cooling coil capacity ?rules of thumb ,articles and equations will be appressiate.
thanks for all.

[icemeister]

Btu/hr = 500 x GPM x DT

DT = Delta T or T(out) - T(in)
1 Ton = 12000 Btu/hr

[triton99]

Make sure that you install either a circuit setter or an autoflow control valve to balance the chilled water flow through the coil.

[rupert]

one method you can use assuming a 10 degree temp drop through the chiller is 2.4gallons per min per ton of cooling and 3.0 gallons per min per ton through your condenser if it is water cooled.

[ceng]

if you are asking the volumn of the system, the rule of thumb of controlling the chiller is 3gallon/ton. McQuay has very detailed formular you can use.

[triton99]

Normally the 3 GPM/ton is for the condenser water. The formula above by icemeister is correct. Q=500 x GPM x DT

[gladstone]

hi friends
thank u very much for your help.

[ceng]

triton99: if gladstone is asking the flow rate, it is 3 gpm/ton,what I said 3 gallon/ton is for column. YOu have to have enough volumn in a chilled water system for the chiller control function properly.

[gladstone]

hi friends
i need more clarification 2 gpm/ton for what :cooling coil capacity in the A.H.U or for chiller evaporator i am sorry i am new in hvac
thanks for all

[triton99]

Ceng, my bad. I should have read closer. I agree that you have to have enough volume in the system. I had a design years ago when I was starting out and the air-cooled chiller kept short cycling. I contacted Trane and they pointed out to me in their catalog under applications, they have a section that talks about it. Their technical support said with the new microprocessors they need at least a one minute loop time for the system to stabilize or it would short cycle. They preferred more, but that was the minimum.

Gladstone: The 3 gpm/ton rule of thumb is for sizing the flowrates through the condensers of water cooled chillers. The calculation for chilled water flow is Q=500 x GPM x DT.

[triton99]

Gladstone: The formula Q=500 x GPM x DT is for chilled water through chillers or coils.

EXAMPLE:
Size chilled water flowrate for 40ton chiller

Q=500 x GPM x DT

(40 ton)(12,000 BTU/Hr)=500 x GPM x (54 - 44 Deg. F)
GPM = 96

Hope this helps!!

[gladstone]

thank u triton for your help now it is clear so am i correct for this sequence to size chiller?
calculating calculating load in ton for given space -size A.H.U in ton of cooling capacity using psychmetric chart-calculate flow rate for cooling coil as equation u give me.
now how size chiller -flow rate and circulating pumps?
thanks for every one help

[thor7000]

Gladstone, if you are having so many problems sizing the system, wouldn't it be to your customers benefit to have it properly designed by an engineer???

[thor7000]

I thought you should design based on 6 GPM per ton for water volume within the system??

If it is an open circuit with a cooling tower I would think 3 GPM would be a little low due to evaporation ect.

Please correct me if I am wrong!!

[rupert]

3 galls per min per ton would be enough due to a makeup water supply keeping the volume of water constant in the cooling tower sump, as it is being evaporated in cooling the condenser water.

[triton99]

I know Trane has always used 3 GPM/ton for condenser water. I think I read a post on this site a while back where manufacturers and engineers are starting to look at other flowrates for the condenser water. I remember not long ago when they wanted constant flow for the evaporator and now variable chilled water flow is common with all manufacturers.

[rupert]

the trane website engineers newsletter archive has some very interesting articles on variable flow rates in chilled water systems.

[coviepresb1647]

Normally the 3 GPM/ton is for the condenser water. The formula above by icemeister is correct. Q=500 x GPM x DT

What is the reference/citation for that formula?