1. Regular Guest
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May 2010
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## Select a chiller

Hey guys,

Attached file is a sketch of chiller system.
Can anyone help on how to select the chiller?
How to apply Q=500xgpmxdeltaT
Thanks.

2. Professional Member
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not sure what you are asking but to to answer your math in Celcius Q=225,000, in degrees F, Q=400,000 you have all the info on your little sketch, but if you are looking for your tonnage it is delt t X gpm/24 and that would be 33 tons thats the best i can see from your sketch.

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I try to select suitable chiller capacity for this system.
How much btu/hr require to cool down the DI water from 29degC to 25degC.

- flowrate = 50-10=40gpm for machine usage
- delta T = 84.2-77=7.2 degC
- Q=500 x 40gpm x 7.2 F = 144,000 btu/hr. (chiller capacity)

4. The thing that isn΄t clear to me is, that you start with 50gpm at the chiller outlet and end with 10gpm on the chiller inlet. Is that correct? This would mean that you constantly drain water out of your system and replace it with fresh water (40gpm @ 34°C)? I would highly recommend a cleanable plate heat exchanger (a cooling loop like you drawn is not very efficient) fitted between the chillers cooling loop and your system to avoid excessive fouling of the chiller heatexchanger. You should add a buffer tank as well into the chiller cooling loop to guarantee a minimum run time of the compressors (estimated 20min.). You are mixing up imperial and metric units in your sketch, that is difficult because, there is a huge difference in 77°F and 77°C. The correct calculation of your cooling load in metric (SI) units is based on the following eqoutation. Cooling capacity=mass flow of the liquid to be chilled (kg/s) x specific heat capacity of the liquid (kJ/(kg*K)) x delta T (in K). Where kg=kilograms, s=second, kJ=kilo Joule, K=Kelvin. The result is the cooling capacity in kJ/s which is kW (kiloWatt). 3,517 kW=1 ton (of refrigeration). Water has a specific heat capacity of 4,18kJ/(kg*K).

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that's a DI water tank with volume=2m3. It's the DI water supply to Heat exchanger, not chiller. 40gpm is the usage of DI water at production machine.
SS chiller pipe inside the DI water tank is to cool down the DI water supply from 29degC to 25degC. Sorry for the unclear sketch.
Note:
- There is an existing chiller connect to the Heat Exchanger.
- The chiller I try so select is writing "New chiller" in the sketch.

6. If the existing chiller does the job right, just replace it by a new one with the same cooling capacity. What is your current chiller model and the chilled water setpoint?

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My advice would be to call an engineer or someone intimately familiar with eqpt selection before you put yourself in a position of having to sit in front of your boss and explain why you bought a chiller that doesn't work based on selection advice given off of an internet forum. When you have that meeting with him, you may want to be sure that the drawing that you provided for everyone to form their opinions from has disappeared.....

8. Professional Member
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Mar 2003
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i do jobs like this, and can tell you that you need more information. you are trying to cool the di water, but have two unknowns , first time, how quikly, and second how does the di heat exhanger perform? only then can you get real capacity required.

9. Regular Guest
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It's not the chiller cannot work.
Because there is an additional production machine, DI water need to cool down from 29degC to 25degC.
Basically is to add in new chiller to cool down DI water as "flange" said.