Need to cool water flow from 160 deg F to 60 deg F - kicking around ideas

[BronYrAur]

Hi all,

I am looking for ideas on the best way to cool water from 160 deg F to 60 deg F. I have been asked to look at a situation that currently uses city water in a once-through system to cool a process. The water is then dumped. I'm trying to think of a closed-loop way to do it and thereby save the water dumping. This process water cools a machine that makes sterile water. I don't think they would want glycol in the process water, so I am probably looking at a heat exchanger no matter what. On the other side, I will obviously need a chiller, but I could incorporate a fluid cooler when ambient permits. Project is near Chicago. I don't think there is a need to recover the heat; they just want to get rid of it.

Given that I need a 100 deg F delta-T, I am guessing that I should incorporate a storage tank to give me some volume/dilution capabilities. The process in intermittent, which further complicates things. I am told that roughly 1,880 gallons per hour of water is used, but again not continuously. So, I don't know a GPM. Maybe figure 1/2 time on and 1/2 time off until I know more, so that would give about 62 GPM.

Anyone have experience with large delta-T like this?

 

[IRstuff]

You will need to get a better grip on the instantaneous flow, since that's what will drive your cooling requirement.

Regardless, your numbers say 460kW average heat transfer required, or 131 tons of cooling, which is non-trivial

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[MedicineEng]

Can you reuse this water in other processes in the plant that are not temperature sensitive or actual require hot water?
Do you have any other process in your plant that rejects cold that you could use as a primary fluid for the heat exchanger?

 

[MintJulep]

In Chicago a fluid-to-air cooler could do all of the job much of the year, and part of the job the rest of the year.

But as IRstuff has already stated, and as you know I'm sure, you need to completely define what "the job" is.

Is there a chiller operating already for other processes? Maybe there is excess cooling capacity available.

 

[goutam_freelance]

You can have two stage cooling. In first stage only water (with glycol if required) is used in close circuit with a cooling tower. In winter this cooling may be adequate. In second stage you may have a chiller in the circuit, activated by temperature signal from first stage outlet. The second stage may be activated in summer. The second stage may be bypassed during winter to save pumping power. See the scheme below(additional details need to be added):

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[DrRTU]

A plate and frame heat exchanger coupled with a hot well / cold well on the cooling side with chiller is the most common way to do this. The cold well side is cooled via fluid cooler or tower as the tower sump can be dry when located indoors. Indoor sump will eliminate PG/EG as the cool source. A split air cooled or water cooled chiller will be the cool source to bring the water down during high ambient In Chicago, we have numerous reps that will help with the plate and frame sizing and material selection. The key will be the water volume selection of your cooling source. Large intermittent demand can be buffered by holding tanks this will work like a thermal capacitor.

 

[SAK9]

Economical heat exchanger design does not permit such large Delta Ts