Water / pond cooling loop for 25T chiller.

[bkmcclarty]

Good day all,
I am currently installing a 25 ton chiller in a cogen facility, and am planning on placing the cooling loop in a large settling pond we have on the front of the property. I am having a hard time sizing the cooling coils, as I find little information on what length per ton of cooling loop I need. I have found a bit for direct burial, on the order of 600' to 800' cooling coil length per ton, but little on submersed cooling.

Does anyone out there have any ideas, or tips?

Thanks in advamce.

 

[willard3]

It is possible to model the heat transfer with information from pipe manufacturers or from ASHRAE.

You are designing your own heat exhanger and it is numerically complicated, but a Heat Transfer textbook will get you there.

Or you can call a heat exchanger manufacturer and see if he can model it. Check his answer carefully.

 

[TBP]

I'm curious - why would a heat exchanger manufacturer be interested in providing free engineering for somebody who isn't interested in buying his product? If bkmcclarty has the capability to "check his (the HX manufacturer) answer carefully", why wouldn't he just do the calculations in the first place?

Just wondering...

 

[MintJulep]

Finite bodies of water are not infinite heat sinks.

 

[Montemayor]

bkmcclarty:

I believe what MintJulep is pointing out is that you are suggesting what is considered an un-steady state heat transfer that is limited to the static heat sink that the pond of water represents. You can't continue to use the pond as a heat sink indefinitely since you're not making up the heat pickup with cooling through vaporization of the water - so the cooling effect will only last to the extent of the pond's size. Hopefully it's more like a Lake, instead of like a pond.

For a submerged pipe with refrigerant inside the pipe, use a "U" of approximately 75 Btu/ft^2-hr-oF for design purposes. I can assure you that this value will work. But with the water temperature increasing, I don't know for how long.

I wouldn't do it this way.

 

[bkmcclarty]

Thanks for the feedback to all,

I had my doubts about this approach, and after consulting a geothermal designer, I was presented with the facts on the performance of this. There is insufficient water quantity for the load I have. My first choice was a simple dedicated cooling tower, but the owner here prefers to experiment, not always considering factual data. I will present the facts at the next facility meeting, and hopefully win over hearts and minds.

Thanks again.

 

[TBP]

I worked in a plant where there was a decorative pond/fountain that also doubled as the fire water reservoir, and cooling water for some equipment. The spray did allow for sufficient cooling of the pond water. What is also noteworthy, is that since this was nice warm water, exposed to the sun - wow - did we have algae or what? We were basically looking after a large outdoor swimming pool. We went through a lot of bromine in the summer months.