geothermal chiller
 

i want to set up a geothermal chiller using a loop running tank water though it. frost line is only 32" in my area so trenching won't be a problem. i had planned on using pvc, i know the heat exchange properties of plastic are not that good, but adding more pipe underground is not a problem either. the 3 questions i have are what size pipe? how much pipe underground? and what flow rate for this loop?


frankie1

The smaller diameter the better, the longer the better, and the faster the flow the better (well more efficient if you get NRe > 2200). These things are all quite easily calculated of course, but we have to first know the heat load in your tank.

I guess I didn't realize how badly I've been missing Thermo until this morning. Glad I'm heading back for the "piled higher and Deeper" soon.

I would think that if you used the pex type tubbing they use for geothermal and radient floor heating would be the best for heat exchange and durability. Thats why they use it. The question is if they use any antimicrobial matierials in it. I wouldnt think they would.

heat load
 

not exactly sure what you mean by heat load? i have a 180 gal display tank with about 320 gal total water circulating. using 3-175 watt metal halides, 2 72" vho actinics on display 1-175 watt metal halide on the refug. 1 mag 24 for skimmer and 2- little giant te-5.5-mdq-sc pumps for return pumps. house stays around 75 degrees F. with no fan on the sump tank would go to 90 degrees.


frankie

Just a thought - I have seen some sort of product used on those home improvement shows for radiant floor heating. They run this flexable hose back and forth on the floor, cover it with wood or concrete and run hot water through it. Could have superior heat exchanging properties...

I used a geothermal loop for my 75 gal in my previous house worked great. A pipe went under the house to the backyard and buried 300 ft of 1" pvc pipe 5' deep. Had a very small PH to always cuirculate the tank water but when needed cooling, a temp contoller would start up a large PH and keep temp to 78. testing showed my tank would exceed 94 on hot days with everything running without the geo-loop. Would use it in my new house except tank is not any where near a outside wall i could use. Had to buy a 1/4 chiller. Need anymore details let me know.

i used 200 feet of black sprinkler hose.. 6 feet in the ground. i run tank water in it. lots os people say dont.. i just never turn it off.. let it run.. other than the winte.. i blow it out....

Would about 400 ft of 1/2" polyethylene work alright? I have the 1/4" already but I don’t think I could get enough volume through it and there would probably be a good deal of friction loss.

I am going to try and connect the 1/2" to the return end of my Mag 12 and control flow with a ball-valve. Hopefully since it is mainly horizontal flow and rest is being pumped 5.5ft up to the tank there will be enough pressure to drive water through it. If that doesn’t work I might have to have a dictated powerhead for it.

I don't anticipate heat being a big problem for the 110gal I'm setting up since I will be using t5's and not MH (hopefully less heat). The geothermal loop is more of a cheap backup chiller in case we lose power for extended periods of time (hurricane alley) and the house AC is offline.

What do you guys think? :strooper:

I am considering a geothermal project for my 75. I just cringe at the though of diggin the trench.

ditto

Mine should be considerably easier as I will bring home a Bobcat w/ a trencher from work:) I am laying some sprinkler lines which go right by the wall with the tank so I figured it would be an oppertune time. However I can still relate as I dug the initial 300 feet of sprinklers with a shovel and madox. What was I thinking!

When all is done, I hope to have a chiller for around $50 (price of tubing). :strooper:

One of my clients is Ditch Witch... they have offerd loaners to me, but The nedt problem becomes SAF (spousal appriciation factor). and the geothermal chille project has a very low SAF.

You just need to increase the SAF by doing something for her. Example: Sweethart, I think I'm going to install thoes sprinklers for your flowerbeds this weekend or; Sweethart I'm going to put in that fountain you always wanted. Then you just secertly put your tubing in and when she asks why its 200ft away from the house and in a ziz-zaz pattern you play dumb :strooper:

I am planning on doing a geothermal cooler for my tanks also. As for the heat load to be honest it is pretty high, I have a system of 4 tanks all with MH's over them in my on AC'd garage. In the heat of the summer the system can climb to 90 degrees if the doors are closed pretty quickly. System has aprox 250 to 300 gallons, (2 75 gallon tanks, 1 40 gallon 1 20 gallon).

I wanted to do a large loop around my yard, but now I am not sure because I relized that I have the water line, gas line, sewer line, and irrigation line going acrost my yard and I don't want to have to worry about hitting any of them. So, what would happen if I did 3 or so trenches as close to gather as I could with the trencher and lay 2 or three layers of pipe in each trench? I am guessing I could put 300 or 400 feet of pipe in the ground in an area of say 10 feet by 75 feet or so. I was planning on using either 3/4 or 1 inch poly pipe, I know it is a little thick, but it would be strong enough I would not worry about it getting broken. Also I was thinking about trying to trench down around 48 inches for the bottom of the trench then go about 3-6 inchs up to the next pipe.

Do you think this would be a large enough system to do the cooling that I need? I'm not sure yet if I want o pump tank water through the system, or do some sort of a water to water heat exchanger with just tap water in the pipes.

Kim

Kim,

It should work about the same. The earth is a fairly large heatsink and you are not really pulling that many BTUS out of the circulation water.

Bean

here is putting mine in.. brought my mini excavator over.. was lots of fun.. my dad wanted to dig so tahts what he is doing... http://i3.photobucket.com/albums/y56...nksetup037.jpg

how far apart do the pipes need to be? it seems like you would be able to stack them very close. that way you would not have to dig that much. do you just have to put it under the frost line? i guess that would be about 18" here.

Black71GP,
I have wondered about any toxicity issues with the black poly sprinkler pipe. It seems you've answered my question:D

i went 6 feet down.. i read about the black pipes and never found anything bad about leaching.. no more than any other plastics.. rubbermaid or antyhing.. so.. works to me.. i coiled a lot of them right on top of each other did like 3 2 foot coils then spaced like 6 inches then a few more and so on..

I apologize if you already read my posts in other geothermal/chiller type threads but I want to cover my basis and get as much input as I can.

If you have a well .. . why dig a ditch at all? Why not just use well water and run it through a coil in the sump?

I too am starting to consider a Geothermal Cooler. Can the pipe, which exits the house, exit the house above the ground and then go into the ground outside? Is this what others are doing or are they drilling through the floors of their houses.

I have a basement and was considering exiting through the siding (wooden area) and then going into the ground from there. I been considering runing the pump 24/7 and use the heater to raise the temp if needed.

Does this sound good?

falconut - see my post just above yours. Do you have well water or town/municipal supplied water?

Looser,
Running your well pump to circulate a small bit of water is a big waste of electricity. Well pumps are usually 3/4 hp minimum.
Better to make a coil of tubing and stuff it down your well so the tubing simply sits in the water down there. Then use a small pump to circulate the water when your tank is calling for cooling. Much easier than digging a ditch:)

Falconut,
The pipe can go through the wall, just insulate the piping for the exposed portion.
Using a heater is a waste. Just turn off the circ pump for the loop. DO NOT RUN TANK WATER THROUGH THE LOOP. You need to run freshwater through it, then run another coil of tubing in your sump.

H20ENG - Actualy its a 1HP pump. But it feeds into a air bladder tank so the pump would barely ever run on a account of circulating water through a coil in my sump. Regardless of the pump size, the energy required to move water out of the well through the coil and back to the well, would be the same as moving the water from the tank to the well and back. Maybe a little less friction running a smaller pump a lot more often but otherwise I don't think the cost would amount to much.

I see where your going, but remember that for good heat transfer you'll need at least 3/8" - 1/2" tubing. That'll drain your pressure tank fairly quick.
You could definitely test it out just to see how much heat gets removed, but if your like me, with little pumps laying around, use one of those:)