12 Feet Under: 1000 Square Feet of Geothermal PC Cooling

[Romir]

Excellent idea mate, nice to see you have the balls to have a go at it, all the more power to you.

Do you have any idea as to how much heat (watts) this system could support?

Anecdotal evidence but:

BTW, it turns out that the thermal flux per-linear-foot of SDR-11 HDPE pipe is almost independent of pipe diameter (at least, for 0.75", 1.00", 1.25" sizes).

Smaller diameter pipe has less surface area, but also thinner walls -- so in each case, the net heat transfer is about 7.1 BTU/hr-LinearFootOfPipe-°F (+/- 1%).

For example, my 3-ton Envision ND038 at stage2 extracts 24,000 BTU/hr from my loop's 1000 ft of in-ground pipe. That's 24 BTU/hr/LinearFootOfPipe, so the required average delta-T across the pipe wall is: 24/7.1 = 3.4°F.

If my math is OK (corrections welcome), this shows that the T.C. of (my) loop piping is only about 20% of the heat transfer picture. The other 80% is in the thermal conductivity of the grout and surrounding soil/rock.

I'll have at least 200 feet in the ground cooling which would be worth 4,800 BTU/hrs or 1406 watts at a 1 degree F delta in that guys setup. I'll have cooler, deeper soil but a higher pipe density due to overlapping the loop once. My geographical location, depth, soil types, water table, and natural water run off to this spot will be the most important factors the cooling capacity.

Xteeeeeme !

don't you think you should get 2 different coolant loops? one "dirty" going in the ground and a clean one to cool the components with heat exchanger in between ???
I know you got a filter, but anyway... gonna have oxidation problem I'd say...

but the idea's great

That was my original plan until finding this high head pump. Its still a possibility after I get the basic loop finished and test ready. I'll want to collect this single loop data for comparison purposes regardless.

All the connections will be above the ground and mostly valved so tinkering won't be a problem.

You might want to rob a movie theater to get the amount of popcorn you'll need. I suspect building this will take a while.

Getting the 1-wire system figured out and operation is going to be my biggest bottleneck. If it isn't worth strapping temperature probes to the tubes buried underground this could go a lot faster. I'm starting to convince myself the loop temperature will be so close there that it doesn't matter or the ground will throw them off. Buried in-line sensors are out of the question.

I could place only one sensor in the trench to get the loops soil temperature and only measure the HDPE pipes temperature in-line at its ends. If that's good enough, the loop could be finished in days with the sensors coming online later.

The piping coil arrived today.


The coil markings. I have two fittings to jam into the ends but need to pick up the double clamps. At this "low" pressure they shouldn't leak. Proper fusion bonded connectors for HDPE piping is quite a bit out of the budget.


The Caterpillar 325 xtreme pc project tool.


The four foot wide bucket with a cameo appear of my house in the top right. That corner is where my computers are and where the HDPE pipes will probably come up. The crawl space is several feet high on the side of the hill so working under there will be easy.