diy idea for a cooling loop

[sharkdude]

http://reefcentral.com/gallery/data/500/637Resize_of_Rotation_of_cooling_loop.jpg

my house is built with a crawl space underneath with about 2-3 feet of clearance. It stays quite cool under there, even in the summer. The general idea is to bury a type of closed loop in the hopes that this would provide some cooling effects to the main tanks during the summer.
I think I could do this with just the main return pump with two valved inputs from the sump. This way I could either draw straight from the sump or send some quantity of water through the loop at a slower rate and hopefully achieve some cooling. When the summer heat is over, I could drain the line and close off the valves. Gravity would work to equalize the levels between input to the cooling loop and the intake to the pump, so I would not be sucking water against significant head pressure as you might expect. kind of like a closed loop application.

Main problem I see is not enough capacity in the cooling loop. A total of 100 feet of thin wall 1 inch pvc gives only about a 4 gallon capacity ( pi x radius squared x length of pipe in inches / 231 cu in per gal).

difficult to estimate how much cooling as variable of length of pipe, temp differnetial of ground, efficiency in heat transfer of pvc, rate of water flow, etc.

what do you guys think? am I nuts or possibly on to something that may work?

maybe a buried and sealed larger reservoir? or thin vinyl tubing in many feet coils?
bury it as deep as possible like 3-5 feet?

I want to keep any pumps or valves easily accessible and not under neath the house, nor do I want to add any additional pumps to conserve electricity.

I am hoping to achieve an approximate 5 degrees F cooling on my estimated 150 gal water volume system during peak summer heat waves.

comments appreciated.

[MayoBoy]

I don't think that you're going to get much heat exchange with PVC. You need to use stainless or titanium. By the time you pay for that, you probably could have bought a chiller.

BTW, here's a handy calculator for pipe volume http://www.csiontheweb.com/reference.htm

[jrhupp]

I agree with MayoBoy that PVC is not your best option. But stainless or titanium are not a nescessity. Many people have simply buried sevral hundred feet of black ABS irrigation line in their back yards for use as a geothermal chiller. Though, you should consider isolating your coolling loop from your tank water. My suggestion would be a two stage design, where you cool a resivour with the coolling loop and then have a heat exchanger in the resivour with tank water circulating through it. While it is a little less efficent, you isolate your tank water from issues associated with running water through sevral hundred feet of line buried in your back yard. The earth is a really big heatsink, so with a properly design system I think you should have no problem dropping your tank temp 5 degrees.

Jay

[WarDaddy]

Do a search for thermal cooling, I think. there are lots of people looking at it. Some do wells down to the water table below 100 ft, and then plumb a closed loop. with the well loop going to a titanium heat exchanger in the sump. It works good, but you have to have 100's of feet of plumbing...

[H20ENG]

Hi Sharkdude,
It can only help. I'd use the black coiled tubing for sprinklers. 3/4 to 1" at least. You may want to run several circuits to keep the overall resistance low, BUT you need a good flowrate through the tubing to get good heat transfer.
Youd also want to plumb the return from the loop as a "reverse return" so the flow stays equal in all circuits.

I always advise against running tank water through a loop, for many reasons (overcooling, stagnant water when off, etc). You can simply coil more tubing in a sump or barrelas an exchanger.

I have the same crawlspace, and would like to utilize it somehow. Its just a pain to get to....

Do a good search on geothermal chillers here. Good insight from guys like Cuby2K, Cseeton, and several other sharp guys. I'm just a flunkie:lol:

[DocApoc]

PEX tubing is used to do Hydronic heating, so it clearly conducts heat well. I have no idea if it's better than PVC or ABS, just something to look into.

[eameres]

hmmnn... now you guys got me thinking. If the passive cooling of my basement sump alone isn't enough, maybe I'll run a pex coil into the sump off the big barrel of top off water I'm planning on having in my basement as well. It should be at a constant temp of around 65deg.

[douggiestyle]

http://reefcentral.com/forums/showthread.php?s=&threadid=817756

this was a good debate. plenty of good ideas.

[sharkdude]

thanks for the link douggie. reading in progress.

when they talk about pumping water through a loop, do they pump into the loop, or do they use a pump to draw through the loop?

[exoticaquatix]

i have heard that if you dont spread your pipes out far enough you can heat the ground to the point your ground loop will stop working. any truth to this?
-nick

[exoticaquatix]

let me elaborate, that was kinda vague......i heard it will stop working for a long time even after being shut off. do you need to get close to the water table to dissapate the heat more quickly? if so ill be looking for houses in a low lying area.
-nick

[BeanAnimal]

<a href=showthread.php?s=&postid=8363940#post8363940 target=_blank>Originally posted</a> by DocApoc
PEX tubing is used to do Hydronic heating, so it clearly conducts heat well. I have no idea if it's better than PVC or ABS, just something to look into.

That is not really a valid statement. Pex tubing is used becuase it is durable and easy to work with. It does not really conduct heat that well at all.... If you use copper for hydronic heating you have to worry about it reacting with the embedding mortar. You have to worry abour corrosion, blockage, bending it, leaks at joints etc. Pex is just SO MUCH easier to install and maintain (at least thus far, as they said the same thing about polybutylene until it started failing 10 years down the road).

Bean

[CoolUsername]

The other thing to worry about (not that you don't have enought already) is the heat added by the pump to run the geothermal cooler. Pumps add heat to the water. Partly because the pump gets warm from the electricity running through it and the small friction of parts, but mostly because the impeler is adding huge amounts of kinetic energy to the water. Heat is just molecular kinetic energy. If the temperature differential is not great enough, you will get diminishing returns on cooloing the harder you have to pump the water through the coils.

I've seen this hashed out many times in the CPU overclocker forums. Application is different principles are the same.

[douggiestyle]

<a href=showthread.php?s=&postid=8375065#post8375065 target=_blank>Originally posted</a> by exoticaquatix
let me elaborate, that was kinda vague......i heard it will stop working for a long time even after being shut off. do you need to get close to the water table to dissapate the heat more quickly? if so ill be looking for houses in a low lying area.
-nick

yes those are all factors. water table, soil type, amount of cooling needed, etc....

those and other variables dictate depth, spacing, length of tubing, etc...