cnygeo
Registered Users
Posts:68
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| 09/02/2008 10:17 AM |
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On another board I check out occasionally there is a guy with a 30gpm artesian well who wants to do a geo system. The problem is that there is a blanket ban on all open-loop systems in his town (somewhere in Michigan). To get around this, he thought of fabricating an in-tank heat exchanger similar to this one: http://www.freewebs.com/rwooldridge/heatpump.htm
Looks like an ideal application for DX to me - have either of you done anything like this? It is pretty similar to the way the ARI tests DX systems, so I imagine it would work. He didn't leave any contact info, but the thread is here: http://hvac-talk.com/vbb/showthread.php?t=181014 if you're interested.
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joe.ami
Registered Users
Posts:385
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| 09/02/2008 10:57 AM |
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What we're talking about is a hybrid pond loop. Any system could work fine provided tank(s) large enough.
Joe |
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joe.ami
Registered Users
Posts:385
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| 09/02/2008 11:12 AM |
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I have tried but am not able to currently contribute to that site (I'm being told to register over and over.......). Too bad sites aren't all as user friendly as this one.
The message I tried to convey is with pond loop knowledge you could design tank size very easily, by using physical dimensions of required loops. perhaps other's have suggestions on loop size reduction due to water/heat energy rapid turn over.
Joe |
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cnygeo
Registered Users
Posts:68
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| 09/02/2008 11:49 AM |
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| OK, thanks. I'll direct him over here if he wants to discuss it. |
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joe.ami
Registered Users
Posts:385
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| 09/03/2008 11:34 PM |
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H/O contacted me today, I'm going to review load info, but as you all know loops are 75% of cost (pond loop vs horizontal) so I have a suspicion where we are headed. I will look forward to suggestions regarding loop size reduction due to constant influx of new heat energy.
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engineer
Registered Users
Posts:439
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| 09/05/2008 9:01 AM |
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I think normal sizing rules for a pond loop would be right out the window in this specialized case given the exchange and flow of water. I'll bet DX would be a great fit. That or rework a water source system to have as its outside heat exchanger a hundred or so feet of copper immersed in a tank with the 30 GPM flowing through it.
A way to tighten up the required calculations would be to find a way to route the 30 GPM through the exchange tank in a manner so as to be able to calculate water velocity across copper tubes in tank, then perform an actual heat transfer calculation based on that for tube length sizing.
My instinct is that a smaller tank would work better than larger as velocity will trump mass of water for heat exchange purposes. 30 GPM will experience a Delta T of less than 1 Deg F per nominal ton. I can even envision a trough or short length of large diameter (12"+) drain pipe with a slinky tube coiled in it.
Essentially one would want to create an open loop system in everything but name... |
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Without data, you only have an opinion. |
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Phil O.
Registered Users
Posts:1
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| 09/06/2008 10:31 AM |
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| I'm the homeowner. Thanks for looking into this for me, guys. The overflow runs through a 6" corrugated pipe about 60' from the overflow at the well to the creek and drops about 15' in elevation on the way there. The pipe currently has a lot of drop right from the well so the pipe is not filled as it flows. By raising the elevation of the pipe slightly just before it goes down the hill it would cause the pipe to fill completely from the overflow point to the elevated point before flowing down the hill. I could snake the pipe around some before it gets to the point where it flows down the hill now to add additional length to the filled portion of the pipe. It is about 25' from the overflow point to the top of the hill now. Would something like this work??? |
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joe.ami
Registered Users
Posts:385
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| 09/11/2008 12:30 AM |
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I don't think we can throw pond loop rules out the window, we just need a sensible reduction scheme for the extra heat energy introduced. I wrote phil today to apologize for my sluggish response, we are seeing back-orders on everything and unprecedented demand. Engineer, I like your idea on creating a sort of co-axial heat exchanger, but as always, if we sign off on it we have to warranty performance. Therefore we need "wrap-your-head-around" supporting data.
Also Clark, I think I recall that Earthlinked is disadvantageous in pond loop application due to the extremely rapid heat transfer. Do you have any loop-in-water experience?
Joe |
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engineer
Registered Users
Posts:439
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| 09/11/2008 9:43 PM |
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I agree that this would be a one-off - essentially a "stream loop" instead of a "pond loop" and would require custom design emphasizing site-specific thermodynamics. I'm a long-out-of-field-electrical engineer, not adequately schooled or experienced in the required calcs. Had I realized early enough that my true interest was in this stuff I'd have switched majors to mechanical engineering and gotten the needed coursework for this app.
If Earthlinked is disadvantaged in a pond application owing to rapid heat transfer (incompatible with the natural convection in a pond app), it may well be dead nuts on for this app - forced convection via the flow of water. I'll bet a variation on my small-slinky-in-a-trough would work, but someone else needs to do the thermo math - someone getting a check for the work, not some Florida dude on the Internet...
Final thought - think about ways to insure turbulent flow of the open loop (did I say "open loop" oops - I meant to say "stream") water over the system tubing |
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Without data, you only have an opinion. |
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joe.ami
Registered Users
Posts:385
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| 09/12/2008 12:28 AM |
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Engineer,
I appreciate your thoughts again and indeed have posed these questions to both a PE (who I just threw a municipal design job to) and a B.S. M.E. turned electrical engineer (dad). Obviously the worst part of all these questions is that as interesting as they are we're getting them about the time of the first cold snap. I have found solutions for a few of our recent contributers and hope to be able to do the same here. Keep your ideas coming, and don't sell that engineer training short...electrical, mechanical, railroad...... it's all good :-)
J |
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joe.ami
Registered Users
Posts:385
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| 09/12/2008 12:52 AM |
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By the by an easy way to use DX as open loop is to run water through an on demand water heater heat exchanger. 60 Kbtu's is about the size of a small microwave oven and could be submersed in a tank as the important components are copper. I'm afraid that this still qualifies as open loop however. It simply has a remote heat exchanger. The footprint is certainly desirable though.
J |
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tuffluckdriller
Registered Users
Posts:416
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| 09/12/2008 5:50 PM |
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The only "loop in water" things we have are where we've drilled in 5' depth water table, and continuous water for the total depth. Those loops perform wonderfully. The efficiency is much higher than expected, as ground water is constantly flowing. With 1 loop per ton, 100' deep, we see around 5.8-6.4 on the COPs of them. I usually attribute that to the ground ALWAYS maintaining 52 deg. F. There's so much water in some of these areas in the ground, that they can't change the temp of the ground from use of geothermal. It's a great fit.
Of course, we don't see this in many installations, but a few of them are. |
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Clark Timothy (clark@pinksdx.com)
VP sales, Tuff Luck Geothermal Drilling
Geothermal, Heating and Cooling that's Dirt Cheap! |
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joe.ami
Registered Users
Posts:385
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| 09/14/2008 10:15 PM |
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Here's the problem Phil,
One engineer (we'll call him-dad) had the idea of digging something like an old farmers well to submerge a heat exchanger into.
Everyone is reluctant to significantly reduce the foot print of the heat exchanger due to possible disparites in flow or temp, therefore this well could cost as much as a horizontal field.
As Clark points out, it would likely out pace more typical designs but those who have to warranty performance are not excited about "going outside the box" on this one. A PE with insurance for such would cheerfully warranty it with a 5Kish price tag for his trouble.
The suggestions Engineer and I had could both still qualify as open loop as the water must pass through a heat exchanger.
If you wanted to go with a conventional footprint, the way to employ your well and pass inspection (as open loop is disallowed) would be to feed enough heat energy to 5, 150' long u-tubes inserted in drain tubes. Can we gaurantee flow?
While I've enjoyed the excersize of your question, I think the short answer and quickest turn around for you at this time is to go horizontal ($1,600 ish ton).
My guess is that operating cost projections would put you in the 4+ thousand/year savings with geo, so while I think there are other answers, delays will cost you thousands. As open loop often requires extra maintenace, maybe a little of the sting is taken out of your situation.
Sorry about the ignorance of your local government. Why should they be different from feds who want to cut dependancy on fossil fuels and foreign oil but can't even renew a measley $500 tax credit for geo?
Joe |
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senecarr
Registered Users
Posts:160
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| 09/15/2008 11:20 AM |
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| Call up Gov. Granholm. She claims to be all about bring renewable energy jobs to MI. Tell her your local gov. isn't letting you provide someone with a renewable energy job. |
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