docjenser
Veteran Member
Posts:1400
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| 31 Oct 2009 03:06 PM |
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quick question, for a slinky install and a 10 ton loopfield with a 6 and a 4 ton heatpump, would one header everything into one header or keep 6 and 4 ton loops separate? Turbulent flow, one large circulation pump versus 2 smaller one, larger volume of the heatexchanger if only one pump is running? etc. What would be more efficient? |
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Bill Neukranz
Veteran Member
Posts:1103
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| 31 Oct 2009 03:48 PM |
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I would think, given the choice, you'd want just one 10 ton slinky loop. I would think you'd gain substantial efficiency when running alone a 6 ton unit into a properly designed single 10 ton slinky loop, or when running along a 4 ton unit into the same loop. Especially if you estimate that the percentage of run time is small where you are simultaneously running both units.
Increased cost of a single loop is more connection piping. And you'll need an additional pump perhaps.
Best regards,
Bill |
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Energy reduction & monitoring</br>
American Energy Efficiencies, Inc - Dallas, TX <A
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docjenser
Veteran Member
Posts:1400
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| 31 Oct 2009 03:54 PM |
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I am not sure if there is more connection piping...One header (although more like 2 inch pipe instead of 1 1/4) going out there instead of two!
Would 2 pumps going from each heatpump feeding into the same header be OK, or should one always have one big pump running?
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Bill Neukranz
Veteran Member
Posts:1103
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| 31 Oct 2009 04:21 PM |
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For example, in my case, I have 5 and 3 ton units sharing an 8 ton vertical borefield. I have 2" HDPE pipe from the pumps inside to the header in the ground outside (w/ 1" HDPE size going up/down each well, and 1" HDPE pipe to/from the pumps to the units).
I would think you'd need to emperically calculate pipe size, pump size, and pump quantity to get the right amount of flow through the heat exchanger with the right amount turbulence through the slinky system at the least amount of power consumption. You would use conventional analysis that takes into account friction, inside diameter, number of fittings, length, pumping power, etc.
Or, if you have access to GSHP water loop design s/w, this will compute all of the correct pipe sizes, pump sizes, and quantity of pumps for you.
Best regards,
Bill |
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Energy reduction & monitoring</br>
American Energy Efficiencies, Inc - Dallas, TX <A
href="http://www.americaneei.com">
(www.americaneei.com)</A></br>
Example monitoring system: <A href="http://www.welserver.com/WEL0043"> www.welserver.com/WEL0043</A>
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docjenser
Veteran Member
Posts:1400
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| 31 Oct 2009 04:29 PM |
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Thanks so far! That brings up another questions. Is turbulent flow an issue with a slinky, since running water trough a curved pipe always creates turbulences....? |
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ACES-Energy
New Member
Posts:67
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| 31 Oct 2009 09:50 PM |
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Turbulence is created at a certain velocity within the pipe defendant on pipe size, irregardless of pipe "curves". |
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docjenser
Veteran Member
Posts:1400
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| 01 Nov 2009 10:08 AM |
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That is true in regards to velocity, however if the pipe is not straight the velocity distribution over the curved section is altered and the flow of fluid is continuously changing. ->more turbulences-> higher fritional losses. For example if ratio of the diameter of the pipe to the diameter of the coil is 1 to 15, the transition from laminar to turbulent flow occurs at a reynolds number of 8000, instead of 4000 for a straight pipe. One experiment has shown, depending on the curve and pipe diameter, pressure drop increases by 40%, and heat transfer increases by 100%. The literature of fluid mechanics is full of other examples. |
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cnygeo
Basic Member
Posts:170
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| 01 Nov 2009 12:41 PM |
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Posted By docjenser on 11/01/2009 10:08 AM
That is true in regards to velocity, however if the pipe is not straight the velocity distribution over the curved section is altered and the flow of fluid is continuously changing. ->more turbulences-> higher fritional losses. For example if ratio of the diameter of the pipe to the diameter of the coil is 1 to 15, the transition from laminar to turbulent flow occurs at a reynolds number of 8000, instead of 4000 for a straight pipe. One experiment has shown, depending on the curve and pipe diameter, pressure drop increases by 40%, and heat transfer increases by 100%. The literature of fluid mechanics is full of other examples. Do you mean that the transition to turbulent flow occurs at a lower Reynold's number? That would make more sense in the context of your statement. I'll have to look up my fluids books tomorrow, but offhand your numbers seem a little off to me - I agree that a curved pipe in general will have greater turbulence and a higher pressure drop, but a ratio of 15-1 seems way too large to cause a 40% increase is pressure drop. The ratio for a typical slinky is more like 50-1 anyway which I doubt would have a measureable effect. I'm willing to be proved wrong, I'll look it up when I get a chance unless you have a reference handy. |
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docjenser
Veteran Member
Posts:1400
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| 01 Nov 2009 02:12 PM |
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Sorry, that is what I meant, it lowers the reynolds number for turbulent flow. slinky is about 1/50 ratio, and the effect is measurable, although much weaker, down to 1/500 ratio. that is the numbers I had in my head. Let me see if I can find some references. I am the first who listens if anyone has good numbers for slinky configuration!
Thanks |
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heatoftheearth
Basic Member
Posts:113
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| 01 Nov 2009 07:06 PM |
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one loop feild, two pumps would be my choice, the efficiency of a 6 ton heat pump on a 10 ton loop will more than compensate for non turbulent flow. B&D makes a nice flowcenter for easily hooking up 2 heat pumps to one feild |
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docjenser
Veteran Member
Posts:1400
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| 02 Nov 2009 10:40 AM |
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Thanks, I will check them out. |
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Alex_in_FL
New Member
Posts:96
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| 02 Nov 2009 03:46 PM |
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The higher the tubulence (within reason) the higher the heat transfer efficiency. Yes, the curves do create some turbulence but there will still be areas with laminar flow if the velocity is too low - and some will be in the transition zone which makes calculations really difficult. The higher velocity will result in turbulent flow at all points.
I have no calculations to back this up but it seems likely that a single field would be the preferred alternative. |
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