[Greenbuilding] thermosiphon questions

[Reuben Deumling]

Thanks, Norbert. That is what I'm fearing.

On Sun, Nov 2, 2014 at 6:06 AM, Norbert Senf <norbert.senf at gmail.com> wrote:

> Nick's result was around 3/4", but I believe in his example the height was
> 16'.
> Off the top, 35' is a very long run, and the rise is low. You definitely
> want to minimize friction - I'd go to 1" smooth (copper) pipe, minimum, as
> a precaution.
> With the situation you describe, I would not expect much heat
> transfer................Norbert
>
> On Sat, Nov 1, 2014 at 6:10 PM, Reuben Deumling <9watts at gmail.com> wrote:
>
>> Is that what Nick's numbers suggested? I tried to follow but got lost
>> somewhere.
>> The tubing is 3/4", the run is 35', the rise is 5' from top of tank to
>> top of tank. The water temperature from the originating tank (heated by
>> solar thermal panels) can be expected to be 120F - 150F. House pressure is
>> I think 60psi.
>>
>> On Sat, Nov 1, 2014 at 1:20 PM, Norbert Senf <norbert.senf at gmail.com>
>> wrote:
>>
>>> In other words, the pipe should be 3/4" or
>>> larger.......................Norbert
>>>
>>> On Sat, Nov 1, 2014 at 3:46 PM, <nick_pine at verizon.net> wrote:
>>>
>>>> One way to design a thermosyphoning system:
>>>>
>>>> 1. Calculate the required water flow, approximately G = 0.04A gpm for
>>>> an A ft^2 collector, eg G = 1.28 gpm for a 4'x8' collector.
>>>>
>>>> 2. Calculate the available thermosyphoning head, Ha = H(62-61.71)/144 =
>>>> 0.002H psi, based on a 10 F temp diff at 100 F and an H foot height
>>>> difference, eg Ha = 0.002x8 = 0.016 psi with H = 8'.
>>>>
>>>> 3. Calculate the minimum supply and return pipe inside diameter d in
>>>> inches, given their total length L in feet.
>>>>
>>>> http://www.calctool.org/CALC/eng/fluid/hagen-poiseuille says dP =
>>>> 32MuLV/d^2, where V is a velocity and d a diameter. A G gpm flow rate makes
>>>> V = cG/d^2 for some constant c, ie dP = kLG/d^4 for some constant k.
>>>>
>>>> Plugging L = 8' and d = 1" and G = 1.28 gpm into the website makes dP =
>>>> 0.001775 psi = k8'x1.28gpm/1^4, so k = 1.73E-4.
>>>>
>>>> In the example above, d = (kLG/Ha)^0.25 = (1.73E-4x16'x1.28gpm/0.016psi)^0.25
>>>> = 0.69" for L = 16'.
>>>>
>>>> Nick
>>>>
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>>>
>>>
>>>
>>> --
>>> Norbert Senf
>>> Masonry Stove Builders
>>> 25 Brouse Road, RR 5
>>> Shawville Québec J0X 2Y0
>>> 819.647.5092
>>> www.heatkit.com
>>>
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>>
>>
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>
>
>
> --
> Norbert Senf
> Masonry Stove Builders
> 25 Brouse Road, RR 5
> Shawville Québec J0X 2Y0
> 819.647.5092
> www.heatkit.com
>
> _______________________________________________
> Greenbuilding mailing list
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>
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