[Greenbuilding] thermosiphon questions

[Reuben Deumling]

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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