[Greenbuilding] thermosiphon questions

[Norbert Senf]

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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