[Stoves] Heat-pipes/thermal-diodes

Thu Jan 30 12:20:37 CST 2014

Dear Ron

>1.   The paper I cited
(http://cfc.kscia.or.kr/new/wwwboard/admin/wwwboard/attach/1087363006/26.pdf
)  was 

Understood. 

>2.   At:  http://www.thermomax.com/Downloads/How%20Works.pdf,  

Understood.

>3.   I am trying to move the discussion away from solar collectors - for
reasons of getting more pots active with a single biomass flame.  

This is exactly why I mentioned the problem of getting the heat into the
heat pipe. Viewed systemically, the heat pipe is an insulator between the
fire and the pot, albeit a good heat conducting one.

As noted in the first paragraph of
http://www.dl.begellhouse.com/download/article/2f3e64f4394d33a5/HPST0102%20(
151-162).pdf

the heat flux for the device is running in the range of 100 W/cm2.

Given the low temperatures in a wood fire, this would be really difficult to
even approach unless it were some kind of oxygen-gas flame. 

The device described is a loop heat pipe, not really a 'heat pipe' the way
the Israelis talk about them. They refer to the real 'diode' type device
that only lets heat rise vertically.

It is approximately a pumped dual phase thermosiphon (as if that makes
sense!) using phase change as the main heat transfer mechanism, which keeps
it small.

The problem lies in the 'Evaporator' thingy which is what I referred to: how
the heck do you get the heat from the fire into the water (or fluid) using
that evaporator thingy. 

If you could get an 80% heat transfer efficiency for a gas-exchanger and
another 80% to a string of pots it would get 64% overall, which is about the
same as an LPG flat topped cooker. Pretty good.

Incidentally the LHP device is sort of like a thermoacoustic generator with
a phase change in the working fluid at the cold end.

Regards

Crispin

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