http://friam.383.s1.nabble.com/A-leetle-thermodynamics-tp2618412p2619357.html
Sounds Tom Robbins-y. Love it.
> Solar cookers can break your heart, but not the laws of
> thermodynamics. Consider this elementary fact, my dear Dr. Watson.
> The insolation on earth near the equator is about 800 W/m2, it is
> less at the end of the day, and much less after sunset. For an
> aperture of 0.1 m2, you getting about 80 W black body, ignoring
> losses. Concentrators have nuttin to do with it! This amounts to
> about 270 BTU/hr from which you could boil a bit less than 2 pints
> of water in an hour, assuming no losses.
> BTW, you can, with care and ceremony, make ice in the Egyptian
> deserts every cloudless night, by exploiting radiation to the stars
> from shallow water trays, and careful control of nucleation,
> convection and vaporization. In fact, the temple priests used to do
> it on the flat roofs of the temples to impress the unwashed on the
> bounty of whatever God they were scamming that week. Much hoopla,
> involving sanctified water brought up from the basement (where it
> had got pretty cool, mixed with yesterday's ice), throwing holy dust
> on the surface (to provide nucleation particles) and wafting the
> surface at just the right time and rate with magic ostrich
> featherwands to actually control heat transfer due to convection and
> vapors. It's just thermodynamics, Nefertiti! And if sometimes the
> ice didn't form, it was because someone's mother-in-law was a
> witch! It's amazing what them religious guys know!!
> I usedta teach elementary courses in thermo in CA and the conversion
> constants are from memory and only roughly correct.
>
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