[extropy-chat] cool (was zombie boffins)

[Mike Lorrey]

This is an interesting effect, and something like the practice of using
lasers to cool matter to near 0 K levels to make BE condensates.

However, by putting hot liquid in a freezer, the hotter vapor rising
off the liquid hits the freezer thermostat, indicating a much higher
temperature inside the freezer than actually exists. It reacts by
sending a higher voltage to the SCR controlling the refrigerant
compressor, and so the freezer goes into a higher operating mode, thus
its coils cool to a colder temperature, and this causes temps inside
the freezer to plummet quicker than if you'd put cool liquid in the
freezer. Because the coldest air settles at the bottom of the freezer,
it is separated from the layer of hot air at the top of the freezer
that is sending the heat signal to the thermostat. The compressor
doesn't back off until this top layer itself cools down, which will
happen last.

--- scerir <scerir at libero.it> wrote:

> Cool!
> But what does it mean? 
> I'm supposing it has to do with 
> the Aristotle-Mpemba effect. 
> 
> "The fact that water has previously been warmed
> contributes to its freezing quickly;
> for so it cools sooner.  Hence many people,
> when they want to cool hot water quickly,
> begin by putting it in the sun. . ."
> - Aristotle [in E.W.Webster, "Meteorologica I",
>             Oxford U.P., Oxford, 1923, 348b-349a]
> 
> It was called, by Aristotle, 'antiperistasis'.
> "The supposed increase in the intensity of a quality
> as a result of being surrounded by its contrary quality,
> for instance, the sudden heating of a warm body
> when surrounded by cold."
> 
> Long time ago a friend told Mpemba (a Tanzanian high
> school student) that when making ice cream, he put
> the hot liquids in the refrigerator to make them freeze
> _faster_.
> 
> Mpemba found that other ice cream sellers in Tanga
> had the same practice.
> 
> This is the Aristotle-Mpemba effect.
> 
> Mpemba, Osborne; "Cool"; Physics Education v.4,
>                  p.172-5(1969)
> 
> (More references available)
> 
> 
> 
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Mike Lorrey
Vice-Chair, 2nd District, Libertarian Party of NH
"Necessity is the plea for every infringement of human freedom.
It is the argument of tyrants; it is the creed of slaves."
                                      -William Pitt (1759-1806) 
Blog: http://intlib.blogspot.com


		
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