Cold Batteries [RE-wrenches]

[R. Sparks Scott]

>Wind chill is very much a factor on in animate objects in regards to how
>fast they loose BTU's.

	Travis;

	If you're being serious here, I have to point out that wind *velocity* can
have an effect on how fast an inanimate object loses stored heat and
reverts to the ambient temperature, but that is not wind chill, it's
convection.
	Wind chill proper is traditionally measured using the "two bulb" method,
where two thermometers are affixed to a small hand-held centrifuge. One
thermometer's mercury bulb is bare (dry bulb) and the other is encased in a
fabric covering, which is moistened with water. The centrifuge is twirled
around a pivot (held in the hand), and the resulting (different)
temperatures used in the calculation of "wind chill".
	Wind chill is a measurement of the effect of evaporation in moving air.
Trailers full of batteries (or unwrapped near-frozen pipes) have no
evaporation, and so are not subject to wind chill, which can cause the
subject (you or me) to be chilled to *below* the ambient temperature.
	Convection on the other hand, will *only* bring the temperature of any
non-evaporative object down to the ambient temperature, where the object
stays until acted upon by an external thermal energy source.
	In the Old West, kegs of beer were kept chilled by wrapping them in burlap
and wetting the fabric down. The evaporation of the water absorbed heat
from the suds, much like a swamp cooler works in a building. In this case,
any air moving over the burlaps would indeed cause wind chill, but only as
long as the burlap was wet. No evaporation, no cooling action, at which
point the beer would attempt to revert to the ambient, which, if beer is
the beverage of choice, would be something warmer than freezing.
	Oh, maybe you WERE kidding.
	Now, tell me how you're going to use series shunts to measure currents in
excess of the meter movements scale???

	-S

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