Cold Batteries [RE-wrenches]

[Kurt Nelson, SunWise]

R. Sparks Scott wrote:
> 

>         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.

Hey Sharkey -- Sorry, got to disagree with you hear.  The wet/dry bulb
is used to measure humidity, and should not be confused with "wind chill
proper".  Even an object with no moisture will experience wind-chill. 
Heated objects such as people and homes are effected by wind-chill
because the wind effects the rate of conductive and convective heat loss
to the structure.  Unheated objects are not effected by wind chill in
the same way.  They will not cool below ambient air temps (unless wet)
but will loose any stored heat faster.  Wet objects can cool below
ambient temps because of the evaporative process, which essentially
"takes" energy to transform a liquid into its vapor state (the same
ammount of energy is released when the vapor condenses back into a
liquid state) -- Kurt Nelson


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