>> Yep, this is correct. Windchill is something that people feel, inanimate
>> objects don't experience it.
[quoted text clipped - 5 lines]
> plugged in over-night. I always try to park with the nose of the car away
> from the wind in either situation.
>>> Yep, this is correct. Windchill is something that people feel,
>>> inanimate
[quoted text clipped - 14 lines]
> or what direction your car is facing, your car's engine will be just
> as cold.
My recall of O level physics isn't what it was, but I think heat can be
transferred from a hot body by radiation, conduction and convection (if in a
fluid such as air) and if that air is being moved forcibly accross a heated
surface isn't that a heat transfer fluid ? so I think the temperature will
fall more quickly than otherwise.
Also there used to be a thing called "cooling by evaporation" where a wet
surface would be cooled as the water on it evaporated under forced
ventilation. So I think "wind chill" is a real physical effect not just
something people feel. Meteorologists measure temperatures using
thermometers that are shielded against the the wind hence the confusion
IMHO.
Mark Olson - 23 Dec 2004 22:29 GMT
> >>> Yep, this is correct. Windchill is something that people feel,
> >>> inanimate
[quoted text clipped - 14 lines]
> > or what direction your car is facing, your car's engine will be just
> > as cold.
> My recall of O level physics isn't what it was, but I think heat can be
> transferred from a hot body by radiation, conduction and convection (if in a
> fluid such as air) and if that air is being moved forcibly accross a heated
> surface isn't that a heat transfer fluid ? so I think the temperature will
> fall more quickly than otherwise.
That is true and is why I said "All good points" above.
> Also there used to be a thing called "cooling by evaporation" where a wet
> surface would be cooled as the water on it evaporated under forced
> ventilation. So I think "wind chill" is a real physical effect not just
> something people feel. Meteorologists measure temperatures using
> thermometers that are shielded against the the wind hence the confusion
Yes, I was aware of the physiological basis for windchill, which is why
I said it was something that people feel. Remember, most cars and most
thermometers don't sweat... YMMV.
Kjell Harnesk - 23 Dec 2004 22:36 GMT
> ventilation. So I think "wind chill" is a real physical effect not just
> something people feel. Meteorologists measure temperatures using
> thermometers that are shielded against the the wind hence the confusion
> IMHO.
Yes, it is a real physical effect in the sense that a body, human or not,
has a harder job keeping warm when it is windy than when it´s calm but my
point was that the body never gets any cooler than the air surrounding it.
If the air temperature is over the freezing point then the washer fluid
will not freeze even in full storm. If it is just a degree below freezing
point it will freeze regardless of windspeed unless You add anti-freezing
stuff.

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K
Scott Thomas - 23 Dec 2004 22:37 GMT
> My recall of O level physics isn't what it was, but I think heat can be
> transferred from a hot body by radiation, conduction and convection (if in a
[quoted text clipped - 5 lines]
> ventilation. So I think "wind chill" is a real physical effect not just
> something people feel.
The _rate_ of cooling can be affected by energy transfers (such as
forcible matter exchange and matter change-of-state), but the absolute
temperature of the system would indicate that the end state of any small
part of the much-larger "closed system" (for this example, an area
affected by cold weather) would not drop below the net temperature as
indicated by the energy contained in that system. A car parked in an
area with a weather temperature of -20°C and no wind will get just as
cold as a car parked in weather of -20°C and high winds - that is,
they'll both reach -20°C, but the second one will get there faster.
Unless my memory of p-chem is way off and I'm just talking out of my
backside, which is always a possibility. :P

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Scott Thomas, thomass@cs.rose-hulman.edu
http://www.cs.rose-hulman.edu/~thomass/