"RCE" wrote in message
...

"Calif Bill" wrote in message
link.net...


Wind Chill. I do not think it refers to living tissue. I think the
definition is how much heat transfer would occur in still air vs. Moving
air. some low speed of air. -15 degrees with a wind chill of -30, says
the same heat loss would occur if the temp was -30 and no wind movement.
Nothing to do with evaporation but with the tendency of the air to heat
up near the warmer object, slowing down heat transfer.


The term "Wind Chill" applies *only* to living tissue. It refers to the
rate of cooling (limited by the ambient temperature) that occurs to
exposed living tissue. The increased rate of cooling can exceed the
living tissue's ability to replace the heat lost and things like frostbite
can quickly occur.



To add:

If it is 20 degrees outside and the wind is howling, producing a "wind
chill" of -10 degrees,
it is equivalent to subjecting exposed tissue to -10 degrees. It's still
20 degrees, ambient.

Eisboch

"RCE" wrote in message
...

"RCE" wrote in message
...

"Calif Bill" wrote in message
link.net...


Wind Chill. I do not think it refers to living tissue. I think the
definition is how much heat transfer would occur in still air vs. Moving
air. some low speed of air. -15 degrees with a wind chill of -30, says
the same heat loss would occur if the temp was -30 and no wind movement.
Nothing to do with evaporation but with the tendency of the air to heat
up near the warmer object, slowing down heat transfer.


The term "Wind Chill" applies *only* to living tissue. It refers to the
rate of cooling (limited by the ambient temperature) that occurs to
exposed living tissue. The increased rate of cooling can exceed the
living tissue's ability to replace the heat lost and things like
frostbite can quickly occur.



To add:

If it is 20 degrees outside and the wind is howling, producing a "wind
chill" of -10 degrees,
it is equivalent to subjecting exposed tissue to -10 degrees. It's still
20 degrees, ambient.

Eisboch


Of course.

The alcohol gone - water remaining & freezing idea seems the most plausible
at this point.

"JoeSpareBedroom" wrote in message news:bbKyh.2321

The alcohol gone - water remaining & freezing idea seems the most
plausible at this point.


Water and water vapor is an interesting and complex subject. I spent the
better part of my career dealing with their effects and properties in
reduced pressure (vacuum chambers) vessels. Water vapor does not follow
natural gas laws and is the bane of those of us trying to create high vacuum
environments (equal to 200-300 miles in space) here on earth.

Place a cup of water in a large vacuum system and begin to remove the air,
reducing the atmospheric pressure. The water will quickly freeze at the
reduced pressure. Continue to reduce the pressure and the block of ice will
suddenly start to rapidly boil ... in the blink of an eye. Continue to
reduce the pressure and it will suddenly freeze again and begin to sublimate
(goes from solid to vapor without becoming a solid).

It also has weird properties when it condenses. Picture a snowflake with
all of it's points. Each point becomes a nucleation site for the next bit
of water vapor. Enough of them and they form an insulating lay whereby no
further nucleation takes place. That's why you don't get 3 inches of frost
on your windshield. The process stops once the outer surface is insulated
sufficiently from the cold glass where the initial nucleation took place.

Eisboch

On Thu, 8 Feb 2007 13:32:33 -0500, "RCE" wrote:


"David Scheidt" wrote in message
...
JoeSpareBedroom wrote:
:"Eisboch" wrote in message
...
:
: "JoeSpareBedroom" wrote in message
: ...
:
:
: What about when it hits the windshield, under those same conditions?
:
:
: Wind will cause an object to lose heat faster ... but will not cool it
: below the ambient temperature.
:
: The evaporation of a liquid is a state change whereby energy is used
and
: heat is given off.
:
: Wind chill is a measurement of rapid cooling of living tissue.
:
: Eisboch
:


:We're going in circles. Stop focusing on the words "wind chill". Focus
on
:this: Assume you're a chemist, and you know for a fact that you
personally
:have correctly created windshield washer fluid that doesn't freeze at (to
ick a number) zero F., why does that fluid actually freeze at a higher
:temperature, say 5 F., when the vehicle is moving and the fluid hits the
:windshield?

Evaporation drives this. Evaporation cools things off; it can cool
things off below ambient temperature, despite multiple people in this
thread saying it can't. Think about how an evaporative cooler works,
or why an alcohol wipe is cool.
Increasing the surface area increases the rate of evaporation. A film
smeared across your windshield by the frozen wipers will evaporate
quickly, leaving a nice thin sheet of ice. Wind, real or apparent
from the car's motion, also increase the rate of evaporation. I also
expect that the alcohol in the solvent evaporates more quickly than
the water, so the ice on the window is mostly water.



This is funny. A whole bunch of experts explaining 9th grade physics.

Eisboch


For a very few of us, 9th grade was well over 45 years ago. I enjoyed and
learned from this discussion.

Remind me not to argue water vapor properties with you.
--
***** Have a super day! *****

John H

"RCE" wrote in message
...

"JoeSpareBedroom" wrote in message
news:bbKyh.2321

The alcohol gone - water remaining & freezing idea seems the most
plausible at this point.


Water and water vapor is an interesting and complex subject. I spent the
better part of my career dealing with their effects and properties in
reduced pressure (vacuum chambers) vessels. Water vapor does not follow
natural gas laws and is the bane of those of us trying to create high
vacuum environments (equal to 200-300 miles in space) here on earth.

Place a cup of water in a large vacuum system and begin to remove the air,
reducing the atmospheric pressure. The water will quickly freeze at the
reduced pressure. Continue to reduce the pressure and the block of ice
will suddenly start to rapidly boil ... in the blink of an eye. Continue
to reduce the pressure and it will suddenly freeze again and begin to
sublimate (goes from solid to vapor without becoming a solid).

All of this happens at what range of temperatures? When you're reducing the
air pressure, the temp is remaining fairly constant?




It also has weird properties when it condenses. Picture a snowflake with
all of it's points. Each point becomes a nucleation site for the next bit
of water vapor. Enough of them and they form an insulating lay whereby no
further nucleation takes place. That's why you don't get 3 inches of
frost on your windshield. The process stops once the outer surface is
insulated sufficiently from the cold glass where the initial nucleation
took place.

Eisboch

I hate to end a very interesting discussion, but the definitive answer
is below, I have copied 3 definitions of wind chill, and the last
paragraph is from USA Today and discusses wind chill and freezing water:

wind-chill factor (wÄ*nd'chÄ*l')
n.
The temperature of windless air that would have the same effect
on exposed human skin as a given combination of wind speed and air
temperature.

Definition: Wind chill accounts for loss of heat when warm air around
a body is replaced with colder air. The factor is an indication of the
effect of the combination of air temperature and wind speed on human
comfort and safety.

Definition: The wind chill index gives a temperature-like number to
indicate what the current weather conditions would feel like on a calm
day. For example, if the temperature is -5°C and the wind chill is -20,
it means your face will feel as cold as it would on a day when the
temperature was -20°C. The wind chill is only given in a weather forecast
if it is expected to be significant.

from USA today:
Answers archive: Can wind chill alone freeze water
By Jack Williams, USATODAY.com
Q: If the temperature is 38 degrees and the wind chill is 27 degrees, will water on roads freeze?


A: No. Wind chill attempts to account for the effects of wind carrying heat away from your body, or the body of an animal. No matter how hard the wind blows, it doesn't change the air's temperature. You find more on this by going to a USATODAY.com file about Wind chill applies only to people, animals.

Also, you should be aware that whenever the temperature is near freezing, water on roads could freeze because the road is in a colder place than where the temperature was measured. Official temperatures are measured about 4 feet above the ground and the ground or the surface of a road can be two or three degrees colder. In other words, if you hear on the radio that the temperature is 35 degrees, this doesn't mean you don't need to worry about ice on the road. You'll find a lot of useful information by going to our winter safety guide.

"JoeSpareBedroom" wrote in message
...

"RCE" wrote in message
...

to reduce the pressure and it will suddenly freeze again and begin to
sublimate (goes from solid to vapor without becoming a solid).



All of this happens at what range of temperatures? When you're reducing
the air pressure, the temp is remaining fairly constant?


As the pressure is reduced, the only temperature left is that remaining in
the water, (aside from any radiant energy). As pressure is reduced, the
vapor pressure changes. Often, high intensity quartz lamps or UV emitters
are used to add energy to the remaining water molecules to excite them to a
state where they can be removed or captured by the vacuum pumps. Otherwise
they cling to the vacuum chamber walls and will slowly sublimate for hours
or days.

Think of your car's radiator. The pressure cap allows the cooling system to
operate at a higher barometric pressure than at atmosphere, raising the
boiling point of water. The opposite happens in the vacuum chambers. To a
less obvious degree, the normal barometric pressure variations at atmosphere
affects dew points, etc. for a given temperature.

BTW ... in my partial sentence quoted above about sublimation ... I meant to
say "goes from solid to vapor without becoming a liquid".

Eisboch

"JLH" wrote in message
...


Remind me not to argue water vapor properties with you.
--


I prefer to call it a "discussion".
Except, I am right. :-)

Eisboch

Reginald P. Smithers III wrote:

One last article from the US govt. on wind chill and radiator freezing:

2. Can windchill impact my car's radiator or exposed water pipe? back

A. The only effect windchill has on inanimate objects, such as car
radiators and water pipes, is to shorten the amount of time for the
object to cool. The inanimate object will not cool below the actual air
temperature. For example, if the temperature outside is -5 degrees
Fahrenheit and the windchill temperature is -31 degrees Fahrenheit, then
your car's radiator will not drop lower than -5 degrees Fahrenheit.

http://www.weather.gov/os/windchill/...glossary.shtml

"RCE" wrote in message
...

"JoeSpareBedroom" wrote in message
...

"RCE" wrote in message
...

to reduce the pressure and it will suddenly freeze again and begin to
sublimate (goes from solid to vapor without becoming a solid).



All of this happens at what range of temperatures? When you're reducing
the air pressure, the temp is remaining fairly constant?


As the pressure is reduced, the only temperature left is that remaining in
the water, (aside from any radiant energy). As pressure is reduced, the
vapor pressure changes. Often, high intensity quartz lamps or UV emitters
are used to add energy to the remaining water molecules to excite them to
a state where they can be removed or captured by the vacuum pumps.
Otherwise they cling to the vacuum chamber walls and will slowly sublimate
for hours or days.

Think of your car's radiator. The pressure cap allows the cooling system
to operate at a higher barometric pressure than at atmosphere, raising the
boiling point of water. The opposite happens in the vacuum chambers. To
a less obvious degree, the normal barometric pressure variations at
atmosphere affects dew points, etc. for a given temperature.

BTW ... in my partial sentence quoted above about sublimation ... I meant
to say "goes from solid to vapor without becoming a liquid".

Eisboch



Well anyway, it appears I've gone beyond my streak of good luck with
windshield fluid. 35 years of driving in frigid climates, and never a
problem until now, when I get not just one, but two products in a row made
by idiots or liars. The stuff's frozen in the tank, at 14 degrees F.