"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

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.

"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.

The wind can't make it colder. It only makes the rate of heat transfer and
cooling of the object faster. Heat transfer is higher in turbulent flow.

Eisboch

"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

"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

"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

On Feb 8, 12:56 pm, "RCE" wrote:
"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.

That's the third time in two days I've heard the term nucleation.

That's the effect you get when you drop a Mentos into a bottle
of diet soda.

Funny - I never looked at frost like that.

"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.

The wind can't make it colder. It only makes the rate of heat transfer
and cooling of the object faster. Heat transfer is higher in turbulent
flow.

Eisboch


Did not realize it applied only to human tissue. Thought it was just a rate
of heat transfer regards air movement.

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

"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.

The wind can't make it colder. It only makes the rate of heat transfer
and cooling of the object faster. Heat transfer is higher in turbulent
flow.

Eisboch


Did not realize it applied only to human tissue. Thought it was just a
rate of heat transfer regards air movement.


Glad to see you finally got it. :-)