On Thu, 08 Feb 2007 18:05:26 GMT, "Calif Bill"
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

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.

It's supposedly based on skin feel. Whose skin is up for debate.
There's a formula for it, but anybody who has spent time in the cold
knows that if the wind can make your nose freeze solid but if you
turn from the wind your nose is okay, the same procedure can apply
to your car's engine block when deciding whether it is best to park
facing the wind, or away from it.
Basically the term has been appropriated by weathermen to keep people
properly scared. Saw a map of temperatures the local joker put up
last night which gave me a momentary shock, until I realized it was
all wind chill temps. Yeah, like anybody knows how the winds are
blowing at these locations. It was inaccurate before it was posted.
As you said, it's all about heat transfer.
Just don't call it wind chill unless you're talking about human skin.
That's taken. Call it air chilled, then nobody can challenge you.

--Vic

"JoeSpareBedroom" wrote in message
...


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.


Well just think. Now, armed with your newly acquired knowledge, sue 'em!

Eisboch

"RCE" wrote in message
...

"JoeSpareBedroom" wrote in message
...


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.


Well just think. Now, armed with your newly acquired knowledge, sue 'em!

Eisboch


The supermarket's been informed. Knowing Wegman's, they'll pull it from the
shelves pretty quickly.

On Thu, 8 Feb 2007 15:09:29 -0500, "RCE" wrote:



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

Commonly "seen" when snow "disappears" even though the temp is below
freezing. Or hanging out the wash in freezing temps but it dries, or
so I've heard.

--Vic

On Thu, 08 Feb 2007 20:16:16 GMT, "JoeSpareBedroom"
wrote:



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.

I wonder if that might crack the tank, rupture the hoses, and fracture
the plastic spray nozzles as we speak. Nah.

--Vic

"Vic Smith" wrote in message
...
On Thu, 08 Feb 2007 20:16:16 GMT, "JoeSpareBedroom"
wrote:



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.

I wonder if that might crack the tank, rupture the hoses, and fracture
the plastic spray nozzles as we speak. Nah.

--Vic

That would be fun.

On Feb 8, 12:32 pm, "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.- Hide quoted text -

- Show quoted text -

What did you expect - this is Usenet.

Everybody is an expert on everything. :)

On Feb 8, 2:11 pm, "RCE" wrote:
"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. :-)

I prefer to call it pizza.

Then again, I'm a little weird.

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.

On Feb 8, 2:09 pm, "RCE" wrote:
"JoeSpareBedroom" wrote in message

...

"RCE" wrote in message
m...

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".

Water at altitude boils at a lower temperature - makes sense to me.