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.