Oddball Question Re Frost on Windshield

[Kevin Rooney]

or use remote start.

Good point. One of the guys I used to work with had one installed in his pickup, and on especially cold days he'd park it in line of sight with our offices (we worked in a rotunda on the 3rd floor). About 10 minutes before quitting time, he'd make a big production out of walking over to a window, and in a loud voice say "OK, what this!" while he pointed the remote at his truck.

He'd often have to duck as someone hurled an object in his direction...

 

[Tom Rankin]

Good point. One of the guys I used to work with had one installed in his pickup, and on especially cold days he'd park it in line of sight with our offices (we worked in a rotunda on the 3rd floor). About 10 minutes before quitting time, he'd make a big production out of walking over to a window, and in a loud voice say "OK, what this!" while he pointed the remote at his truck.

He'd often have to duck as someone hurled an object in his direction...

I have a remote starter, a gift from Laurie, and I love it!

It works up to 400 or so feet away, if you have a clear line of sight.

Once in a while it freaks people out who are standing next to the car and it starts 'itself'.

 

[Little Rickie]

I have a remote starter, a gift from Laurie, and I love it!

It works up to 400 or so feet away, if you have a clear line of sight.

My wife got me one for a xmass gift...along with one for herself.

Once in a while it freaks people out who are standing next to the car and it starts 'itself'.

Thanks for the tip!

Now what about that frost build up inside tents?

 

[Kevin Rooney]

Now what about that frost build up inside tents?

It's condensation from your breath, and to a lesser extent, your body.

 

[DougPaul]

Putting some mositure resistant material over the windshield held in by the wiper blades usually solves the problem. Cardboard works but if conditions are right, it can get damp and freeze to the windshield.

Any waterproof surface on top of the glass will cause the frost to form on it rather than on the glass. And any water between the backside of the surface and the glass/car body can freeze.

Doug

 

[DougPaul]

Supposedly spraying a mixture of 3 parts vinegar to 1 part water on the windshield at night will prevent frost from forming. The acetic acid in the vinegar raises the melting point of water....

I hope you mean "lowers the melting point"...

In any case, if it gets cold enough, a surface can still frost up.

Frost formation requires the temp to be 1) below 32F (or the melting point if the surface is treated) and 2) below the dew point (which may be above or below 32F).

Doug

 

[Stash]

I live in Maine. One car points east. One west. Neither gets frosty. They're in an unheated garage.


...oh. And I keep my snowshoes USED FOR HIKING in the garage too. They don't frost up either.

 

[Little Rickie]

I thought my body blocked the radiant heat from the nuclear decay of heavy atoms during the full full moon on cloudless nights when the planets align thus having a tidal effect on my body fluids because of the weakend subatomic energy glue causing the cold air to pass through the tent and collide with my water vapor.

 

[Kevin Rooney]

I thought my body blocked the radiant heat from the nuclear decay of heavy atoms during the full full moon on cloudless nights when the planets align thus having a tidal effect on my body fluids because of the weakend subatomic energy glue causing the cold air to pass through the tent and collide with my water vapor.

I think you're on to something.

But Doug Paul is the only one authorized to calculate the coefficient of the "weakend subatomic energy glue". If any of the rest of us attempted it Homeland Security would be on our doorstep, and our families would never see us again.

Or is "week-end subatomic energy glue"?

 

[DougPaul]

But Doug Paul is the only one authorized to calculate the coefficient of the "weakend subatomic energy glue".

I give you and anyone else my permission and encouragement to calculate said coefficient.

If any of the rest of us attempted it Homeland Security would be on our doorstep, and our families would never see us again.

Only if you if you tell someone about it...

Doug

 

[DougPaul]

And IIRC, radiative heat transfer is to the 4th power of the temperatures of the two bodies, so when the glass (the first body) more directly faces outer space (the second body and where the temp is really cold), and there are no barriers, the radiative cooling is huge.

Correct. It is called black body radiation. See, for instance: http://en.wikipedia.org/wiki/Black_body

The "color" of the radiation is also a function of temperature: http://hyperphysics.phy-astr.gsu.edu/hbase/bbrc.html
* deep space has a temp of 2.7 deg K (-270 C) and peaks in the microwave region (Cosmic microwave background: http://en.wikipedia.org/wiki/Microwave_background_radiation) A clear night sky (space seen through the atmosphere) will be somewhat warmer.
* the normal temps at which we live (~298K = ~25C) peak in the far infrared
* flames (~1300K = ~1000C) peak in the near visible but include significant radiation in the visible red
* Stars range from 4000K (red) to 7000K (blue) http://hyperphysics.phy-astr.gsu.edu/hbase/wien.html The sun (~5270K) peaks in the green region

If you place two objects in a "perfect" mirrored chamber such that all radiation from each object hits the other, the hotter one will radiate more energy toward the cooler one until they are both the same temperature. (The hotter object cools down and the cooler object warms up.)

Remove the perfect mirror and substitute cold clear sky and relatively warm terrestrial objects such as windshields. Objects which radiate more total energy than they receive (such as windshields exposed to the sky) will cool down, perhaps enough for frost to form if the air has a dew point a bit below 0C.

Doug

 

[Nessmuk]

Correct. It is called black body radiation. See, for instance: http://en.wikipedia.org/wiki/Black_body

I think that's effectively what I said, without specific reference to the Stefan-Boltzman Law that most here would likely not care about.

But more importantly, John, good to see you are of a scientific mind, I didn't know that. I hope to see you next September 7, if not before at one of our common events.

 

[DougPaul]

I think that's effectively what I said, without specific reference to the Stefan-Boltzman Law that most here would likely not care about.

Several of us have been saying essentially the same thing starting with wx7man's partially correct theory 1 in post #4 and me in post #6.

So there have been quite a few repeats each offering different sets of details...

Doug

 

[Little Rickie]

Several of us have been saying essentially the same thing starting with wx7man's partially correct theory 1 in post #4 and me in post #6.

So there have been quite a few repeats each offering different sets of details...

Doug

I'm glad we can all agree on this with different words. Peace has come to the universe and balance back to the forum. God bless us all, to each and everyone of us health happyness and prosperty..

 

[TCD]

Fellow nerds -

You all would probably enjoy this book:

http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=stripbooks&field-keywords=quantum&x=19&y=21

It has a fairly lengthy discussion of the struggles of physicists to explain the mechanisms behind blackbody radiation. The writing is a little sloppy (a few pronoun - antecedent failures, etc.) but the story telling is good.

TCD

 

[erugs]

I do appreciate the variety of answers here. Thanks for all assistance in taking care of this nagging question. (Just because I only thought of it one time, and just for a moment or two, doesn't mean it wasn't nagging.)

 

[Little Rickie]

I think you're on to something.

Have you noticed the frost is worse if you've been drinking alcohol?