Plane on a treadmill part deux.....

[darrenf]

So, for the meteorologists out there....

Can the wind chill ever get water to freeze if the air temp does not drop to freezing?

[tgrayson]

Originally Posted by darrenf

Can water freeze above 32 degrees Fahrenheit?

If the pressure is high enough. Phase changes of substances varies with temperature and pressure. Our "normal" melting and boiling temperatures assumes 1 atmosphere.

(Wind chill won't do it.)

[darrenf]

Originally Posted by tgrayson

If the pressure is high enough. Phase changes of substances varies with temperature and pressure. Our "normal" melting and boiling temperatures assumes 1 atmosphere.

(Wind chill won't do it.)

Thank you.

I am in a debate on another forum and a gentleman who states he teaches science at a local high school just does not get this. He is convinced that frost has formed on his windshield at 35 degrees because of windchill.

And this is what he teaches his students!!! God help our future.

[tgrayson]

Originally Posted by darrenf

not get this. He is convinced that frost has formed on his windshield at 35 degrees because of windchill.

There is a temperature drop when the pressure drops; the Bernoulli effect over the car might produce this.

[darrenf]

Originally Posted by tgrayson

There is a temperature drop when the pressure drops; the Bernoulli effect over the car might produce this.

That's my thought to. But he attributes it to "wind chill" alone.

[tgrayson]

Originally Posted by darrenf

That's my thought to. But he attributes it to "wind chill" alone.

Ask him how wind chill works.

(And ask how heat can spontaneously flow from a cold body into a warmer body, a violation of the 2nd law of thermodynamics.)

[darrenf]

Originally Posted by tgrayson

Ask him how wind chill works.

(And ask how heat can spontaneously flow from a cold body into a warmer body, a violation of the 2nd law of thermodynamics.)

Already done. I mentioned earlier I think he needs to revisit thermodynamics, and at that point he got tired of "tutoring" me. If we wanted to continue I would have to pay him $45/hour. Scary man, scary.

[tgrayson]

Originally Posted by darrenf

Already done.

What's his background? BS in some area of science? Or education degree?

[darrenf]

Originally Posted by tgrayson

What's his background? BS in some area of science? Or education degree?

For your entertainment.....

Just received this in a PM.

This thread is boring to SX and will be to others tomorrow. You don't even understand the information in the links you send. What do you think the purpose of the Stevenson Shield is????? Possibly to block WIND?????????????? Why do you think they talk about clear CALM nights???????????????? I'm tired of this thread myself. I won't confuse you with facts, your mind is made up. If you can't accept what science has for over a century, oh well.

[Berkut]

Hi, I voted no just to be contrary.

[tgrayson]

Originally Posted by darrenf

Stevenson Shield is????? Possibly to block WIND??

Hmmm...

A Stevenson screen or Instrument shelter is a meteorological screen to shield instruments against precipitation and direct heat radiation from outside sources, while still allowing air to circulate freely around them.[1] I

[darrenf]

Originally Posted by Berkut

Hi, I voted no just to be contrary.

[darrenf]

Originally Posted by tgrayson

Hmmm...

A Stevenson screen or Instrument shelter is a meteorological screen to shield instruments against precipitation and direct heat radiation from outside sources, while still allowing air to circulate freely around them.[1] I

Funny eh?

This was my response.

I weep for our future. I can only surmise that you also teach intelligent design in your biology class. A Stevenson shield is not designed to block the wind, it is designed to allow wind to pass through while shielding instruments from precipitation and radiation. Do you really teach at Ab$%#i? How would the parents there feel if they knew their "Science" teacher didn't understand science?

[tgrayson]

Originally Posted by darrenf

Funny eh?

He's fighting a rearguard action while retreating.

[darrenf]

Surprisingly I got a response. This is just too good.

I really do teach at Ab$%#i and we had the highest scores in Atlantic County for the state science test. Intelligent design is a dirty word in my vocabulary. I apologize for not researching Stevenson Shield, but still, why do you think they specify CALM nights? As far as any molecule of water never being subjected to to below freezing temperatures, maybe you don't believe that some of the water you are now drinking (or soon will be) was once dinosaur pee. If you can't understand the messages I posted in the forum, I weep for our future too. Every molecule of water on Earth has been subjected to below freezing temperatures. Some of them have not fully recovered from the last time, so they exist as an AVERAGE in above freezing water. Please do some research. I'm not replying to public, or private messages about this until I receive $45

[tgrayson]

Originally Posted by darrenf

Every molecule of water on Earth has been subjected to below freezing temperatures. Some of them have not fully recovered from the last time, so they exist as an AVERAGE in above freezing water.

What????!! Water molecules have memory?

[darrenf]

TG, Should I keep this voyeuristic experience going?

[tgrayson]

Originally Posted by darrenf

TG, Should I keep this voyeuristic experience going?

Only if you like pulling legs off of bugs.

[darrenf]

Originally Posted by tgrayson

Only if you like pulling legs off of bugs.

[Cessnaflyer]

I thought wind chill was only for living beings and not for water molecules.

[seagull]

Originally Posted by tgrayson

What????!! Water molecules have memory?

They've been clearly traumatized! We should start a fund for them, so they can receive proper attention to help them to recover. We probably could get donations from High School science teachers! Frozen, melted, evaporated, sublimated. The Horror!

TG, a certain 15 year old (with a cool website), had this to say about it:

Yes! Of course, the logical counter-argument is that since there were times in the history of the earth were all water existed as a gas, it could be argued as well that they have not yet recovered from being too hot.
Isn't it ironic when people are wrong even if their basic assumptions were correct?
Not to mention that really many water molecules are quite new because of photosynthetic and respiratory reactions.
Or do the hydrogen ions and oxygen molecules have memories as well?
And all the electrons?
Not to mention that those molecules are later used to create Carbon Dioxide, Carbon Monoxide, Ozone, and thousands of other compounds that contain oxygen or hydrogen. Clearly we are all on the point of being deep-frozen.

[tgrayson]

Originally Posted by seagull

T Isn't it ironic when people are wrong even if their basic assumptions were correct?

That was my thought as well; I didn't see how his assumption supported his theory in the first place. But it's one of those remarks that makes your jaw drop and you aren't sure where to start ripping first. Your son's way of illustrating the silliness was very good.

[tgrayson]

Originally Posted by Cessnaflyer

I thought wind chill was only for living beings and not for water molecules.

I would expect it to be true of anything that generated heat; for instance, a piece of machinery. The heated air around the object would reduce rate of heat loss, producing an increase in temperature of the object. Removing the thermal layer should produce a reduction in temperature of the surface of the object.

Regardless, the temperature of the object will not be less than ambient temperature; it's just cooler than it would be without the wind.

[Realms09]

"Wind chill" is simply the TV weather man term for forced convection, which is distinguished from free convection. On a calm wind day you will exchange heat (energy) with the environment through a free convective cell. Air around you heats up, it expands and becomes less dense, then it rises up and is replaced by cool air. In order for free convection to work there needs to be a density gradient in the ambient air, i.e., gravity. That's no different than what we learn about cloud formation in Jeppesen 101.

Forced convection operates on the same principle but uses something other than just gravity to facilitate the movement of air, such as a ceiling fan or neighboring high and low pressure systems.

In both cases the heat transfer is proportional to the temperature difference between the surface of the object of interest and the ambient temperature, so you will not cool to below ambient due to "wind chill" alone.

However, I can imagine scenarios where a cup of water will self-cool from above freezing to freezing. Take the cup of water, wrap it around the sides with an adiabatic blanket, and put a vacuum on the top. Water will evaporate (get rid of its most energetic molecules) and cool in the process until phase equilibirum is reached, which could be below freezing.

[ILSstud]

Congratulations Mister Science Teacher Man...200 dollars have been donated to the "Water Molecule Emotional Outreach Fund" ...

Scary to think indeed....wind chill is nothing more than a moving mass of air REMOVING latent heat from our bodies. We interpret that as a colder temperature than the ambient, but it is simply an illusion. Out of curiousity, ask him if a plane will fly on a tread mill. I am curious what HIS response is....