Wind Chill question

[Warstud]

Originally Posted By: NOAA
Wind Chill is the term used to describe the rate of heat loss on the human body resulting from the combined effect of low temperature and wind. As winds increase, heat is carried away from the body at a faster rate, driving down both the skin temperature and eventually the internal body temperature. While exposure to low wind chills can be life threatening to both humans and animals alike, the only effect that wind chill has on inanimate objects, such as vehicles, is that it shortens the time that it takes the object to cool to the actual air temperature (it cannot cool the object down below that temperature).

 

[GreeCguy]

Originally Posted By: morepwr
I would say no since the orchards near here with both citrus and avocados use wind machines when the temps drop below 30.


Wind machines are used for two reasons in the Citrus business.

One, if the danger is frost. A wind machine is used to keep the air moving so that the frost doesn't settle.

Two, if there is a layer of warm air above the cool air, (temp inversion), the goal is to bring the warm air down into the grove to keep it from freezing.

On an extremely cold night, wind machines would actually make the grove colder.

 

[GreeCguy]

Originally Posted By: IndyIan

For trees specifically, wind does increase the "freezer burn" effect in sensitive trees like fruit trees. But thats more of a sublimation issue.


Especially if the tree is in a "sappy" condition, say for example if the weather has been warm prior to the cold snap. Fruit will freeze under "wind chill" conditions.

As an experiment, take an empty gallon milk jug and add a teaspoon of water. Now, tie that jug to your car and drive down the road when the outside temp is say 37 degrees. The water will freeze.

 

[Kestas]

Flawed argument. The water inside the jug will stay 37 deg.

 

[GreeCguy]

Originally Posted By: Kestas
Flawed argument. The water inside the jug will stay 37 deg.


I've done it and it works.

I have used old antifreeze jugs to hold gasoline/oil mix for my chainsaws. When I lived in Alabama, I would wash these out and to make sure all the water was gone before I added the gas/oil mix, I would tie them to my bumper or mirror and drive down the road. The gas station was two miles down the road and by the time I arrived, the water would be frozen and all you had to do was knock them on your hand and little chunks of ice would fall out of the jug and nary a drop of water would be in the jug.

 

[Shannow]

Jugs left open, or sealed ?

 

[GreeCguy]

I left the caps on mine, I didn't want road dirt in my jugs.

 

[Shannow]

then wind chill doesn't affect the water contained therein...

 

[GreeCguy]

Then why did the water freeze?

 

[Trav]

Originally Posted By: bepperb
No, the closer to ambient temperature of an item the less "wind chill" it experiences. A tree is at the same temperature as the air (more or less depending on sunshine I guess) and feels no effect.

Wind Chill is the added cooling effect on a warm object the moving air has, but wind cannot cool an object below the temperature of the air.


This puts another twist in the discussion. Trees and plants are living things and if they generate heat then wouldn't the effect on them be similar?
Quote:
Another possibility, she said, is that many plants — in the Northeast, especially those that bloom early in the spring — generate their own heat for various reasons.


http://www.nytimes.com/2011/04/12/science/12qna.html?_r=0

http://biology.stackexchange.com/questions/222/do-plants-produce-any-heat

 

[hisilver]

I can't imagine how a plant or tree 'generates' heat. The friction of water/nutrients traveling through the zylem and phloem? The inherent heat/energy in all matter?

 

[Trav]

No idea, but in the example they gave they sure seem to be able to.
So the question remains does wind chill have an effect on them? I mean a living tree or plant isn't like a piece of firewood outside.

Way above my pay grade.

 

[GreeCguy]

Originally Posted By: Trav
No idea, but in the example they gave they sure seem to be able to.
So the question remains does wind chill have an effect on them? I mean a living tree or plant isn't like a piece of firewood outside.

Way above my pay grade.



While I am by no means a scientist, I have seen real world experience when wind chill will severally damage an orange tree and will freeze the fruit on the tree. Wind is one of the many things citrus growers fear as it's so hard to battle.

 

[Warstud]

When I was in the military out doing desert training... someone tied a leather flask full of water to our truck. After a few hours of driving around....the water was nice and cold.

 

[Shannow]

Same down here with the aforementioned canvas water bags on the front bumper...leather/canvas gets damp, and evaporation cools the contents.