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Old 02-10-2012, 11:29 PM   #15
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Regardless of what my wife thinks, no.
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Old 02-11-2012, 10:14 AM   #16
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Quote:
Originally Posted by djbmsu View Post
The fact is wind chill ONLY effects skin, nothing else
period !
(advanced apology to all engineers...)(and anyone else who reads all of this)

Any wind increases the temperature loss of an object to the ambient temperature on all objects exposed to the wind, not just skin. This is why you can blow on hot coffee to reduce the surface temperature.

Wind cannot reduce the temperature below the ambient temperature, only to the actual temperature. If the temperature is 32 degrees Fahrenheit or below, the time it takes for an object to freeze will be shortened.

Conversely, if you place an ice cube in a non-freezing room, the ice cube will melt faster if you blow room air on it.

It is true that wind affects the perception of temperature on our skin, which explains the term WINDCHILL, which is the perceived measurement of heat transfer theory on a human face at 5 feet above ground level, blah, blah, blah.

The original post asks the effect on water. The answer is "Yes," it speeds heat loss on all exposed objects; and "No," it will not freeze unless the air temperature is already freezing.

Respectfully submitted,

(I had surgery on my knee and have ENTIRELY TOO MUCH TIME to kill)
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Old 02-11-2012, 01:22 PM   #17
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Does water freeze if windchill is below 32 degrees but the actual temp is above 32 degrees?
Only if the water has been connected to a flux capacitor.
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Old 02-11-2012, 01:35 PM   #18
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Did u know that -40F is also -40 celsius, thats the only point I believe they come together.
found that out snowmobiling in canada once upon a time . A little , no a lot off topic but??? and thats without the Flux Capacitor
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Old 02-11-2012, 04:25 PM   #19
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Wind chill is the opposite of heat index. It makes cold really cold and heat index makes hot realy hot, I think, maybe, sort of.
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Old 02-11-2012, 05:38 PM   #20
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Wind chill is the opposite of heat index only in the context of human perception of the actual temperature. They are determined very differently.

Wind chill is a simple formula based solely on wind speed and temperature - as already stated above.
NWS Wind Chill Index

Heat index is another simple formula based solely on humidity and temperature.
National Weather Service Heat Safety

And yes, -40C = -40F and is the only point where that happens.
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Old 02-11-2012, 07:04 PM   #21
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Sorry but I believe the consensus answer here is incorrect. Assuming you're talking about an exposed water surface and not water in a sealed container, there would be evaporative cooling and the water would be a little cooler than the air temperature (evaporation would be increased by moving air over the surface). So it would be possible to have some freezing even though the air temperature remained just above the freezing point.
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Old 02-11-2012, 07:51 PM   #22
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So js, can the ∆H_evaporation of (average city water at 1ATM) ever by greater than ∆H_fusion(0C) + ∆H_liquid(ambient -> 0C) of (average city water)? In the context of the OP the answer is exceedingly doubtful. Hence, the consensus answer IS CORRECT. And please, let's not even delve into the Mpemba effect.

Context is everything in a forum question, especially a scientific one. It's not reasonable to list every extenuating/control condition when providing a simple working answer to a simple question with simple conditions and stay within the simple context asked. Then - for reasons already posted - the posts pile on taking things out of that context and hammering every conceivable - often laboratory conditions required - alternative.

The presumed context of the OP's post on an RV forum is that of a puddle, bucket, or hose-full of water (as in a connection from the pedestal to the RV). Most of these contexts do not even expose the water directly to the air. Hence evaporative cooling is not even a factor.

In the case of a bucket or puddle, the surface area of the exposed water, if aligned so as to maximize wind induced evaporative effects, will STILL require the ∆H_evaporation to be greater than the combined effects of 1) thermal transmission from the warmer water immediately below the wind exposed water (wind also keeping the water continually mixed) and 2) exceeding the ∆H_fusion(0C) + ∆H_liquid(ambient -> 0C) of the water in order for ice to form.

In practical working terms in the context of this scenario, the water will NOT freeze.
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Old 02-11-2012, 08:10 PM   #23
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If its 25 degrees outside and the humidity is 80% what is the heat index?
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Old 02-11-2012, 08:19 PM   #24
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Heat index is considered valid only if the actual temperature is above 27 C (80 F), dew point temperatures greater than 12 C (54 F), and relative humidities higher than 40%.

http://www.campbellsci.com/documents...s/heatindx.pdf
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Old 02-11-2012, 08:27 PM   #25
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Quote:
Originally Posted by nosticks View Post
We need more simple answers like those posted above.

I cringe at a question like the OP asked. It's usually followed by at least one response from some retired and bored engineer presenting his doctoral thesis on thermodynamics, then eventually argued by some retired professor until the thread no longer resembles the original question.
:r ofl:
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Old 02-11-2012, 09:49 PM   #26
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Originally Posted by BudtheDiplomat View Post

Quote:
Originally Posted by nosticks View Post
We need more simple answers like those posted above. ...
And then those simple, elegant, and accurate answers are corrupted and misguided by the inevitable cutesie and/or inaccurate posts that then require nauseatingly detailed further explanation just to set the thread back on the elegantly simple answers path originally posted.... Sheesh....

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Old 02-12-2012, 11:26 AM   #27
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CO_kid
Heat index is considered valid only if the actual temperature is above 27 C (80 F), dew point temperatures greater than 12 C (54 F), and relative humidities higher than 40%.

http://www.campbellsci.com/documents...s/heatindx.pdf
I know I was just being funny.
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Old 02-12-2012, 11:34 AM   #28
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It's amazing how many different ways NO can be expressed.
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