Re: wind chill
[ Follow Ups ] [ Post Followup ] [ Class Discussion Groups ] Posted by Christopher Pesci on October 05, 1997 at 22:11:48:
In Reply to: wind chill posted by shane frederick on September 16, 1997 at 15:14:29:
: For example consider the following two locations:
: Location A Ambient temperature = -10 Wind Chill = -50
: Location B Ambient temperature = -50 Wind Chill = -50 (Calm): If you stuck a big block of 100 degree aluminum outside in these two locations,
: would it cool to 100 - X degrees in the same amount of time at both location?ANSWER: No. The reason the wind chill is lower at location A is due to the heat transfer coefficient,
which is a function of wind velocity. Reason being, heat transfer is
Q = h(T2-T1)
Where Q is heat flux, and h is heat transfer coefficient.
The higher the wind speed, the higher h is, hence, the
higher the heat flux. (quicker cooling time)
Although, a solid metal object is much more dependent on heat transfer through
conduction rather than convection. But convetion can play a major role in the overall heat transfer
of an object.: Does it matter what the intial temperature of the body is, what it is composed of?
ANSWER: h is dependent on the type of material, as well as the initial temperature.: Does a wind chill temperature really "feel" as cold in both locations. Is there
: any psychophysical evidence of this, or are the wind chill
: formulas based on some physical test, like the one described above?
ANSWER: Turn you fan on in you room, do you feel cooler.
: (4) Can you freeze water by blowing dry air over it quickly, even if the ambient temperature of the air exceeds 0.
No, you can cool the water faster, but if the temperature of the surrounding atmosphere does not reach 0 C, then the water will not freeze.
Please note, I am not trying to act smart, just
had a really good teacher for heat transfer.-Chris