Can you have a Wind Chill Factor at almost Absolute Zero?

Question

Say 1 or 2 above absolute zero, gaseous helium blowing by quickly, is there a Chill Factor?

Answer 1

Wind Chill = The effect that wind has on our perception of cold

At close to absolute 0, we would have no feeling. Every piece of exposed skin would be numb and frozen. There would be no perception of feeling colder with some wind.

Answer 2

Wind chill factor.

Say I heat an object up, say a brick, and stick it outdoors where the air temperature is 10 degrees F with no wind and it takes 5 minutes to cool down to the air temp.
If the air temp were to rise for the next step in my experiment to 20 degrees, I would expect that the brick would take longer to cool off - but it doesn't. What happened? Even though the air temperature had gone up, the wind had also picked up and was removing the heat from the brick at a faster rate. I can therefore say that, even though the air temperature is 20 degrees, the wind gives it the same effect at removing heat from an object as if it were 10 degrees.
That is what is meant when the weather man says the temperature is 10 degrees but with the wind chill, it will feel like minus 5 degrees.
The important thing to remember is that the object will not get any colder than the air temperature - regardless of the wind speed - it will only lose whatever temperature it has that is greater than the air temp much faster - that's why we blow on the spoon when the soups too hot.

Answer 3

Of course asking what a person's skin would feel like at 1K is ridiculous. So lets say the wind chill is the difference between a) The temperature of a still gas surrounding a physical object being held at a fixed temperature by supplying a particular amount of heat per unit time, and b) the temperature of a moving gas in contact with the same object at the same temperature and same rate of heat supply. (It seems to me that this is the meaning the questioner intended.)

In the still gas situation, the temperature will drop exponentially as one moves away from the heated object (see first reference for details). Blowing cold air on the object changes the shape of the exponential dropoff, making it steeper. This leads to faster diffusion of hot particles away from the object, cooling it faster.

There are two cases where this explanation is not valid.

1) If the thermal velocity of the particles is not significantly higher than the velocity of the wind. Helium boils at 4.2K, so lets assume we are at 5K. We can calculate the average thermal velocity of the air in each direction by equating the thermal and kinetic energies

1/2 kT=1/2 m v^2 where K is Boltzman's constant (1.4*10^23), T is the temperature(5), m is the atomic mass of helium in kilograms(.004) divided by avagadros number (6.02^10^23) and v is the velocity.

I get v=103 m/s

so if your wind speed is small compared to this number, you should be able to use ordinary thermodynamic equations to calculate the wind chill.

2) If the objects are moving slowly enough that quantum mechanics becomes important. This happens when pL is not >> h, where p is momentum, L is the typical size of the objects being studied and h is planck's constant 6.6*10^-34. Working backwards I get L of about 10 angstroms.

It looks like both 1) and 2) can be satisfied, so not only is a cooling effect present, it can be calculated using standard thermodynamic equations.

Answer 4

wind chill is a term that is used in accordance with the amount of heat a body can produce. If a body can produce enough heat to keep them warm at 10 degrees F and also keep the body warm at 20 degrees F with 10 mph winds you would say there is a 10 degree chill factor. Because the body cannot keep warm at -273 C there is no point in discussing the topic. A wind chill factor is inconvievable.

Also, absolute zero refers to a state of non-motion. In this sense, wind chill would really be more like wind warmth. But it still doesnt make any sense.

Answer 5

well marvin, the term is wind chill temperature, not wind chill factor. if you have seen a chart before, the graph of wind velocity with apparent temperature is not linear. apparent temperature decreases with increasing wind speed in a curve (exponential decay-like graph).

as expected, there is an asymptote right at the bottom which by definition, will never be reached regardless of wind velocity. at extremely high velocities, you are more likely to reach a state where the collision of helium molecules on a measured object becomes a factor. here, the the collisions impart kinetic energy and thus, heat. as long as the helium gas is moving, absolute zero cannot be achieved this way.

to even get close to 0K, the speed required would be ridiculously high, such that the machine accelerating this gas would impart counterproductive heat to the gas itself.

Answer 6

There would be no wind at absolute zero as molecules are no longer moving -- in order for there to be wind you need gas, and in order to have a gas you need molecules to be excited and moving... Also, wind is created by temperature differences - in order to have a temperature difference you'd obviously need to have a temperature that was higher than absolute zero.

Answer 7

Wind chill only refers to something that generates it's own heat. A person, a house, etc.

Answer 8

A good motivation is what is needed: compassion without dogmatism, without complicated philosophy; just understanding that others are human brothers and sisters and respecting their human rights and dignities. That we humans can help each other is one of our unique human capacities.

-His Holiness the Dalai Lama

Answer 9

At absolute zero, there is no longer any electron movement, so there would be no way to measure it if there were.

Answer 10

conceivably?

Sure