neal@druhi.ATT.COM (XGPB30000-McBurnettND(DR9225)289) (01/26/91)
Yes, the wind chill can be below absolute zero (-273 C). This is because it is not really a measure of temperature, but an equivalent temperature for the purposes of determining heat loss from bare human skin which is at normal skin temperature. At such low values the original formula would not really be valid, but conceputally there is no problem with the wind chill being below 0 K. With enough wind, you would die more quickly from exposure at 50 K (say, in a helium atmosphere) than you would at 0 K (ignoring the fact that your surroundings would be solid: what is the heat conductivity of solid helium?) -Neal McBurnett // AT&T Bell Labs, Denver // neal@druhi.ATT.COM, att!druhi!neal
jcampbel@SRC.Honeywell.COM (Jim Campbell) (02/07/91)
At 0K, heat transfer happens by conduction (since the entire environment is solid) NOT convection as is normally the case when considering wind chill. Since conduction heat transfer is much more efficient than convection, a wind chill of below 0K is pretty much meaningless. I do not believe that Wind Chill Index would be a measure of anything when it returns a value below absolute zero.
edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.)) (02/07/91)
In article <1991Feb6.234637.2628@src.honeywell.com>, jcampbel@SRC.Honeywell.COM (Jim Campbell) writes: >At 0K, heat transfer happens by conduction (since the entire environment is >solid) NOT convection as is normally the case when considering wind chill. The situation was not 0K moving wind. Rather, it was cold, but not 0K, moving wind. >Since conduction heat transfer is much more efficient than convection, a >wind chill of below 0K is pretty much meaningless. Okay, it was a VERY fast wind. Remember, this is just theoretical -- nobody is saying that it is actually going to happen, just that it is "possible" to lose heat more quickly than one would lose heat from "air" at 0K. >I do not believe that Wind Chill Index would be a measure of anything when >it returns a value below absolute zero. It's a measure of heat loss. -- edp (Eric Postpischil) "Always mount a scratch monkey." edp@jareth.enet.dec.com
hoford@sequoia.upenn.edu (John Hoford) (02/08/91)
In article <1991Feb6.234637.2628@src.honeywell.com>, jcampbel@SRC.Honeywell.COM (Jim Campbell) writes: >At 0K, heat transfer happens by conduction (since the entire environment is >solid) NOT convection as is normally the case when considering wind chill. >Since conduction heat transfer is much more efficient than convection, a >wind chill of below 0K is pretty much meaningless. I think the way wind chill must be something like if there is a wind at a given temperature a human would lose heat at a give rate. what temperature would be required for the human to lose heat at the same rate without the wind