On Tue, 3 Jul 2007 10:38:54 -0700 "Zoltan Finks" <[EMAIL PROTECTED]> wrote:
> Yes, wind + cold = evil. > > To this day, I still don't know how it works with humidity and cold. > I've been told that humidity makes it feel colder, but I have been > told the opposite too. When my father was in the Naval reserve, he traveled from Miles City, Montana, which was -30 F to Tacoma, Washington, which was +30 F. He said it felt colder on the dock in Tacoma in the same clothing. > Through all my MN winters, I couldn't figure it out. I do know, though, > that one's skin gets very dry there in the winter. > > I'm sure some of the scientifically-inclined will chime in and answer > my mystery, yes? Yes. Your skin gets dry, not because you're outside when it's cold, but because you're inside when it's cold. Humidity is actually RELATIVE humidity: the percent humidity is relative to how much water vapor air at a given temperature will hold [not the actual terminology, but a useful first understanding, see http://en.wikipedia.org/wiki/Relative_humidity]. So a relative humidity of 30% means that the air is holding 30% of the amount of water it can possibly hold at that temperature. Now it turns out, that the hotter it is, the more water vapor the air can hold. That is, say the air is 40 F. At 100% humidity, the amount of water in the air will be about 8 grams per kilogram of air. If the air is 104 F, 100% humidity will mean 50 grams water per kilogram of air. Likewise, if the air is -4 F, 100% humidity will mean about 2 grams water per kilogram of air. So, say it's -4 F and 50% humidity outside. That means there is 1 gram of water per kilogram of air. Now you bring the air inside and warm it up to 68 F. At this temperature, 100% humidity would mean about 14 grams of water per kilogram of air, but you have only 1 gram of water per kilogram of air. Thus the humidity inside is 1/14 = 7% and it's MUCH drier. Does that help? Craig _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
