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Wind chill: how to calculate? Is there such thing as wind warmth ?

  1. Aug 6, 2012 #1
    Wind chill: how to calculate? Is there such thing as wind "warmth"?

    If it is really hot outside, and the air were warmer than your skin, would you feel warmer when it blows on you? Would there still be some sort of chilling effecT?

    I'm guessing it's like basic convection. If the the fluid is warmer, the fluit will transfer heat to the body, and you will end up with some heating.
     
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  3. Aug 6, 2012 #2
    Re: Wind chill: how to calculate? Is there such thing as wind "warmth"?

    I think the coolness you feel is just not described by convection. Evaporation of water from your skin also plays a major role in the temperature you perceive of air around you. The loss of heat through evaporation and gain/loss due to conduction together decide whether wind is cool or warm. So in principle, yes, you can feel wind "warmth". But only if you are not sweating profusely at that moment.
     
  4. Aug 7, 2012 #3

    russ_watters

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    Re: Wind chill: how to calculate? Is there such thing as wind "warmth"?

    Almost. Because of evaporation, our bodies' ability to cool itself comes largely from sweat. So cooling amount is based on wind and wet bulb temperature. Wet bulb temp is based on dry bulb (normal) temp and humidity. There are no natural environments where wet bulb temp is high enough to cause a "wind heating" effect, so such a term does not exist. Even on a 110F day in Phoenix, your body can still cool itself -- better than on a 95F day in Philadelphia.
     
    Last edited: Aug 7, 2012
  5. Aug 7, 2012 #4

    sophiecentaur

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    Re: Wind chill: how to calculate? Is there such thing as wind "warmth"?

    But 'wind chill' doesn't only refer to evaporative cooling, surely(?). It must also involve wind speed (forced convection effects) against a dry clothed body.
    Isn't it "wind warmth" inside a fan oven?
     
  6. Aug 7, 2012 #5

    russ_watters

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    Re: Wind chill: how to calculate? Is there such thing as wind "warmth"?

    Wind chill doesn't include evaporative cooling at all...or clothes, for that matter. Wind chill is defined only for cold weather, when your skin is essentially dry. The nearest analogue for hot weather is Wet Bulb Globe Temperature (not the same as wet bulb temperature), which uses a formula to estimate the effects of ambient sunlight and wind on a wet bulb (you, in a sweaty tshirt) on a hot day.

    Yes, wind heating is what happens in a convection oven.

    Fyi, wind chill and WBGT both have good wiki pages.
     
  7. Aug 7, 2012 #6

    russ_watters

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    Re: Wind chill: how to calculate? Is there such thing as wind "warmth"?

    Also, "heat index" (is one I don't like because it is purely subjective) tries to equate what it feels like on a dry vs a humid day.
     
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