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exactly why they had to warm up their
balls
----- Original Message -----
Sent: Tuesday, November 18, 2003 3:17
PM
Subject: Re: [smartBridges] Airpoint gone
mad and turned into AB
Wow, Eje! That must have been a cool place to
work!!
Sevak
On Mon, 2003-11-17 at 22:10, Eje Gustafsson wrote:
When your start talking that high wind speed then I have to give and
your correct.
I remember when I worked for the Aeronautical Research Institute of
Sweden the super sonic wind tunnels we had there they had some
gigantic containers with metal globes in them. Before they ran a test
they started a heated in these containers to heat up the balls in
there. while they built up preasure. Why just because as you say the
air gets such a cooling effect that if they didn't warm up the air
the sudden burst (3-5 seconds) would freeze down the metal arm the
model was mounted on and the model and the pressure would risk break
the now chilled down item. So to avoid these accidents they had to
heat the air to avoid the humidity etc in the air to cause problems.
But my understanding that one large problem was just that humidity so
it was not just to raise the temp but also to "dry it up".
Best regards,
Eje "Aya" Gustafsson mailto:[EMAIL PROTECTED]
The Family Entertainment Network http://www.fament.com
Phone : 620-231-7777 Fax : 240-376-7272
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--
SA> John, you're absolutely right! Moisture evaporation is
SA> another method of cooling in addition to wind. But you are
SA> incorrect regarding "no matter how much wind there is it can't be
SA> colder than the air temperature."
SA> There are several modes of cooling by motion of air molecules
SA> over a surface -without the need for evaporation.
SA> For example, on a molecular level, all air within a given
SA> volume over, say Nevada, is at the same temperature of 90*. This
SA> means that all the molecules bouncing around in random directions
SA> collectively have an AVERAGE temperature of 90*. The molecular
SA> speeds are actually very fast and taken together have a skewed
SA> bell curve look. It is the speed of the molecules alone that
SA> determines the temperature! If a wind blows, the random
SA> directions of the molecules have a new resultant direction in the
SA> direction of the wind. This new vector has on average a much
SA> lower speed than the other random directions that the molecules
SA> are shooting off in. Given a test subject also at the ambient
SA> temp of 90* within the path of the wind (and this new vector), the
SA> molecules extract energy from the object in the direction of the
SA> new vector (i.e. wind). This extraction of energy is cooling the
SA> object.
SA> In another application of this same principle, think what
SA> happens to supersonic jet planes. The speed at which they strike
SA> molecules -no matter what temperature they're at because they can
SA> only cool at sonic or subsonic speeds- will heat up the normal
SA> surface (the flying edge) of the plane.
SA> Hope this clears it up. (yes, I'm a physicist.)
SA> Sevak
SA> On Mon, 2003-11-17 at 11:53, John Banes wrote:I think you
SA> guys are mixing up cooling and chill factor. Chill factor is the
SA> result of moisture evaporation lowering the surface temperature below
SA> ambient temperature.
SA> In humans we always have moisture on our skin so the wind causes it to
SA> evaporate faster lowering the temperature below the actual air temperature.
SA> I would guess that on a rainy day your wet radio might also have a chill
SA> factor, but if it is dry there is no evaporation therefore no chill factor.
SA> No matter how much wind there is it can't be colder than the air
SA> temperature.
SA> John
SA> ----- Original Message -----
SA> From: "Dimitrios Sidiropoulos" <[EMAIL PROTECTED]>
SA> To: <[EMAIL PROTECTED]>
SA> Sent: Monday, November 17, 2003 7:50 AM
SA> Subject: Re: [smartBridges] Airpoint gone mad and turned into AB
>> Eje,
>>
>> Do not forget that the unit radiates heat at all times.
>> If it is 10*F and no wind the temp inside the unit will be 10+.
>> If there is wind (still at 10F) it will absorbe more heat from the unit
SA> and it will
>> lower it's temp closer to the 10F.
>>
>> If you test the specs of a unit at -40F inside a freezer then the temp
SA> inside the
>> unit will higher then -40 (lets say -38) if there is wind at -40 then the
SA> temp
>> inside the unit is closer to -40 (although still not -40)The faster the
SA> wind blows
>> the closer it gets the ratior temp to the real temperature.
>>
>> So yes!! Wind does affect the temperature of the radiator all though it
SA> has no
>> effect on the radiating ellement, etc.
>>
>> Thank you
>> Dimitri
>>
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