h a l f b a k e r yI CAN HAZ CROISSANTZ?
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My housemate came up with this one.
A thermometer to read the temperature both inside the car and the outside temperature also.
We have one for our house and it does help to know how to dress in the mornings. In a car you would know whether to put on a coat or take it off before getting out.
Also
if you needed a hat to shade against the sun's heat.
Or to pput a hat on to keep warmth in the body.
Indoor/Outdoor Thermometer
http://www1.jaycar....tView.asp?ID=QM6326
So very baked [reap, Oct 04 2004]
[link]
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I have this installed in my car.
All you need is to purchase a standard indoor/outdoor thermometer [link] from your local electronics shop, and place "outdoor" sensor in your wheel arches. |
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Why wheel arches?? You won't be measuring your engine bay temperature, and you won't have the skin effect (if it was exposed to the moving air). |
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A friend of mine from uni has actually bought the extension kits for this and measures the temperature inside, outside, in the air intakes and inside the outlet from his turbo. |
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Baked in higher-end Buicks I've seen and most cars with digital temp controls. |
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Mm, yeah, pretty Baked, both for cars and for houses. |
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[reap] actually there would be no skin effect at all unless the sensor were wet. Wind-chill only effects things that are wet. Actually there would be a very tiny temperature increase due to the friction of the wind, but that couldn't really be a factor unless you're car goes _way_ faster than mine. |
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"It does help to know how to dress in the mornings" |
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The transparent parts of your walls let you "see" outside and they can be opened to also let you "feel" outside. |
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// Wind-chill only effects things that are wet. // |
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It also affects things that are heated. That's why computers have fans, despite not usually being wet. |
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That's not wind-chill though. The computer fan will only cool the heatsink to air temperature, not below. |
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Check out how a Psychrometer works, it measures the difference between the air temperature and the wind-chill factor. |
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// That's not wind-chill though. // |
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"Wind-chill" is an estimation of an equivalent stil-air temperature given an object is above ambient and in a moving airstream. |
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As you point out, thanks to the Second Law of Thermodynamics, the gas stream - no matter how cold - cannot cool the object below its own temperature. |
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But it is a crude approximation, depending on the pressure, specific heat and conductivity of the gas, the surface area of the object, and the velocity of the flow. |
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The typical model is for a human-sized object in air at 1 nominal atmosphere. |
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The wet bulb/dry bulb temperature is linked to absolute humidity which itself is a function purely of temperature, pressure and the gas composition - velocity has no influence, unless by Bernoulli's Principle a change in pressure results. |
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//velocity has no influence// that can't be quite right, otherwise you wouldn't have to whirl it round your head. |
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The velocity only needs to be "non-zero" i.e. no "dead air" around the device. If the air is moving, then the velocity doesn't matter until frictional heating starts to become a significant factor. That's fairly fast in normal air - certainly supersonic. If it were more significant, airframe icing wouldn't be anything like the problem it is. |
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