elementary science question

why do I feel cooler when I drive my car with the windows open?

http://en.wikipedia.org/wiki/Wind_chill
-this has the same explanation, which you can read off the above link.

Originally posted by robbie carrobie
why do I feel cooler when I drive my car with the windows open?

Because only nerds drive with their windows up?

Originally posted by humy
http://en.wikipedia.org/wiki/Wind_chill
-this has the same explanation, which you can read off the above link.

Its not entirely clear and peppered with equations, i simply want to understand the concept.

I would assume that as I travel in my truck and the air passes over and around my vehicle I should generate heat due to air friction and it should therefore be that the ambient temperature should feel warmer rather than cooler. I just want to understand why air passing over a moving object like a car becomes cooler and not hotter. The same as a fan I suspect.

Originally posted by Eladar
Because only nerds drive with their windows up?

ha! 😀

Originally posted by robbie carrobie
Its not entirely clear and peppered with equations, i simply want to understand the concept.

I would assume that as I travel in my truck and the air passes over and around my vehicle I should generate heat due to air friction and it should therefore be that the ambient temperature should feel warmer rather than cooler. I just want to understand w ...[text shortened]... sing over a moving object like a car becomes cooler and not hotter. The same as a fan I suspect.

The reason is heat transport is enhanced due to the movement of air. When something is warmer than the surrounding air, a layer of warmer air surrounds the object. Wind moves away this layer of warmer air, after which new air molecules are heated up.

Originally posted by KazetNagorra
The reason is heat transport is enhanced due to the movement of air. When something is warmer than the surrounding air, a layer of warmer air surrounds the object. Wind moves away this layer of warmer air, after which new air molecules are heated up.

Thats amazing, so my truck as it travels along is constantly having this layer of warm air removed and thus it feels cooler inside the cab. Is it the same phenomena wherever you go, say 30,000 feet or reentry back into the atmosphere from space? because I assume that air density has some correlation to heat transport.

Originally posted by robbie carrobie
Its not entirely clear and peppered with equations, i simply want to understand the concept.

The link is perfectly clear on the concept and without stating any equation first. Just read it. It says:

"...Explanation

A surface loses heat through conduction, convection, and radiation.[1] The rate of convection depends on the difference in temperature between the surface and its surroundings. As convection from a warm surface heats the air around it, an insulating boundary layer of warm air forms against the surface. Moving air disrupts this boundary layer, or epiclimate, allowing for cooler air to replace the warm air against the surface. The faster the wind speed, the more readily the surface cools.

The effect of wind chill is to increase the rate of heat loss and reduce any warmer objects to the ambient temperature more quickly. It cannot, however, reduce the temperature of these objects below the ambient temperature, no matter how great the wind velocity. ..."

-no equations stating there or before that bit and, as you can see, it states the concept perfectly clearly.

Originally posted by robbie carrobie
Thats amazing, so my truck as it travels along is constantly having this layer of warm air removed and thus it feels cooler inside the cab.

No, it is the surface of your skin that is being discussed not the cab of your truck. If your window is open, the air inside the cab moves around and the warm air near your skin is replaced with cooler air.

Also not mentioned in this thread is the fact that evaporation of sweat from your skin can have a significant cooling effect (that's why we sweat) - and evaporation is significantly enhanced by air movement for partly the same reasons as the wind chill explanation - still air has higher moisture content near your skin whereas moving air moves the water vapour away so more can evaporate.

Originally posted by humy
The link is perfectly clear on the concept and without stating any equation first. Just read it. It says:

"...Explanation

A surface loses heat through conduction, convection, and radiation.[1] The rate of convection depends on the difference in temperature between the surface and its surroundings. As convection from a warm surface heats the air around it, ...[text shortened]... s stating there or before that bit and, as you can see, it states the concept perfectly clearly.

KazetNagorras explanation was much simpler and easier to assimilate, he would make a great teacher, nevertheless, I sincerely thank you for taking the time Humy.

Originally posted by twhitehead
No, it is the surface of your skin that is being discussed not the cab of your truck. If your window is open, the air inside the cab moves around and the warm air near your skin is replaced with cooler air.

Also not mentioned in this thread is the fact that evaporation of sweat from your skin can have a significant cooling effect (that's why we sweat) ...[text shortened]... ure content near your skin whereas moving air moves the water vapour away so more can evaporate.

Ok, I understand now, its the layer of air around me that is being driven away by the motion of my truck as it creates air turbulence. Its still amazing though and now a new phenomena I did not consider, evaporation of moisture. It appears that we are literally liquid cooled.

The post that was quoted here has been removed

lets set the controls to the heart of the sun to find out 😀

Originally posted by robbie carrobie
why do I feel cooler when I drive my car with the windows open?

The effect is increased if you put your arm out the window and wear sunglasses.

Seriously Robbie, do they not have fans in Scotland? Does the wind not blow in Scotland?