Is it true, air gets cooler if forced through a small hole or gap?

Question

Not just air but any fliud in fact.

I read this in a book and am wondering if it is actually true.

or if only part of this statement is true.

Normally i would wiki something like this up before asking on Y!A.

Thanks

Answer 1

It would get cooler if it was released from the small tube to a larger sized volume, the temp law says P*V = Constant * T, meaning temp is directly proportional to product of pressure and volume, if pressure/volume is decreased then temp will go down.

Answer 2

My farts are usually warm-So no

Answer 3

Yes, in fact it does. You can even do a simple test:

1) Get a spray bottle.

2) But boiling water inside the spray bottle.

3) Spray it onto your arm or hand.

You'll notice that it doesn't hurt because it's not hot anymore.

Answer 4

Who Cares?!

Answer 5

I would imagine due the to the pressure build up it would get hotter.

Answer 6

If you force a fluid through a small hole, the fluid gets cooler and the hole gets hotter.  The effect is called adiabatic expansion and it's how fridges and freezers work.

Answer 7

It is true for gases, provided that they expand rapidly on the far side of the hole. If they expand rapidly they do not have time to aborb heat from their surroundings - this is called adiabatic expansion (adiabatic means the energy stays the same). Hence in order to force gas out of the way on the other side they must expend energy and this can only come from cooling.

It is NOT true of liquids. Liquids, unlike gases, are incompressible, and so do not expand on the far side of the hole.

Answer 8

I would have thought so as the gas needs to be compressed to get through the small hole - causing the molecules/atoms to be squeezed together, this state is usually caused by a temperature drop (gas - liquid - solid) so therefore compressing the atoms/molecules would drop the temperature