Joule-Thomson Process

"You may try this by going to your favorite auto garage and using their air line to spin screwdrivers in the air"

Spinning gears is much more fun. Put one on a horizontal pencil, spin it up and let it gently off the pencil and watch it run out the door.

Have you ever wondered why there's a picture of you in all the area garages saying "Call the police if this guy asks to use the air hose."?

But, as long as you're causing trouble anyway, if you ever get the use of anybody's liquid nitrogen tank, try it with that. You can get some tremendous expansion on hot days!

thanks, but my purpose is not ordinary life as you mentioned. as you know, based on the thermodynamic, in the joule thomson process, like a JT Valve in the gas industry, pressure drop of gas flow causes reduction in its temp.(except H2, NE, HE). in this process, there is no heat/ work exchange. the enthalpy is constant.

I'm willing to be clarified the concept(mechanism or reason) of the temp. change.

I agree with your words. But, My question seeks the concept of the matter. I don't mean it justified by the formula, PV=nRT, as done by greendog. Let me please to say my question in details as follows,

Consider a JT( throttling) process, adiabatic free expansion, in which a fluid passes a restriction ( like a valve),

1. If the fluid is a real gas, the temperature decreases(or increase) due to drop in pressure. why or how does this temperature reduction(or rise) take place?
2. If the fluid is an ideal gas, the temperature doesn't change. why or how does the temperature remain constant?

I guess you want to know why gas does what it does. I guess no one can answer a question like that. Why is water wet? Who knows?

I can tell you why gas does what it does. Send me £500 in small bills (the ones that have Kris's picture on them instead of that Liz person) and I'll explain about stuffed cabbage and pickled beans.

There is no similarity between these two subject(wet and temp. change). Please think about the query carefully.

For more clarification, Lets review the concept of the temperature by thermodynamic. By definition, temperature is the degree of hotness or coldness of a material. Or, temperature is a measurement of the average kinetic energy of the molecules in an object or system. The greater the heat absorbed by a material, the more rapidly the atoms within the material begin to move( or vibration), and thus the greater the rise in temperature. So, changing in temperature of a material denotes the energy change in it. Now, we should come back to our discussion, seek an answer for this question, how does the energy of a real gas, undergoes a throttling process( adiabatic free expansion), change? What about a ideal gas?

By definition the energy is unchanged in both gases(real or ideal). The use of English language words might complicate matters. So I'm want to apoligize for any confusion I caused by asking why water is wet. Some things just are what they are and there is no way to know why that is.