Properties of Hydrogen.

[cryotechnic]

If a gas under pressure is expanded to a lower pressure, the tempereature of the gas will drop.

One of the properties of hydrogen is that after expansion the temperature of the hydrogen will rise.... Can someone explain this to me?
I've read on the internet that Hydrogen has a negative Joule-Thompson coefficient.
But still, so far I haven't found much information in the net.

Does someone have any figures or further info related to this for me?

I've also heard that there are 2 types of Hydrogen. But from that I haven't found anymore info.

Thanks!
Cryotechnic

 

[EdStainless]

For each gas there is a J-T inversion conditions which are defined by the pressures (before and after) and the starting temperature. If you expand from above it you get heating, below it and you get cooling.
You can find the math in any thermodynamics text, this is the basis for air liquifaction and seperation.
Note: ideal gases will not change temp on throttling. This is one effect that is a result of real gases being non-ideal.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[cryotechnic]

Thank you EdStainless.
So, if I understand correctly, is it possible to generate heat with any gas that is expanded, as long as this gas answers to its inverse condition.

I'm working in an airseparation plant myself. The thing is, that in the whole proces, all the gases are getting colder after expansion. There is no point in the process where one of the gasses is beyond it's inversion point.

I was not aware of this inversion point. Apparently the inversion point of Hydrogen (but also Helium) is at a very low temperature.

Thanks
Cryotechnic