Science Buddies: "Ask an Expert"

Hi All,

Never have received a good answer from this .... but sure you can answer it for me!!

Scenario: liguid gas, say nitrogen is more dense and very cold - if you put it in a sealed container so it can not escape (or expand)- say a high strength metal cylider then:

will it remain at the low temperature inside the cylinder?

And if it does (since it can not expand into a gas changing to room temperature) then:

why will it not cool the walls of the cylinder and outer air indefinitely?

Perpetual fridge? Obviously not but why??

In otherwords what it the temperature of liquid nitrogen in a sealed container? What is the temperature of the INNER wall of the container and what it the temperature of the OUTER wall of the container. and why?

THANKS!


Thanks

Andrew

astrever - I think the perpetual fridge is not going to work. The cylinder, and it's gas contents, will ultimately reach whatever ambient temperature the cylinder is exposed to. The nitrogen will not stay at its initial temperature. There is a danger of creating a real "bomb" here as the boiling point of liquid nitrogen is -196 C. That's a minus. Liquid nitrogen is usually stored in highly insulated thermos type containers called Dewar flasks. These are always vented to the atmosphere so gas that is 'boiling' off can escape as it warms. In that your design says the vessel is sealed and gas cannot escape, as the nitrogen 'boils off' the pressure inside will rise to unbelievable and unsafe levels. Possibly upwards of 50,000 PSI at around room temperature. This will certainly burst any container. As an example, nitrogen gas used for welding and other industrial applications is stored in very high pressure vessels rated around 2000-3000 PSI. In that your question was a theoretical, I'm confident you will not try to obtain liquid nitrogen or observe what happens in this scenario. Hopefully my explanation will suffice.

Rick Marz