Naked Science Forum
General Science => General Science => Topic started by: BlueSun on 30/12/2011 21:41:10
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I was thinking ....
how much pressure can I create by placing liquid nitrogen in a container with a small opening at the top?
lets just say the container is unbreakable and the outside temperature is 100f heating the container to the same heat as well.
there is a critical pressure point of LIN to consider of 492.3 psia, what happens to it above such pressure?
thanks for your wisdom
:) ;) :D ;D 8D 8 :o) O8)
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The property you are interested in is Vapor Pressure.
http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=5
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fencyclopedia.airliquide.com%2Fimages_encyclopedie%2FVaporPressureGraph%2Fnitrogen_vapor_pressure.gif&hash=c45c450efd56ad50e0b6d96a73262d21)
Unfortunately, I'm only seeing vapor pressure charts for low temperatures.
Nitrogen filled welding cylinders are distributed as pressurized gas, so the vapor pressure at "Room Temperature" is exceeding 2000 psi or so.
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According to my handy-dandy thermo calculator, if you heat LN2 at atmospheric pressure to 100f (37.8C) and don't allow it to expand or escape, it will reach a pressure of 308,425kPa (that's about 44,732 psi) and it will form a supercritical fluid.
Don't know much about supercritical fluids, but I think they are neither a gas or a liquid.
To stay below the critical pressure (3390kPa), you'd have to let it expand to about 22 times its original volume.
BTW, it's not all that easy to heat the stuff. If you put it in a non-insulated container, water from the atmosphere will freeze on the container and slow down the heat transfer. People have made vehicles that run on liquid nitrogen, but one of the major problems is ice forming on the heat exchanger.
(Standard atmospheric pressure is 100kPa)