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sc298
Oct18-09, 04:13 PM
I am looking for an equation to determine the pressure produced by boiling a liquid.
(On the net I can only find information on the effect that pressure has on boiling point)

for example, the pressure produced by heating liquid nitrogen to 0K.

Any help would be great!

Thank you
russ_watters
Oct19-09, 12:41 AM
"Boiling" means to heat a liquid to where the partial pressure of the gas is above ambient pressure. So if you confine a liquid and heat it, the pressure produced corresponds to the partial pressure or saturated vapor pressure at that temperature. You find this from a table, ie a steam table or similar. There are some on the web and any good thermo book will have a bunch of tables for different fluids in it.

Tables for Nitrogen might not go up that high - the pressures would be huge as that is well above the critical point for nitrogen (the point at which you can no longer distinguish liquid from gas - you can no longer define "boiling").
Phrak
Oct19-09, 01:26 AM
You wouldn't heat Nitrogen to zero Kelvin. You would cool it.

Zero Kelvin is really cold.
russ_watters
Oct19-09, 01:33 AM
Lol, sorry - I saw 0K and thought 0C.
Phrak
Oct19-09, 01:40 AM
Lol, sorry - I saw 0K and thought 0C.

You could talk to Redbelly about my blunder converting between Celcius and Kelvin. It went on for several posts :redface:
sc298
Oct19-09, 02:23 PM
You wouldn't heat Nitrogen to zero Kelvin. You would cool it.

Zero Kelvin is really cold.

I meant heat Liquid Nitrogen to 0C (273K)
Phrak
Oct20-09, 01:05 AM
Look up the phase diagram of N2. Pick the coordinate were the temperature is 273K. Where this line crosses the liquid-gas transition is the pressure you are interested in.

It looks like about 500 psi to me.
russ_watters
Oct20-09, 01:33 AM
Do you have a link to a phase diagram? I couldn't find one.
sc298
Oct20-09, 01:09 PM
Look up the phase diagram of N2. Pick the coordinate were the temperature is 273K. Where this line crosses the liquid-gas transition is the pressure you are interested in.

It looks like about 500 psi to me.


Hero!

Many thanks!
Phrak
Oct20-09, 08:17 PM
Do you have a link to a phase diagram? I couldn't find one.

I googled images for N2 phase diagram. I only found a crude one.