Liquid Nitrogen Expansion Factor

Hi himanshu,

The density of liquid nitrogen does not change with a change in pressure. It only changes with differences in temperature. I believe that the Peng-Robinson equation of state can predict the density of LN2 with reasonable accuracy, given temperature and the critical parameters (Pc, Tc, acentric factor) for LN2.

Refer here: http://en.wikipedia.org/wiki/Equation_of_state

Mike

Thank you very much from your response.

It has given quite useful information but still i could not resolve my query.

I may be missing some of things to interpreate but it would be grateful if you can solve it.

We are receiving liquid N2 tanker for our unit where supplier is quoting invoice based on Standard cubic meter where as we can simply cross check this by volume of liquid nitrogen increase in our tank having 7-8 bar g pressure.

i.e my question is 1 liter of 7-8 bar g liquid nitrogen will give how much amount of gasous nitrogen?

By considering 680-690 ratio i am not able to findout close value to the mentioned.

The volume given to you by your supplier in M3 are at standard conditions, 1 atmosphere and 0°C if you are using metric measure, and so the conversion is simple regardless of the pressure.

To answer your specific question. 1 liter at 7-8 bar will give essentially the same amount of gas as 1 liter liquid a 1 bar. This, again, is because the gaseous nitrogen volume you are given by your supplier is at standard conditions. The pressure on the liquid is not pertinent to the question nor is the pressure of the gas.

If you do not understand that then you will not be able to solve this puzzle.

sm3 means exactly that: Standard Cubic meter.

A cubic meter of liquid nitrogen, regardless of pressure, will deliver 695 'standard cubic meters' of gaseous nitrogen.

Now...at 7 bar gauge pressure (add atm for an absolute pressure of 8.1 bar) you will need 7.946 sm3 gaseous nitrogen to fill 1m3 of space.

Therefore 1m3 of liquid nitrogen vaporized at 8.1 bar and 15.6 Celcius (standard temp) will fill 87.5 m3 of space. 695/7.946=87.5.

Also, depending on your vaporization equipment..you will also have losses to take into account (generally for 3 cryogenic cold ends its about 300sm3 and 100sm3/hr of cool down time not pumping after that)

1 m3 of liquid N2 = 695 sm3 ....no matter the temp or pressure. How much that 695 sm3 will actually occupy depends entirely on temp and press.

Hope this sheds some light on the subject.

[quote\] Now...at 7 bar gauge pressure (add atm for an absolute pressure of 8.1 bar) you will need 7.946 sm3 gaseous nitrogen to fill 1m3 of space. [\quote] i don't quite get this statement. How did you get the 7.946 sm3?

A gram-mole of any gas at standard temperature and pressure [STP] occupies 22.4L.

What is needed is the specific gravity of <...liquid nitrogen...> at its chosen temperature, which is a search activity, and the temperature of the gaseous <...nitrogen...> at <...7.0-8.0 bar g. pressure...>, which is a selection activity.

Once these are known, use the Ideal Gas Equation to calculate the volume at the higher pressure compared to STP.

These calculations are well within the domain of the 6th form Chemistry Student.

"Robert is your Mother's brother." _{- Anon}