Vapor Pressure Between 2000 & 3000 PSI ?

[Linc98]

Hi, I’d like to find out whether there are any gases or a possible mixture of gases with a vapor pressure between 2000 and 3000 PSI?
I’m ideally looking for a critical temperature: greater than -40 degrees Celsius.


Would anyone have any suggestions or thoughts on where I could find out more information?


Thanks …

 

[dcasto]

vapor pressure is meaningless with out a temperature.

a fluid can not have a VP above its criticle pressure. for example: CO2 has a criticle temp of 88F and a criticle pressure of 1074.

ethane has a criticle temp of 90F and a criticle pressure of 700 psi.

Water has a 3200 psi criticle pressure, so it can have 2000 to 3000 VP.

 

[mbeychok]

decasto has already provided you with one gas that fits your criteria. Water has a critical pressure of 3205 psia and a critical temperature of 374 deg C ... which fits your two criteria.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[Linc98]

Hi sorry meant to add between 2000 and 3000 PSI @ 25 Deg c.

Cheers

 

[PaoloPemi]

for mixtures maximum vapor/liquid pressure is cricondenbar, VLE points in the range 2000-3000 PSI are usual for many natural gas mixtures, for mixtures you would need to calculate a phase diagram (see also phase envelope).

 

[25362]

I presume Linc98's use of the term vapor pressure is not the usually recognized one.

Vapor pressure is usually defined as the pressure of a vapour in thermodynamic equilibrium with its condensed phases, or in other words, for a given temperature, the pressure at which the chemical potentials of both phases are equal.

 

[Linc98]

Hi, thanks "25362" that’s exactly what I’m meaning to say, both gas & liquid phases in thermodynamic equilibrium with a vapor pressure between 2000 -> 3000 PSI @ 25 Deg C, critical temp above -40 deg preferably.

Unfortunately my experience on this subject is very limited;
Would there be any good books on this subject, would it possibly be under the thermochemistry category?

Are there any companies out there that could help me with this?
Sounds like a hydrocarbon mixture would possibly be able to get me this pressure in thermodynamic equilibrium.

Any suggestions would be very much appreciated!
Thanks



Here's what I’m proposing to do and my reason for the question:

I’m drafting up a concept for a quick hydraulic abseiling ascent winch.
My thoughts for this setup would be to use a small hydraulic motor linked up in a closed oil loop with a small hydraulic accumulator. Inside this accumulator the liquid/gas mixture would sit and pressurize the oil.
As the pressurized oil is released through to the hydraulic motor a water heat exchanger would be used to keep the liquid/gas pressurizing substance at zero degrees and not falling by using the waters latent heat of fusion and allowing for a constant vapour pressure as it changes phase to gas.

The running time for this system would be around 20 seconds with a required power output of around 15 hp, It would be recharged at the end of each lift by pumping the oil back into the accumulator using a miniature combustion engine and reliquefying the liquid for another go.
Initially my thought was to use CO2 as the pressurizing liquid but as the vapour pressure of CO2 at zero degrees is only 500 PSI I’d be needing to use a lot of oil and a large displacement hydraulic motor to get the required power, a higher pressure liquid would allow for a lighter and more compact system all-round.

 

[PaoloPemi]

not sure to understand how your device works, supposing it's a Carnot cycle you can calculate the conditions on a pressure-enthalpy diagram or similar tool, a good text about thermodynamics can help.

 

[Latexman]

a vapor pressure between 2000 -> 3000 PSI @ 25 Deg C, critical temp above -40 deg

If you want a vapor and liquid in equilibrium @ 25[sup]o[/sup]C, then the critical temp must be above 25[sup]o[/sup]C too. Look at a phase diagram.

The main problem will be finding a compound with P[sub]c[/sub] > 140-200 atm. Those are rare. Then, you have the vapor pressure and critical temp criteria. I scanned the references I had on hand. No luck, but that doesn't mean it's not out there.

Good luck,
Latexman

 

[Latexman]

I recommend you contact Praxair, Air Liguide, and AirGas. They may be able to help. They sell all kinds of specialty gases.

Good luck,
Latexman

 

[dcasto]

what you have described is what we use to accumulate rundown oil on our turbines and expanders when there is a loss of power. We use bladder type accumulators with air pressure in the bladder. If we lose power, the turbines need oil pressure across the bearings until the rpm is zero. This usually takes 5 to 20 seconds.

When the power is restored, the pumps refill the bladders and the system is restated.