saturation point
saturation point
(OP)
Is it correct that if the saturation pressure is less than the partial pressure of a gas then that gas exists in a vapor state.
and if the saturation pressure is greater than the partial pressure tha that gas exists in a liquid state?
and if the saturation pressure is greater than the partial pressure tha that gas exists in a liquid state?





RE: saturation point
I don't think so. I believe it's the other way around.
Regards,
Speco
RE: saturation point
If the saturation pressure is greater than the partial pressure of a component, this is the same as the partial pressure of a component being less than the saturation pressure and that component will be a vapor.
If you are below the critical temperature of a component and the component is in a gaseous state, it is usually called a vapor.
If you are above the critical temperature of a component and the component is in a gaseous state, it is usually callled a gas.
Good luck,
Latexman
RE: saturation point
RE: saturation point
if there are two gasses in a pressurizd container that reads 100 PSIA. and hypothetically we introduce both at once with one gas at a partial pressure of 70 PSIA and the other a partial presssure at 30 PSIA. and still hypothetically the first gas totally condenses into a liquid. would the second gas still be at a partial pressure of 30 PSIA or would it be at 100 PSIA?
RE: saturation point
Good luck,
Latexman
RE: saturation point
say we have a typical aftercooler for a gas compressor.
and that the system is at 100 PSIA and the two gasses enter at 300F and are cooled to 100F, and the first gas condenses to a liquid at 200F.
would the second gas stay at 30PSIA and bring the entire operating pressure to 30PSIA or would it would it go to 100PSIA?
RE: saturation point
If this is a flowing, operating system, it's going to depend on the controls.
Good luck,
Latexman
RE: saturation point
specifically do you see constant pressure (neglecting inherent pressure drop of heat exchanger) or do you see an operating pressure inline with partial pressure of the uncondensed gas???
RE: saturation point
In a compressor system there is usually a control valve or process downstream that restricts flow so the inventory of the gas can build-up to the desired pressure. Again, remember PV = nRT. Inventory is the n part. Even if 70% condenses and the temperature is lowered, you can compress the remaining gas into a volume between the compressor and the restriction to get the pressure desired. There is no specific answer to you question. It depends on what pressure you want and the limitations of the compressor, pipe, and fittings.
A wise man once told me, "if you want the right answer, you have to ask the right question".
Good luck,
Latexman
RE: saturation point
vapour pressure:pressure at which a liquid boils (temperature is kept constant,pressure is lowered)
consider the pressure in the cooler:
if the heat removal in the cooler is kept constant then you can have 3 cases:
both gasses remain super heated:the pressure is the sum of the partial pressures (high gas flow)
one gas superheated,the other is partial condensed:the pressure is about equal to the superheated partial pressure (medium gas flow)
one gas superheated, the other completely condensed:the pressure is lower than the superheated partial pressure
(low gas flow)