Thermodynamic properties of a liquid-gas mixture

[Rafe Zayed]

How can I calculate thermodynamic property like entropy and enthalpy of 70% steam and 30% air mixture ?( at about 90 degree Celsius and 10 MPa)

 

[JBA]

The boiling point of water at 10 Mpa is 311°C

 

[berkeman]

How can I calculate thermodynamic property like entropy and enthalpy of 70% steam and 30% air mixture ?( at about 90 degree Celsius and 10 MPa)

Welcome to the PF.

This is a pretty useful website that you may find helpful in your learning: http://www.thermopedia.com/content/1150/

 

[Chestermiller]

Do you mean 30 mole %? Are you willing to assume that the mixture is an ideal gas mixture? What are the reference states of the air and water relative to which you desire to determine the entropy and enthalpy?

 

[Rafe Zayed]

Do you mean 30 mole %? Are you willing to assume that the mixture is an ideal gas mixture? What are the reference states of the air and water relative to which you desire to determine the entropy and enthalpy?

No I mean 30% by mass fraction.
And at this high pressure ,water will be liquid. So I am not sure whether I can treat them as gas mixture or liquid gas mixture.
Any suitable reference point will do.Basically I want to find the property of a liquid -gas mixture

 

[Chestermiller]

What is the equilibrium vapor pressure of water vapor at 90 C?

 

[Rafe Zayed]

What is the equilibrium vapor pressure of water vapor at 90 C?

According to internet I found it to be around 70000 Pa

 

[Chestermiller]

According to internet I found it to be around 70000 Pa

Good. So that's about 0.07 MPa. If you're willing to tentatively approximate the gas phase as an ideal gas mixture, then that would be the partial pressure of water vapor in the gas phase. And at a total pressure of 10 MPa, what would be the mole fraction of water vapor in the gas phase? From these results, what would be the mass fractions of air and water in the gas phase? On the basis of 1 kg of water and air, what would be the mass of air? What would be the mass of water vapor in the gas phase? How much water would that leave for the liquid phase?

 

[Rafe Zayed]

Good. So that's about 0.07 MPa. If you're willing to tentatively approximate the gas phase as an ideal gas mixture, then that would be the partial pressure of water vapor in the gas phase. And at a total pressure of 10 MPa, what would be the mole fraction of water vapor in the gas phase? From these results, what would be the mass fractions of air and water in the gas phase? On the basis of 1 kg of water and air, what would be the mass of air? What would be the mass of water vapor in the gas phase? How much water would that leave for the liquid phase?

Sorry ,I didn't get that.At this pressure will there be any water vapour?Won't all the water vapour turn into liquid?

 

[Chestermiller]

Sorry ,I didn't get that.At this pressure will there be any water vapour?Won't all the water vapour turn into liquid?

Not all, but most.