Saturated vapour pressure vapour quality and T-S diagram location

[Brett0]

TL;DR

Linking closed container saturation vapour pressure and T-S diagram location

Hi all.,

Just hoping to get a better fundamental insight into a few things.
If we start with this:

http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/vappre.html

so we have a closed container at a given temperature, then we can find it's saturation pressure. All good so far.

In the following figure ignore the actual value of 1MPa. Let's just assume that the P=1 MPa line is the hypothetical saturation pressure for our hypothetical substance at our hypothetical temperature as we defined above.

The question is where does that put us on the line between 1 and 2 as I've marked in blue circles in this picture? Anywhere along that line is at the same temperature and pressure. I suppose I'm looking to link this to the description given in the hyperphysics post.

Any help much appreciated.

Brett

 

[Chestermiller]

Along the line from 1 to 2, you have a combination of saturated liquid and saturated vapor. The mass of saturated liquid is proportional to the distance on the diagram between the point on the line and point 2. The mass of saturated vapor is proportional to the distance on the diagram between the point on the line and point 1. This is called the "lever rule."

 

[Brett0]

Indeed that's true. At the equilibrium point described in the hyperphysics link where is that point along the 1-2 line? or am I looking at this wrong.

 

[Chestermiller]

Indeed that's true. At the equilibrium point described in the hyperphysics link where is that point along the 1-2 line? or am I looking at this wrong.

You are looking at it wrong. In a given problem, you need to determine the amounts of liquid and vapor from an energy balance or from some other additional condition. The point can be anywhere on that line.

 

[Brett0]

I see I see. So we could have two hypothetical vessels that have both reached vapour liquid equilibrium at the same temp and pressure but may have different enthalpy values which will lead them to be at different points on the line?

 

[Chestermiller]

I see I see. So we could have two hypothetical vessels that have both reached vapour liquid equilibrium at the same temp and pressure but may have different enthalpy values which will lead them to be at different points on the line?

Yes, that is correct.

 

[Brett0]

Brilliant.
Along those lines, does that mean that in say, an air-conditioning condenser (Where the fluid is in the same region, ie within the saturation curves) there is actual liquid in the line, as in liquid in a "Pool" as we would commonly view it, together with refrigerant vapour?

 

[Chestermiller]

Brilliant.
Along those lines, does that mean that in say, an air-conditioning condenser (Where the fluid is in the same region, ie within the saturation curves) there is actual liquid in the line, as in liquid in a "Pool" as we would commonly view it, together with refrigerant vapour?

Sure