# Thermodynamics -- Calculate the pressure and temperature

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1. Aug 15, 2015

### ps3stephen

1. The problem statement, all variables and given/known data
A rigid vessel of volume 5m^3 contains 1.0 kg of water and steam at 19 degree C.Find the pressure and the mass of liquid and vapour in the vessel.

The vessel is now heated unit the water is just evaporated. Calculate the the pressure and temperature of this process. The volume should be constant since it is a rigid vessel. Please help with this part. Thank you.

T= 19 degree C
v=50m^3/kg
Psat=0.02196 bar (from steam tables)
vf=0.100164*10^-2 m^3/kg
vg=61.34 m^3/kg
mvapour=0.0815 kg
mliquis=0.0185 kg

2. Relevant equations
v = (1 – x)vf + x vg

3. The attempt at a solution

2. Aug 15, 2015

### Bystander

You're going to have to move your feet at least one step --- what is one thing you know?

3. Aug 15, 2015

### ps3stephen

Well, the volume is constant.

4. Aug 15, 2015

### Bystander

Anything else?

5. Aug 15, 2015

### ps3stephen

everything i know is stated up there.

6. Aug 15, 2015

### Bystander

How many phases?

7. Aug 15, 2015

### ps3stephen

It should be at the superheated vapour state since it state the water is just evaporated.

8. Aug 15, 2015

### Bystander

Mass, volume, number of phases --- need anything else?

9. Aug 15, 2015

### ps3stephen

Mass and volume are given. I just have no clue about what its about when it just evaporated. Volume should be constant since it is a rigid tank.

10. Aug 15, 2015

### Staff: Mentor

Your answer for liquid water in part 1 should be 0.9185 kg. You must have a typo in post #1.

For part 2, if there is no liquid water remaining in the container, what does the specific volume of the water vapor have to be?

Chet

11. Aug 15, 2015

### ps3stephen

specific volume should be 50m^3/kg. so i should be find the temperature and pressure from the steam table?

12. Aug 15, 2015

### Staff: Mentor

Sure

13. Aug 16, 2015

### ps3stephen

so, i have specific volume of 50 m^3/kg from the steam table and do interpolation to find the temperature and pressure correspond to the specific volume of 50 m^3/kg?

14. Aug 16, 2015

Sure