Thermodynamics -- Calculate the pressure and temperature

[ps3stephen]

Homework Statement

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

Homework Equations

v = (1 – x)vf + x vg

The Attempt at a Solution

 

[Bystander]

Please help with this part

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

the water is just evaporated

 

[ps3stephen]

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

Well, the volume is constant.

 

[Bystander]

Anything else?

 

[ps3stephen]

Anything else?

everything i know is stated up there.

 

[Bystander]

How many phases?

 

[ps3stephen]

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

 

[Bystander]

superheated vapour

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

 

[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.

 

[Chestermiller]

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

 

[ps3stephen]

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

 

[Chestermiller]

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

Sure

 

[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?

 

[Chestermiller]

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?

Sure