# Thermodynamics reversible isothermal process

1. Nov 24, 2012

### nakas12

1. The problem statement, all variables and given/known data
A system containing 10kg of water undergoes a reversible isothermal process. The initial state can be characterized as saturated vapor at 300°C. The pressure in the final state is 1MPa. The heat transfer during the process in (inKJ)

2. Relevant equations

Q = m(U2-U1)+W
W = PdV
v1 = V/m
v1 = specific volume at initial state
V = volume

3. The attempt at a solution
The specific volume values were found using the thermodynamic tables for water. I figured that since it was an isothermal process and would be adiabatic. I wanted somebody to see if my answer is correct.

v1=.02167
v2=.25794
V1= 2.5795
V2=2.5794
mass=1.91
T1 =T2 =300°C
Q = mCvo(T2-T1)+W
Q = .717(300-300)+PdV

Q = 0 +1000(2.5794-.2167)
Q = 2362.7

2. Nov 25, 2012

### Staff: Mentor

What is the equilibrium vapor pressure of water at 300C? How does that compare with a pressure of 1 MPa? What is the volume of the water vapor at the equilibrium vapor pressure?

3. Nov 26, 2012

### rude man

I would go as follows:

1. Assume liquid water is incompressible.
2. What is the vapor pressure of saturated vapor/water at 300C? Is it above or below 1 MPa?
3. What's it take in joules to change 10 kg of saturated vapor to saturated liquid (at 300C)?