- #1
Kicior94
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Homework Statement
An amount of water substance having a mass of 1 kg is contained in a vessel at a pressure of 1 MPa. It is heated for some time after which the pressure is 3 MPa. The volume of the vessel is 0.1 m3. Assuming no work is done by or to the substance, calculate the final temperature of, and the heating done to, the contents of the vessel.
Homework Equations
I am not sure about them. I believe, they would be:
## m=m_g + m_f ## , ##V=v_f m_f +v_g m_g## and ##PV=nRT## , ##ΔQ+ΔW=ΔU##
Thermodynamic and transport properties of fluids.
The Attempt at a Solution
I have stated that ##m_f+m_g=m=1kg## and ##v_g m_g + v_f m_f = 0.1 m^3##. It is also known that ##P_1=1MPa=10 bar## and ##P_2=30 bar##.
I have attempted to read the value of a temperature from 'Saturated Water and Steam section' for ##P=10bar## which would give me ##179.9°C##. Assuming that volume is constant throughout the whole process as the mixture is in a vessel it gave me ##{\frac{P_2 T_1}{P_1}}=T_2## but it gave me the wrong answer.
I have then tried to obtain the value of ##v_g## for 'Saturated Water and Steam' and it the value would be 0.1944 ##[kg/m^3]##. Solving for ##m_f## and ##m_g## by assuming that since ##m_f+m_g=1kg## and so ##dryness fraction=x=mg/1=mg## did actually either got me nowhere or I just do not know what to do with these values.
I need help to know what kind of assumptions should I use and have I chosen appropriate equations for solving this problem. Thanks