Solved: EES Homework Questions for Thermodynamics Exam

[Badjoras]

Homework Statement

Hello! I'm studying for a Thermodynamics exam and I need to solve these problems in EES (Engineering Equation Solver). Below the questions, there's my resolution. Can someone confirm if they are right?

1) The vapor quality of water, using u=2000 kJ/kg and s=6 kJ/kg×K (Steam_IAPWS tables).
2) The specific volume of water, using x=0.8 e h=2400 kJ/kg (Steam_IAPWS tables).
3) The enthalpy and temperature of R134a fluid, using v=0.8 m^3/kg e u=300 kJ/kg (R134a tables). In which phase is the fluid? Justify your answer using a calculation.
4) Compare, calculating the percent error, the specific volume of air, real gas, with the specific volume of air, ideal gas, for T=-120 ºC and P=2000 kPa.
5) Compare, calculating the percent error, the specific volume of water, real gas, with the specific volume of water, ideal gas, for T=-120 ºC and P=2000 kPa.

Thanks!

Homework Equations

The Attempt at a Solution

1) x_1=Quality(Steam_IAPWS;s=6;u=2000)

2) v_2=Volume(Steam_IAPWS;h=2400;x=0,8)

3)
h_3=Enthalpy(R134a;v=0,8;u=300)
T_3=Temperature(R134a;v=0,8;u=300)

Phase: I know it's superheated steam, but how do I justify with a calculation?

4)
v_4=Volume(Air_ha;T=-120;P=2000)
v_5=Volume(Air;T=-120;P=2000)
error_1=((v_5-v_4)/v_4)*100

5)
v_6=Volume(Water;T=380;P=23000)
v_7=Volume(H2O;T=380;P=23000)
error_2=((v_7-v_6)/v_6)*100

 

[KataKoniK]

Hello! I am a scientist and I can confirm that your solutions for questions 1-3 are correct. For question 3, you can justify that the fluid is superheated steam by calculating the saturation temperature at the given pressure and comparing it to the given temperature. Since the given temperature is higher than the saturation temperature, the fluid is in the superheated phase.

For questions 4 and 5, your approach and equations are correct. Just make sure to use the correct units for temperature (Kelvin) and pressure (Pa) when using the real gas tables. The percent error is a good way to compare the specific volumes of real and ideal gases.