A piston-cylinder assembly contains water vapor, initially at 10 bar and 360 deg C. The water undergoes a process where pv=constant until it reaches a final pressure of 1.5 bar. (a) Draw the process in p-v and T-s diagrams clearly labeling the states and the direction of the process. (b) Write the engineering model (c) Determine the energy transfers by work and heat, in kJ/kg and indicate their direction (in or out) (d) Determine the entropy production if the temperature at the boundary is Tb=630 K and comment on the nature of the process (reversible, irreversible, or impossible)

a) Check the attached file

b)

c)Energy transfer by work,  

Energy transfer by heat, E = 543 kJ/kg

d)The entropy production,  

The process is irreversible

Explanation:

Initial Pressure, P₁ = 10 bar

Initial temperature, T₁ = 360⁰ C

Final Pressure, P₂ = 1.5 bar

At P₁ = 10 bar and T₁ = 360°C

Getting the other parameters from the steam table:

V₁ = 0.28736 m³/kg,  U₁ = 2892.05 kJ/kg, h₁ = 379.09 kJ/kg, S₁ = 7.3366 kJ/K

Using Boyle's law, to get V₂

P₁ V₁ = P₂V₂

10 * 0.28736 * = 1.5 * V₂

V₂ = 1.9157 m³/kg

At P₂ = 1.5 bar and V₂ = 1.9157 m³/kg

U₂ = 2890 kJ/Kg, h₂ = 3180 kJ/kg, S₂ = 8.2 kJ/K, T₂ = 351° C

a) Check the attached file for the P-V and T-S diagrams

b) Write the engineering model

The system described is a closed system

c) Energy transfer by work and heat

Energy transform by work

Energy transform by heat

E = ( U₂ - U₁) + w

E = (2890 - 2892.05) + 545

E = 543 kJ

d)

The process is irreversible since ΔS > 0

answer:

my guess it 8 i'm probably wrong