Question

Water initially a saturated liquid at 150°C is contained within a piston-cylinder assembly. The water undergoes a process to the corresponding saturated vapor state, during which the piston moves freely in the cylinder. There is no heat transfer with the surroundings. If the change of state is brought about by the action of a paddle wheel, determine the net work per unit mass, in KJ/Kg, and the amount of entropy produced per unit mass in KJ/Kg*K.

Answer 1

net work per unit mass=2114KJ/kg

mount of entropy produced per unit mass =4.996KJ/kg K

Step-by-step explanation:

Hello!

To solve this problem use the following steps.

1. we will call one to the initial state and two to the final state

2) find the enthalpy and entropy of the two states using thermodynamic tables.

note: Through laboratory tests, thermodynamic tables were developed, these allow to know all the thermodynamic properties of a substance (entropy, enthalpy, pressure, specific volume, internal energy etc ..)

through prior knowledge of two other properties such as quality and temperature.

h1=Enthalpy(Water;T=150;x=0) = 632.3KJ/kg

h2=Enthalpy(Water;T=150;x=1) =2746 KJ/kg

s1=Entropy(Water;T=150;x=0) = 1.842 KJ/kg K

s2=Entropy(Water;T=150;x=1) = 6.838 KJ/kg K

3. uses the first law of thermodynamics that states that the energy entering a system must be the same as the one that goes out, taking into account the above we infer the following equation for work

W=h2-h1=2114KJ/kg

4. Find the difference between entropies between states 1 and 2.

S=s1-s1= 6.838-1.842= 4.996KJ/kg K