- #1
ConnorM
- 79
- 1
Homework Statement
The mass flow rate through a steam turbine operating under steady conditions is 100 kg/s. Steam enters the turbine at 12 MPa and 400oC. A mixture of vapour and liquid water exits the turbine at 10 kPa. At the exit state 93% of the mass of the water is in vapour form. The turbine loses heat to the surroundings at the rate
of 3 MW. Kinetic and potential energy effects can be ignored.
a) Draw a schematic of the system and clearly indicate the system boundary
using a dashed line. Indicate and label the mass flow inlets and outlets. Using
arrows, illustrate the energy transfers between the system and surroundings
by heat transfer and by work.
b) Write a 1st law energy balance for the system that agrees with your schematic. Cancel all unnecessary terms, providing justification for why these terms can be cancelled.
c) Draw the process on a T-s diagram, clearly indicating the state points and the isobars corresponding to the state points.
d) Calculate the power generated by the turbine in MW.
e) Calculate the change in specific entropy from inlet to exit in kJ/KgK.
Homework Equations
Question 2
s1=sf + x[ sg - sf ]
Also since there is one inlet and one exit,
m=m1=m2
I am pretty sure this equation will be useful as well,
0= Q - W + m[ (h1 - h2) + ((v12 - v22)/2) + g(z1 + z2) ]
but since kinetic and potential energy is negligible I think I can cancel out ((v12 - v22)/2) + g(z1 + z2)]
That would leave me with,
0= Q - W + m[ (h1 - h2) ]
The Attempt at a Solution
For the second question I'm not really sure what to do, I think that what I would have to do is find sg from using 12 MPa, 400oC and looking at the steam table for water.
I'm not sure what I could do next because I would have 2 unknowns for the equation,
s1=sf + x[ sg - sf ]
Last edited: