Example 4-2
Superheated steam at 900°F and 200 psia expands
through an ideal, adiabatic turbine. The final state is
saturated vapor. If the power output is 80 hp, determine
a) the final temperature
b) the final pressure
c) the mass flow rate
d) What should the inlet pipe diameter be so that the
inlet velocity is 45 ft/s?
Solution:
a) For an ideal, adiabatic turbine, the entropy balance is
1
2
s
s
=
The inlet entropy is given by
1
Btu
entropy(steam,
200,
900)
1.81
lbm R
s
P
T
=
=
=
=
⋅
The quality of a saturated vapor is unity. The exit state has
the same entropy as the inlet, so
o
2
temperature(steam,
1,
1)
183 F
T
x
s
s
=
=
=
=
b) To find the exit pressure, use
2
pressure(steam,
1,
1)
8.01psia
P
x
s
s
=
=
=
=
c) From the first law,

This ** preview** has intentionally

**sections.**

*blurred***to view the full version.**

*Sign up*