Modern Engineering Thermodynamics

202 CHAPTER 6: First Law Open System Applications
FIGURE 6.27
Problem 47.
W = 20.0 hp
48.* Determine the power required to drive a boiler feed pump that
isothermally pumps 400. kg/s of saturated liquid water at
30.0°C to 8.00 MPa.
49. An adiabatic Refrigerant-22 turbine is mechanically coupled to an
adiabatic steam compressor. Saturated R-22 vapor at 100.°F
enters the turbine and exits as saturated vapor at −20.0 o F. The
steam enters the compressor as a saturated vapor at 14.7 psia
and exits at 1000. psia, 1600.°F. If the steam mass flow rate is
5.00 lbm/s, find the R-22 mass flow rate.
50.* 3.00 kg/s of air is compressed in the steady flow, steady state,
two-stage compressor shown schematically in Figure 6.28. Find
the interstage temperature (T 2 ). Assume the air is an ideal gas
with constant specific heats.
m air = 3.00 kg/s
T 1 = 100. K
p 1 = 1.00 atm
FIGURE 6.28
Problem 50.
51. In a steady flow process, a 1300. hp adiabatic steam turbine is
supplied with 10.0 × 10 3 lbm of steam per hour. At the inlet to
the turbine, the pressure of the steam is 500. psia and its
velocity is 100. ft/s. The temperature of the steam leaving the
turbine is 60.0°F, its quality 0.870, and its velocity is 700. ft/s.
On leaving the turbine, the steam is condensed at constant
pressure and exits the condenser as a saturated liquid at 60.0°F
with negligible velocity. Find the temperature of the steam
supplied to the turbine and the heat transfer rate in the
condenser.
52.* Saturated liquid water at 70.0°C enters an aergonic boiler at
station 1 in Figure 6.29. The boiler receives heat energy at a
1 2 3 4
Boiler
Turbine Condenser
m = ?
Q Boiler = 10.0 × 10 3 kJ/s
FIGURE 6.29
Problem 52.
1 2 3
1st stage
W 1 = 200. kJ/s
Q 1 = 80.0 kJ/s
2nd stage
T 2 = ?
p 1 = 10.0 atm
W 2 = 317.2 kJ/s
Q 2 = 100. kJ/s
W Turbine = ? Q Condenser =?
T 3 = 211.9 K
p 3 = 74.5 atm
rate of 10.0 × 10 3 kJ/s. Superheated steam at 20.0 MPa and
800.°C leaves the boiler and enters an insulated turbine at
station 2. The turbine exhausts to an aergonic condenser at a
pressure of 200. kPa and a quality of 80.0% at station 3. The
condenser cools the water to a saturated liquid at 100. kPa at
station 4. Determine (a) the mass flow rate of water, (b) the
power of the turbine, and (c) the heat transfer rate of the
condenser.
53. 0.500 lbm/s of hydraulic oil (density = 55.6 lbm/ft 3 and specific
heat = 0.520 Btu/(lbm · R)) is adiabatically pumped from 14.7
psia to 3014.7 psia with a 10.0 hp gear-type hydraulic pump.
Determine the temperature rise in the oil as it passes through
the pump.
54. An adiabatic air turbine is used to drive a compressor plus
another device as shown in Figure 6.30. Assuming the working
fluid (air) to be an ideal gas, find
a. The mass flow rate of the air
b. The power required to drive the compressor.
1
Compressor
T 1 = 100.°C
FIGURE 6.30
Problem 54.
Q = 200. kJ/s
T
2 2 = 1500.°C
Turbine
T 3 = 200.°C
W = 150. kW
55. It is proposed to construct a power plant on the shores of Lake
Michigan. To preserve the essential qualities of the lake, a local
environmental activist organized the community, which passed
an ordinance requiring that condenser coolant obtained from
the lake be returned to the lake at temperatures no warmer than
5.00°F above the temperature at which the water was withdrawn
from the lake. The following are some of the design parameters
of the proposed plant:
a. Steam flow through condenser: 10.0 × 10 3 lbm/h.
b. Inlet steam conditions: saturated vapor at 1.00 psia.
c. Outlet condensate conditions: saturated liquid at 1.00 psia.
d. External heat loss from condenser: equal to 8.00% of the
energy extracted from the steam during condensation.
e. Lake water has a specific heat of 1.00 Btu/(lbm · R)
Find the required flow rate of coolant from Lake Michigan.
56. Determine the air velocity in the 0.250 in diameter neck of a
balloon required to inflate an initially empty balloon to a
diameter of 1.00 ft in 60.0 s. Assume the density of the air in the
balloon remains constant during the inflation process.
57. Explain why the final temperature resulting from the adiabatic
filling of a rigid vessel with an ideal gas is independent of the
filling pressure.
58.* Incompressible hydraulic oil with a density of ρ = 880. kg/m 3 and
specific heat of c = 2.10 kJ/(kg · K) is pumped from a reservoir at
35.0°C into a fully extended rigid hydraulic cylinder. Determine
the temperature of the oil in the cylinder when its pressure reaches
35.0 MPa.
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