Modern Engineering Thermodynamics

356 CHAPTER 10: Availability Analysis
the steam in the pipe when the local environment (ground
state) is saturated liquid water at 20.0°C.
39.* Saturated liquid ammonia at 0.00°C flows through a pipe
located 10.0 m below the floor in a refrigeration system with a
velocity of 3.30 m/s. Determine the specific flow availability of
the ammonia in the pipe when the local environment (ground
state) is saturated liquid ammonia at 0.00°C.
40. Superheated Refrigerant-22 at 100. psia and 100.°F flows
through a tube in a large industrial air conditioner 50.0 ft
above the ground at a velocity of 20.0 ft/s. Determine the
specific flow availability of the refrigerant in the tube when the
local environment (ground state) is saturated liquid
Refrigerant-22 at 0.00°F.
41.* Saturated liquid Refrigerant-134a at 12.0°C flows through a
tube in an automobile air conditioning system at a velocity of
0.300 m/s. The tube is 1.00 m above the ground. Determine
the specific flow availability of the refrigerant in the tube when
the local environment (ground state) is saturated liquid
Refrigerant-134a at 0.00°C.
42.* Superheated mercury vapor at 2.00 MPa flows at a velocity
of 7.50 m/s through a pipe in a portable nuclear power
plant. The pipe is 0.500 m above the ground. Determine the
specific flow availability of the mercury in the pipe. Use
saturated liquid mercury at 0.100 MPa as the local
environment (ground state).
43. Air (an ideal gas here) at 100. psia and 150.°F flows through a
pipe in a factory with a velocity of 10.0 ft/s. The pipe is located
75.0 ft above the floor. Determine the specific flow availability
of the air in the pipe when the local environment (ground
state) is at 14.7 psia and 70.0°F.
44.* Saturated water vapor enters an isentropic turbine of a power
plant at 4.00 MPa and exits at 1.00 × 10 −3 MPa. Neglecting
kinetic and potential energy effects, determine the difference in
specific flow availability between the entrance and exit of the
turbine. Use saturated liquid water at 20.0°C as the local
environment (ground state).
45. Steam enters the isentropic turbine of power plant at 200. psia
and 500.°F. How much does the change in specific flow
availability between the inlet and exit of the turbine increase if
the exit pressure is lowered from 14.7 psia to 1.00 psia?
Neglect all kinetic and potential energy effects. Use saturated
liquid water at 80.0°F as the local environment (ground state).
46. A small portable nuclear-powered steam turbine has an inlet
state of 200. psia, 600.°F and an outlet temperature of 95.0°F.
Assuming that the exit state is also a saturated vapor,
determine the change in specific flow availability between the
inlet and exit of the turbine. Neglect all kinetic and potential
energy effects. Use saturated liquid water at 70.0°F as the local
environment (ground state).
47.* A horizontal pipe carrying superheated steam at 30.0 MPa and
1000.°C suddenly develops a small crack. Steam enters the
crack at 30.0 m/s and passes through it in a steady state,
adiabatic, aergonic process to exit at 0.101 MPa with a velocity
of 250. m/s. Determine the specific flow availabilities at the
inlet and outlet of the crack, and calculate the irreversibility
per unit mass of steam exiting the crack. Use saturated liquid
water at 20.0°C as the local environment (ground state).
48.* Superheated steam at 8.30 kg/s, 1.00 MPa, and 400.°C enters a
horizontal, stationary, insulated nozzle with a negligible
velocity and expands to 10.0 × 10 −3 MPa. The friction and
other irreversibilities within the nozzle cause the exit velocity
to be only 85.0% of that produced by an isentropic expansion.
Taking the local environment (ground state) to be that of
saturated liquid water at 20.0°C, determine
a. The inlet specific flow availability.
b. The exit specific flow availability.
c. The irreversibility rate inside the nozzle.
49. A large, uninsulated steam turbine receives superheated steam
at 40.0 lbm/s, 1000.°F, and 800. psia and exhausts it to 1.00
psia with a quality of 92.0%. If the turbine is assumed to be
internally reversible, determine the heat loss from the surface
of the turbine if the power output is 30.0 × 10 3 kW. The
surface temperature of the turbine is uniform at 225°F and the
local environment (ground state) is saturated liquid water at
20.0°C. Neglect all flow stream kinetic and potential energies
in this problem.
50. A steady flow, steady state air compressor handles 4000. ft 3 /min
measured at the intake state of 14.1 psia, 30.0°F and a velocity
of 70.0 ft/s. The discharge is at 45.0 psia and has a velocity of
280. ft/s. Both the inlet and exit stations are located 4.00 ft
above the floor. Using the specific flow availability relative to
the local environmental (ground state) temperature of 80.0°F
and a pressure of 14.7 psia, determine
a. The discharge temperature and the power required to drive
the compressor if the process is reversible and adiabatic.
b. The discharge temperature and the power required to
drive the compressor if the process is irreversible and
adiabatic with a compressor work transport efficiency
of 80.0%.
51.* Determine the work required to compress 15.0 kg/min of
superheated steam in an uninsulated, reversible compressor
from 0.150 MPa, 600.°C to 1.50 MPa, 500.°C in a steady state,
steady flow process. Neglect any changes in kinetic and
potential energy. Use the flow availability approach to
calculate the specific flow availabilities at the inlet and exit if
the environmental temperature is 20.0°C. Choose the local
environment (ground state) to be saturated liquid water at the
environmental temperature.
52. An adiabatic, steady flow compressor is designed to compress
superheated steam at a rate of 50.0 lbm/min. At the inlet to
the compressor, the state is 100. psia and 400.°F; and at the
compressor exit, the state is 200. psia and 600.°F. Neglecting
any kinetic or potential energy effects, calculate (a) the power
required to drive the compressor and (b) the rate of
availability destruction by the compressor. Use saturated liquid
water at 80.0°F as the local environment (ground state).
53.* A steady flow air compressor takes in 5.00 kg/min of
atmospheric air at 101.3 kPa and 20.0°C and delivers it at an
exit pressure of 1.00 MPa. The air can be considered an ideal
gas with constant specific heats. Potential and kinetic energy
effects are negligible. If the process is not reversible but is
adiabatic and polytropic with a polytropic exponent of n =
1.47, calculate
a. The power required to drive the compressor.
b. The entropy production rate of the compressor.
c. The entrance and exit specific flow availabilities if the
ground state local environmental temperature and pressure
are 20.0°C and 101.3 kPa.
54. An uninsulated, irreversible steam engine whose surface
temperature is 200.°F produces 50.0 hp with a steam mass