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ME370 Final(fall-TuTh-2013).docx
ME 370
December 2013
Name: ___________________
ID: ___________________
Final Exam – TuTh Section
1. Water is the working fluid in a Rankine Cycle that produces 100 MW of power. Turbine inlet conditions are 8 MPa, 480° C. The condenser pressure is 8 kPa. The turbine is 90% efficient and the pump is 80% efficient.
(a) Show the cycle on a T-s diagram
(b) Calculate the mass flow rate of steam
(c) Determine the cycle efficiency
(d) Determine the mass flow rate of the condenser cooling water, in kg/h, if water enters at 15° C and exits at 35° C (3,5,4,3)
Name: ___________________
ID: ___________________
2. Pressurized Air is to be used to drive a reversible adiabatic turbine (shown). Determine the size of the tank (in m3) to produce 75 w for 60 minutes. Assume the temperature of air in the tank remains at 20° C due to heat transfer from the environment. (10)
Name: ___________________
ID: ___________________
3. For the steady state feed water heater (mixing chamber) shown , calculate the rate of net entropy generation. (9)
Name: ___________________
ID: ___________________
4. An ideal gas contained in a piston-cylinder assembly is compressed isothermally in an internally reversible process.
(a) Determine if the entropy change of the gas is greater than, equal to or less than zero, justify your answer
(b) Determine if for the same change of state, the entropy change for an irreversible process is greater than, equal to or less than part (a)
(5,3)
Name: ___________________
ID: ___________________
5. A Heat pump is used to heat a house during winter. The house is maintained at 20° C and loses 14 kW when the outside temperature is -5° C. The motor driving the compressor is rated at 2.5 kW
(a) Is the rated motor sufficient for an ideal heat pump?
(b) Is the rated motor sufficient if the COP of actual heat pump is one third of the ideal heat pump?
(4,4)
ME370 Final(fall-MW-2013).docx
ME 370
December 2013
Name: ____________________
ID: ____________________
Final Exam – MW Section
1. A 500 MW Rankine Cycle based Steam Power Plant operates between a condenser pressure of 8 kPa and a boiler pressure of 6 MPa. The vapor leaving the boiler is at 400° C. The turbine and pump efficiencies are 88% and 80% respectively.
-Show the cycle in a T – s diagram
-Determine the cycle efficiency
-Determine the required mass flow rate of steam in the power plant
-Determine the mass flow rate of condenser cooling water in kg/h if water enters at 15°C and exits at 25° C. (3,6,3,3)
Name: ____________________
ID: ____________________
2. Steam enters a turbine at 300° C and exhausts at 20 kPa. Isentropic efficiency of the turbine is 70%.
What is the maximum turbine inlet pressure if the exhaust is not to be in the 2-phase region? (8)
Name: ___________________
ID: ___________________
3. An ideal gas contained in a piston-cylinder assembly is compressed isothermally in an internally reversible process.
(a) Determine if the entropy change of the gas is greater than, equal to or less than zero, justify your answer
(b) Determine if for the same change of state, the entropy change for an irreversible process is greater than, equal to or less than part (a)
(6,3)
Name: ____________________
ID: ____________________
4. Is it possible to design an adiabatic compressor to increase the air pressure from 70 kPa and 27° C to 140 kPa 127° C ? (8)
Name: ____________________
ID: ____________________
5. A closed rigid container has a volume of 2 m3 and is filled with 4 kg of water at 200 kPa. Heat is transferred from the surroundings (Tsurr = 160° C) until the water has just turned into vapor.
Determine the entropy change of the system and the surroundings and show that the “principle of increase of entropy” is satisfied. (10)
Name: ____________________
ID: ____________________
6. One technique for operating a steam turbine at part-load power output is to throttle the steam to a lower pressure before it enters the turbine as shown. Assuming an ideal turbine, determine the pressure to which the steam must be throttled in order to produce 80% of the full-load output. (5)
ME370 Final(2012).docx
2012
ME 370 – Final
A Rankine Cycle based steam power plant produces 200 MW of power. Steam exits the boiler at 3 MPa and 500° C. The turbine exit is at 40 kPa. Isentropic efficiencies of the turbine and pump are 75% and 70% respectively.
(a) Show the cycle on a T-s diagram
(b) Calculate the mass flow rate of steam
(c) Determine the heat transfer rates in the boiler and condenser in MW
(d) Determine the cycle efficiency
(e) Determine the mass flow rate of the condenser cooling water, in kg/h, if water enters at 15° C and exits at 35° C
(3,4,2,2,2)
Steam enters a turbine at 300° C and exhausts (exits) at 20 kPa. Isentropic efficiency of the turbine is 70%. What is the maximum turbine inlet pressure if the exhaust is not to be in the 2-phase region?
(8)
Steam at 800 kPa and 300° C is bled off from a large supply line and allowed to enter an initially evacuated rigid tank (volume = 0.3 m3). When the pressure in the tank reaches 100 kPa, the inlet valve is closed and the temperature in the tank is reported to be 150° C. If the ambient temperature is 25° C,
determine if the process is possible from a Principle of Increase of Entropy perspective?
(10)
Pressurized Air is to be used to drive a reversible adiabatic turbine (shown). Determine the size of the tank (in m3) to produce 75 w for 60 minutes. Assume the temperature of air in the tank remains at 20° C due to heat transfer from the environment.
ME370 Final(2011).docx
ME 370
Spring 2011
Final Exam
1. In a 200 MW Rankine Cycle based Steam Power Plant, vapor leaving the boiler is at 4 MPa and 400° C. The condenser temperature is 45° C. The turbine and pump efficiencies are 85% and 80% respectively.
-Show the cycle on a T-s diagram
-Determine the cycle efficiency
-Determine the required mass flow rate of steam in the power plant
-Determine the mass flow rate of condenser cooling water in kg/h if water enters at 15° C and exits and 25° C. (4,8,3,3)
2. Steam enters an adiabatic nozzle at 7 MPa and 500° C with a velocity of 70 m/s and exits at 5 MPa and 450° C.
-Determine the exit velocity of the steam
-Determine the nozzle efficiency (6,4)
3. An inventor claims to have developed an adiabatic compressor in which 6 kg/s of air are compressed from 100 kPa and 37° C to 350 kPa with a power input of 785 kW.
Evaluate the inventor’s claim (10)
4. One technique for operating a steam turbine at part-load power output is to throttle the steam to a lower pressure before it enters the turbine as shown.
Assume an ideal turbine, determine the pressure to which the steam must be throttled in order to produce 80% of the full-load output.
(12)
ME370_HW#2_Solutions.pdf
ME370_HW#1_Solutions.pdf
ME370_HW#3_Solutions.pdf
ME370_HW#4_Solutions.pdf
HW5&6_Solutions_ME370.pdf
ME370_Ch10_RankineCycle.pdf
Final cheatsheet.pdf
