Heat Exchanger

Front 1

Refer to the drawing of an operating water cleanup system. All valves are identical and are initially 50 percent open (see figure below). To lower the temperature at point 7, the operator should adjust valve __________ in the open direction. A. A B. B C. C D. D

Back 1

D.

Front 2

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Increasing the oil flow rate through the heat exchanger will cause the oil outlet temperature to _________ and the cooling water outlet temperature to __________. (Assume cooling water flow rate remains the same.) A. decrease; decrease B. decrease; increase C. increase; decrease D. increase; increase

Back 2

D.

Front 3

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Assume that the inlet lube oil and inlet cooling water temperatures are constant and cooling water flow rate remains the same. Decreasing the oil flow rate through the heat exchanger will cause the oil outlet temperature to _________ and the cooling water outlet temperature to _________. A. increase, increase B. increase, decrease C. decrease, increase D. decrease, decrease

Back 3

D.

Front 4

Refer to the drawing of an operating water cleanup system (see figure below). Valves A, B, and C are fully open. Valve D is 80 percent open. All temperatures are as shown. If valve D is then throttled to 50 percent, the temperature at point... A. 3 will decrease. B. 4 will increase. C. 5 will increase. D. 6 will decrease.

Back 4

B.

Front 5

Refer to the drawing of an operating water cleanup system (see figure below). Valves A, B, and C are fully open. Valve D is 20 percent open. All temperatures are as shown. Valve D is then quickly opened to 100 percent. The temperature at point... A. 3 will increase. B. 4 will decrease. C. 5 will decrease. D. 7 will increase.

Back 5

B.

Front 6

Refer to the drawing of an operating water cleanup system (see figure below). All valves are identical and are initially 50 percent open. To lower the temperature at point 4, the operator can adjust valve ______ in the ______ direction. A. A; open B. B; shut C. C; open D. D; shut

Back 6

B.

Front 7

The rate of heat transfer between two liquids in a heat exchanger will be increased if the: (Assume single-phase conditions and a constant specific heat.) A. temperature of the hotter liquid is decreased by 20EF. B. temperature of the colder liquid is increased by 20EF. C. flow rates of both liquids are decreased by 10 percent. D. flow rates of both liquids are increased by 10 percent.

Back 7

D.

Front 8

Refer to the drawing of a lube oil heat exchanger (see figure below). The heat exchanger is operating with the following parameters: Toil in = 174EF Toil out = 114EF cp-oil = 1.1 Btu/lbm-EF múoil = 4.0 x 104 lbm/hr Twater in = 85EF Twater out = 115EF cp-water = 1.0 Btu/lbm-EF ú= ? mwater What is the mass flow rate of the cooling water? A. 8.8 x 104 lbm/hr B. 7.3 x 104 lbm/hr C. 2.2 x 104 lbm/hr D. 1.8 x 104 lbm/hr

Back 8

A.

Front 9

A liquid-to-liquid counterflow heat exchanger is operating with single-phase conditions and a constant specific heat for each liquid. Which one of the following will decrease the heat transfer between the two liquids? A. The temperature of both liquids is increased by 20EF. B. The temperature of both liquids is decreased by 20EF. C. The flow rate of the hotter liquid is increased by 10 percent. D. The flow rate of the colder liquid is decreased by 10 percent.

Back 9

D.

Front 10

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following information, which one of the following is the temperature of the oil exiting the heat exchanger (Toil-out)? múoil = 2.0 x 104 lbm/hr múwater = 3.0 x 104 lbm/hr cp-oil = 1.1 Btu/lbm-EF cp-water = 1.0 Btu/lbm-EF Tcw-in = 92EF Tcw-out = 125EF Toil-in = 180EF Toil-out = ? A. 135EF B. 140EF C. 145EF D. 150EF

Back 10

A.

Front 11

Which one of the following will reduce the rate of heat transfer between two liquids in a heat exchanger? (Assume single-phase conditions and a constant specific heat for both liquids.) A. The inlet temperatures of both liquids are decreased by 20EF. B. The inlet temperatures of both liquids are increased by 20EF. C. The inlet temperature of the hotter liquid is increased by 20EF. D. The inlet temperature of the colder liquid is increased by 20EF.

Back 11

D.

Front 12

The rate of heat transfer between two liquids in a heat exchanger will be increased if the: (Assume single-phase conditions and a constant specific heat capacity.) A. temperature of both liquids is decreased by 20EF. B. temperature of both liquids is increased by 20EF. C. flow rate of the colder liquid is decreased by 10 percent. D. flow rate of the hotter liquid is increased by 10 percent.

Back 12

D.

Front 13

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following information, which one of the following is the temperature of the oil exiting the heat exchanger (Toil-out)? múoil = 1.5 x 104 lbm/hr múwater = 2.5 x 104 lbm/hr cp-oil = 1.1 Btu/lbm-EF cp-water = 1.0 Btu/lbm-EF Tcw-in = 92EF Tcw-out = 125EF Toil-in = 160EF Toil-out = ? A. 110EF B. 127EF C. 135EF D. 147EF

Back 13

A.

Front 14

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following existing conditions: cp-oil = 1.1 Btu/lbm-EF cp-water = 1.0 Btu/lbm-EF múoil = 1.2 x 104 lbm/hr múwater = 1.61 x 104 lbm/hr Toil in = 170EF Toil out = 120EF Twater out = 110EF Twater in = ? Which one of the following is the approximate cooling water inlet temperature (Twater in) in this heat exchanger? A. 65EF B. 69EF C. 73EF D. 77EF

Back 14

B.

Front 15

Refer to the drawing of a lube oil heat exchanger (see figure below). The lube oil heat exchanger is in service with the following inlet temperatures: Lube oil inlet temperature: 120EF Cooling water inlet temperature: 60EF Assuming cooling water flow rate is greater than lube oil flow rate, which one of the following pairs of heat exchanger outlet temperatures is possible? (Assume both fluids have the same cp.) Lube Oil Cooling Water Outlet Temp Outlet Temp A. 100EF 100EF B. 90EF 90EF C. 80EF 80EF D. 80EF 100EF

Back 15

C.

Front 16

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following existing conditions: múoil = 1.8 x 104 lbm/hr múwater = 3.3 x 104 lbm/hr cp-oil = 1.1 Btu/lbm-EF cp-water = 1.0 Btu/lbm-EF Tcw-in = 90EF Tcw-out = 120EF Toil-in = 190EF Toil-out = ? Which one of the following is the temperature of the oil exiting the heat exchanger (Toil-out)? A. 110EF B. 120EF C. 130EF D. 140EF

Back 16

D.

Front 17

Refer to the drawing of a lube oil heat exchanger (see figure below). The lube oil heat exchanger is in service with the following inlet temperatures: Lube oil inlet temperature: 130EF Cooling water inlet temperature: 70EF Assuming cooling water flow rate is greater than lube oil flow rate, which one of the following pairs of heat exchanger outlet temperatures is possible? (Neglect any difference between fluid specific heat.) Lube Oil Cooling Water Outlet Temp Outlet Temp A. 90EF 100EF B. 90EF 110EF C. 100EF 100EF D. 100EF 110EF

Back 17

A.

Front 18

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following information, which one of the following is the temperature of the cooling water exiting the heat exchanger (Tcw-out)? múoil = 1.5 x 104 lbm/hr múwater = 2.5 x 104 lbm/hr cp-oil = 1.1 Btu/lbm-EF cp-water = 1.0 Btu/lbm-EF Toil-in = 160EF Toil-out = 110EF Tcw-in = 92EF Tcw-out = ? A. 110EF B. 115EF C. 120EF D. 125EF

Back 18

D.

Front 19

The rate of heat transfer between two liquids in a heat exchanger will be decreased if the: (Assume single-phase conditions and a constant specific heat for both liquids.) A. inlet temperature of the hotter liquid is increased by 20EF. B. inlet temperature of the colder liquid is decreased by 20EF. C. flow rates of both liquids are decreased by 10 percent. D. flow rates of both liquids are increased by 10 percent.

Back 19

C.

Front 20

Refer to the drawing of a lube oil heat exchanger (see figure below). The lube oil heat exchanger is in service with the following inlet temperatures: Lube oil inlet temperature: 110EF Cooling water inlet temperature: 75EF Assuming cooling water flow rate is greater than lube oil flow rate, which one of the following pairs of heat exchanger outlet temperatures is possible? (Neglect any difference between fluid specific heats.) Lube Oil Cooling Water Outlet Temp Outlet Temp A. 100EF 100EF B. 100EF 90EF C. 90EF 100EF D. 90EF 90EF

Back 20

D.

Front 21

Refer to the drawing of an operating water cleanup system (see figure below). All valves are identical and are initially 50 percent open. To raise the temperature at point 4, the operator can adjust valve ______ in the ______ direction. A. A; shut B. B; shut C. C; open D. D; open

Back 21

C.

Front 22

Refer to the drawing of a lube oil heat exchanger (see figure below). The lube oil heat exchanger is in service with the following inlet temperatures: Lube oil inlet temperature: 130EF Cooling water inlet temperature: 70EF Assuming cooling water flow rate is greater than lube oil flow rate, which one of the following pairs of heat exchanger outlet temperatures is not possible? (Assume both fluids have the same specific heat.) Lube Oil Cooling Water Outlet Temp Outlet Temp A. 90EF 86EF B. 100EF 85EF C. 110EF 84EF D. 120EF 83EF

Back 22

D.

Front 23

Refer to the drawing of a lube oil heat exchanger (see figure below). The lube oil heat exchanger is in service with the following inlet temperatures: Lube oil inlet temperature: 130EF Cooling water inlet temperature: 70EF Assuming that cooling water flow rate is significantly larger than lube oil flow rate, which one of the following pairs of heat exchanger outlet temperatures is possible? (Assume both fluids have the same specific heat.) Lube Oil Cooling Water Outlet Temp Outlet Temp A. 100EF 90EF B. 100EF 100EF C. 110EF 90EF D. 110EF 100EF

Back 23

A.

Front 24

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following lube oil cooling system conditions: The lube oil flow rate in the lube oil heat exchanger is 200 lbm/min. The lube oil enters the heat exchanger at 140oF. The lube oil leaves the heat exchanger at 100oF. The specific heat of the lube oil is 0.8 Btu/lbm-oF. The cooling water flow rate is 400 lbm/min. The cooling water enters the lube oil heat exchanger at 60oF. The specific heat of the cooling water is 1.0 Btu/lbm-oF. What is the approximate temperature of the cooling water leaving the lube oil heat exchanger? A. 76oF B. 85oF C. 92oF D. 124oF

Back 24

A.

Front 25

Refer to the drawing of a lube oil heat exchanger (see figure below). The heat exchanger is operating with the following parameters: Qú oil = 1.0 x 107 Btu/hr Toil in = 170EF Toil out = 134EF Twater in = 85EF Twater out = 112EF cp-oil = 1.1 Btu/lbm-EF cp-water = 1.0 Btu/lbm-EF ú= ? mwater Which one of the following is the mass flow rate of the cooling water? A. 4.5 x 105 lbm/hr B. 3.7 x 105 lbm/hr C. 2.5 x 105 lbm/hr D. 1.2 x 105 lbm/hr

Back 25

B.

Front 26

Refer to the drawing of an operating water cleanup system (see figure below). Valves A, B, and D are fully open and valve C is 50 percent open. If valve C is opened to 100 percent, how will the temperatures at points 3 and 6 be affected? Point 3 Point 6 A. Decrease Decrease B. Decrease Increase C. Increase Decrease D. Increase Increase

Back 26

D.

Front 27

Refer to the drawing of an operating water cleanup system (see figure below). All valves are identical and are initially 50 percent open. To raise the temperature at point 7, the operator should adjust valve __________ in the close direction. A. A B. B C. C D. D

Back 27

D.

Front 28

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following existing conditions: múoil = 1.8 x 104 lbm/hr múwater = 3.3 x 104 lbm/hr cp-oil = 1.1 Btu/lbm-EF cp-water = 1.0 Btu/lbm-EF Tcw-in = 90EF Tcw-out = 120EF Toil-in = 170EF Toil-out = ? What is the approximate temperature of the oil exiting the heat exchanger (Toil-out)? A. 110EF B. 120EF C. 130EF D. 140EF

Back 28

B.

Front 29

Refer to the drawing of an operating water cleanup system (see figure below). If cooling water flow rate is 1.0 x 106 lbm/hr, what is the approximate water flow rate in the cleanup system? A. 2.2 x 105 lbm/hr B. 3.2 x 105 lbm/hr C. 2.2 x 106 lbm/hr D. 3.2 x 106 lbm/hr

Back 29

A.

Front 30

Refer to the drawing of a lube oil heat exchanger (see figure below). The lube oil heat exchanger is in service with the following inlet temperatures: Lube oil inlet temperature: 130EF Cooling water inlet temperature: 70EF Assume that cooling water mass flow rate is less than lube oil mass flow rate, and that both fluids have the same specific heat. Which one of the following pairs of heat exchanger outlet temperatures is not possible? Lube Oil Cooling Water Outlet Temp Outlet Temp A. 100EF 105EF B. 105EF 105EF C. 110EF 90EF D. 115EF 90EF

Back 30

C.

Front 31

A main turbine-generator was operating at 80 percent load with the following initial steady-state lube oil and cooling water temperatures for the main turbine lube oil heat exchanger: Toil in = 174EF Toil out = 114EF Twater in = 85EF Twater out = 115EF Six months later, the following current steady-state heat exchanger temperatures are observed: Toil in = 177EF Toil out = 111EF Twater in = 85EF Twater out = 115EF Assume that the total heat exchanger heat transfer coefficient and the cooling water mass flow rate do not change, and that the specific heat values for the cooling water and lube oil do not change. Also, assume that the lube oil system is a closed system. Which one of the following could be responsible for the differences between the initial and current steady-state heat exchanger temperatures? A. The current main turbine-generator load is lower than the initial load. B. The current main turbine-generator load is higher than the initial load. C. The current main turbine lube oil mass flow rate is less than the initial flow rate. D. The current main turbine lube oil mass flow rate is greater than the initial flow rate.

Back 31

C.

Front 32

Refer to the drawing of a lube oil heat exchanger (see figure below). The lube oil heat exchanger is in service with the following inlet temperatures: Lube oil inlet temperature: 120EF Cooling water inlet temperature: 60EF Assuming cooling water flow rate is greater than lube oil flow rate, which one of the following sets of heat exchanger outlet temperatures is possible? (Neglect any difference between fluid specific heats.) Lube Oil Cooling Water Outlet Temp Outlet Temp A. 90EF 100EF B. 90EF 85EF C. 95EF 100EF D. 95EF 85EF

Back 32

B.

Front 33

A main turbine-generator was operating at 80 percent load with the following initial steady-state lube oil and cooling water temperatures for the main turbine lube oil heat exchanger: Toil in = 174EF Toil out = 114EF Twater in = 85EF Twater out = 115EF Six months later, the current steady-state heat exchanger temperatures are: Toil in = 174EF Toil out = 120EF Twater in = 85EF Twater out = 120EF Assume that the lube oil mass flow rate does not change, and that the specific heat values for the cooling water and lube oil do not change. Also, assume that the main turbine lube oil system is a closed system. The differences between the initial and current steady-state heat exchanger temperatures could be caused by the current main turbine-generator load being __________ with the current heat exchanger cooling water mass flow rate being ___________. A. higher; lower B. higher; higher C. lower; lower D. lower; higher

Back 33

C.

Front 34

Refer to the drawing of a lube oil heat exchanger (see figure below). The lube oil heat exchanger is in service with the following inlet temperatures: Lube oil inlet temperature: 130EF Cooling water inlet temperature: 70EF Given that cooling water mass flow rate is greater than lube oil mass flow rate, which one of the following pairs of heat exchanger outlet temperatures is not possible? (Neglect any difference between the fluid specific heat capacities.) Lube Oil Cooling Water Outlet Temp Outlet Temp A. 90EF 105EF B. 90EF 100EF C. 110EF 95EF D. 110EF 85EF

Back 34

C.

Front 35

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Assume that the inlet lube oil and inlet cooling water temperatures are constant and the lube oil flow rate remains the same. If the cooling water flow rate increases, the lube oil outlet temperature will _________ and the cooling water outlet temperature will _________. A. increase, increase B. increase, decrease C. decrease, increase D. decrease, decrease

Back 35

D.

Front 36

Refer to the drawing of an operating parallel-flow lube oil heat exchanger (see figure below). Assume that lube oil (LO) inlet temperature is greater than cooling water (CW) inlet temperature. Unlike a counter-flow heat exchanger, in a parallel-flow heat exchanger the _____________ temperature can never be greater than the __________ temperature. A. LO outlet; CW inlet B. LO outlet; CW outlet C. CW outlet; LO inlet D. CW outlet; LO outlet

Back 36

D.

Front 37

Refer to the drawing of an operating process water cleanup system (see figure below). Assume there is no heat loss from the process water cleanup system to the surroundings and the process water flow rate does not change. If valve D closes fully, what will be the final steady-state temperature of the process water flowing through the filter? A. 212EF B. 302EF C. 450EF D. 540EF

Back 37

D.

Front 38

A counter-flow heat exchanger is being used to cool the lube oil system for a main turbine and generator. The main turbine and generator was initially operating at 100 percent load with the following stable heat exchanger conditions: Toil in = 174EF Toil out = 114EF Twater in = 85EF Twater out = 115EF Main turbine and generator load was reduced, and the heat exchanger cooling water mass flow rate was decreased to one-half of its initial value, resulting in the following stable current conditions: Toil in = 178EF Toil out = 138EF Twater in = 85EF = Twater out ? Assume that the lube oil mass flow rate and the specific heats of both fluids did not change. Which one of the following is the current cooling water outlet temperature? A. 115EF B. 125EF C. 135EF D. 145EF

Back 38

B.

Front 39

Severe stress in a mechanical component, induced by a sudden, unequally distributed temperature reduction is a description of... A. fracture stress. B. brittle fracture. C. thermal shock. D. pressurized thermal shock.

Back 39

C.

Front 40

The major thermodynamic concern resulting from rapidly cooling a reactor vessel is... A. thermal shock. B. stress corrosion. C. loss of shutdown margin. D. loss of subcooling margin.

Back 40

A.

Front 41

Steam has been admitted to a main condenser for 25 minutes with no cooling water. Initiating full cooling water flow rate at this time will... A. reduce the stress on the condenser shell by rapidly cooling the shell. B. reduce the stress on the condenser tubes by rapidly cooling the tubes. C. induce large thermal stresses on the condenser shell. D. induce large thermal stresses on the junctions between the condenser tubes and the tubesheet.

Back 41

D.

Front 42

Refer to the drawing of an operating lube oil heat exchanger (see figure below). If scaling occurs inside the cooling water tubes, cooling water outlet temperature will __________ and lube oil outlet temperature will __________. (Assume oil and cooling water flow rates remain the same.) A. decrease; decrease B. decrease; increase C. increase; decrease D. increase; increase

Back 42

B.

Front 43

Which one of the following will occur to reduce the heat transfer rate in a parallel-flow heat exchanger as scaling increases on the exterior surface of the tubes? (Assume no operator actions.) A. Flow rate through the tubes will decrease. B. Surface area of the tubes will decrease. C. Thermal conductivity of the tubes will decrease. D. Delta-T across the tubes will decrease.

Back 43

C.

Front 44

A nuclear power plant is operating at steady-state conditions with the main generator supplying 1,000 MW to the power grid. Assume main generator load remains constant. If one percent of the tubes in the main condenser become plugged, condenser absolute pressure will ___________; and condenser hotwell temperature will _________. A. increase; increase B. decrease; increase C. increase; decrease D. decrease; decrease

Back 44

A.

Front 45

Refer to the drawing of an operating lube oil heat exchanger (see figure below). If deposits accumulate on the outside of the cooling water tubes, cooling water outlet temperature will __________ and oil outlet temperature will __________. (Assume oil and cooling water inlet temperatures and flow rates remain the same.) A. increase; decrease B. increase; increase C. decrease; decrease D. decrease; increase

Back 45

D.

Front 46

A main turbine-generator is operating at 80 percent load with the following initial steady-state temperatures for the main turbine lube oil heat exchanger: Toil in = 174EF Toil out = 114EF Twater in = 85EF Twater out = 115EF After six months of main turbine operation, the following final steady-state lube oil heat exchanger temperatures are observed: Toil in = 179EF Toil out = 119EF Twater in = 85EF Twater out = 115EF Assume that the final cooling water and lube oil flow rates are the same as the initial flow rates, and that the specific heat values for the cooling water and lube oil do not change. Which one of the following could be responsible for the differences between the initial and final heat exchanger steady-state temperatures? A. The heat exchanger tubes have become fouled with scale. B. The temperature of the cooling water source has increased. C. The final main turbine-generator load is higher than the initial load. D. The final main turbine-generator load is lower than the initial load.

Back 46

A.

Front 47

Refer to the drawing of two system curves for a typical main condenser cooling water system (see figure below). Which one of the following will cause the system curve to shift from the solid curve toward the dashed curve? A. The main condenser tubes are cleaned. B. The main condenser tubes become increasingly fouled. C. Cooling water flow rate is increased by 25 percent by starting an additional cooling water pump. D. Cooling water flow rate is decreased by 25 percent by stopping one of the operating cooling water pumps.

Back 47

A.

Front 48

Refer to the drawing of two system curves for a typical main condenser cooling water system (see figure below). Which one of the following will result in the system curve shifting from the solid curve toward the dashed curve? A. The main condenser tubes are cleaned. B. The main condenser tubes become increasingly fouled. C. Cooling water system flow rate is increased by 25 percent by starting an additional cooling water pump. D. Cooling water system flow rate is decreased by 25 percent by stopping one of the operating cooling water pumps.

Back 48

B.

Front 49

Borated water is flowing through the tubes of a heat exchanger being cooled by fresh water. The shell side pressure is less than tube side pressure. What will occur as a result of a tube failure? A. Shell side pressure will increase and the borated water system will be diluted. B. Shell side pressure will decrease and the borated water inventory will be depleted. C. Shell side pressure will increase and the borated water inventory will be depleted. D. Shell side pressure will decrease and the borated water system will be diluted.

Back 49

C.

Front 50

Refer to the drawing of an operating cooling water system (see figure below). Which one of the following effects would occur as a result of the failed tube in the heat exchanger? A. Level in the surge tank increases. B. Flow in the low pressure (LP) system reverses. C. Pressure in the low pressure (LP) system decreases. D. Low pressure (LP) fluid heat exchanger outlet temperature decreases.

Back 50

D.

Front 51

A nuclear power plant is operating normally at 50 percent power. Which one of the following will result from a cooling water tube rupture in the main condenser? A. Increased condenser vacuum. B. Increased conductivity of the condensate. C. Decreased condensate pump available net positive suction head. D. Decreased condensate pump flow rate.

Back 51

B.

Front 52

Which one of the following effects will occur as a result of multiple tube failures (leaks) in the main condenser of a nuclear power plant at 50 percent power? A. Condensate depression will decrease. B. Condensate conductivity will increase. C. Condensate oxygen concentration will decrease. D. Condenser inlet cooling water flow rate will decrease.

Back 52

B.

Front 53

Refer to the drawing of an operating cooling water system (see figure below). Which one of the following will occur as a result of the indicated tube failure in the heat exchanger? A. High pressure (HP) fluid inventory increases. B. Pressure in the low pressure (LP) system decreases. C. Temperature in the low pressure (LP) system increases. D. Level in the surge tank decreases.

Back 53

D.

Front 54

The following 100 percent power conditions existed before a nuclear power plant outage: Main condenser pressure: 1.20 psia Cooling water inlet temperature: 60EF Cooling water outlet temperature: 92EF During the outage, 6 percent of the main condenser tubes were plugged. After the outage, the following 100 percent power conditions exist: Main condenser pressure: 1.31 psia Cooling water inlet temperature: 60EF Cooling water outlet temperature: ? Which one of the following is the approximate cooling water outlet temperature after the outage? A. 92EF B. 94EF C. 96EF D. 98EF

Back 54

B.

Front 55

A nuclear power plant was initially operating at steady-state 50 percent power with 50 gpm of main condenser cooling water inleakage through a cooling water tube rupture. Power was then increased, and is currently stable at 60 percent. Assume that the size of the cooling water tube rupture does not change, and that the main condenser cooling water inlet pressure and inlet temperature do not change. When compared to the flow rate of main condenser cooling water inleakage at 50 percent power, the flow rate of main condenser cooling water inleakage at 60 percent power is ____________ because the main condenser pressure at 60 percent power is __________. A. higher; lower B. higher; higher C. lower; lower D. lower; higher

Back 55

D.

Front 56

During normal nuclear power plant operation, a main condenser develops an air leak which decreases vacuum at a rate of 1 inch Hg/min. Which one of the following will increase because of this condition? A. Extraction steam flow rate B. Condenser hotwell temperature C. Low pressure turbine exhaust steam moisture content D. Steam cycle efficiency

Back 56

B.

Front 57

During normal nuclear power plant operation, why does air entry into the main condenser reduce the thermodynamic efficiency of the steam cycle? A. The rate of steam flow through the main turbine increases. B. The condensate subcooling in the main condenser decreases. C. The enthalpy of the low pressure turbine exhaust increases. D. The air mixes with the steam and enters the condensate.

Back 57

C.

Front 58

A nuclear power plant is operating at steady-state 100 percent power. Assuming that condenser cooling water inlet temperature and flow rate do not change, if condenser vacuum decreases, condensate temperature will... A. increase because condensate subcooling has decreased. B. increase because condenser saturation pressure has increased. C. decrease because condensate subcooling has increased. D. decrease because condenser saturation pressure has decreased.

Back 58

B.

Front 59

A nuclear power plant is operating at steady-state 100 percent power when air inleakage causes main condenser vacuum to decrease from 28 inches Hg to 27 inches Hg. Assume the steam inlet quality and mass flow rate of steam through the main turbine remain unchanged, and that condenser cooling water inlet temperature and flow rate do not change. When the plant stabilizes, turbine exhaust quality will be_________ and turbine exhaust temperature will be _________. A. higher; higher B. higher; lower C. lower; higher D. lower; lower

Back 59

A.

Front 60

A nuclear power plant is operating near rated power with the following initial conditions: Main steam pressure: 900 psia Main steam quality: 100 percent, saturated vapor Main condenser pressure: 1.0 psia Air leakage into the main condenser results in the main condenser pressure increasing and stabilizing at 2.0 psia. Assume that all main steam parameters (e.g., pressure, quality, and mass flow rate) remain the same and that the main turbine efficiency remains at 100 percent. Which one of the following is the approximate percent by which the main generator output will decrease as a result of the main condenser pressure increase? A. 5.0 percent B. 6.3 percent C. 7.5 percent D. 8.8 percent

Back 60

C.

Front 61

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following initial parameters: Cooling water inlet temperature (Tcw-in ) = 75EF Cooling water outlet temperature (Tcw-out ) = 95EF Oil inlet temperature (Toil-in ) = 150EF Oil outlet temperature (Toil-out ) = 120EF Air introduction to the heat exchanger results in some of the heat exchanger tubes becoming uncovered. As a result, Tcw-out decreases to 91EF. Assume the inlet temperatures, mass flow rates, and specific heats of both fluids remain the same. Which one of the following will be the resulting temperature of the oil exiting the heat exchanger (Toil-out)? A. 126EF B. 130EF C. 134EF D. 138EF

Back 61

A.

Front 62

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following initial parameters: Cooling water inlet temperature (Tcw-in ) = 75EF Cooling water outlet temperature (Tcw-out ) = 105EF Oil inlet temperature (Toil-in ) = 140EF Oil outlet temperature (Toil-out ) = 100EF Air introduction to the heat exchanger results in some of the heat exchanger tubes becoming uncovered. As a result, Tcw-out decreases to 99EF. Assume that the mass flow rate and specific heat of both fluids remain the same, and that Toil-in does not change. Which one of the following will be the approximate temperature of the oil exiting the heat exchanger (Toil-out)? A. 99EF B. 108EF C. 116EF D. 122EF

Back 62

B.

Front 63

Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following initial parameters: Cooling water inlet temperature (Tcw-in ) = 75EF Cooling water outlet temperature (Tcw-out ) = 95EF Oil inlet temperature (Toil-in ) = 150EF Oil outlet temperature (Toil-out ) = 110EF Air leakage into the heat exchanger causes some of the heat exchanger tubes to become uncovered. As a result, Tcw-out decreases to 89EF. Assume the inlet temperatures, mass flow rates, and specific heats of both fluids remain the same. Which one of the following will be the new approximate temperature of the oil exiting the heat exchanger (Toil-out)? A. 116EF B. 122EF C. 130EF D. 138EF

Back 63

B.

Front 64

Refer to the drawing of an operating lube oil heat exchanger (see figure below). The heat exchanger was operating with the following initial parameters: Cooling water inlet temperature (Tcw-in ) = 71EF Cooling water outlet temperature (Tcw-out ) = 91EF Oil inlet temperature (Toil-in ) = 175EF Oil outlet temperature (Toil-out ) = 125EF The heat exchanger was vented, resulting in the following current parameters: Cooling water inlet temperature (Tcw-in ) = 71EF Cooling water outlet temperature (Tcw-out ) = 95EF Oil inlet temperature (Toil-in ) = 175EF Oil outlet temperature (Toil-out ) = ? Assume that the mass flow rates and specific heats of both fluids were unchanged. Which one of the following is the current lube oil outlet temperature (Toil-out)? A. 115EF B. 120EF C. 130EF D. 135EF

Back 64

A.