Heat Exchangers and Condensers
Question 69 of 103 QID: B7316 (P7316)Add Flag Knowledge: K1.07 [2.7/2.8] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating parallel-flow lube oil heat exchanger (see figure below). Unlike a counter-flow heat exchanger, in the parallel-flow heat exchanger the __________ temperature will ALWAYS be greater than the __________ temperature.
LO outlet; CW outlet
Question 66 of 103 QID: B374Add Flag Knowledge: K1.11 [2.8/2.8] Topic: Heat Exchangers and Condensers A pressure gauge on a condenser reads 27 inches of mercury (Hg) vacuum. What is the absolute pressure corresponding to this vacuum? (Assume that standard atmospheric pressure equals 15 psia.)
1.5 psia
Question 38 of 103 QID: B2933 (P2934)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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: 130°F Cooling water inlet temperature: 70°F Assuming the cooling water flow rate exceeds the 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
100°F 90°F
Question 65 of 103 QID: B2832 (P4517)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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) = 75°F Cooling water outlet temperature (Tcw-out) = 105°F Oil inlet temperature (Toil-in) = 140°F Oil outlet temperature (Toil-out) = 100°F Air introduction to the heat exchanger results in some of the heat exchanger tubes becoming uncovered. As a result, Tcw-out decreases to 99°F. 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
108°F
Question 71 of 103 QID: B1933 (P1934)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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)? ṁoil = 1.5 x 10^4 lbm/hr ṁwater = 2.5 x 10^4 lbm/hr cp-oil = 1.1 Btu/lbm-°F cp-water = 1.0 Btu/lbm-°F Tcw-in = 92°F Tcw-out = 125°F Toil-in = 160°F Toil-out = ?
110°F
Question 16 of 103 QID: B3732 (P3732)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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: 130°F Cooling water inlet temperature: 70°F 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
110°F 90°F (because water mass flow is less, it must have a higher temp. difference than oil!)
Question 41 of 103 QID: B5517 (P5516)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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: 130°F Cooling water inlet temperature: 70°F 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
110°F 95°F
Question 19 of 103 QID: B3733 (P3783)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers A condensate pump is taking suction on a main condenser hotwell, containing water at 100°F, and discharging the water at a volumetric flow rate of 100,000 gpm to the main feedwater system. The main feedwater system heats the water to 400°F before it enters the reactor vessel. Assume there is no leakage, and no bypass or recirculation flow paths are in use. What is the approximate volumetric flow rate of the feedwater entering the reactor vessel?
115,000 gpm
Question 33 of 103 QID: B5418 (P5417)Add Flag Knowledge: K1.18 [2.8/2.9] Topic: Heat Exchangers and Condensers 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 ) = 71°F Cooling water outlet temperature (Tcw-out ) = 91°F Oil inlet temperature (Toil-in ) = 175°F Oil outlet temperature (Toil-out ) = 125°F The heat exchanger was vented, resulting in the following current parameters: Cooling water inlet temperature (Tcw-in ) = 71°F Cooling water outlet temperature (Tcw-out ) = 95°F Oil inlet temperature (Toil-in ) = 175°F 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)?
115°F
Question 76 of 103 QID: B1531 (P1533)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following existing conditions: ṁoil = 1.8 x 104 lbm/hr ṁwater = 3.3 x 104 lbm/hr cpoil = 1.1 Btu/lbm-°F cpwater = 1.0 Btu/lbm-°F Tcw-in = 90°F Tcw-out = 120°F Toil-in = 170°F Toil-out = ? What is the approximate temperature of the oil exiting the heat exchanger (Toil-out)?
120°F
Question 85 of 103 QID: B1435 (P3432)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following existing conditions: ṁoil = 1.8 x 104 lbm/hr ṁwater = 3.3 x 104 lbm/hr cpoil = 1.1 Btu/lbm-°F cpwater = 1.0 Btu/lbm-°F Tcw-in = 90°F Tcw-out = 120°F Toil-in = 170°F Toil-out = ? What is the approximate temperature of the oil exiting the heat exchanger (Toil-out)?
120°F
Question 87 of 103 QID: B1331Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following existing conditions: ṁoil = 1.8 x 104 lbm/hr ṁwater = 3.3 x 104 lbm/hr cpoil = 1.1 Btu/lbm-°F cpwater = 1.0 Btu/lbm-°F Tcw-in = 90°F Tcw-out = 120°F Toil-in = 170°F Toil-out = ? Which one of the following is the approximate temperature of the oil exiting the heat exchanger (Toil-out)?
120°F
Question 28 of 103 QID: B6516 (P6516)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers Refer to the drawing of a heat exchanger (see figure below). The heat exchanger is in service with the following inlet temperatures: Service water inlet temperature: 130°F Cooling water inlet temperature: 70°F Assume that both fluids have the same specific heat, and that service water mass flow rate is greater than cooling water mass flow rate. Which one of the following pairs of heat exchanger outlet temperatures is possible? Service Water Outlet Temp. / Cooling Water Outlet Temp.
120°F / 82°F
Question 59 of 103 QID: B2733 (P2733)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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: 130°F Cooling water inlet temperature: 70°F Assuming that 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 Outlet Temp / Cooling Water Outlet Tem
120°F / 83°F
Question 51 of 103 QID: B4817 (P4816)Add Flag Knowledge: K1.18 [2.8/2.9] Topic: Heat Exchangers and Condensers 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 ) = 75°F Cooling water outlet temperature (Tcw-out ) = 95°F Oil inlet temperature (Toil-in ) = 150°F Oil outlet temperature (Toil-out ) = 110°F Air leakage into the heat exchanger causes some of the heat exchanger tubes to become uncovered. As a result, Tcw-out decreases to 89°F. 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)?
122°F
Question 55 of 103 QID: B2534 (P2532)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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)? ṁoil = 1.5 x 104 lbm/hr ṁwater = 2.5 x 104 lbm/hr cpoil = 1.1 Btu/lbm-°F cpwater = 1.0 Btu/lbm-°F Toil-in = 160°F Toil-out = 110°F Tcw-in = 92°F Tcw-out = ?
125°F
Question 68 of 103 QID: B4018 (P4016)Add Flag Knowledge: K1.18 [2.9/3.0] Topic: Heat Exchangers and Condensers 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) = 75°F Cooling water outlet temperature (Tcw-out) = 95°F Oil inlet temperature (Toil-in) = 150°F Oil outlet temperature (Toil-out) = 120°F Air introduction to the heat exchanger results in some of the heat exchanger tubes becoming uncovered. As a result, Tcw-out decreases to 91°F. 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)?
126°F
Question 64 of 103 QID: B835Add Flag Knowledge: K1.11 [2.8/2.8] Topic: Heat Exchangers and Condensers A pressure gauge on a main condenser reads 2 psiv. What is the approximate absolute pressure in the main condenser?
13 psia
Question 61 of 103 QID: B1631 (P1634)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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)? ṁoil = 2.0 x 104 lbm/hr ṁwater = 3.0 x 104 lbm/hr cpoil = 1.1 Btu/lbm-°F cpwater = 1.0 Btu/lbm-°F Tcw-in = 92°F Tcw-out = 125°F Toil-in = 180°F Toil-out = ?
135°F
Question 72 of 103 QID: B2131Add Flag Knowledge: K1.11 [2.8/2.8] Topic: Heat Exchangers and Condensers Which one of the following is the approximate condenser vacuum (inches Hg vacuum) when condenser pressure is 16 inches Hg absolute?
14 inches Hg vacuum
Question 60 of 103 QID: B3631 (P3632)Add Flag Knowledge: K1.03 [2.4/2.6] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating water cleanup system (see figure below). If cooling water flow rate is 1.0 x 10^6 lbm/hr, what is the approximate water flow rate in the cleanup system?
2.2 x 10^5 lbm/hr
Question 93 of 103 QID: B1633Add Flag Knowledge: K1.11 [2.8/2.8] Topic: Heat Exchangers and Condensers Which one of the following is the approximate condenser vacuum when condenser pressure is 7 inches Hg absolute?
23 inches Hg vacuum
Question 78 of 103 QID: B1035Add Flag Knowledge: K1.11 [2.8/2.8] Topic: Heat Exchangers and Condensers A condenser absolute pressure of 4 inches Hg is equivalent to..
26 inches Hg vacuum.
Question 50 of 103 QID: B934 (P3132)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers Refer to the drawing of a lube oil heat exchanger (see figure below). The heat exchanger is operating with the following parameters: Q_dotoil = 1.0 x 10^7 Btu/hr Toil in = 170°F Toil out = 134°F Twater in = 85°F Twater out = 112°F cp-oil = 1.1 Btu/lbm-°F cp-water = 1.0 Btu/lbm-°F 0= ? mwater Which one of the following is the mass flow rate of the cooling water?
3.7 x 10^5 lbm/hr
Question 13 of 103 QID: B3032 (P3081)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers The volumetric flow rate of cooling water entering a heat exchanger is 500 gpm. Given the following: Cooling water pressure entering and leaving the heat exchanger is 10 psig. Cooling water inlet temperature is 90°F. Cooling water outlet temperature is 160°F. Heat exchanger inlet and outlet piping have the same diameter. What is the approximate volumetric flow rate of the cooling water exiting the heat exchanger?
509 gpm
Question 52 of 103 QID: B834 (P2034)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating lube oil heat exchanger (see figure below). Given the following existing conditions: cpoil = 1.1 Btu/lbm-°F cpwater = 1.0 Btu/lbm-°F ṁoil = 1.8 x 104 lbm/hr ṁwater = 1.65 x 104 lbm/hr Toil-in = 170°F Toil-out = 120°F Twater-out = 110°F Twater-in = ? Which one of the following is the cooling water inlet temperature (Twater-in) in this heat exchanger?
50°F
Question 43 of 103 QID: B34Add Flag Knowledge: K1.13 [2.7/2.9] Topic: Heat Exchangers and Condensers What is the saturation temperature for a boiling water reactor operating at 920 psig?
536.5°F
Question 90 of 103 QID: B3431Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers Refer to the drawing of a lube oil heat exchanger (see figure below). The heat exchanger is operating with the following parameters: cp-oil = 1.1 Btu/lbm-°F cp-water = 1.0 Btu/lbm-°F Toil in = 174°F Toil out = 114°F Twater in = 85°F Twater out = 121°F ṁoil = 4.0 x 104 lbm/hr ṁwater = ? What is the mass flow rate of the cooling water?
7.3 x 10^4 lbm/hr
Given the following parameter values for a feedwater heater: Feedwater inlet temperature: 320°F Feedwater inlet pressure: 1,000 psia Feedwater mass flow rate: 1.0 x 10^6 lbm/hr Extraction steam pressure: 500 psia Assume that the extraction steam enters the heater as a dry saturated vapor and leaves the heater as a saturated liquid at 500 psia. Which one of the following is the mass flow rate of extraction steam required to increase feedwater temperature to 380°F?
8.4 x 10^4 lbm/hr
Question 45 of 103 QID: B1033Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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-°F cp-water = 1.0 Btu/lbm-°F ṁoil = 1.8 x 10^4 lbm/hr ṁwater = 1.65 x 10^4 lbm/hr Toil in = 115°F Toil out = 90°F Twater out = 110°F Twater in = ? Which one of the following is the approximate cooling water inlet temperature (Twater in) for this heat exchanger?
80°F
Question 35 of 103 QID: B2132 (P2133)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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: 120°F Cooling water inlet temperature: 60°F 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 Outlet Temp / Cooling Water Outlet Temp
80°F / 80°F
Question 44 of 103 QID: B2233 (P2434)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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: 130°F Cooling water inlet temperature: 70°F 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? (Assume both fluids have the same cp.) Lube Oil Outlet Temp / Cooling Water Outlet Temp
90°F / 100°F
Question 29 of 103 QID: B7517 (P7516)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers Refer to the drawing of a heat exchanger (see figure below). The heat exchanger is in service with the following inlet temperatures: Cooling water inlet temperature = 70°F Service water inlet temperature = 130°F Assume that both fluids have the same specific heat, and that cooling water mass flow rate is greater than service water mass flow rate. Which one of the following pairs of heat exchanger outlet temperatures is not possible? Cooling Water Outlet Temp. / Service Water Outlet Temp.
90°F / 110°F
Question 47 of 103 QID: B4416 (P4416)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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: 120°F Cooling water inlet temperature: 60°F 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 Water Outlet Temp / Cooling Water Outlet Temp
90°F / 85°F
Question 73 of 103 QID: B2632 (P2633)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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: 110°F Cooling water inlet temperature: 75°F 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 Outlet Temp / Cooling Water Outlet Temp
90°F / 90°F
Question 92 of 103 QID: B36Add Flag Knowledge: K1.02 [2.6/2.6] Topic: Heat Exchangers and Condensers Why is proper venting of a shell-and-tube heat exchanger important?
An air bubble reduces the heat transfer coefficient of the heat exchanger.
Question 17 of 103 QID: B1231 (P1231)Add Flag Knowledge: K1.07 [2.7/2.8] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating water cleanup system (see figure below). All valves are identical and are initially 50% open. To lower the temperature at point 4, the operator can adjust valve ______ in the ______ direction.
B; shut shutting Valve "B" will reduce the flow rate of warm water from the system. This reduces the amount of warm water flowing through the system and reduces the amount of time the water remaining in contact with the cooler cooling water. Both of these effects will lower the temperature at point "4".
Question 32 of 103 QID: B2732 (P2732)Add Flag Knowledge: K1.07 [2.7/2.8] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating water cleanup system (see figure below). All valves are identical and are initially 50% open. To raise the temperature at point 4, the operator can adjust valve ______ in the ______ direction.
C; open
Question 30 of 103 QID: B5716 (P5716)Add Flag Knowledge: K1.07 [2.7/2.8] Topic: Heat Exchangers and Condensers 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.
CW outlet; LO outlet CW outlet can NOT be greater than LO outlet in the Parallel Heat Exchanger but CW outlet can be greater/equal/less than LO outlet in the Counter Flow Heat Exchanger
Question 75 of 103 QID: B1931 (P1134)Add Flag Knowledge: K1.17 [2.7/2.8] Topic: Heat Exchangers and Condensers Which one of the following effects will occur as a result of multiple tube failures (leaks) in the main condenser with the plant at 50% power? (Assume condenser vacuum does not change.)
Condensate conductivity will increase because the water sources for cooling most main condenser is not treated for the same strict purity controls as the condensate, and the pressure of the cooling water is higher than the low pressure condenser; a tube failure (leak) will result in the high pressure impure cooling water flowing into the low pressure pure condensate. An INCREASE in conductivity of the condensate is one of the first indications of problems in the condenser.
Question 20 of 103 QID: B111 (P1834)Add Flag Knowledge: K1.10 [2.8/2.8] Topic: Heat Exchangers and Condensers During normal reactor operation, a main condenser develops an air leak which decreases vacuum at a rate of 1 inch Hg/min. Which one of the following would increase because of this condition?
Condenser hotwell temperature Air leak into condenser increases the absolute pressure in the condenser. As the saturation pressure increases in the condenser, the saturation temperature in the condenser also increases. Air leakage into the condenser also increases the volume of air (noncondensible gas) and acts as a shield insulating the tubes carrying the circulating water. This reduces the amount of heat the circulating water can remove from the steam. Again, this increases the saturation pressure and saturation temperature in the condenser. This results in an INCREASE in temperature of the water collecting in the condenser hotwell.
Question 49 of 103 QID: B733Add Flag Knowledge: K1.10 [2.8/2.8] Topic: Heat Exchangers and Condensers Which one of the following changes will result in increased subcooling of the condensate water in the condenser hot well?
Decrease the main turbine generator MW load. The answers pose three actions that will decrease the ability of the circulating water system to remove heat and one that lowers the heat energy entering the condenser. The cases that reduce heat removal will (assuming a constant heat input) decrease subcooling. Less heat removal capacity left for subcooling after the latent heat of vaporization is removed. In the final case, lowering the main turbine generator load implies that there is a decrease in the amount of steam energy admitted to the main condenser. If condenser circulating water flow remains constant then the temperature of the condensate will decrease resulting in increased subcooling.
A nuclear power plant is operating at full power with 2°F of condensate subcooling. Which one of the following changes will decrease subcooling of the condensate entering the main condenser hot well? (Assume condensate temperature does not change.)
Decreased main turbine steam flow maintaining circulating water temperature and flow rate while lowering the steam flow would allow the circulating water to remove more heat from the condensed steam. Removing more heat from the condensed steam would lower the saturation pressure and saturation temperature. A lower value for the saturation temperature would result in a lower value for the condensate cooling (depression).
Which one of the following changes will result in increased subcooling of the condensate water in the main condenser hotwell?
Decreased main turbine-generator MW load
Question 81 of 103 QID: B232Add Flag Knowledge: K1.09 [2.7/2.8] Topic: Heat Exchangers and Condensers A reactor is shut down with a reactor coolant temperature of 400°F and all control rods fully inserted. What is the major adverse consequence resulting from rapidly reducing the reactor coolant temperature to 250°F?
Excessive stress on the reactor vessel wall
Question 36 of 103 QID: B632 (P3232)Add Flag Knowledge: K1.04 [2.8/2.8] Topic: Heat Exchangers and Condensers 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% open. If valve C is opened to 100%, how will the temperatures at points 3 and 6 be affected? Point 3 Point 6
Increase Increase Valve "C" is opened from 20% to 50%. More hot water from system flows through heat exchanger. Temperature at point "6" will increase as the cooling water absorbs more heat. Since more heat energy is now entering the non-regulative heat exchanger and nothing indicates an increase in the cooling capacity of the cold side, the temperature at point 3 must also increase.
Question 15 of 103 QID: B7117Add Flag Knowledge: K1.04 [2.8/2.8] Topic: Heat Exchangers and Condensers A nuclear power plant is shut down with core decay heat being removed by the residual heat removal (RHR) system. Assume that only the RHR heat exchangers are removing heat from the reactor vessel (RV), and that the RHR system provides complete thermal mixing in the RV. Given the following information: Reactor core rated thermal power = 2,950 MW Core decay heat rate = 0.5% rated thermal power RHR system heat removal rate = 5.7 x 10^7 Btu/hr RHR and reactor coolant cp = 1.05 Btu/lbm-°F Combined RV and RHR inventory = 450,000 lbm Which one of the following actions will establish a reactor cooldown rate between 20°F/hour and 30°F/hour?
Increase RHR heat exchanger flow rate to increase the cooldown rate by 10°F/hour.
Question 25 of 103 QID: B6716 (P6716)Add Flag Knowledge: K1.04 [2.8/2.8] Topic: Heat Exchangers and Condensers A nuclear power plant is shut down with core decay heat being removed by the residual heat removal (RHR) system. Assume that only the RHR heat exchangers are removing heat from the reactor vessel (RV), and that the RHR system provides complete thermal mixing of the RV. Given the following information: Reactor core rated thermal power: 2,950 MW Core decay heat rate: 0.5% rated thermal power RHR system heat removal rate: 5.3 x 107 Btu/hr Reactor coolant cp: 1.05 Btu/lbm-°F Combined RV and RHR inventory: 425,000 lbm Which one of the following actions will establish a reactor cooldown rate between 20°F/hour and 30°F/hour?
Increase RHR heat exchanger flow rate to increase the cooldown rate by 20°F/hour.
Question 84 of 103 QID: B333 (P333)Add Flag Knowledge: K1.17 [2.7/2.8] Topic: Heat Exchangers and Condensers A nuclear power plant is operating normally at 50% of rated power. Which one of the following will result from a cooling water tube rupture in the main condenser?
Increased conductivity of the condensate
Question 89 of 103 QID: B1133Add Flag Knowledge: K1.12 [2.9/3.0] Topic: Heat Exchangers and Condensers A nuclear reactor is shut down at 400 psia during a maintenance outage when all forced core coolant flow is lost. Which one of the following will enhance natural circulation within the reactor vessel?
Increasing reactor vessel water level above the steam separators.
Question 46 of 103 QID: B234Add Flag Knowledge: K1.17 [2.7/2.8] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating cooling water system (see figure below) that is transferring heat between a low pressure (LP) and high pressure (HP) water system. Which one of the following effects will initially occur as a result of a tube failure in the heat exchanger?
LP fluid heat exchanger outlet temperature will increase.
Question 39 of 103 QID: B1535 (P1234)Add Flag Knowledge: K1.17 [2.7/2.8] Topic: Heat Exchangers and Condensers 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?
Level in the surge tank decreases.
Question 26 of 103 QID: B3535 (P234)Add Flag Knowledge: K1.17 [2.7/2.8] Topic: Heat Exchangers and Condensers 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?
Low pressure fluid heat exchanger outlet temperature decreases. (colder load will leak and mix with hot load, thus temp. decs (gets colder) )
Question 10 of 103 QID: B7616Add Flag Knowledge: K1.04 [2.8/2.8] Topic: Heat Exchangers and Condensers A nuclear power plant is shut down with core decay heat being removed by the residual heat removal (RHR) system. Assume that only the RHR heat exchangers are removing heat from the reactor vessel (RV), and that the RHR system provides complete thermal mixing in the RV. Given the following information: Reactor core rated thermal power= 2,950 MW Core decay heat rate = 0.6% rated thermal power RHR system heat removal rate = 8.1 x 107 Btu/hr RHR and RV coolant cp = 1.05 Btu/lbm-°F Combined RV and RHR inventory = 450,000 lbm Which one of the following actions will establish a reactor cooldown rate between 20°F/hour and 30°F/hour?
Reduce RHR heat exchanger flow rate to decrease the cooldown rate by 20°F/hour.
Question 24 of 103 QID: B1536Add Flag Knowledge: K1.13 [2.7/2.9] Topic: Heat Exchangers and Condensers Which one of the following describes the state of water at 160 psig and 366°F?
Subcooled liquid
Question 53 of 103 QID: B1433Add Flag Knowledge: K1.13 [2.7/2.9] Topic: Heat Exchangers and Condensers Which one of the following is the state of water at 120 psig and 340°F?
Subcooled liquid
Question 74 of 103 QID: B1335Add Flag Knowledge: K1.13 [2.7/2.9] Topic: Heat Exchangers and Condensers Which one of the following describes the state of water at 35 psia and 240°F?
Subcooled liquid
Which one of the following describes the state of water at 150 psig and 360°F?
Subcooled liquid
Which one of the following describes the state of water at 160 psig and 372°F?
Superheated vapor
Which one of the following is the state of water at 20 psia and 250°F?
Superheated vapor
A main turbine-generator was operating at 80% load with the following initial steady-state lube oil and cooling water temperatures for the main turbine lube oil heat exchanger: Toil in = 174°F Toil out = 114°F Twater in = 85°F Twater out = 115°F Six months later, the following current steady-state heat exchanger temperatures are observed: Toil in = 177°F Toil out = 111°F Twater in = 85°F Twater out = 115°F 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?
The current main turbine lube oil mass flow rate is less than the initial flow rate. (because water temp and mass flowrate didnt change, it's still extracting the same heat, thus Q never changed).
uring normal nuclear power plant operation, why does air entry into the main condenser reduce the thermodynamic efficiency of the steam cycle?
The enthalpy of the low pressure turbine exhaust increases. The presence of air and noncondensibles greatly reduces condenser efficiency because the steam must diffuse through a film of air and noncondensibles before reaching the condensing surface. A temperature gradient is created because the air and noncondensibles blanket the condenser tubes. This blanketing of the tubes with the noncondensible gas with reduces the cooling capability of the condenser. The saturated steam in the condenser is not cooled as much as before. This results in a higher saturation temperature and a higher saturation pressure. The pressure in the condenser is the same as the saturation pressure. Therefore the condenser pressure will be higher. The higher pressure in the condenser prevents the steam from cooling down at a lower temperature and pressure. At higher pressure the specific enthalpy is higher. For example from the Mollier Diagram, if 900 psi steam enters an ideal turbine and exhaust to a 1 psi condenser the specific enthalpy is approximately 780 Btu/lbm. If the same 900 psi steam exits an ideal turbine to a condenser at 2 psi the specific enthalpy is about 812 Btu/lbm. An increase of 32 Btu/lbm that is not available to do work in the turbine.
Question 11 of 103 QID: B3635 (P3633)Add Flag Knowledge: K1.15 [2.6/2.8] Topic: Heat Exchangers and Condensers A main turbine-generator is operating at 80% load with the following initial steady-state temperatures for the main turbine lube oil heat exchanger: Toil in = 174°F Toil out = 114°F Twater in = 85°F Twater out = 115°F After six months of main turbine-generator operation, the following final steady-state lube oil heat exchanger temperatures are observed: Toil in = 179°F Toil out = 119°F Twater in = 85°F Twater out = 115°F 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?
The heat exchanger tubes have become fouled with scale.
Question 34 of 103 QID: B1732 (P1732)Add Flag Knowledge: K1.03 [2.4/2.6] Topic: Heat Exchangers and Condensers 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.)
The inlet temperature of the colder liquid is increased by 20°F.
Question 27 of 103 QID: B7676 (P7676)Add Flag Knowledge: K1.03 [2.4/2.6] Topic: Heat Exchangers and Condensers Which one of the following will increase the heat transfer rate between two liquids in a heat exchanger? (Assume single-phase conditions and a constant specific heat for both liquids.)
The inlet temperature of the hotter liquid increases by 20°F.
Question 88 of 103 QID: B4616 (P4617)Add Flag Knowledge: K1.15 [2.6/2.8] Topic: Heat Exchangers and Condensers 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?
The main condenser tubes are cleaned.
Question 96 of 103 QID: B104Add Flag Knowledge: K1.01 [2.7/2.7] Topic: Heat Exchangers and Condensers Which one of the following describes the proper sequence for placing a steam (shell) and water (tube) heat exchanger into service?
The water side is valved in before the steam side to minimize thermal shock.
Question 95 of 103 QID: B535Add Flag Knowledge: K1.14 [3.1/3.2] Topic: Heat Exchangers and Condensers What is the reason for ensuring that a piping system is completely filled and vented prior to initiating system flow?
To minimize the potential for water hammer
Question 42 of 103 QID: B1232Add Flag Knowledge: K1.10 [2.8/2.8] Topic: Heat Exchangers and Condensers Assuming that condenser cooling water inlet temperature and flow rate do not change, if condenser vacuum improves, condensate temperature will...
decrease because condenser saturation pressure has decreased.
Question 3 of 103 QID: B431 (P632)Add Flag Knowledge: K1.08 [2.9/3.0] Topic: Heat Exchangers and Condensers 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 _________.
decrease, decrease
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 _________.
decrease, decrease
Question 70 of 103 QID: B434Add Flag Knowledge: K1.11 [2.8/2.8] Topic: Heat Exchangers and Condensers A steam-driven turbine exhausts to a condenser. As condenser vacuum is increased, the turbine backpressure will _________ and the turbine power output will _________.
decrease; increase
Question 82 of 103 QID: B1833 (P2233)Add Flag Knowledge: K1.16 [2.5/2.6] Topic: Heat Exchangers and Condensers 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.)
decrease; increase
Question 77 of 103 QID: B6617 (P6616)Add Flag Knowledge: K1.16 [2.5/2.6] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating lube oil heat exchanger (see figure below). If mineral deposits accumulate on the inside of the cooling water tubes, cooling water outlet temperature will __________ and lube oil outlet temperature will __________. (Assume that the lube oil and cooling water inlet temperatures and flow rates do not change.)
decrease; increase Since it takes more heat energy to drive the heat across the thicker scale with the lower thermal conductivity, the temperature of the oil leaving the heat exchanger INCREASES over the initial temperature of the oil leaving the heat exchanger. The oil heat transfer rate initially decreases which cause the oil to heat up as the warmer oil returns to the lube oil system. Because initially the heat transfer rate of the lube oil decreases less heat is transferred across the tube into the cooling water. On the cold side the initial reaction will be a DECREASE in cooling water outlet temperature. As the heat transfer decreases, each pound mass of cooling water picks up less energy.
Question 67 of 103 QID: B1234 (P32)Add Flag Knowledge: K1.16 [2.5/2.6] Topic: Heat Exchangers and Condensers 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.)
decrease; increase The inlet temperature of the oil is now hotter than it was before the scale buildup. This continues until a new steady state T is established equal to the original but with oil temperatures on the inlet and outlet higher and high enough to drive the same heat load across the newly "insulated" barrier. On the cold side the initial reaction will be a decrease in cooling water outlet temperature. As the heat transfer decreases, each pound mass of water picks up less energy. Once the stored energy on the hot side becomes sufficient to again drive the heat load across the barrier the system should stabilize with the outlet temperature back where it began. Therefore the equation author must have been seeking the INITIAL change only.
Question 23 of 103 QID: B832 (P1632)Add Flag Knowledge: K1.03 [2.4/2.6] Topic: Heat Exchangers and Condensers 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 capacity.)
flow rate of the colder liquid is decreased by 10%. decreasing the flow rate of the colder liquid will INITIALLY DECREASE the heat transfer rate. This will eventually lead to an increase in the temperature on the hot side (assuming a constant heat load input) and an equilibrium situation where the hot side temperatures are greater and the heat transfer rate is the same. also, flow rates of both liquids are decreased by 10%. decreasing the mass flow rate of the both liquids will INITIALLY result in the heat transfer rate DECREASING. Assuming a constant heat input on the hot side, the delta temperatures on the hot side will increase until such time as equilibrium is reestablished with higher temperature differences seen across both sides of the heat exchanger and the heat transfer rate back to where it began.
Question 37 of 103 QID: B631 (P1832)Add Flag Knowledge: K1.03 [2.4/2.6] Topic: Heat Exchangers and Condensers 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 for each liquid.)
flow rate of the hotter liquid is increased by 10%. increasing the flow rate of the hotter liquid will INITIALLY INCREASE the heat transfer rate. Again, the new steady state equilibrium would be lower temperatures on the hot side and the same heat transfer (assuming a constant heat load input). flow rates of both liquids are increased by 10%. increasing the mass flow rate of the both liquids will result in the heat transfer rate INCREASING.
Question 31 of 103 QID: B2531 (P2632)Add Flag Knowledge: K1.03 [2.4/2.6] Topic: Heat Exchangers and Condensers 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.)
flow rates of both liquids are decreased by 10%.
Question 58 of 103 QID: B1432 (P1432)Add Flag Knowledge: K1.03 [2.4/2.6] Topic: Heat Exchangers and Condensers 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.)
flow rates of both liquids are increased by 10%.
Question 86 of 103 QID: B932Add Flag Knowledge: K1.02 [2.6/2.6] Topic: Heat Exchangers and Condensers Reduced heat transfer performance in a heat exchanger will result from...
gas collection in the shell.
Question 12 of 103 QID: B2736 (P3534)Add Flag Knowledge: K1.10 [2.8/2.8] Topic: Heat Exchangers and Condensers A nuclear power plant is operating at steady-state 100% 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 _________.
higher; higher
Question 56 of 103 QID: B7736 (P7736)Add Flag Knowledge: K1.12 [2.5/2.7] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating lube oil heat exchanger (see figure below). The heat exchanger was initially placed in continuous service 6 months ago. During the 6-month period of operation, mineral deposits have accumulated inside the heat exchanger tubes. The following parameters are currently stable at their initial values: Cooling water mass flow rate Cooling water inlet temperature Cooling water outlet temperature Lube oil mass flow rate Compared to their initial values, the current lube oil inlet temperature is __________; and the current lube oil outlet temperature is __________.
higher; higher
Question 57 of 103 QID: B2133Add Flag Knowledge: K1.10 [2.8/2.8] Topic: Heat Exchangers and Condensers During normal plant operation at 100% power, a main condenser develops an air leak that degrades vacuum at a rate of 1 inch Hg/min. Assuming the plant continues to operate at 100% power, condenser hotwell temperature will...
increase because condensation of turbine exhaust steam is occurring at a higher temperature. Air leak into condenser increases the absolute pressure in the condenser. As the saturation pressure increases in the condenser, the saturation pressure in the condenser also increases. As air leakage into the condenser increases the air (noncondensible gas) acts as a shield insulating the tubes carrying the circulating water. This reduces the amount of heat the circulating water can remove from the steam. This increases the saturation pressure and saturation temperature in the condenser. This results in an increase in the water collecting in the condenser hotwell.
Question 40 of 103 QID: B2633 (P2634)Add Flag Knowledge: K1.10 [2.8/2.8] Topic: Heat Exchangers and Condensers A nuclear power plant is operating at steady-state 100% power. Assuming that condenser cooling water inlet temperature and flow rate do not change, if condenser vacuum decreases, condensate temperature will...
increase because condenser saturation pressure has increased. "Condenser vacuum decreases" means that the absolute pressure goes up. This would correspond to a higher saturation pressure and temperature. At a higher saturation pressure it takes more less heat removal to condense a lbm of steam (hfg is smaller) so if we assume constant heat removal (circulating water mass flow and inlet temp given as constant) then there is a greater heat removal capacity per lbm left to subcool the liquid; subcooling increases. BUT, given for example a decrease in vacuum from 1 psia to 2 psia we see that while we gain 14° subcooling (equal to change in hfg since subcooling 1 lbm one °F takes one BTU), Tsat increases 25°. Therefore condensate temperature actually increases 11° (14° more subcooling but a 25° higher starting point).
Question 103 of 103 QID: B1236Add Flag Knowledge: K1.18 [2.8/2.9] Topic: Heat Exchangers and Condensers During power plant operation, the accumulation of air and non-condensible gases in the main condenser will...
increase turbine backpressure.
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 __________.
increase; increase
Question 79 of 103 QID: B332 (P331)Add Flag Knowledge: K1.17 [2.7/2.8] Topic: Heat Exchangers and Condensers 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 1% of the tubes in the main condenser become plugged, condenser absolute pressure will ___________; and condenser hotwell temperature will _________.
increase; increase Plugging the tubes will reduce the area for heat transfer to occur. Since less heat transfer occurs, condenser absolute pressure will INCREASE because less energy transferred out of the steam. Condenser is a saturated system, therefore if saturation pressure increases, saturation temperature will also increase. Hotwell temperature which INCREASE
Question 94 of 103 QID: B31Add Flag Knowledge: K1.07 [2.7/2.8] Topic: Heat Exchangers and Condensers Decreasing the temperature of the lube oil leaving a lube oil heat exchanger is normally accomplished by...
increasing the cooling water flow rate.
Question 48 of 103 QID: B633 (P2832)Add Flag Knowledge: K1.09 [2.7/2.8] Topic: Heat Exchangers and Condensers 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...
induce large thermal stresses on the junctions between the condenser tubes and the tubesheet.
Question 83 of 103 QID: B156Add Flag Knowledge: K1.16 [2.5/2.6] Topic: Heat Exchangers and Condensers The buildup of scale on heat-transfer surfaces in the reactor vessel...
is controlled by using reactor water cleanup system and condensate system demineralizers.
QID: B7625 (P7625)Add Flag Knowledge: K1.15 [2.6/2.8] Topic: Heat Exchangers and Condensers Refer to the drawing of an operating lube oil heat exchanger (see figure below). The heat exchanger was initially placed in continuous service 6 months ago. During the 6-month period of operation, mineral deposits have accumulated inside the heat exchanger tubes. The following parameters are currently stable at their initial values: Lube oil mass flow rate Lube oil inlet temperature Lube oil outlet temperature Cooling water inlet temperature Compared to their initial values, the current cooling water outlet temperature is __________; and the current cooling water mass flow rate is __________.
lower; greater
Question 9 of 103 QID: B4918 (P4917)Add Flag Knowledge: K1.17 [2.7/2.8] Topic: Heat Exchangers and Condensers A nuclear power plant was initially operating at steady-state 50% rated thermal power with 50 gpm of main condenser cooling water inleakage through a cooling water tube rupture. Thermal power was then increased and is currently stable at 60%. 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% power, the flow rate of main condenser cooling water inleakage at 60% power is ____________ because the main condenser pressure at 60% power is __________.
lower; higher As thermal power increases more heat is transferred to the main condenser through the turbine. This results in a decrease in condenser vacuum or an increase in condenser pressure. Since the in leakage parameters do not change including the size of the leak, the result will be less flow through the ruptured pipe. The reason flow decreases as condenser pressure increases is due to the reduction in differential pressure between the condenser and the cooling water.
Question 2 of 103 QID: B5317 (P5316)Add Flag Knowledge: K1.07 [2.6/2.8] Topic: Heat Exchangers and Condensers A main turbine-generator was operating at 80% load with the following initial steady-state lube oil and cooling water temperatures for the main turbine lube oil heat exchanger: Toil in = 174°F Toil out = 114°F Twater in = 85°F Twater out = 115°F Six months later, the current steady-state heat exchanger temperatures are: Toil in = 174°F Toil out = 120°F Twater in = 85°F Twater out = 120°F 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 ___________.
lower; lower
Question 98 of 103 QID: B1135Add Flag Knowledge: K1.14 [3.1/3.2] Topic: Heat Exchangers and Condensers After starting a large motor-driven centrifugal cooling water pump, the pump discharge valve should be opened slowly to minimize the...
potential for a water hammer.
Question 102 of 103 QID: B635Add Flag Knowledge: K1.14 [3.1/3.2] Topic: Heat Exchangers and Condensers The discharge valve for a large operating centrifugal pump should be positioned slowly to minimize the...
potential for causing water hammer.
Question 99 of 103 QID: B531Add Flag Knowledge: K1.02 [2.6/2.6] Topic: Heat Exchangers and Condensers A liquid-to-liquid heat exchanger containing trapped air on the shell side will be less efficient because the air...
reduces the fluid contact with the heat transfer surface.
Question 63 of 103 QID: B1136Add Flag Knowledge: K1.16 [2.5/2.6] Topic: Heat Exchangers and Condensers Tube scaling in a parallel flow heat exchanger causes heat transfer rate to decrease because the...
thermal conductivity of the scale is very low.