nbsr thermodynamic performance analysis | nist
TRANSCRIPT
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NBSR Thermodynamic Performance Analysis
C E N T E R F O R N E U T R O N R E S E A R C H , N AT I O N A L I N S T I T U T E O F S TA N D A R D S A N DT E C H N O LO GY, 1 0 0 B U R E A U D R .
G A I T H E R S B U R G , M D, U S A 2 0 8 9 9
Omar Cavazos
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Background•B.S. in Mechanical Engineering at Texas A&M University-Kingsville
• Graduated in May 2018
•Masters student in Engineering Technology (Mechanical Systems) at the University of North Texas starting Fall 2018
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Motivation• Optimized thermodynamic parameters increase the
operational range of the NBSR secondary cooling system.
• Impact of environmental conditions.
• Monthly energy savings.
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Project Overview
Reference Review
Analyze NBSR Cooling System
Thermodynamic Model Development
Optimization
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NBSR System Overview
Primary Loop
Secondary Loop
Heavy Water Water
Reactor
Main Heat Exchangers
Cooling Towers
Air Exit
Air Inlet
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Thermodynamics of Cooling Towers•Evaporative Cooling
•Dry & Wet-bulb Temperature
https://www.suezwatertechnologies.com/handbook/cooling_water_systems/fig31-3.jsp
Hensley J., “Cooling Tower Fundamentals.”, SPX Cooling Technologies, (2009).
United States Department of Energy, “ Cooling Towers: Understanding Key Components of Cooling Towers and How to Improve Water Efficiency.” (2011).
𝒏𝒏 = (𝑡𝑡𝑖𝑖 − 𝑡𝑡𝑜𝑜)(𝑡𝑡𝑖𝑖 − 𝑡𝑡𝑤𝑤𝑤𝑤) x 100
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Assumptions and LimitationsLimitations:•The reactor outlet temperature must be below 130 °F.
•The reactor inlet temperature is less than 110 °F.
•The secondary cooling flow rate can not be less than 6,000 GPM.
Assumptions:•Cooling tower cells are combined.
•Heat transfer through the pipes and friction is neglected.
•Secondary and primary pumps are modeled as 1 pump each.
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NIST, “Safety Analysis Report for the National Institute of Standards and Technology Reactor – NBSR.” National Institute of Standards and Technology
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Secondary Loop Diagram
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Input Process Parameters•Reactor Power 20 MW
•Primary Flow 8,760 GPM
•Secondary Flow= 10,400 GPM
•Secondary Aux Flow= 711.4 GPM
•SCV-20 Position = 0%
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Heat Exchanger Data
Hot Side Cold SideInlet Temp (°F)
Outlet Temp (°F)
Flow (GPM) Inlet Temp (°F)
Outlet Temp (°F)
Flow (GPM) Heat Duty (kW)
HE-1A 113.6 100.4 4250 77 90 4500 8,555.92HE-1B 113.6 102.4 4250 77 92 4800 10,529.39HE-2 103.16 80.52 170 77 83.44 102 89.45HE-6 101.96 95.15 222.8 77 91.5 567.5 829.52HE-9 108.43 102 7.96 77 82 41.9 30.67HE-10 95 90 490 77 80 388.6 170.89
Table 1. Heat Exchanger Parameters
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• Wet-bulb Temp = 67 °F• Dry Bulb Temp= 87 °F• Relative Humidity of Ambient Air = 34.94 %
• Cooling Tower Airflow= 405.99 𝑚𝑚3
𝑠𝑠
Cooling Tower Parameters2
1
3
4
77°F
91°F
67°F𝜙𝜙 = 34.94%
87°F𝜙𝜙 = 100%
∑𝑖𝑖𝑖𝑖 �̇�𝑚h=∑𝑜𝑜𝑜𝑜𝑡𝑡 �̇�𝑚h=�̇�𝑚𝑎𝑎1+�̇�𝑚3ℎ3 = �̇�𝑚𝑎𝑎2ℎ2 + �̇�𝑚4ℎ4
�̇�𝑚𝑎𝑎 = �̇�𝑚3(ℎ3−ℎ4)ℎ2−ℎ1 −(𝜔𝜔2−𝜔𝜔1)ℎ4
Çengel Y. A. Boles, M. A. “Thermodynamics: An engineering approach.” Boston: McGraw-Hill (2015).
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Model Overview
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Cooling Towers
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Cooling Tower Efficiency Calculator𝒏𝒏 = (𝑡𝑡𝑖𝑖 − 𝑡𝑡𝑜𝑜)
(𝑡𝑡𝑖𝑖 − 𝑡𝑡𝑤𝑤𝑤𝑤) x 100
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Model VerificationHistorical Data Temperature (°F) Simulink Model Temperature (°F) Relative Error ( %)
Reactor Inlet 100.4 99.5 0.90Reactor Outlet 114.5 114.7 0.17Cooling Tower (Outlet) 75 76.6 2.13
Table 2. Case 1 at 7/15/18 11:30 a.m.
Historical Data Temperature (°F) Simulink Model Temperature (°F) Relative Error ( %)
Reactor Inlet 104.5 102.4 2.01Reactor Outlet 118.5 117.1 1.18Cooling Tower (Outlet) 80 79.5 0.63
Table 4. Case 3 at 7/15/18 7:30 p.m.
Table 3. Case 2 at 7/15/18 5:30 p.m. Historical Data Temperature (°F) Simulink Model Temperature (°F) Relative Error ( %)
Reactor Inlet 104 101.3 2.60Reactor Outlet 118.2 116.4 1.52Cooling Tower (Outlet) 78 78.6 0.77
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Analysis and Results• Conducted by varying environmental wet-bulb
temperatures, secondary flow rates, and SCV-position.
• MATLAB script was written to perform simulations.
• Model converged at 0.00001 deviation.
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Effect of Secondary Flow Rate at Benchmark
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6000 7000 8000 9000 10000
Secondary Flow Rate (GPM)
98
100
102
104
106
108
110
112
114
116
118
Temp
eratu
re(°F
)
Reactor Inlet Temperature
Reactor Outlet Temperature
6000 7000 8000 9000 10000
Secondary Flow Rate (GPM)
70
75
80
85
90
95
100
Temp
eratu
re(°F
)
Cooling Tower Inlet Temperature
Cooling Tower Outlet Temperature
6000 7000 8000 9000 10000
Secondary Flow Rate (GPM)
60
62
64
66
68
70
72
74
76
78
80
Optim
al Ef
ficien
cy(%
)
• 67℉ Wet-bulb, 34.94% Relative Humidity
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Effect of Secondary Flow Rate during Summer
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6000 7000 8000 9000 10000
Secondary Flow Rate (GPM)
120
122
124
126
128
130
132
134
136
138
Tem
pera
ture
(°F)
Reactor Inlet Temperature
Reactor Outlet Temperature
6000 7000 8000 9000 10000
Secondary Flow Rate (GPM)
95
100
105
110
115
120
Tem
pera
ture
(°F)
Cooling Tower Inlet Temperature
Cooling Tower Outlet Temperature
6000 7000 8000 9000 10000
Secondary Flow Rate (GPM)
60
62
64
66
68
70
72
74
76
78
80
Optim
al Ef
ficien
cy(%
)
• 90℉ Wet-bulb, 60 % Relative Humidity
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Effect of Secondary Flow Rate during Winter
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6000 7000 8000 9000 10000
Secondary Flow Rate (GPM)
70
72
74
76
78
80
82
84
86
88
90Te
mpe
ratu
re(°F
)Reactor Inlet Temperature
Reactor Outlet Temperature
6000 7000 8000 9000 10000
Secondary Flow Rate (GPM)
40
45
50
55
60
65
70
Tem
pera
ture
(°F)
Cooling Tower Inlet Temperature
Cooling Tower Outlet Temperature
6000 7000 8000 9000 10000
Secondary Flow Rate (GPM)
58
60
62
64
66
68
70
72
74
76
78
Optim
al Ef
ficien
cy(%
)
• 35℉ Wet-bulb, 60 % Relative Humidity
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Effect of Wet-bulb Temperature at Benchmark
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30 40 50 60 70 80 90
Wet-bulb Temperature (°F)
70
80
90
100
110
120
130
140
Tem
pera
ture
(°F)
Reactor Inlet Temperature
Reactor Outlet Temperature
30 40 50 60 70 80 90
Wet-bulb Temperature (°F)
40
50
60
70
80
90
100
110
120
Tem
pera
ture
(°F)
Cooling Tower Inlet Temperature
Cooling Tower Outlet Temperature
30 40 50 60 70 80 90
Wet-bulb Temperature (°F)
58
58.2
58.4
58.6
58.8
59
59.2
59.4
59.6
59.8
60
Optim
al Ef
ficien
cy(%
)
• 10,400 GPM
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Effect of Wet-bulb Temperature at 6,500 GPM
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30 40 50 60 70 80 90
Wet-bulb Temperature (°F)
70
80
90
100
110
120
130
140
Tem
pera
ture
(°F)
Reactor Inlet Temperature
Reactor Outlet Temperature
30 40 50 60 70 80 90
Wet-bulb Temperature (°F)
40
50
60
70
80
90
100
110
120
Tem
pera
ture
(°F)
Cooling Tower Inlet Temperature
Cooling Tower Outlet Temperature
30 40 50 60 70 80 90
Wet-bulb Temperature (°F)
74.5
75
75.5
76
76.5
77
77.5
Opt
imal
Effi
cienc
y(%
)
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Performance of SCV-20 at Benchmark
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0 20 40 60 80 100
SCV-20 Position (%)
95
100
105
110
115
120
125Te
mper
ature
(°F)
Reactor Inlet Temperature
Reactor Outlet Temperature
0 20 40 60 80 100
SCV-20 Position (%)
75
80
85
90
95
100
Temp
eratu
re(°F
)
Cooling Tower Inlet Temperature
Cooling Tower Outlet Temperature
0 20 40 60 80 100
SCV-20 Position (%)
58
60
62
64
66
68
70
72
74
76
78
Optim
al Ef
ficien
cy(%
)
• 67℉ Wet-bulb, 34.94% Relative Humidity, 10,400 GPM
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Performance of SCV-20 during Winter
0 20 40 60 80 100
SCV-20 Position (%)
70
75
80
85
90
95
100Te
mpe
ratu
re(°F
)Reactor Inlet Temperature
Reactor Outlet Temperature
0 20 40 60 80 100
SCV-20 Position (%)
40
45
50
55
60
65
70
75
80
Tem
pera
ture
(°F)
Cooling Tower Inlet Temperature
Cooling Tower Outlet Temperature
0 20 40 60 80 100
SCV-20 Position (%)
74
76
78
80
82
84
86
88
90
Optim
al Ef
ficien
cy(%
)
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• 35℉ Wet-bulb, 60 % Relative Humidity, 6,500 GPM
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Key Findings1. Secondary flowrate•For every decrease of 500 GPM cooling tower efficiency increased by ~ 3.4% and increased reactor inlet temperature by ~ 0.5%.
2. Wet-bulb temperatures•For every 6.875 °F increase in wet-bulb temperature, reactor inlet temperatures increase by ~7%.
3. SCV-20 position•For every 10% SCV-20 position change, cooling tower efficiency will increase by ~2.5% and reactor inlet temperature will increase by ~0.6%.
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Energy Savings•If 6,500 GPM secondary flow rate was implemented during summer months cooling tower efficiency would increase by about 27 % and save approximately $5,800 per month.
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Future Work•Thermodynamic engine for NBSR Augmented Reality Simulator.
•Model will be available when further analysis is needed.
•Engineering changes affecting the reactor thermodynamics can be analyzed using the model.
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Conclusion
•Thermodynamic model was created.
•Decreasing secondary flow rate improves cooling tower efficiency.
•Energy savings will be present.
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Acknowledgements•Dr. Daǧistan Şahin
•Dr. Xue Yang
•Daniel Mattes
•Joseph Dura
•Julie Borchers
•Reactor Operations and Engineering
•Special thanks to Samuel MacDavid, Scott Arneson, Paul Liposky, Marcus Schwaderer, Dan Khan, Randolph Strader and NCNR reactor operators
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DisclaimerCertain commercial equipment, instruments, or materials are identified in this study in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.
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Thank You
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