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

1

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

2

Motivation• Optimized thermodynamic parameters increase the

operational range of the NBSR secondary cooling system.

• Impact of environmental conditions.

• Monthly energy savings.

3

Project Overview

Reference Review

Analyze NBSR Cooling System

Thermodynamic Model Development

Optimization

4

NBSR System Overview

Primary Loop

Secondary Loop

Heavy Water Water

Reactor

Main Heat Exchangers

Cooling Towers

Air Exit

Air Inlet

5

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

6

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.

7

NIST, “Safety Analysis Report for the National Institute of Standards and Technology Reactor – NBSR.” National Institute of Standards and Technology

Secondary Loop Diagram

8

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%

9

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

10

• 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).

11

12

Model Overview

13

Cooling Towers

14

Cooling Tower Efficiency Calculator𝒏𝒏 = (𝑡𝑡𝑖𝑖 − 𝑡𝑡𝑜𝑜)

(𝑡𝑡𝑖𝑖 − 𝑡𝑡𝑤𝑤𝑤𝑤) x 100

15

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

16

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.

17

Effect of Secondary Flow Rate at Benchmark

18

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

Effect of Secondary Flow Rate during Summer

19

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

Effect of Secondary Flow Rate during Winter

20

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

Effect of Wet-bulb Temperature at Benchmark

21

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

Effect of Wet-bulb Temperature at 6,500 GPM

22

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(%

)

Performance of SCV-20 at Benchmark

23

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

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(%

)

24

• 35℉ Wet-bulb, 60 % Relative Humidity, 6,500 GPM

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%.

25

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.

26

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.

27

Conclusion

•Thermodynamic model was created.

•Decreasing secondary flow rate improves cooling tower efficiency.

•Energy savings will be present.

28

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

29

30

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.

31

Thank You

32