NBSR Thermodynamic Performance Analysis.pdf

NBSR THERMODYNAMIC PERFORMANCE ANALYSIS

Omar Cavazos Mentors: Daǧistan Şahin, Daniel Mattes

National Institute of Standards and Technology Center for Neutron Research

100 Bureau Dr., Gaithersburg, MD 20899 USA

ABSTRACT

National Institute of Standards of Technology (NIST) has a 20 MW, heavy water moderated nuclear reactor (NBSR: National Bureau of Standards Reactor). During normal operations, the secondary cooling water outlet temperature is maintained between 90 ℉ to 96 ℉, which is below the outside temperature, specifically in the summer months when temperatures exceed 100 ℉. This negative temperature difference significantly reduces heat transfer through the cooling towers, resulting in an underutilized cooling system.

The cooling tower effectiveness can be significantly improved by increasing the cooling tower secondary water temperature. A model of the reactor cooling system was developed to analyze various process parameters to improve the calorimetric performance of the NBSR and calculate the optimum safe operating temperatures. The proposed changes will substantially increase the operational band of the secondary cooling system resulting in optimized process performance. Considering only the warmer months, savings would be approximately $80,000 per year. Simulink software in conjunction with the Thermolib add-in was selected to develop the thermodynamic model, which includes components such as cooling towers, heat exchangers, and pumps. The optimization analysis was conducted by varying environmental temperatures, secondary loop flow rates, and secondary cooling water temperatures. The data produced from the model was compared to historical NBSR data. Overall, this thermodynamic analysis will greatly benefit the operation of the NBSR for years to come by reducing the impact of environmental/weather conditions on the performance of the NBSR.

Key Words: thermodynamic, cooling system, optimization, cooling towers

1. BACKGROUND

National Bureau of Standards Reactor (NBSR) facility contains a primary and secondary coolant system. The primary loop removes the heat generated in the reactor core and prevents fission product release to the environment [1]. The primary coolant is heavy water and the secondary coolant is light water. The primary cooling system consists of pumps, heat exchangers, and valves, as shown in figure 1.

Figure 1. NBSR Schematic

However, the secondary coolant system transfers primary loop heat to the atmosphere by using cooling towers as shown in figure 2. The main heat exchangers (HE-1A & HE-1B) transfer heat from the primary coolant to the secondary water. The secondary system also removes heat from other systems such as the D20 Purification System and Thermal Shield Cooling Water System [1].

Figure 2. Secondary Loop Diagram [2] In addition, the NBSR cooling system is designed to remove enough heat to support operation at a 20 MW and remove the decay heat generated after shutdown from extended full-power operations [1]. Overall, the optimization of the NBSR cooling system is expected to result in energy savings.

2. SIMULINK MODEL

The thermodynamic model was designed based on secondary system diagrams, NBSR historical data, and component specifications. Some limitations on the project include that the reactor outlet temperature must be below 130 °F [1], the reactor inlet temperature must be less than 110 °F and the secondary cooling flow rate cannot be less than 6,500 GPM. Some assumptions made include combining the cooling tower cells, neglecting heat transfer through the pipes and modeling the secondary/primary pumps modeled as 1 pump each. A benchmark set at July 15, 2018 11:30 am was chosen to calibrate the NBSR thermodynamic model. The model was adjusted to perform as expected from the input process parameters and component specifications. Table 1 shows input process parameters used to calibrate the thermodynamic model.

Table 1. Input Process Parameters [3]

Primary Flow Rate

(GPM)

Secondary Flow Rate

(GPM)

Wet-bulb Temperature (°F)

Relative Humidity

Case 1 10,400 8,760 67 34.94

The uncertainty of the instrumentation used on NBSR was analyzed. Instrumentation calibration procedures were reviewed to gather the uncertainties which are present with the input process parameters given to thermodynamic model. Table 2 shows the uncertainty for instrumentation considered for the input data.

Table 2. Input Data Uncertainty [4-12]

TD-1-1 TD-1-2 FIA-12 FI-17 TRCA-3 FIA-40 TI-13 TI-33

Uncertainty

2 2 2 2 1 2 2 2

Equation 1 was used the calculate the total uncertainty of approximately 5.38 % on the instrumentation used to provide the input data used to calibrate the model at benchmark.

𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇 𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑈𝑇𝑇𝑇𝑇𝑈𝑈𝑈𝑈𝑇𝑇𝑈𝑈 = �(𝐴𝐴)2 + (𝐵𝐵)2 +(𝐶𝐶)2 . . . (6)

Table 3. Heat Exchanger Parameters [13-20] Hot Side Cold Side

Inlet 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 8,555.92

HE-1B 113.6 102.4 4250 77 92 4800 10,529.39

HE-2 103.16 80.52 170 77 83.44 102 89.45

HE-6 101.96 95.15 222.8 77 91.5 567.5 829.52

HE-9 108.43 102 7.96 77 82 41.9 30.67

HE-10 95 90 490 77 80 388.6 170.89

The model was created using Thermolib blocks which contain all the required thermodynamic equations for simulation. Subsystems were used in the model to reduce the complexity of the model. In addition, it was designed to perform as effectively as possible. Also, the model was divided as a primary loop and a secondary loop. The secondary loop was chosen as the main interface because it is main section responsible of the NBSR cooling. An initial condition block was used in the model in order the avoid algebraic loop errors. Algebraic loops occur when an input port with direct feedback is driven by the output of the same Simulink block. In addition, 3-way valves were used the spilt the flow correctly for the main heat exchangers and auxiliary heat exchangers as shown figure 3.

Figure 3. Main Interface of Thermodynamic Model The primary loop was significantly simplified in the model. The primary loop mainly consists of one pump, the reactor, core and the 2 main heat exchangers which interact with the secondary loop.

To estimate the dynamic thermal behavior of the block, the heat exchangers were assumed to have a certain thermal mass heat capacity (J/K), which was estimated from component specifications [21].

Figure 4. Primary Loop Portion of Thermodynamic Model

Mixer blocks were used to combine the flow properly in the model. A mass flow from input (mode

2) pump as indicated by the Thermolib user manual was used to provide the required flow rate to the primary loop. The primary flow can be adjusted by means of using a MATLAB script written to conduct simulations. The pressure provided to primary pump was set to be approximately 50 psi as indicated by reference documents [22]. Also, the auxiliary heat exchangers were modeled as 3 heaters. In addition, the heater block heats up or cools down the fluid by adding or subtracting a given heat flux to the medium’s enthalpy [21].

Figure 5. Auxiliary Heat Exchanger in Model The cooling towers were modeled as 2 counter flow heat exchangers. Also, the secondary cooling was fed in the hot side and the air was fed through the cold side. The wet air block provided by Thermolib simulated the air that provided evaporative cooling. The parameters such as air humidity, wet-bulb temperature, and air flow rate were provided to the air block. In addition, the SCV-20 bypass valve was implemented in the model. The maximum flow rate that passes through SCV-20 was regulated to be at 4,000 GPM as indicated in the specifications for the DeZURIK valve [23]. Valve position was determined by a Simulink constant block which has a variable linked to the MATLAB script.

Figure 6. Cooling Towers

In addition, a thermodynamic analysis was performed on the cooling towers to calculate the relative humidity of the air and the required air flow to provide the required cooling as indicated by the cooling water specifications. Figure 7 shows a schematic of the cooling towers with its specifications at benchmark.

Figure 7. Cooling Tower Diagram [24-25]

The cooling towers are of the counter flow type. Air is drawn into the towers from the bottom and exits through the top portion [26-27]. The secondary water from the main heat exchangers is sprayed downwards towards the upcoming air. The purpose of spraying is to expose a large surface area of water to the air [28]. As the water falls some of the water evaporates and cools the remaining secondary water. Then the air is drafted towards the top by using mechanical fans. The cooled water then collects at the bottom of the tower basin and gets recirculated back to the secondary loop [28]. Equations 2 & 3 were used to solve for the mass flow rate of the air needed for the cooling towers at benchmark state. Psychometric data was used to calculate the relative humidity of the air and the volumetric flow rate of the air. Equation 4 was used to calculate the optimal cooling tower efficiency [29].

∑ �̇�𝑚𝑖𝑖𝑖𝑖 h=∑ �̇�𝑚𝑜𝑜𝑜𝑜𝑜𝑜 h=�̇�𝑚𝑎𝑎1+�̇�𝑚3ℎ3 = �̇�𝑚𝑎𝑎2ℎ2 + �̇�𝑚4ℎ4 (2)

�̇�𝑚𝑎𝑎 = �̇�𝑚3(ℎ3−ℎ4)

(ℎ2−ℎ1)−(𝜔𝜔2−𝜔𝜔1)ℎ4 (3)

Cooling Tower Efficiency(𝑈𝑈) = (𝑜𝑜𝑖𝑖 - 𝑜𝑜𝑜𝑜)

(𝑜𝑜𝑖𝑖 - 𝑜𝑜𝑤𝑤𝑤𝑤) x 100 (4)

3. MODEL VERIFICATION

The model was run 3 times to verify its feasibility. July 15, 2018 was chosen as the benchmark date for study. The model was run at 11:30 am, 5:30 pm, then at 7:30 pm. Also, the model converged at 0.00001 deviation. The input parameters for each case 1 were determined by use of reactor control logs, historical NBSR trended data, and component specifications. Table 3 shows the input parameters for the 3 cases. The NBSR historical trended data and the “reactor at desktop application” were used to determine the input values shown below.

Table 3. Input Parameters for 3 Cases (3)

Primary Flow Rate

(GPM)

Secondary Flow Rate

(GPM)

Wet-bulb Temperature (°F)

Relative Humidity

Case 1 8,760 10,400 67 34.94 Case 2 8,791 10,425 69 48.46 Case 3 8,980 10,389 70 50.14

The results of case 1 show that model has a relative error between 0.17 and 2.13 % at the benchmark. It is shown that the cooling tower temperature has the most relative error in this case as shown in table 4. Table 5 shows that the relative error of the secondary side outlet temperatures of the heat exchangers ranged between 0.00001 to 0.2 %.

Table 4. Case 1 at 7/15/18 11:30 am (3)

Historical Data Temperature (°F)

Simulink Model Temperature (F)

Relative Error

Reactor Inlet 100.4 99.5 0.90 Reactor Outlet 114.5 114.7 0.17 Cooling Tower 75 76.6 2.13

Table 5. Heat Exchanger Verification at Case 1 (3)

The results of case 2 show that the reactor inlet had the highest relative error. Overall, the relative error of case 2 ranged between 0.77 to 2.60 %.

Historical Data Secondary Outlet Temperature

(°F)

Simulink Model Secondary Outlet Temperature

(°F)

Relative Error

HE-1A 90.00 90.08 0.0889

HE-1B 92.00 91.99 0.0109

HE-2 83.44 83.43 0.0001

HE-6 91.50 91.51 0.0109

HE-9 82.00 82.05 0.0610

HE-10 80.00 79.84 0.2000

Table 6. Case 2 at 7/15/18 5:30 pm (3)

Historical Data Temperature (°F)

Simulink Model Temperature (F)

Relative Error

Reactor Inlet 104 101.3 2.60 Reactor Outlet 118.2 116.4 1.52 Cooling Tower 78 78.6 0.77

The results of case 3 show that the relative error ranged between 0.63 to 2.01 %. Overall, the model is shown to work properly after verifying it 3 times. The completion of the model verification allows the model to optimize the NBSR cooling system.

Table 7. Case 3 at 7/15/18 7:30 am

Historical Data Temperature (°F)

Simulink Model Temperature (F)

Relative Error

Reactor Inlet 104.5 102.4 2.01 Reactor Outlet 118.5 117.1 1.18 Cooling Tower 80 79.5 0.63

4. OPTIMIZATION

After the model was verified, 3 different cases were analyzed using the verified Simulink model.

Case 1 consists of varying the secondary flowrate and observing the effects on the reactor core and cooling towers while SCV-20 at 0 %. Figure 6 shows the plots generated from the MATLAB script shown in appendix A which shows the effects of secondary flow at the benchmark input parameters. It is shown that decreasing the secondary flowrate increases reactor temperatures, increases cooling tower inlet temperature, decreases cooling tower outlet temperature, and increases cooling tower efficiency. It was shown that for every decrease of 500 GPM cooling tower efficiency increased approximately 3.4% and increased reactor inlet temperature by approximately 0.5%. Figure 7 shows the results of case 1 during summer conditions which were chosen to be at 90 °F wet-bulb at 60 % relative humidity. Figure 8 displays case 1 but at winter conditions which were chosen to be at 35 °F wet-bulb at 60 % relative humidity. It was discovered the summer conditions shifted the results from figure 6 upwards and in the winter conditions downwards.

Mattes, Daniel A. (Fed) All simulation value errors are within the total measurement error for the input input values

Figure 6. Effect of Secondary Flowrate at Benchmark

Figure 7. Effect of Secondary Flow rate during Summer

Figure 8. Effect of Secondary Flow rate during Summer

6000 7000 8000 9000 10000

Secondary Flow(GPM)

Te m pe ra tu re

F)

Reactor Inlet Temperature

Reactor Outlet Temperature

6000 7000 8000 9000 10000

Secondary Flow(GPM)

Te m pe ra tu re

F)

Cooling Tower Inlet Temperature

Cooling Tower Outlet Temperature

6000 7000 8000 9000 10000

Secondary Flow(GPM)

O pt im al

E ffi ci en cy

6000 7000 8000 9000 10000

Secondary Flow(GPM)

Te m pe ra tu re

F)

Reactor Inlet Temperature

Reactor Outlet Temperature

6000 7000 8000 9000 10000

Secondary Flow(GPM)

Te m pe ra tu re

F)

Cooling Tower Inlet Temperature

Cooling Tower Outlet Temperature

6000 7000 8000 9000 10000

Secondary Flow(GPM)

O pt im al

E ffi ci en cy

6000 7000 8000 9000 10000

Secondary Flow(GPM)

Te m pe ra tu re

F)

Reactor Inlet Temperature

Reactor Outlet Temperature

6000 7000 8000 9000 10000

Secondary Flow(GPM)

Te m pe ra tu re

F)

Cooling Tower Inlet Temperature

Cooling Tower Outlet Temperature

6000 7000 8000 9000 10000

Secondary Flow(GPM)

O pt im al

E ffi ci en cy

In case 2, the effect of the wet-bulb temperatures was analyzed in respect to reactor temperatures, cooling tower temperatures, and cool tower efficiency while SCV-20 at 0 %. It was observed every change of 6.875 °F wet-bulb, increased reactor inlet temperatures by approximately 7%. as shown in figure 8. After conducting case 1, a secondary flowrate 6,500 GPM was chosen to analyze case 2 and 3. Figure 10 displays the effect of wet-bulb temperature at a flow rate of 6,500 GPM. It was discovered that lowering the secondary flowrate to 6,500 GPM during summer wet-bulb temperature improved cooling tower efficiency by approximately 27%. In addition, reactor inlet temperature decreased by approximately 5 % when the secondary flow rate decreased from 10,400 GPM to 6,500 GPM. Overall it was shown that wet-bulb temperatures have a significant effect on the secondary cooling system of the NBSR.

Figure 9. Effect of Wet-bulb Temperature at Benchmark

Figure 10. Effect of Wet-bulb Temperature at 6,500 GPM

30 40 50 60 70 80 90

Wet-bulb Temperature (°F)

Te m pe ra tu re

F)

Reactor Inlet Temperature

Reactor Outlet Temperature

30 40 50 60 70 80 90

Wet-bulb Temperature (°F)

Te m pe ra tu re

F)

Cooling Tower Inlet Temperature

Cooling Tower Outlet Temperature

30 40 50 60 70 80 90

Wet-bulb Temperature (°F)

58.2

58.4

58.6

58.8

59.2

59.4

59.6

59.8

O pt im al

E ffi ci en cy

30 40 50 60 70 80 90

Wet-bulb Temperature (°F)

Te m pe ra tu re

F)

Reactor Inlet Temperature

Reactor Outlet Temperature

30 40 50 60 70 80 90

Wet-bulb Temperature (°F)

Te m pe ra tu re

F)

Cooling Tower Inlet Temperature

Cooling Tower Outlet Temperature

30 40 50 60 70 80 90

Wet-bulb Temperature (°F)

74.5

75.5

76.5

77.5

O pt im al

E ffi ci en cy

In case 3, secondary cooling valve (SCV)-20 position was varied in increments of 10 %. An increase of SCV-20 valve position increased cooling tower efficiency by approximately 2.5% and increased reactor inlet temperature by approximately 0.6% as shown figure 11. Figure 12 shows the same scenario but during winter conditions and a secondary flowrate of 6,500 GPM. It is shown that at a lower flow rate and colder temperatures, the cooling tower efficiency increases.

Figure 11. Effect of SCV-20 Position at Benchmark

Figure 12. Effect of SCV-20 Position during Winter

Overall, the cooling towers consume about 300 kW at high setting, at approximately $0.1 per kWh, this equates to $21,600 per month. If only 3 cooling towers were used at low setting, power consumption would be reduced to approximately 78 kW, corresponding to $5,600 per month. If 6,500 GPM secondary flow rate was implemented during summer months cooling tower efficiency would increase by approximately 27 % and save $5,800 per month.

0 20 40 60 80 100

SCV-20 Position (%)

Te m pe ra tu re

F)

Reactor Inlet Temperature

Reactor Outlet Temperature

0 20 40 60 80 100

SCV-20 Position (%)

Te m pe ra tu re

F)

Cooling Tower Inlet Temperature

Cooling Tower Outlet Temperature

0 20 40 60 80 100

SCV-20 Position (%)

O pt im al

E ffi ci en cy

0 20 40 60 80 100

SCV-20 Position (%)

Te m pe ra tu re

F)

Reactor Inlet Temperature

Reactor Outlet Temperature

0 20 40 60 80 100

SCV-20 Position (%)

Te m pe ra tu re

F)

Cooling Tower Inlet Temperature

Cooling Tower Outlet Temperature

0 20 40 60 80 100

SCV-20 Position (%)

O pt im al

E ffi ci en cy

5. CONCLUSION

This project is crucial to the future thermodynamic performance of the NBSR. Currently, the thermodynamic model is available for further analysis if needed. In addition, engineering changes related to NBSR’s thermodynamic model can be analyzed using the model to predict trends and outcomes. The results obtained from the optimization analysis were feasible and adequate for the goals of this project. Most notably, decreasing the flow rate was found to be the most feasible way to improve the performance of NBSR cooling system. In addition, the results from this project can be used to develop test procedures to verify the conclusions developed during this project.

6. ACKNOWLEDGMENTS

Special thanks to Samuel MacDavid, Scott Arneson, Marcus Schwaderer, Paul Liposky and Randolph Strader, and the reactor operators for providing technical input.

7. DISCLAIMER

Certain 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.

8. REFERENCES

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

2. Liposky P., “Piping & Instrumentation for Secondary System Drawing: E-60-036.”

National Institute of Standards and Technology, Rev.20, (1980).

3. National Institute of Standards and Technology, “Reactor Control Room Log (7/15/18).”, Rev. 2-18, (2018).

4. Deeb S., “Instrumentation and Control Procedure BTUR-1: Reactor Thermal Power Recorder”, NIST Center for Neutron Research, Rev A., (2015).

5. Keyser D., “Instrumentation and Control Procedure FIA-40: Reactor Outlet Indicator Alarm”, NIST Center for Neutron Research, Rev B., (2018).

6. MacDavid S., “Instrumentation and Control Procedure TRCA-3: Reactor Inlet Temperature Recorder/Controller”, NIST Center for Neutron Research, Rev C., (2018).

7. NIST Center for Neutron Research, “NBSR Instrument Test Procedure FI-17: Secondary Auxiliary Cooling Flow Indicator.”, (2010).

8. NIST Center for Neutron Research, “NBSR Instrument Test Procedure FI-12: Secondary Cooling Water Flow Indicator.”, (2010).

9. NIST Center for Neutron Research, “NBSR Instrument Test Procedure TI-33:HX-1B Secondary Outlet Temperature Indicator.”, (2012).

10. NIST Center for Neutron Research, “NBSR Instrument Test Procedure TIA-12: Cooling Tower Basin Temperature Indicator/Alarm.”, (2012).

11. NIST Center for Neutron Research, “NBSR Instrument Test Procedure FI-33:HX-1B Secondary Outlet Temperature Indicator.”, (2012).

12. NIST Center for Neutron Research, “NBSR Instrument Test Procedure TI-13:HX-1A Secondary Outlet Temperature Indicator.”, (2012).

13. Alfa Laval Thermal, “M10-BWFG (HE-2) Plate Heat Exchanger Specification Sheet.’” (1994).

14. Alfa Laval Thermal, “AX30-BWFG (HE-1A) Plate Heat Exchanger Specification Sheet.’” (1994).

15. Alfa Laval Thermal, “Plate Heat Exchangers.’”

16. Keyser D., MacDavid S., Sahin D., Strader R., “Alfa Laval Heat Exchanger Evaluation.”

NIST Center for Neutron Research, (2015).

17. Tranter. “Installation and Operation Manual: Superchanger Plate & Frame Heat

Exchanger.”, (2007).

18. Alfa Laval Thermal, “M6-MFG (HE-9) Plate Heat Exchanger Specification Sheet.’”

(2003).

19. Taco, “HE-10 Plate Heat Exchanger Specifications.” (2011).

20. Tranter, “UX-296 (HE-6) Superchanger Specification Sheet.” (1989).

21. EUtech, “Thermolib 5.4 User’s Manual.” EUtech Scientific Engineering, (2016).

22. Aurora, “Main Secondary Pump Curve Type 410.’, (2007).

23. DeZURIK, “Maxum RCV Rotary Control Valves Technical Specifications.” (2009)

24. Baltimore Aircoil Company, “Submittal Data Form: Model 3781C-2 Cooling Tower Unit.”, (2011).

25. BALCKE-DÜRR . “BALCKE-DÜRR Model Cooling Tower Information.”

26. Hensley J., “Cooling Tower Fundamentals.”, SPX Cooling Technologies, (2009).

27. United States Department of Energy, “Cooling Towers: Understanding Key Components of Cooling Towers and How to Improve Water Efficiency.” (2011).

28. Çengel Y. A. Boles, M. A. “Thermodynamics: An engineering approach.” Boston:

McGraw-Hill (2015).

29. Engineering Toolbox, “Cooling Tower Efficiency.”

https://www.engineeringtoolbox.com/cooling-tower-efficiency-d_699.html

9. APPENDIX A

MATLAB SCRIPT:

%%%%%%%%%%%%%%%Script For NBSR Performance Analysis%%%%%%%%%%%Omar Cavazos %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%opens model%%%%%%%%%%%%%%%%%%%%%%%%%%%% open_system('Fullmodelwtopumps2') %%%%Switches for different cases 0-3 %%%case 0 single run single_run=0 %%%Case 1 is Varying Flowates Study vary_v_dot=0 %%%Case 2 is Varying Temperatures Study vary_temp=0 %%%Case 3 is Varying SCV-20 Position Study vary_scv20=1 %%%input parameters% %%Reactor Power in MW% mw=20;

%%Reactor Power in Watts% reactor_power=mw*10^6;

%%%Primary Loop Volumetric Flowrate in GPM prim_vdot=8760;

%%%Primary Loop Mass Flowrate in g/s prim_mdot=prim_vdot*(6.3e-5)*(1000^2);%g/s %%%Secondary Loop Volumetric Flowrate in GPM secondaryflow=6500 %%%Secondary Loop Mass Flowrate in g/s % sec_mdot=sec_vdot*(6.3e-5)*(1000^2);%g/s %%%primary pump pressure in psi primpump=50;

primpump_pressure=primpump*6894.75729;

%%%secondary pump pressure in psi secpump=80;

secpump_pressure=secpump*6894.75729;

%%%SCV-20 Valve Position scv20pos=0 scv20position=scv20pos/100;%%%Airflow for cooling towers %%%Airflow Volumetric Flowrate in m^3/s air_vdot_si=405.99;

%%%Airflow Volumetric Flowrate in GPM air_vdot=air_vdot_si*15850.372;

%%%airflow Mass Flowrate in g/s air_mdot=air_vdot*(6.3e-5)*(1000^2);%g/s air_flow=air_mdot/29.97;%mol/s %Environmental Wetbulb Temperature in Fahrenheit for Cooling Towers Twb=35;

rel_humidty=60;

%convert from F to Kelvin wet_bulb=((5/9)*(Twb-32))+273.15;

%checks for error error=0.00001;

%%%preallocation of error varibles ctinlet_diff=zeros(1000,1);

ctinlet_all=zeros(11,1);

ctoutlet_diff=zeros(1000,1);

ctoutlet_all=zeros(11,1);

ct_eff_diff=zeros(1000,1);

ct_eff_all=zeros(11,1);

react_inlet_diff=zeros(1000,1);

react_inlet_all=zeros(11,1);

react_outlet_diff=zeros(1000,1);

react_outlet_all=zeros(11,1);

average_all=zeros(11,1);

%%%%%%%%%%%%Single Run is Case0 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if single_run==1 sec_mdot=secondaryflow*(6.3e-5)*(1000^2) stop_switch=0;

sim('Fullmodelwtopumps2');

for i=1:(length(ctinlet)-1) ctinlet_diff(i,1)=abs(ctinlet(i,1)-ctinlet(i+1,1));

ctoutlet_diff(i,1)=abs(ctoutlet(i,1)-ctoutlet(i+1,1));

ct_eff_diff(i,1)=abs(ct_eff_diff(i,1)-ct_eff_diff(i+1,1));

react_inlet_diff(i,1)=abs(react_inlet_diff(i,1)-react_inlet_diff(i+1,1));

react_outlet_diff(i,1)=abs(react_outlet_diff(i,1)-react_outlet_diff(i+1,1));

if ctinlet_diff(i,1)<=error && ctoutlet_diff(i,1)<=error &&...

ct_eff_diff(i,1)<=error && react_inlet_diff(i,1)<=error...

&& react_outlet_diff(i,1)<=error stop_switch=1;

break end end end %%%%%%%%%%Varying Secondary Flowates Case1%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if vary_v_dot==1 secondaryflow=6000 sec_vdot=secondaryflow-500;

for q=1:9 sec_vdot=sec_vdot+500;

sec_mdot=sec_vdot*(6.3e-5)*(1000^2) stop_switch=0;

sim('Fullmodelwtopumps2');

for i=1:(length(ctinlet)-1) ctinlet_diff(i,1)=abs(ctinlet(i,1)-ctinlet(i+1,1));

ctoutlet_diff(i,1)=abs(ctoutlet(i,1)-ctoutlet(i+1,1));

ct_eff_diff(i,1)=abs(ct_eff_diff(i,1)-ct_eff_diff(i+1,1));

react_inlet_diff(i,1)=abs(react_inlet_diff(i,1)-react_inlet_diff(i+1,1));

react_outlet_diff(i,1)=abs(react_outlet_diff(i,1)-react_outlet_diff(i+1,1));

if ctinlet_diff(i,1)<=error && ctoutlet_diff(i,1)<=error &&...

ct_eff_diff(i,1)<=error && react_inlet_diff(i,1)<=error...

&& react_outlet_diff(i,1)<=error stop_switch=1;

break end end ctinlet_all(q,1)=ctinlet(end,1);

ctoutlet_all(q,1)=ctoutlet(end,1);

ct_eff_all(q,1)=ct_eff(end,1);

react_inlet_all(q,1)=react_inlet(end,1);

react_outlet_all(q,1)=react_outlet(end,1);

end %%%write results csv file csvwrite('ct_inlet_result_case1.csv',ctinlet_all(1:q,1));

csvwrite('ct_outlet_result_case1.csv',ctoutlet_all(1:q,1));

csvwrite('ct_eff_result_case1.csv',ct_eff_all(1:q,1));

csvwrite('react_inlet_result_case1.csv',react_inlet_all(1:q,1));

csvwrite('react_outlet_result_case1.csv', react_outlet_all(1:q,1));

%%%set x and y values for plots x1=secondaryflow:500:secondaryflow+4000;

y1=react_inlet_all(1:q,1);

x2=secondaryflow:500:secondaryflow+4000;

y2=react_outlet_all(1:q,1);

x3=secondaryflow:500:secondaryflow+4000;

y3=ctinlet_all(1:q,1);

x4=secondaryflow:500:secondaryflow+4000;

y4=ctoutlet_all(1:q,1);

x5=secondaryflow:500:secondaryflow+4000;

y5=ct_eff_all(1:q,1);

figure('Units','normalized','Position',[0 0 1 1]) %%%Plot Reactor Temperatures VS Secondary Flow subplot(1,3,1) plot(x1,y1,x2,y2,'LineWidth',2.4) grid on set(gca,'fontsize',13) xlabel('Secondary Flow(GPM)') ylabel('Temperature(°F)') legend('Reactor Inlet Temperature', 'Reactor Outlet Temperature','Location','Northeast') %%%Plot Cooling Tower Temperatures VS Secondary Flow%%%%%%%%%%%%%%%%%%%%%%% subplot(1,3,2) plot(x3,y3,x4,y4,'LineWidth',2.4) grid on set(gca,'fontsize',13) %title('Effect of Secondary Flow','FontSize',20) xlabel('Secondary Flow(GPM)') ylabel('Temperature(°F)') legend('Cooling Tower Inlet Temperature', 'Cooling Tower Outlet Temperature','Location','Northeast') %%%%%%%%%%%%%%%Cooling Tower Efficiency vs Secondary Flow%%%%%%%%%%%%%%%%%% subplot(1,3,3) plot(x5,y5,'LineWidth',2.4) grid on set(gca,'fontsize',13) xlabel('Secondary Flow(GPM)') ylabel('Optimal Efficiency(%)') end %%%%%%%%%%Varying Wetbulb Temperature Case2%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if vary_temp==1 %%% Varying Wetbulb Temperatures in intervals of 8 Twb=35;

sec_mdot=secondaryflow*(6.3e-5)*(1000^2) %Environmental Wetbulb Temperature in Fahrenheit for Cooling Towers Twbulb=Twb-6.875;

rel_humidty=60;

for q=1:9 Twbulb=Twbulb+6.875 wet_bulb=((5/9)*(Twbulb-32))+273.15;

stop_switch=0;

sim('Fullmodelwtopumps2');

for i=1:(length(ctinlet)-1) ctinlet_diff(i,1)=abs(ctinlet(i,1)-ctinlet(i+1,1));

ctoutlet_diff(i,1)=abs(ctoutlet(i,1)-ctoutlet(i+1,1));

ct_eff_diff(i,1)=abs(ct_eff_diff(i,1)-ct_eff_diff(i+1,1));

react_inlet_diff(i,1)=abs(react_inlet_diff(i,1)-react_inlet_diff(i+1,1));

react_outlet_diff(i,1)=abs(react_outlet_diff(i,1)-react_outlet_diff(i+1,1));

if ctinlet_diff(i,1)<=error && ctoutlet_diff(i,1)<=error &&...

ct_eff_diff(i,1)<=error && react_inlet_diff(i,1)<=error...

&& react_outlet_diff(i,1)<=error stop_switch=1;

break end end ctinlet_all(q,1)=ctinlet(end,1);

ctoutlet_all(q,1)=ctoutlet(end,1);

ct_eff_all(q,1)=ct_eff(end,1);

react_inlet_all(q,1)=react_inlet(end,1);

react_outlet_all(q,1)=react_outlet(end,1);

end %%%write results csv file%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% csvwrite('ctinlet_result_case2.csv',ctinlet_all(1:q,1));

csvwrite('ctoutlet_result_case2.csv',ctoutlet_all(1:q,1));

csvwrite('ct_eff_result_case2.csv',ct_eff_all(1:q,1));

csvwrite('react_inlet_result_case2.csv',react_inlet_all(1:q,1));

csvwrite('react_outlet_result_case2.csv', react_outlet_all(1:q,1));

%%%set x and y values for plots%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% x1=Twb:6.875:Twb+55;

y1=react_inlet_all(1:q,1);

x2=Twb:6.875:Twb+55;

y2=react_outlet_all(1:q,1);

x3=Twb:6.875:Twb+55;

y3=ctinlet_all(1:q,1);

x4=Twb:6.875:Twb+55;

y4=ctoutlet_all(1:q,1);

x5=Twb:6.875:Twb+55;

y5=ct_eff_all(1:q,1);

figure('Units','normalized','Position',[0 0 1 1]) %%%Plot Reactor Temperatures VS Wet-Bulb Temperature subplot(1,3,1) plot(x1,y1,x2,y2,'LineWidth',2.4) grid on set(gca,'fontsize',13) xlabel('Wet-bulb Temperature (°F)') ylabel('Temperature(°F)') legend('Reactor Inlet Temperature','Reactor Outlet Temperature','Location','Northwest') %%%Plot Cooling Tower Temperatures VS Wet-Bulb Temperature subplot(1,3,2) plot(x3,y3,x4,y4,'LineWidth',2.4) grid on set(gca,'fontsize',13) %title('Effect of Wet-bulb Temperature','FontSize',20) xlabel('Wet-bulb Temperature (°F)') ylabel('Temperature(°F)') legend('Cooling Tower Inlet Temperature', 'Cooling Tower Outlet Temperature','Location','Northwest') %%%%%%%%%%%%%%%Cooling Tower Efficiency vs Wet-Bulb Temperature%%%%%%%%%%%% subplot(1,3,3) plot(x5,y5,'LineWidth',2.4) grid on set(gca,'fontsize',13) xlabel('Wet-bulb Temperature (°F)') ylabel('Optimal Efficiency(%)') end %%%%%%%%%%Varying SCV-20 Position Case3%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if vary_scv20==1 %%% Varying SCV-20 Position in intervals of 10 sec_mdot=secondaryflow*(6.3e-5)*(1000^2) scv20pos=-10 for q=1:11 scv20pos=scv20pos+10 scv20position=scv20pos/100 stop_switch=0;

sim('Fullmodelwtopumps2');

for i=1:(length(ctinlet)-1) ctinlet_diff(i,1)=abs(ctinlet(i,1)-ctinlet(i+1,1));

ctoutlet_diff(i,1)=abs(ctoutlet(i,1)-ctoutlet(i+1,1));

ct_eff_diff(i,1)=abs(ct_eff_diff(i,1)-ct_eff_diff(i+1,1));

react_inlet_diff(i,1)=abs(react_inlet_diff(i,1)-react_inlet_diff(i+1,1));

react_outlet_diff(i,1)=abs(react_outlet_diff(i,1)-react_outlet_diff(i+1,1));

if ctinlet_diff(i,1)<=error && ctoutlet_diff(i,1)<=error &&...

ct_eff_diff(i,1)<=error && react_inlet_diff(i,1)<=error...

&& react_outlet_diff(i,1)<=error stop_switch=1;

break end end ctinlet_all(q,1)=ctinlet(end,1);

ctoutlet_all(q,1)=ctoutlet(end,1);

ct_eff_all(q,1)=ct_eff(end,1);

react_inlet_all(q,1)=react_inlet(end,1);

react_outlet_all(q,1)=react_outlet(end,1);

end %%%write results csv file csvwrite('ctinlet_result_case3.csv',ctinlet_all(1:q,1));

csvwrite('ctoutlet_result_case3.csv',ctoutlet_all(1:q,1));

csvwrite('ct_eff_result_case3.csv',ct_eff_all(1:q,1));

csvwrite('react_inlet_result_case3.csv',react_inlet_all(1:q,1));

csvwrite('react_outlet_result_case3.csv', react_outlet_all(1:q,1));

%%%set x and y values for plots x1=0:10:100;

y1=react_inlet_all(1:q,1);

x2=0:10:100;

y2=react_outlet_all(1:q,1);

x3=0:10:100;

y3=ctinlet_all(1:q,1);

x4=0:10:100;

y4=ctoutlet_all(1:q,1);

x5=0:10:100;

y5=ct_eff_all(1:q,1);

figure('Units','normalized','Position',[0 0 1 1]) %%%Plot Reactor Temperatures VS SCV-20 subplot(1,3,1) plot(x1,y1,x2,y2,'LineWidth',2.4) grid on set(gca,'fontsize',13) xlabel('SCV-20 Position (%)') ylabel('Temperature(°F)') legend('Reactor Inlet Temperature', 'Reactor Outlet Temperature','Location','Northeast') %%%Plot Cooling Tower Temperatures VS SCV-20 subplot(1,3,2) plot(x3,y3,x4,y4,'LineWidth',2.4) grid on set(gca,'fontsize',13) %title('Effect of SCV-20 Position','FontSize',20) xlabel('SCV-20 Position (%)') ylabel('Temperature(°F)') legend('Cooling Tower Inlet Temperature', 'Cooling Tower Outlet Temperature','Location','Northeast') %%%%%%%%%%%%%%%Cooling Tower Efficiency vs SCV-20 Position%%%%%%%%%%%%%%%%% subplot(1,3,3) plot(x5,y5,'LineWidth',2.4) grid on set(gca,'fontsize',13) xlabel('SCV-20 Position (%)') ylabel('Optimal Efficiency(%)') end