Construction and Operation of Experimental Simulator with
Thermodynamic Modeling
John Koch (NSF SURF Mentee)Manpreet Bham
Dr. David K. Jeong (NSF SURF Mentor)
Mechanical Engineering, Arkansas State University
John Koch
Content
• Background
• Research Objectives
• Construction and Operation
• Thermodynamic Modeling
• Results and Discussions
• Conclusion
• Future Work
• Acknowledgements
John Koch
Background: CSP
Thermal Energy Storage with
Molten Salts
HotCold
Parabolic Trough
Technology
SOURCE: http://johnbrianshannon.com/spain/Manpreet Bham
Background: CSP• Typical thermal efficiency of renewable power plant is about 10%
• Energy is stored though the phase transition from solid to liquid form of the molten salts
• Energy is released through the phase transition from liquid to solid form during recrystallization of molten salts
• The recrystallization of the molten salts is used to create steam through heat transfer to power a steam turbine
Q=mCpΔTm= mass of molten salt
Cp= Specific Heat of Salt
ΔT= Temperature change
Manpreet Bham
Background: Molten Salts
• Liquid phase of salts that are solids at ambient temperature
• Typical synthetic salt temperature range (NaNO3-KNO3): 220-550°C
• Applications
– Heat transfer fluids for thermal energy storage in Concentrated Solar Power Plants (CSP) or other industrial applications
– Primary and secondary moderators for Nuclear Molten Salt Reactor
• Problem: Keeping the salts in molten phase
Manpreet Bham
Research Objectives
– Use computational methods to find the eutectic temperature and melting point of molten salt alternatives• Using Total Gibbs Energy Minimization
– G = H - TS
– Compare the computational results with experimental data
– Develop more efficient synthesized molten salt for CSP (Mixture of three nitrates: NaNO3,LiNO3,KNO3)
– Validate results with experimental simulator for long term operation
John Koch
Experimental Simulator
• Small scale simulator to test the performance of molten salt developed in our laboratory
• Simulator design mainly focused on molten salt region of Andasol Plant– Using Reynolds's, Thermal
and Geometric analogy of Andasol Plant (6000:1)
• First simulator in the world– 3 other universities have also
targeted construction similar simulators
John Koch
Experimental Simulator• Thermal energy storage simulator
• Equipment:
– 5.5 gallon tank with heating ring
– 0.5 hp Pump Motor
– Closed Pipe loop with heating coil
– K Type Thermocouples
– Watlow EZ-ZONE Controller
– Omega Multi-zone Controller
– 2 types of insulation held by TAPE
• Designed to produce results in time spans of 3, 6 and 9 months
• Maximum operating temperature for components is 500°C
John Koch
Experimental Simulator: Construction
• funded by ASTA and NSF– Design and construction of control panel
– Corrected spacing and orientation of the heating tapes around the pipes• Level the tanks and pipes
– Fabricate bridge for wires to run to the control panel
– Install bridge and connect the heating tapes, heating band, and thermocouples to the control panel
– Added Kaowool insulation around the piping over the heating tapes • After testing heated tapes and pump for appropriate behavior using water at 50°C as the
working fluid
– 20 days of observing the setup up running water at 50°C for leakage test
– Insulate tank with Kaowool insulation
John Koch
Experimental Simulator: Operation
• The system will be turned on
• The computer program will be started and calibrated
• Tank Containing Salts will be heated using Watlowcontroller
• Using Multi-Zone controller heating tapes on pipe will start transferring heat to maintain temperature
• Then pump on tank will be started to circulate the fluid at adjusted speed
• Temperature measurement program will start taking readings periodically
Manpreet Bham
Thermodynamic Modeling with Total Gibbs Energy Minimization
John Koch
Computational
• Program: Matlab R2011a
• NaNO3-KNO3 (Manpreet Bham)
• LiNO3-KNO3 (John Koch)
• Derivation of Gibbs Energy Minimization for a Binary System
• Develop programs for thermodynamic modeling to find melting point of binary salts
John Koch
Thermodynamic Modeling for Binary System (1/3)
EXCESSSTD
i
iitot GGGXG
2
1
ixsiiidi GXRTGG ,, )ln(
TT
T
TTC
T
TTHG mp
mp
p
mp
mp
fiid ln)(
,
2
21,
121,2,
1
21,
221,1,
X
GXGG
X
GXGG
xs
xsxs
xs
xsxs
Manpreet Bham
)ln(2121 cTTbTaXXG
1
21,
221,1,X
GXGG
xs
xsxs
2
21,
121,2,X
GXGG
xs
xsxs
Thermodynamic Modeling for Binary System (2/3)
LiNO3-KNO3 NaNO3-KNO3GIBBS EXCESS TERMS
)( 2112121 XcXbXaXXG
1
21,
221,1,X
GXGG
xs
xsxs
2
21,
121,2,X
GXGG
xs
xsxs
Manpreet Bham
2211 GXGXGtot
))ln(())ln(( 2,22,21,11,1 xsidxsid GXRTGXGXRTGX
)ln()1ln(ln)(
)1(
)ln()1()ln(ln)(
2
1122,
2,
2,
2,
2,
2,1
2
1111,
1,
1,
1,
1,
1,1
cTTbTaXXTRTTT
TTC
T
TTHX
cTTbTaXXTRTTT
TTC
T
TTHX
mp
mp
p
mp
mp
f
mp
mp
p
mp
mp
f
),( 1 TXfGtot
Thermodynamic Modeling for Binary System (3/3)
LiNO3-KNO3
2211 GXGXGtot
))ln(())ln(( 2,22,21,11,1 xsidxsid GXRTGXGXRTGX
)()1ln(ln)(
)1(
)2)(1()ln(ln)(
11122,
2,
2,
2,
2,
2,1
2
111111,
1,
1,
1,
1,
1,1
bXaXXTRTTT
TTC
T
TTHX
bXbXaXXTRTTT
TTC
T
TTHX
mp
mp
p
mp
mp
f
mp
mp
p
mp
mp
f
NaNO3-KNO3
Results: LiNO3-KNO3
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1350
400
450
500
550
600
650
mol KNO3
Te
mp
era
ture
(K
)
Figure 1. KNO3-LiNO3
w/o excess
Kleppa
ASU
• ASU data is from experimental method of DSC• Without excess is only the Standard Gibbs energy ( )
STDG
John Koch
Results: NaNO3-KNO3
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1400
450
500
550
600
650
Mol Fraction
Tem
pera
ture
[K
]
Figure. KNO3-NaNO3
w/o excess
Kleppa
ASU
KNO3Manpreet Bham
Conclusion
• Derived the Total Gibbs Energy Equation for binary system
• Mathematically modeled the Total Gibbs Energy minimization for predicting melting temperature or chemical composition at equilibrium
• Modeling accuracy can be enhanced by applying more accurate curve fitting regression method
• Accomplished construction of experimental simulator scaled down from Andasol CSP in Spain
John Koch
Future Work
• More accurate relationship for excess Gibbs energy in binary system– Experiment to find the coefficients
• Design computational modeling for ternary compounds– Compare with experimental data from the Differential
Scanning Calorimeter (DSC), Thermogravimetric Analyzer (TGA)
• Evaluate performance of salt with experimental simulator for long term application
John Koch
Ackowledgements
• Arkansas Science and Technology Authority (ASTA)
• National Science Foundation (NSF)
• Arkansas State University Office of Research & Technology Transfer (ORTT)
John Koch
THANK YOU!!
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