Lin, TFESC2015, August 2015 1 /18 Modeling and optimization of a multi-tubular solar receiver for solar-driven high temperature electrolysis Meng Lin 1 , Sophia Haussener 1 1 Laboratory of Renewable Energy Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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Modeling and optimization of a multi-tubular solar receiver for … · solar receiver for solar-driven high temperature electrolysis Meng Lin 1, Sophia Haussener 1 1Laboratory of
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Lin, TFESC2015, August 2015 1 /18
Modeling and optimization of a multi-tubular solar receiver for solar-driven high
temperature electrolysis
Meng Lin1, Sophia Haussener1
1Laboratory of Renewable Energy Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL),
Lausanne, Switzerland
Lin, TFESC2015, August 2015 2 /18
• Solar driven high-temperature co-/electrolysis
Motivation and Introduction
Receiver
PV
Electricity
Steam/CO2700-1000oC
Electrolyzer
H2/CO
H2O/CO2
Siemens
Eloenerji
~20%
~20%DLR Prototype
Radiative heat transfer
Flow boiling in tubes
Natural convection
Conduction
Solar energy
Concentration
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Motivation and IntroductionFlow boiling with complex physics:• Nucleating of bubbles• Bubbles growth and coalescence• Segregation of vapor and liquid phase• Evaporation of liquid in mist flow and
partial films
Heat transfer in receiver cavity:• Non-uniform distribution of
heat flux• Non-uniform temperature
distribution
1D separated model for two
phase flow
3D numerical model for
heat transfer inside the receiver cavity
Convergence(Temperature)
ResultsYes
No
1D
Hea
t flu
x p
rofil
e al
on
g th
e tu
be
Ray tracing
Solar flux at aperture
3D simulation difficult
3D simulation necessary
Thome, J. R. (2004). Engineering data book III. Wolverine Tube Inc.
1D model (single tube): Boiling flow inside tubes
3D model (multi-tube): Heat transfer inside the receiver
Conduction (insulation)
Conduction (tube wall)
Radiation Natural convection
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Model development (1D model for single tube)
1D model for two-phase flow in horizontal tube:
Escanes, F., Perez-Segarra, C. D., & Oliva, A. (1995). Numerical simulation of capillary-tube expansion devices. International Journal of Refrigeration, 18(2), 113-122.
Assumptions (in control volume):1. The velocity of liquid and gas are constant but not necessarily equal.2. Thermodynamic equilibrium between phases (temperature and pressure are equal).3. Empirical correlations are used to relate the frictional pressure drop and the void
fraction to the independent variables of the flow. 4. CO2 and H2O are considered well mixed.
Collier, J. G., & Thome, J. R. (1994). Convective boiling and condensation. Oxford university press.
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Model development (1D model for single tube)
i om m=ɺ ɺ
i o g,o g,o g,i g,i l,o l,o l,i l,i W( )
sin( )
p p A m v m v m v m v P z
mg
τθ
− = − + − + ∆
+
ɺ ɺ ɺ ɺ ɶ
W l,o l,i g,o g,o l,o ,i g,i l,i( ) ( ) ( )gq P z m e e m e e m e e∆ = − + − + −ɺ ɺ ɺ ɺ
Mass conservation:
Momentum equation :
Energy equation :
Conservation equations
2
W 28
fm
Aτ
ρ=ɺ
W W( )q T Tα= −ɺ
Empirical correlations
Escanes, F., Perez-Segarra, C. D., & Oliva, A. (1995). Numerical simulation of capillary-tube expansion devices. International Journal of Refrigeration, 18(2), 113-122.
Thome, J. R. (2004). Engineering data book III. Wolverine Tube Inc.
Heat transfer coefficient based on flow pattern:
Gas phase:
Liquid phase:
0.12 0.55 0.5 0.67nb r r w55 ( log )p p M qα − −= −
0.69 0.4 lcb l l0.0133Re Pr
kαδ
=
For each element::::
gα
lα
A heat transfer coefficient profile in radial direction
3D heat transfer coefficient profile
All elements
Cooper (1984)
Kattan (1998)
Lin, TFESC2015, August 2015 8 /18
Example: Absorber tubeBoundary conditions:
1D model(Matlab code)
3D model(Fluent)
Outside wall: Concentrated solar power (typical distribution)
Inner wall: heat transfer coefficient and fluid temperature
Wall ends: Non-slip and adiabatic
Inlet condition: Temperature, flow rate, pressure
Tube wall: heat flux
Heat losses
Pressure outlet
4heat losses W nc W o0.8 (T T )q T hσ= + −ɺ
solarq C DNI= ×ɺ
21/6
128/279/16
0.3870.60 , 10
1 (0.559 / Pr)
RaNu Ra
= + ≤
+ Churchill and Chu (1975)Tube
0360
90
180
270
Lobon et al. (2014)
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Model validation Parameters ValueTube length 510 mInner radius 0.05 mOuter radius 0.07 m
Inlet temperature 478.15 KMass flow rate 0.47 kg/s
Direct normal isolation 822 W/m2
Optical efficiency 0.632Inlet pressure 3.43 MPa
Heat loss (liquid) 1278 W/m2
Heat loss (two phase) 1828 W/m2
Heat loss (vapor) 2323 W/m2
Lobón, D. H., Baglietto, E., Valenzuela, L., & Zarza, E. (2014). Modeling direct steam generation in solar collectors with multiphase CFD. Applied Energy, 113, 1338-1348.
0 100 200 300 400 500
460
470
480
490
500
510
520
530
540
550
560
570 Predicted data Experimental data
Tem
per
atu
re (
K)
Lenght (m)Length (m)
0 100 200 300 400 500
3.05x106
3.10x106
3.15x106
3.20x106
3.25x106
3.30x106
3.35x106
3.40x106
3.45x106
Pre
ssu
re (
Pa)
Lenght (m)
Predicted data Experimental data
Length (m)
Lin, TFESC2015, August 201510 /18
Performance evaluation
• Solar thermal efficiency: heat losst
solar,receiver
1Q
Qη = −
ɺ
ɺ
• Maximum wall-fluid temperature difference :
• Mean heat transfer coefficient in two-phase flow region:
The SOPHIA research project is funded by the Fuel Cell and Hydrogen Joint Under-taking (FCH JU) under the Grant Agreement Number 621173. The information contained in this work reflects the views of the authors only.