Post on 20-Apr-2020
Influence of wind on receivers for solar power towers
OpenFOAM user conference 2014 Institute of Solar Research, German Aerospace Center Robert Flesch
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 1
German Aerospace Center (DLR)
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 2
Aeronautics Space
Transport Energy
Outline
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 3
1. Introduction
2. Experiment
5. Validation 3. CFD setup
4. CFX comparison 6. Heat loss mechanism
Cavity Receiver for Solar Power Towers
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 4
Questions Approach
Aim and Approach
(1) What influence has wind on the losses?
• Different receiver inclinations
• Different wind directions
• Different wind speeds
(2) Can the influence of wind be analyzed with CFD?
• RANS approach
(1) Experiment
• Wind tunnel experiment
• Similarity approach
(2) CFD simulations
• Wind tunnel setup
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 5
Experimental Approach
• Similarity – main dimensionless numbers • Reynolds number Re = 𝑢∞ 𝐷𝑖 𝜌
𝜇ref
• Grashof number Gr = 𝑔 𝐷𝑖3𝜌2
𝜇ref2
Tw−T∞𝑇ref
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 6
• Cryogenic wind tunnel cologne • Ambient temperature -173°C • Scaling factor 3.5
Inclination Angle ϕ
Reducing the ambient temperature
Upscaling
Experimental Approach Local heat transfer
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 7
Zone 0 Zone 1 Zone 2 Zone 3 Zone4
Benefits using OpenFOAM Concerns about using OpenFOAM
CFD approach Why using OpenFOAM?
• License costs
• High computational effort for heat loss simulation
• Open source code
• Expandability
• Clarity concerning the used models
• Training period
• Lack of documentation
• Reliability (Results)
• Prevalence
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 8
CFD approach Model setup
• Mesh creation
• ANSYS ICEM
• Appr. 3.5∙106 Elements
• Environment
• Wind tunnel setup
• Nitrogen -173°C
• Ideal Gas
• Janaf thermo
• Polynomial transport
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 9
• Turbulence model
• k-ω-SST
• Prt=0.85
• Solver
• OpenFOAM 2.3.0
• buoyantPimpleFoam
CFD approach Boundary conditions I
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 10
Inner walls
mut mutLowReWallFunction;
k → 0
omega compressible::omegaWallFunction;
alphat calculated;
T fixedValue;
Outer walls
mut mutkWallFunction;
k compressible::kqRWallFunction;
omega compressible::omegaWallFunction;
alphat calculated;
T zeroGradient;
CFD approach Boundary conditions II
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 11
Inlet (natural convection) U pressureInletOutletVelocity p_rgh totalPressure T inletOutlet
Outer walls
mut mutkWallFunction;
k compressible::kqRWallFunction;
omega compressible::omegaWallFunction;
alphat calculated;
T FixedValue T∞
Inlet (forced convection) U fixedValue p_rgh zeroGradient T fixedValue
CFX Nu = 305
OpenFOAM Nu = 308
Results CFX comparison
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 12
• Highest velocity 5 m/s • Horizontal receiver • Head-on wind • Same fluid property functions
Validation
DLR.de • Chart 13
ϕ
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08
ϕ ϕ
Validation
DLR.de • Chart 14
ϕ
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08
ϕ ϕ
Validation
DLR.de • Chart 15
ϕ
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08
ϕ ϕ
Validation
DLR.de • Chart 16
ϕ
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08
ϕ ϕ
Validation Loss Mechanism
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 17
Re2
Gr = 0 Re2
Gr = 1,29 Re2
Gr = 3,59
Experiment CFD Experiment CFD Experiment CFD
Zone 0
Zone 1
Zone 2
Zone 3
Zone 4
Validation Loss Mechanism
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 18
Re2
Gr = 0 Re2
Gr = 1,29 Re2
Gr = 3,59
Experiment CFD Experiment CFD Experiment CFD
Zone 0
Zone 1
Zone 2
Zone 3
Zone 4
Simulation Experiment
Validation Model errors
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 19
• Constant wall temperature
• Constant heat flux in zones
• Deviation in cases of nonuniform heat transfer
• No conduction
• Conduction in cylinder and through insulation
• Aperture is adiabatic
• Aperture is not adiabatic
Summary Outlook
Summary and Outlook
• Influence of wind • horizontal receivers → small influence • increasing inclination angle → increasing influence
• CFD simulations • Capable to predict the changes due to wind
• Absolute values are slightly underpredicted
• OpenFOAM • Powerful CFD tool • Improvable documentation
• Analysis of reduction strategies using OpenFOAM
• Prospective use of OpenFOAM in solar research
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 20
Thank you for your attention! Questions? Project Start-SF contract 323-2010-006
Backup
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 21
Validation
DLR.de • Chart 22
ϕ
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08
ϕ ϕ
Turbulent heat transfer
> Influence of wind on receivers for solar power towers > Robert Flesch • 2014-10-08_OFUC_Flesch_WindSolarReceiver > 2014/10/08 DLR.de • Chart 23