1. Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Owen CLUS

2. 2006 European PHOENICS User meeting
Wimbledon, 30th Nov. 1st Dec., 2006
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Owen CLUS
Jalil OUAZZANI Marc MUSELLI Vadim NIKOLAYEV Girja SHARAN
Daniel BEYSENS
Université de Corse
Arcofluid
CEA/CNRS-ESPCI Paris
Indian Inst. of Management, Ahmedabad

3. Atmospheric vapour harvesting by radiative cooling
Researches for condensing atmospheric vapor as alternative water resource in arid areas without energy supplying
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)

4. Atmospheric vapour harvesting by radiative cooling
Innovative formulations
cheap polymers
LDPE, paint
high IR emissivity
Radiative budget W/m²
Surface 3 to 8°C below Tambient
Researches for condensing atmospheric vapor as alternative water resource without energy supplying
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
CLEAR SKY
substrate
Insulation
polymer
basis
Radiative Filler
ROOF
GROUND

5. Pilots, Prototypes
Experimental prototypes
FRANCE
FRANCE
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
1 m²
1 m²
30 m²
0.6 L / night
10 L / night
Dew = 30 % of rain
Quantitative
systems
15 m² 7 L / night
800 m²
300 L/ night
INDIA
CROATIA

6. CFD simulations of radiative condensers
The CFD tool has been developed for helping decision and technical choices before implementing these huge systems without preliminary empirical tests
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)

7. Radiative condenser as thermal machine
condensation in weak wind, limit free / forced convection
variability of meteorological data induces long time outdoor experiments
no description for complex shapes without empirical corrections
Condenser shape and thermal properties
Wind flow
Radiative cooling
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Free convection heating
forced convection heating

8. Radiative cooling inclusion in CFD
Specific radiative cooling for each shape
angular sky emissivity
isotropic radiator emissivity
dR = (εs,θ σTamb4 – εr σTrad4) dΩ
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
εr = 0.94

9. Radiative cooling inclusion in CFD
FORTRAN tool for integrating radiative budget on various shapes
angular integration
dissipation law included in Phoenics computation: ER = f(T)
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Radiator Temp. (°C)
Radiative budget (W/m²)

10. Radiative condenser described in CFD
3 Dimensions virtual reality description
Convective heating for every shapes and for various wind speeds is given by Iterative calculation
Radiative cooling power ER is dissipated for each radiator cell. TRAD (one phase model as in dry air)
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
LOG Wind Profile ER
Volumes
Grid
Radiative cooling
P T ρ
u v w
Convective heating
Shape Materials

11. Cone-shaped condenser simulation
Wind speed variations for 0.25 ; 0.5 ; 1.0 and 2.0 m/s at 10 m
WIND PROFILE
side tilt variations for 50 ; 40 ; 35 ; 30 ; and 25 Deg.
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)

12. Cone-shaped condenser simulation
30° tilted
More efficient
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)

13. Cone-shaped condenser prototype (France)
30° tilted
7.3 m², Φ 3 m
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
3.160 L water / night
38 % more water than on the 1m² planar condenser

14. CFD simulations validation
Comparison of simulated efficiency with physical measurements on real system on 5 various condensers from 0.16 to 255 m² installed during long period
1 m² planar condenser is the reference because always set up simultaneously nearby each system
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)

15. Radiative condenser as thermal machine
1 m² REF
(B)
(C)
7.3 m²
(D)
30 m²
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
(B)
(E)
3 ridges 255 m²

16. Comparison “Temperature gain” / “Dew gain”
Surface Temperature TCOND,
Simulations rough results
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Non quantitative comparison, the cooler the surface, the better the dew yield.

17. Comparison “Temperature gain” / “Dew gain”
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
“Dew gain” related to 1 m² REF condenser water volume.
“Cooling power” or “temperature gain” related with Ta and 1 m² REF:

18. Comparison “Temperature gain” / “Dew gain”
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
“Dew gain” related to 1 m² REF condenser water volume.
“Cooling power” or “temperature gain” related with Ta and 1 m² REF:

19. Comparison “Temperature gain” / “Dew gain”
Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
“Dew gain” related to 1 m² REF condenser water volume.
“Cooling power” or “temperature gain” related with Ta and 1 m² REF:

20. Conclusion
INDIA
Little set of data is needed to conclude the validation of the program
This program has been advantageously used in Dew factory project for orientation and yields prospective
Next step is to develop a two phases dew condensation simulation for more accurate quantitative results

21. Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)
Owen CLUS
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