Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)

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

2. Owen CLUS Jalil OUAZZANI Marc MUSELLI Vadim NIKOLAYEV Girja SHARAN Daniel BEYSENS Université de Corse Arcofluid Université de Corse CEA/CNRS-ESPCI Paris Indian Inst. of Management, Ahmedabad CEA/CNRS-ESPCI Paris 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)

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. polymer basis Radiative Filler Insulation substrate Atmospheric vapour harvesting by radiative cooling • Innovative formulations • cheap polymers LDPE, paint • high IR emissivity Radiative budget - 70 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 ROOF GROUND

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

8. Radiative cooling inclusion in CFD dR = (εs,θσTamb4 – εr σTrad4) dΩ • Specific radiative cooling for each shape • angular sky emissivity • isotropic radiator emissivity εr = 0.94 Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)

9. Radiative budget (W/m²) Radiator Temp. (°C) 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)

10. ER Radiative cooling Convective heating P T ρ u v w Shape Materials 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 Volumes Grid

11. Wind speed variations for 0.25 ; 0.5 ; 1.0 and 2.0 m/s at 10 m WIND PROFILE Cone-shaped condenser simulation • 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 waterthan 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. (A) 0.16 m² 30 m² 1 m² REF 7.3 m² (D) (B) (C) (E) 3 ridges 255 m² Radiative condenser as thermal machine Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD) (B)

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. INDIA Conclusion • 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 CONTACT : http://www.opur.u-bordeaux.fr/