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

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

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)

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 substrate Insulation polymer basis Radiative Filler ROOF GROUND

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

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)

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

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

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)

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

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)

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

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

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)

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

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.

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:

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:

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:

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

Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD) Owen CLUS CONTACT : http://www.opur.u-bordeaux.fr/