CONDENSEURS RADIATIFS DE LA VAPEUR DEAU ATMOSPHERIQUE

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Radiation-cooled Dew Water Condensers Studied by
Computational Fluid Dynamic (CFD)
Owen CLUS
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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)
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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)
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Atmospheric vapour harvesting by radiative
cooling

• Innovative formulations
• cheap polymers
• LDPE, paint
• high IR emissivity

Radiative budget - 70 W/m² Surface 3
to 8C 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
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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
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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)
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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
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Radiative cooling inclusion in CFD
dR (es,? sTamb4 er sTrad4) dO

• Specific radiative cooling for each shape
• angular sky emissivity
• isotropic radiator emissivity

er 0.94
Radiation-cooled Dew Water Condensers Studied by
Computational Fluid Dynamic (CFD)

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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)

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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
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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)
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Cone-shaped condenser simulation
30 tilted More efficient
Radiation-cooled Dew Water Condensers Studied by
Computational Fluid Dynamic (CFD)
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Cone-shaped condenser prototype (France)
30 tilted
7.3 m², F 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
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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)
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Radiative condenser as thermal machine
Radiation-cooled Dew Water Condensers Studied by
Computational Fluid Dynamic (CFD)
(B)
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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.

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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
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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
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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
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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

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