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
Owen CLUS Université de Corse
Studied
by Computational
Fluid Dynamic
Jalil OUAZZANI
Arcofluid
Marc MUSELLI Université
de Corse
(CFD)
Vadim NIKOLAYEV
Girja SHARAN
Daniel BEYSENS
International Organization For Dew Utilization
CEA/CNRS-ESPCI Paris
Indian Inst. of Management, Ahmedabad
CEA/CNRS-ESPCI Paris
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
Radiative budget - 70 W/m²
LDPE, paint
Surface
3 to 8°C below
Tambient
Researches
for condensing
atmospheric
 high IR emissivity
vapor as alternative water resource without
CLEAR
SKY
energy
supplying
Radiation-cooled
Dew Water Condensers
Studied by Computational Fluid Dynamic
polymer
basis
(CFD)
Insulation
substrate
ROOF
GROUND
Radiative
Filler
Pilots, Prototypes
FRANCE
FRANCE
Experimental
prototypes
1 m²
Radiation-cooled
Dew Water
Condensers
30
m²
10 L / night
1 m²
0.6 L / night
Studied by Computational Fluid Dynamic
of (CFD)
rain
15 m²
7 L /Dew
night= 30 % INDIA
Quantitative
systems
CROATIA
800 m²
300 L/ night
CFD simulations of radiative condensers
The CFD tool has been developed for helping
decision and technical choices before
implementing these huge systems without
Radiation-cooled
Dew Water Condensers
preliminary empirical tests
Studied by Computational Fluid Dynamic
(CFD)
Radiative condenser as thermal machine
Radiative
cooling
Wind flow
Condenser
shape and
thermal
properties
 condensation in
weak wind, limit free /
forced convection
Radiation-cooled Dew Water
Condensers
 variability
of
data
Studied by Computationalmeteorological
Fluid Dynamic
Free
induces long time
convection
(CFD)
outdoor experiments
heating
forced
convection
heating
α
r
R
 no description for
complex shapes
without empirical
corrections
Radiative cooling inclusion in CFD
Specific radiative cooling for each shape
dR = (εs,θ σTamb4 – εr σTrad4) dΩ
 angular sky emissivity
 s,  1  1   s 
 isotropic radiator emissivity
εr = 0.94
1
bcos 
Radiation-cooled Dew Water Condensers
Studied by Computational Fluid Dynamic
SKY
(CFD)
εm
dΩ
0.94
εs,θ
θ
α
1
Radiative cooling inclusion in CFD
FORTRAN tool for integrating radiative budget on various shapes
 angular integration
 dissipation law included in Phoenics
computation: ER =clairf(T)
BILANS RADIADIFS (en ciel nocturne
à 15°C)
Radiation-cooled Dew Water Condensers
Studied by Computational Fluid Dynamic
(CFD)
Puissance dissipée (W/m²)
Radiative budget (W/m²)
0
plan 0.0°
-10
plan 30°
cone 20°
-20
cone 30°
-30
cone 40°
-40
-50
-60
-70
-80
5
10
15
Température
Foil (°C) (°C)
Radiator
Temp.
20
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 Dew
in dry air)
Radiation-cooled
Water Condensers
Studied by Computational Fluid Dynamic
LOG Wind
Volumes
Grid (CFD)
Profile
ER
P T ρ
u v w
Radiative
cooling
Shape
Materials
Convective
heating
Cone-shaped condenser simulation
 Wind speed variations for 0.25 ; 0.5 ; 1.0 and 2.0 m/s at 10 m
 side tilt variations for 50 ; 40 ; 35 ; 30 ; and 25 Deg.
Radiation-cooled Dew Water Condensers
Studied by Computational
WIND Fluid Dynamic
(CFD)
PROFILE
Cone-shaped condenser simulation
Radiation-cooled Dew Water Condensers
30° tilted
Studied by Computational FluidMore
Dynamic
efficient
(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
Radiation-cooled
Dew
 1 m² planar condenser
is the Water
referenceCondensers
because
always set by
up simultaneously
nearby each
Studied
Computational
Fluidsystem
Dynamic
(CFD)
Radiative condenser as thermal machine
0.16 m²
(A)
1 m² REF
30 m²
7.3 m²
Radiation-cooled Dew Water Condensers
Studied by Computational Fluid Dynamic
(CFD)
(B)
(B)
(C)
(D)
(E)
3 ridges
255 m²
Comparison “Temperature gain” / “Dew gain”
Surface Temperature TCOND,
Simulations rough results
Radiation-cooled Dew Water Condensers
 Non quantitative
Studied by Computationalcomparison,
Fluid
Dynamic
the cooler
(CFD) the surface, the better
the dew yield.
Comparison “Temperature gain” / “Dew gain”
<DT0>
<DewX/dew Ref>
Radiation-cooled Dew Water Condensers
Studied by Computational Fluid Dynamic
(CFD)
1 m² 30°
tilted
planar
0.16 m2
PMMA
plate
30 m², 30°
tilted
planar
7.32 m²
cone
3 ridges,
255 m²
1.00
0.65
1.05
1.40
1.15
1.00
0.68
0.91
1.38
0.81
“Cooling power” or “temperature
gain” related with Ta and 1 m² REF:
Tcond  Ta
T0 
TRe f  Ta
“Dew gain” related to 1 m² REF
condenser water volume.
H COND
H 0 
H REF
Comparison “Temperature gain” / “Dew gain”
<DT0>
<DewX/dew Ref>
Radiation-cooled Dew Water Condensers
Studied by Computational Fluid Dynamic
(CFD)
1 m² 30°
tilted
planar
0.16 m2
PMMA
plate
30 m², 30°
tilted
planar
7.32 m²
cone
3 ridges,
255 m²
1.00
0.65
1.05
1.40
1.15
1.00
0.68
0.91
1.38
0.81
2
“Cooling power” or 1“temperature
m² 30°
0.16 m
gain” related with Ta tilted
and 1 m² REF:
PMMA
Tcond
T0 
TRe f
<DewX/dew Ref>
<DT0>

Ta
1.00

Ta
1.00
0.65
0.68
“Dew
related
REF
30 m², gain”
30° 7.32
m² to 13m²
ridges,
tilted
cone
255 m²
condenser
water volume.
H COND1.15
H (mm) 
0.91
1.38 H REF0.81
1.05
1.40
Comparison “Temperature gain” / “Dew gain”
<DT0>
<DewX/dew Ref>
Radiation-cooled Dew Water Condensers
Studied by Computational Fluid Dynamic
(CFD)
1 m² 30°
tilted
planar
0.16 m2
PMMA
plate
30 m², 30°
tilted
planar
7.32 m²
cone
3 ridges,
255 m²
1.00
0.65
1.05
1.40
1.15
1.00
0.68
0.91
1.38
0.81
2
“Cooling power” or 1“temperature
m² 30°
0.16 m
gain” related with Ta tilted
and 1 m² REF:
PMMA
Tcond
T0 
TRe f
<DewX/dew Ref>
<DT0>

Ta
1.00

Ta
1.00
0.65
0.68
“Dew
related
REF
30 m², gain”
30° 7.32
m² to 13m²
ridges,
tilted
cone
255 m²
condenser
water volume.
H COND1.15
H (mm) 
H REF0.81
0.91
1.38
1.05
1.40
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/