Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

Owen CLUS

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

2006 European PHOENICS User meeting

Wimbledon, 30th Nov. 1st Dec., 2006Radiation-cooled Dew Water

Condensers Studied by Computational Fluid Dynamic

(CFD) Owen CLUS

Jalil OUAZZANI Marc MUSELLI

Vadim NIKOLAYEV Girja

SHARANDaniel BEYSENS

Université de CorseArcofluidUniversité de CorseCEA/CNRS-ESPCI Paris Indian Inst. of Management, Ahmedabad CEA/CNRS-ESPCI Paris

International Organization For Dew Utilization International Organization For Dew Utilization

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

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

Researches for condensing atmospheric vapor as alternative water resource without

energy supplyingRadiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

ROOF

CLEAR SKY

GROUND

substrate

Insulation

Radiative budget - 70 W/m²

Surface 3 to 8°C below Tambient

Innovative formulations cheap polymers

LDPE, paint high IR emissivity

polymerbasis

Radiative Filler

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

Pilots, Prototypes

1 m²

Dew = 30 % of rain

Quantitativesystems

15 m² 7 L / night

800 m² 300 L/ night

Experimental prototypes

30 m² 10 L / night1 m² 0.6 L / night

FRANCE FRANCE

CROATIA

INDIA

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

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

Wind flow

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

α

r R

Condenser shape and thermal properties

Free convection heating

Radiative cooling

forced convection heating

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

Radiative cooling inclusion in CFD

cos

1

, 11 bss

dR = (εs,θ σTamb4 – εr σTrad

4) dΩ

εr = 0.94

α

θ

1

0.94 dΩSKY

εm

εs,θ

α

θ

1

0.94 dΩSKY

εm

εs,θ

Specific radiative cooling for each shape

angular sky emissivity

isotropic radiator emissivity

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

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)

-80

-70

-60

-50

-40

-30

-20

-10

0

5 10 15 20

BILANS RADIADIFS (en ciel nocturne clair à 15°C)

plan 0.0°

plan 30°

cone 20°

cone 30°

cone 40°

Pui

ssan

ce d

issi

pée

(W/m

²)

Température Foil (°C)Radiator Temp. (°C)

Rad

iati

ve b

ud

get

(W/m

²)

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

Radiative condenser described in CFD

3 Dimensions virtual reality description

Shape Materials

LOG Wind Profile

Convective

heating

Radiative cooling

Radiative cooling power ER is dissipated for each radiator cell. TRAD (one phase model as in dry air)

GridVolumes

Convective heating for every shapes and for various wind speeds is given by Iterative calculation

P T ρ

u v w

ER

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

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° tiltedMore 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

3.160 L water / night

38 % more water than on the 1m² planar condenser

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

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

(B)(A)

0.16 m²

(D)

30 m²

(C)

7.3 m²

(E)

3 ridges 255 m²

1 m² REF

(B)

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

Comparison “Temperature gain” / “Dew gain”

Non quantitative comparison, the cooler the surface, the better

the dew yield.

Surface Temperature TCOND,

Simulations rough results

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

Comparison “Temperature gain” / “Dew gain”

“Dew gain” related to 1 m² REF condenser water volume.

“Cooling power” or “temperature gain” related with Ta and 1 m² REF:

af

acond

TT

TTT

Re

0

REF

COND

H

HH 0

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

Comparison “Temperature gain” / “Dew gain”

“Dew gain” related to 1 m² REF condenser water volume.

“Cooling power” or “temperature gain” related with Ta and 1 m² REF:

af

acond

TT

TTT

Re

0

REF

COND

H

HmmH )(

Radiation-cooled Dew Water Condensers Studied by Computational

Fluid Dynamic (CFD)

Comparison “Temperature gain” / “Dew gain”

“Dew gain” related to 1 m² REF condenser water volume.

“Cooling power” or “temperature gain” related with Ta and 1 m² REF:

af

acond

TT

TTT

Re

0

REF

COND

H

HmmH )(

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/