MICRO-NANO POROUS MATERIALS FOR HIGH PERFORMANCE THERMAL...
Transcript of MICRO-NANO POROUS MATERIALS FOR HIGH PERFORMANCE THERMAL...
14/11/2005 | Envelope & Coverings | PAGE 1
MICRO-NANO POROUS MATERIALS
FOR HIGH PERFORMANCE
THERMAL INSULATION
Daniel QUENARD – Hébert SALLEECentre Scientifique et Technique du Bâtiment – CSTB – French Building Research InstituteEnvelope & Coverings Department - Material Physics DivisionTel : 33 4 76 76 25 46 – Email : [email protected]
2nd International Symposium onNANOTECHNOLOGY in CONSTRUCTIONBILBA0 – 13-16 nov. 2005
Date | SERVICE OU DEPARTEMENT | PAGE 2
From Energy Wasting …
"Almost half of Europe’s energy is consumed in its 160 million buildings.”
ENERGY END-USE EFFICIENCYBy Andrew WarrenMETERING INTERNATIONAL ISSUE 1 2005
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Green Paper on Energy Efficiencyor Doing More with Less
FINAL ENERGY DEMANDEurope 2002 Buildings Industry Transport Total
Residential/Tertiary Unit437.8 306 338.9 1083 Mtep40.4 28.3 31.3 %
France 46 25 29 %
Heating 69 %DHW + cooking 19 %
Electricity 12 %
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… to Energy Saving
Among the different measures (efficient boilers, thermal & PV solar collectors) to reduce energy consumption, for both residential and non-residential buildings,
Improvement of building envelopes is by far the most reliable and most cost-effective way to reduce both energy use and CO2 emissions
Thermal Insulation (roofs, walls, windows)Thermal Insulation (roofs, walls, windows),Airtightness & Solar gains
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Thermal Insulation
Source : http://perso.wanadoo.fr/rbm
Source : http://arcticinuit.free.fr
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Insulating Materials
VIPVacuum Insulation Materials
Mineral Wool Core MaterialFumed Silica
Airtight Foil
MW, EPSλ = 35 – 40 mW/mK
VIPλVIP = 5 - 10 mW.mK
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Fumed Silica
Production Process in a Flame
SiCl4 + 2 H2 + O2 → SiO2 + 4 HCl
BurnerSiCl4 + 2 H2 + O2 SiO2
SiO2SiO2
SiO2
SiO2
proto- primary aggregates agglomeratesparticles particles
Source : WACKER Ceramic
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Wacker HDK® PYROGENIC SILICATAMPED DENSITY
Fumed silica appears as a fluffy white powder characterized by an extremly low tamped density down to ~ 50 kg/m3.
Density of SiO2 : ~ 2200 kg/m3
Primary particles do not exist as individual units outside the flame
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Hygrothermal Propertiesof Micro-Nano Porous Silica
Porosity Porosity –– Density Density –– Specific AreaSpecific Area
Pore Size DistributionPore Size Distribution
Water Vapor AdsorptionWater Vapor Adsorption
Thermal Conductivity vs Pressure, Moisture & TemperatureThermal Conductivity vs Pressure, Moisture & Temperature
VIP : Vacuum Insulation PanelVIP : Vacuum Insulation Panel
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Density, Porosity & Specific area
MaterialReference
TotalPorosity
(Pyc.)
%
BulkDensity(Pyc.)
kg/m3
ApparentDensity
(EN 1602)
kg/m3
SkeletonDensity(Pyc.)
kg/m3
SpecificArea
(BET)
m2/g
SIL1 93 ± 1 191 ± 4 192 ± 4 2578 213
SIL2 94 ± 1 161 ± 4 162 ± 4 2454 208
MW or EPS : 13 to 40 kg/m3
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Thermal Conductivity in Porous Materials
rgsrgse λ+λ=λ+λ+λ=λ +
1 : solid conduction (phonons)2 : gas conduction (molecules)3 : radiation (photons)
( ) sggs 1 λ⋅ε−+λ⋅ε=λ +
ε : porosity > 90 %
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Thermal Conductivityvs Total Pressure & Pore Size
1E-3 0.01 0.1 1 10 100 1000
4
8
12
16
20
24
28
Pressure hPa
Fumed Silica 1 CSTB Fumed Silica 2 CSTB Precipitated Silica CSTB Fumed Silica ZAE PU Foam
The
rmal
con
duct
ivity
10-3
W/m
.K δ
100 µm
0.1 µm
Thermal Probe
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Gas Thermal Conductivityvs Total Pressure & Pore Size
g
0gg
PT.C1⋅δ
+
λ=λ
C : constantλg0 : free air conductionδ : pore size.
1 : Low Pressure Pg
2 : Confinement / Knudsen Effect :pore size δ < lm mean free path - δ ∼ 0,1 µm (air)
source : www.empa.ch
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Humid Air
N2 78,08 % O2 20,95 % Ar 0,93 %
CO2 0,03 % Xe, Kr, Ne, He 0,01 %
Dry Air
+ Water Vapor H20
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Water Molecule – Molecular Adsorption
Water Molecule Size
0.3 - 0.4 nm
H
O
H Molecular Adsorption
Capillary Condensation
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Capillary CondensationKelvin-Laplace Law
( )( ) ( )RHLn1cosT2
RTMR lpK ⋅β⋅σ⋅⋅⋅ρ−=
0.1 µm99 % RH
0,1 µm
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Molecular Adsorption& Capillary Condensation
0.0 0.2 0.4 0.6 0.8 1.00.00
0.05
0.10
0.15
0.20
0.25 Fumed Silica 1 CSTB Fumed Silica 2 CSTB Fumed Silica NRC Fumed Silica ZAE
Wat
er c
onte
nt k
g/kg
Relative humidity
Molecular Adsorption
Capillary Condensation
Water moleculein pores
RH increases
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Thermal Conductivity vs Water Content
0 5 10 15 20
20
30
40
50
60
Fumed Silica 1 CSTB Fumed Silica 2 CSTB
The
rmal
Con
duct
ivity
10-3
W/m
.K
Water Content %
Temperature : 23 °CAtmospheric Pressure
u : Water Content
uBeu ⋅+λ=λ
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Thermal Conductivity vs Vapor Pressure
0 5 10 15 20 25 30
20
30
40
50
60
Fumed Silica 1 CSTB Fumed Silica 2 CSTB
The
rmal
Con
duct
ivity
10-3
W/m
.K
Vapor Pressure hPa
Temperature : 23 °CAtmospheric Pressure
T=23°C – HR = 70 %Pv = 20 hPa
PV = RH.Pvs(T)
( )PvFeu eD1 ⋅⋅−+λ=λ
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Thermal Conductivity vs Total Pressure& Water Content
0.01 0.1 1 10 100 1000
5
10
15
20
25
30
35
40
Fumed Silica 2 CSTB dry 30% RH 54% RH 70% RH 80% RH
The
rmal
Con
duct
ivity
10
-3 W
/m.K
Pressure hPa
RH%
SaturatedVapor
PressurehPa
30 8,4354 15,1770 19,6680 22,47
100 28,08
Salt Solution
SampleProbe
Chamber : T=23 °C
80 %
P - N2, O2 = variablePv - H2O = constant
P - N2, O2 = variablePv - H2O = variable
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Thermal Conductivity vs Temperature
280 300 320 340 360 380 400 420 440 460 480 500 5202
3
4
5
6
7
8
Fumed Silica 1 CSTB Fumed Silica 2 CSTB Fumed Silica ZAE Precipitated Silica ZAE Fumed Silica 1 NRC
The
rmal
con
duct
ivity
10
-3 W
/m.K
Temperature K
ET
316 3
rσ⋅=λ
Temperature : 23 °CPressure ~ 10-2 mbar
Extinction Coefficient5000 < E < 12000 m-1
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Simplified Model
( ) ( )( )⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
⋅δ⋅+
λ⋅ε+⋅−+λ⋅ε−+⎟
⎟⎠
⎞⎜⎜⎝
⎛ σ⋅=λ ⋅
PTC1
eD11ET
316 0gPF
s
3
ev
Radiation GasLow PressureConfinement
Solid + Water
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Conclusion
MicroMicro--Nano Porous Silica are good candidates to make VIPNano Porous Silica are good candidates to make VIP’’ss
The Thermal Conductivity is close to The Thermal Conductivity is close to 5 mW/m.K5 mW/m.K at a presssure at a presssure of 10 hPa (0,01 bar).of 10 hPa (0,01 bar).
Due to their high specific area and the microDue to their high specific area and the micro--nano size of their nano size of their pores, porous silica are very sensitive to moisture. Protection pores, porous silica are very sensitive to moisture. Protection against water molecules penetration are essential.against water molecules penetration are essential.
With an initial pressure of 0,01 hPa, there is a safety margin oWith an initial pressure of 0,01 hPa, there is a safety margin of f 3 order of magnitude 3 order of magnitude …… but durability will strongly depend on but durability will strongly depend on the airtightness of the envelope (foil + welding).the airtightness of the envelope (foil + welding).
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Supports & Acknowledgements
The results presented in this paper have been obtained within the framework of 3 projects :> Characteristion of Nanoporous Silica - ADEME-EDF-CSTB> European Project VIP-PSS
> Vacuum Insulation Panel – Product & Service System
> Annexe 39 IEA (International Energy Agency )> HIPTI : High Performance Thermal Insulation
Acknowledgements :> B. Yrieix : EDF - S. Kherrouf : ADEME – Peter Randel : WACKER> H. Sallée - C. Pompéo - FD. Menneteau : CSTB