Présentation sur les matériaux à changement de phase par Prof. C. Völker TU Kaiserslautern

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Department of
Civil Engineering
Simulations and measurements of
Phase Change Materials (PCM)
in buildings
Jun.-Prof. Dr.-Ing. Conrad Völker
Modelling in Building Physics
Civil Engineering

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Department of
Civil Engineering
Motivation
§ overheating in summer due to
§ climate change
§ glass façades
§ light-weight construction
§ Phase Change Material increase heat capacity
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 2

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Department of
Civil Engineering
Phase Change Materials
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 3

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Department of
Civil Engineering
Phase Change Materials
§ salt hydrates
§ low material costs
§ high storage density
§ paraffin
§ chemical stability
§ no supercooling
§ alcohols
§ fatty acids
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 4

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Department of
Civil Engineering
Phase Change Materials
§ specific heat capacity with ΔT=20°C
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 5

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Department of
Civil Engineering
Gypsum plaster with PCM
§ PCM
§ micro-encapsulated paraffin
§ BASF micronal
§ plastic capsule (5 - 20 µm)
§ θmelt = 25°C - 28°C (90%)
18°C - 28°C (100%)
§ gypsum plaster
§ maxit clima 26
§ 20 % paraffin
§ 1 cm layer ~80 kg in test room
§ latent heat = 16.5 kJ/kg
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 6
Microscope (ESEM)
Gypsum plaster

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Department of
Civil Engineering
Gypsum plaster with PCM
§ Differential scanning calorimetry
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 7

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Department of
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Salt mixture
§ composition
§ 96,5 % CaCl2·6H2O
§ 2 % KCl
§ 0,5 % NaCl
§ 1 % Ba(OH)2·8H2O
§ θmelt = 30°C
§ disadvantage
§ phase separation
§ hygroscopic
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 8

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Department of
Civil Engineering
Measurements
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 9
Picture: Franke

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Department of
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Measurements
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 10

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Department of
Civil Engineering
Measurements
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 11

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Department of
Civil Engineering
Measurements
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Department of
Civil Engineering
Measurements
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Department of
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∑Φ=Θρ kiRLL Vc !
[ ])t()t(AhV)(c WiPCM,WiWWWWW Θ−Θ=ΘΘρ !
[ ])t()t(AU iAAWAW Θ−Θ=
[ ])t()t(AU iAFF Θ−Θ+
)t(lzAgr F ⋅⋅⋅⋅+
[ ])t()t(nVc iARLL Θ−Θρ+
)t(iΦ+
[ ])t()t(Ah WiPCM,Wi Θ−Θ−
indoor air
exterior wall
window
solar
ventilation
internal gains
PCM
Simulation – Simplified model
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 14

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Department of
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Simulation – Simplified model
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 15
0
5
10
15
20
25
30
35
40
18/09 19/09 20/09 21/09 22/09 23/09 24/09 25/09date
θ [°C]
0
5
10
15
20
25
30
35
40
18/09 19/09 20/09 21/09 22/09 23/09 24/09 25/09date
θ [°C]
simulation vs. measurement

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Department of
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Simulation – Simplified model
Reasons for differences:
§ simplified model
§ simplified walls:
§ adiabatic
§ heat capacity of walls
§ temperature gradient in wall
§ solar reflection as a constant
§ …
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 16

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Department of
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Simulation – ESP-r
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10
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40
14.9. 16.9. 18.9. 20.9. 22.9. 24.9. 26.9.
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14.9. 16.9. 18.9. 20.9. 22.9. 24.9. 26.9.
θ[°C]
measurement simulation

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Department of
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Simulation – ESP-r
§ Optimization of θmelt
§ Optimum means minimal
overheating
100
200
300
400
500
600
22 23 24 25 26 27 28 29 30
100
200
300
400
500
600
22 23 24 25 26 27 28 29 30
θlimit = 25°C
θlimit = 26°C
θlimit = 27°C
θlimit = 28°C
overheating[h]
θmelt [°C]
1 cm
3 cm
θmelt [°C]
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 18

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Department of
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§ Optimization of layer thickness
§ For l = 16.5 kJ/kg:
layer thickness up
to 3 cm useful
1cmohnePCM
1cmPCM
2cmPCM
3cmPCM
4cmPCM
5cmPCM
0
100
200
300
400
500
600
θlimit
overheating[h]
25°C 26°C 27°C 28°C
1cmwithoutPCM
Simulation – ESP-r
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 19

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Department of
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Simulation – ESP-r
§ Optimization of heat conductivity
22
24
26
28
30
32
3.6 4.6 5.6 6.6 7.6 8.6 9.6 10.6
walltemperature[
°
C]
d = 2 cm
λ = 0.21 W/mK
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Department of
Civil Engineeringwalltemperature[
°
C]
§ Optimization of heat conductivity
§ d ≤ 3 cm and l = 16.5 kJ/kg no impact
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26
28
30
32
3.6 4.6 5.6 6.6 7.6 8.6 9.6 10.6
d = 2 cm
λ = 0.42 W/mK
Simulation – ESP-r
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 21

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Department of
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§ Optimization of heat conductivity
§ d ≤ 3 cm and l = 16.5 kJ/kg no impact
22
24
26
28
30
32
3.6 4.6 5.6 6.6 7.6 8.6 9.6 10.6
λ = 0.63 W/mK
d = 2 cm
Simulation – ESP-r
walltemperature[
°
C]
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 22

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Department of
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§ Optimization of heat conductivity
§ d ≤ 3 cm and l = 16.5 kJ/kg no impact
§ thicker layers: higher λ neccessary
22
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26
28
30
32
3.6 4.6 5.6 6.6 7.6 8.6 9.6 10.6
22
24
26
28
30
32
3.6 4.6 5.6 6.6 7.6 8.6 9.6 10.6
d = 2 cm d = 6 cm
Simulation – ESP-r
walltemperature[
°
C]
datedate
23/05/14 Jun.-Prof. Dr.-Ing. Conrad Voelker 23

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Department of
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Conclusion
§ Within experimental measurements a reduction of
room temperatures of 2 K - 5 K was found
§ numerical models were developed & validated
§ phase change temperature range between 23°C and
26°C is recommended
§ For the investigated PCM-plaster, s ≤ 3 cm is
recommended
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