Transcript Slide 0

Romanian Academy of Science
Institute of Physical Chemistry “Ilie Murgulescu”
Spl. Independentei 202, 060021 Bucharest,
(PCM)-EPOXI COMPOSITE BUILDING MATERIALS
2
D.Constantinescu ,
3
L.Dumitrache ,,C.Perianu
1
P.M.Pavel
2
Marin ,
1
A.Stoica ,
3
M.Ladaniuc
1
M.Olteanu .
and
1AR-ICF “Ilie Murgulescu” , 2 INCERC Bucharest , 3ICECHIM Bucharest
[email protected]
Heat transfer coefficients determination
1/kchf = 1/kexp – d1 / λ
Amplifier
interface
Nano composites preparation
Energy storage aims to reduce the conventional energy consumtion with a direct impact on CO2
emissions.
The advantages of phase change materials:
A constant temperature domain for the phase transformation, chosen for each application.
High storage density 70-100 kWh/m3
Directions of research on heat storage in phase change materials :
▪Finding new materials with superior performances
▪Elimination of existent material disadvantages.
An epoxi-PCM was obtained and characterized whereas PCM was used polyethylene glycol of different
molecular weights (1000, 1500, 2000).
κexp = qchf (T1 - Tc) = [qexp - qsens] /(T1 - Tc)
CH3
C
O
CH2
CH
+
CH2 CH2
Experimental set-up for heat transfer coefficient determination
*interface pipe for transfer fluid-PEG
O
CH3
H
N
CH2
PEG +
3,2
epoxy
45
2,6
o
T[ C]
T2
35
T
T3
o
2,4
30
Maximum PCM in an epoxi matrix
OH
N CH2 CH2 N CH2 CH2 N CH2 CH2 N
CH2
Ties
CH2 CH CH2 O
Tint
0
400
600
450
400
1000
1200
* Ties and Tint are the temperatures of the transfer fluid at exit respectively entrance
at the interface PEG-transfer fluid, Tf is the phase change temperature, ΔT = Ties - Tint
Kinetics of hardening reaction for
the studied systems in isotherm regime
from DSC experiments
350
300
Time evolution of qexp, qchf and kchf
6
The thermo-physical properties of the PEG-epoxi composites.
qexp
100
250
Type
200
Temperature
0C
Density
ρ
Kg/m3
Dimensional
variation, d
mm (L,B,W)
Tempera
ture
0C
150
0
0
0
500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500
time,minutes
Epoxy
PEG
1500
Epoxy
PEG
1000
0
20
40
50
60
70
1206.9
1182.7
1211.5
1186.9
1171.2
1168.5
0
20
40
50
60
70
1208.8
1173.7
1219.1
1197.9
1171.5
0
20
40
50
1183.5
1183.2
1170.0
1177.1
-0.35 0.10 0.42
-0.29 0.17 0.74
0.89 0.83 0.95
0.18 0 0.48
0.40 0 1.49
0.55 0.35 0.72
0.65 0.36 0.24
1.13 0.64 0.50
15
20
30
40
Tm
Tf
0.206
0.207
0.211
0.222
0.250
0.212
15
20
30
40
Tm
Tf
0.233
0.234
0.238
0.254
0.267
0.241
15
20
30
40
Tf
0.216
0.218
0.232
0.233
0.214
Thermal
diffusivity
Mean value
m2/s
8.43 10-8
6.55 10-8
Specific heat ,c,
kJ/(kgK)
c
λ
aρ
2.64
2.65
2.70
2.84
3.20
2.72
2.31
2.32
2.36
2.52
2.65
2.39
5
80
4
60
3
kchf
2
Epoxy
PEG
2000
50
DSC for epoxi-PEG 1000 +Al

W/(mK)
100
-50
-500
Thermal
conductivity
kchf [ KW/m K]
reaction heat (J/g)
800
t [ s ]
0
Material characterization and testing
200
500
OH
O
1,8
20
CH2 CH CH2 O
CH2
Hardening reaction of epoxi resin with PCM
2,0
25
*T0 = [T1(t0) + T4(t0)]/2 = 39.76 oC is the mean temperature of
PEG at the start of thermal discharge,
Tfin = [T1(tfin) + T4(tfin)]/2 -34.1 oC is the mean temperature of PEG
at the end of thermal discharge,
Tmed = [T1(t) + T4(t)]/2 is the mean temperature of PEG at the
momemnt t,
Δt-time between two readings of T1 and T4,
VPEG = 25 10-6 m3is volume,
cPEG = 2440 J/KgK specific heat,
PEG = 1210.1 Kg/m3 density of PEG.
2
CH2
OH
2,2
T1
HO CH
DSC for PEG 1500+Al
2,8
40
PCM
CH2
O CH2 CH CH2
3,0
T4
O
O CH2 CH CH2
qsens = PEGVPEGcPEG(T0 - Tfin)[1 - (Tmed - Tfin)/(T0 - Tfin)]/(AcΔt )
Tf
H
CH2 CH2 N
H
TETA
OH
*qchf is the rate of heat flow during the phase change,
qexp is the rate of experimental heat flow,
qsens is the rate of sensible heat flow,
Tc = (Tint + Ties)/2 is the mean temperature of the transfer fluid.
Experimental cell
Temperature distribution in the PEG 1500 system at thermal discharge
Ropoxid 501+I 3361 , 0 PCM - Ropoxid 501+I 3361
PCM had no influence on the kinetics of the hardening process
DSC for PEG 2000+Al
H2O
T [ C ]
Mechanical properties : strength, modulus and dimensional stability
Thermal stability: Thermal resistance, flame retardancy and reduced smoke emissions
Decreased permeability to gases, water and hydrocarbons
3 2 1
vacuu
m
R
o
p CH2 CH CH2 O
o
O
x
i
Ropoxid 501
d
5
H
0 H
N CH2 CH2 N
1 H
0
Properties of nanocomposites substantially improved:
Thermostat
air
5
30% epoxy resin Ropoxid 501 + 70% PEG +Al powder melted and mixed .
Then hardener TETA or I 3361 was used
HO CH
▪The PCM-epoxi nano-composite materials obtained as cross-linked three dimensional
structures are attractive for space heating and cooling of buildings able to reduce the space
and costs for containerization.
▪The use of PCM in buildings is possible only if some regulations and performance
criteria are applied in accordance with the European Directions: resistance and stability,
fire security, human health and environmental protection, energy saving and thermal
insulation.
▪The stability of buildings depends on materials used for.
*kchf is the heat transfer coefficient at the interface PEG-transfer
fluid during phase change,
d1 /λ is the thermal resistance of the PEG layer between the
thermocouple T1 and the interface PEG-transfer fluid,
kexp is the experimental heat transfer coefficient between the
thermocouple T1 and the transfer fluid,
λ = 0.234 W/mK is the thermal conductivity of PEG,
d1 = 0.004 m is the distance between the thermocouple T1 and the
interface PEG-transfer fluid.
5
4
3
2
1
w1
w0
H2O
Demands for a Phase Change Material
Physico-chemical:
-Phase change temperature in the required
domain
-High latent heat of phase change and caloric
capacity
-High thermal conductivity
-Low undercooling
-Low volume changes
-Reversible phase transition
-Good physical and chemical stability
Kinetical :
Nano composites PEG 1000 ,1500,
-High nucleation and crystal grow velocity
PEG 2000 for different applications
Economical :
-low cost
-Reciclability
-Non-toxicity
thermocouples
2
Objectives and importance of energy storage in PCM
PC
qchf [ KW/m ] qexp [KW/m ]
1
M.Constantinescu ,
40
2
20
1
qchf
0
0
0
200
400
600
800
1000
1200
t[s]
qexp = cccDc(Tint - Ties)/Ac
*Ac = 0.001 m2 is the surface of the interface between PEG and transfer fluid,
Dc = 0.5 l/min is the flow rate,
c = 998.2 Kg/m3 is the density and
cc = 4183 J/KgK specific heat of the transfer fluid.
where: * Tf is the phase change temperature, “a” was calculated from thermal conductivity , thermal diffusivity
and density were measured in standard conditions. The maximum error for dimensional variation was ± 1.5%
even after PCM was melted.
CONCLUSIONS
SEM micrographs for polyethylene glycol (PEG) 2000
SEM micrographs for polyethylene glycol (PEG) 1500
SEM micrographs for polyethylene glycol (PEG) 1000
1.The nanocomposite materials for buildings were obtained by using melted (PCM + 0.1 wt%Al powder for enhancing the thermal conductivity of the
system ) 70 wt%, incorporated in an epoxidic resin 30 wt%. For all Epoxi-PCM materials was used Ropoxid 501 (Policolor), with 26% hardener
threeethylentetramine (TETA) or I 3361 (Policolor). The composition of the materials was PCM ( polyethyleneglycoles 1000, 1500 and 2000) 70wt%
and 30%epoxy resin, which hardened at the ambient temperature in 24 h and the process was ended in 7 days as can be seen from the process kinetics.
2.The materials were characterized and present good mechanical, thermal and chemical properties suitable for building materials.
3.The transfer coefficients calculated from the thermal discharging experiments in the shown set up indicated an acceptable value and time evolution.
4.These nano composites can be used for different applications in active or pasive systems, depending on their melting temperature. The geometry used
depends also on their melting temperature and on the chosen application.
5. Energy storage in building materials will reduce the conventional energy consumptions, will increase the living comfort, decreasing the CO2
emissions.