▪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.

Properties of nanocomposites substantially improved:Mechanical properties : strength, modulus and dimensional stability Thermal stability: Thermal resistance, flame retardancy and reduced smoke emissionsDecreased permeability to gases, water and hydrocarbons

M.Constantinescu1, D.Constantinescu2, L.Dumitrache3,,C.Perianu Marin2, A.Stoica1, M.Ladaniuc3 P.M.Pavel1 and M.Olteanu1.

1AR-ICF “Ilie Murgulescu” , 2 INCERC Bucharest , 3ICECHIM Bucharestmariella_const@yahoo.com

Romanian Academy of ScienceInstitute of Physical Chemistry “Ilie Murgulescu” Spl. Independentei 202, 060021 Bucharest,

CH2

O

CH CH2 O C O CH2

CH3

CH3

CH

O

CH2

+

Hardening reaction of epoxi resin with PCM

Nano composites preparation

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 stabilityKinetical : -High nucleation and crystal grow velocityEconomical : -low cost -Reciclability -Non-toxicity

Material characterization and testing

DSC for PEG 2000+Al DSC  for epoxi-PEG 1000 +Al

SEM micrographs for polyethylene glycol (PEG) 2000

30% epoxy resin Ropoxid 501 + 70% PEG +Al powder melted and mixed .

Then hardener TETA or I 3361 was used

Objectives and importance of energy storage in PCM

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).

DSC for PEG 1500+Al

CONCLUSIONS1.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.

NHH

CH2 N CH2 CH2 N CH2 CH2

H HCH2

HN

H

CH2

CH

CH2

HO

O

N CH2 N CH2 CH2 N CH2 CH2CH2 NCH2CHCH2O

OH

CH2CHCH2O

OH

CH2 CH CH2 O

OH

CH2 CH CH2 O

OHCH2

CH

CH2

HO

O

PCM

epoxy

Maximum PCM in an epoxi matrix Nano composites PEG 1000 ,1500, PEG 2000 for different applications

PC

H2O

H2O

vacu

um

5 3 2 1

Warm water

thermocouples

w0

w1

12345

Amplifierinterface

air

Thermostat

Experimental set-up for heat transfer coefficient determination*interface pipe for transfer fluid-PEG

Experimental cell

SEM micrographs for polyethylene glycol (PEG) 1500 SEM micrographs for polyethylene glycol (PEG) 1000

(PCM)-EPOXI COMPOSITE BUILDING MATERIALS

-500 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500-50

0

50

100

150

200

250

300

350

400

450

500

00

0

reac

tion

heat

(J/

g)

time,minutes

Kinetics of hardening reaction for the studied systems in isotherm regime from DSC experiments

Ropoxid 501+I 3361 , 0 PCM - Ropoxid 501+I 3361 PCM had no influence on the kinetics of the hardening process

The thermo-physical properties of the PEG-epoxi composites.

TypeTemperature

0CDensity

ρ Kg/m3

Dimensional variation, dmm (L,B,W)

Temperature

0C

Thermal conductivity W/(mK)

Thermal diffusivity

Mean valuem2/s

Specific heat ,c, kJ/(kgK)

EpoxyPEG 2000

020

40506070

1206.91182.71211.51186.91171.21168.5

-0.35 0.10 0.42-0.29 0.17 0.740.89 0.83 0.95

1520

30 40Tm

Tf

0.2060.2070.2110.2220.2500.212

8.43 10-8 2.642.652.702.843.202.72

EpoxyPEG 1500

02040506070

1208.81173.71219.11197.91171.5

0.18 0 0.480.40 0 1.490.55 0.35 0.72

1520

30 40Tm

Tf

0.2330.2340.2380.2540.2670.241

6.55 10-8 2.312.322.362.522.652.39

EpoxyPEG 1000

0204050

1183.51183.21170.01177.1

1520

30 40Tf

0.2160.2180.2320.2330.214

0 200 400 600 800 1000 120020

25

30

35

40

45

Tf

Tint

Ties

T4

T3T

2

T1

T [

o C

]

t [ s ]

1,8

2,0

2,2

2,4

2,6

2,8

3,0

3,2

T

[ oC ]

T

* 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

Temperature distribution in the PEG 1500 system at thermal discharge

1/kchf = 1/kexp – d1 / λ

*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.

κexp = qchf (T1 - Tc) = [qexp - qsens] /(T1 - Tc)

*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.

qsens = PEGVPEGcPEG(T0 - Tfin)[1 - (Tmed - Tfin)/(T0 - Tfin)]/(AcΔt )

*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.

0 200 400 600 800 1000 12000

20

40

60

80

100

q chf [

KW

/m2 ]

q e

xp [

KW

/m2 ]

t [ s ]

0

1

2

3

4

5

6

qexp

qchf

kchf

kch

f [ KW

/m2K

]

Time evolution of qexp, qchf and kchf

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 andcc = 4183 J/KgK specific heat of the transfer fluid.

ρa

λc

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.

0.65 0.36 0.241.13 0.64 0.50

PEG +

Ropoxid 501

Ropoxid 501

TETA

Heat transfer coefficients determination