Romanian Academy of Science Institute of Physical Chemistry

Romanian Academy of Science Institute of Physical Chemistry “Ilie Murgulescu” Spl. Independentei 202, 060021 Bucharest, (PCM)-EPOXI COMPOSITE BUILDING MATERIALS 1 2 3 2 1 3 M. Constantinescu , D. Constantinescu , L. Dumitrache , , C. Perianu Marin , A. Stoica , M. Ladaniuc 1 1 P. M. Pavel and M. Olteanu. 1 AR-ICF “Ilie Murgulescu” , 2 INCERC Bucharest , 3 ICECHIM Bucharest mariella_const@yahoo. com Objectives and importance of energy storage in PCM 5 4 3 2 1 w 0 wa Warm ter *kchf is the heat transfer coefficient at the interface PEG-transfer fluid during phase change, d 1 /λ is thermal resistance of the PEG layer between thermocouple T 1 and the interface PEG-transfer fluid, kexp is the experimental heat transfer coefficient between thermocouple T 1 and the transfer fluid, λ = 0. 234 W/m. K is thermal conductivity of PEG, d 1 = 0. 004 m is the distance between thermocouple T 1 and the interface PEG-transfer fluid. Thermostat 3 2 1 H 2 O vacuum 5 R o p o x i d 5 0 1 κexp = qchf (T 1 - Tc) = [qexp - qsens] /(T 1 - Tc) Experimental set-up for heat transfer coefficient determination *interface pipe for transfer fluid-PEG + Ropoxid 501 PEG + *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 epoxy qsens = PEGVPEGc. PEG(T 0 - Tfin)[1 - (Tmed - Tfin)/(T 0 - Tfin)]/(AcΔt ) *T 0 = [T 1(t 0) + T 4(t 0)]/2 = 39. 76 o. C is the mean temperature of PEG at the start of thermal discharge, Tfin = [T 1(tfin) + T 4(tfin)]/2 -34. 1 o. C is the mean temperature of PEG at the end of thermal discharge, Tmed = [T 1(t) + T 4(t)]/2 is the mean temperature of PEG at the momemnt t, Δt-time between two readings of T 1 and T 4, VPEG = 25 10 -6 m 3 is volume, c. PEG = 2440 J/Kg. K specific heat, PEG = 1210. 1 Kg/m 3 density of PEG. PCM TETA Maximum PCM in an epoxi matrix * 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 Hardening reaction of epoxi resin with PCM Type Temperature 0 C Density ρ Kg/m 3 Epoxy PEG 2000 0 20 40 50 60 70 1206. 9 1182. 7 1211. 5 1186. 9 1171. 2 1168. 5 Epoxy PEG 1500 0 20 40 50 60 70 1208. 8 1173. 7 1219. 1 1197. 9 1171. 5 Epoxy PEG 1000 0 20 40 50 1183. 5 1183. 2 1170. 0 1177. 1 Material characterization and testing DSC for PEG 1500+Al DSC for epoxi-PEG 1000 +Al Time evolution of qexp, qchf and kchf The thermo-physical properties of the PEG-epoxi composites. 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 PC air 30% epoxy resin Ropoxid 501 + 70% PEG +Al powder melted and mixed. Then hardener TETA or I 3361 was used 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 ØMechanical properties : strength, modulus and dimensional stability ØThermal stability: Thermal resistance, flame retardancy and reduced smoke emissions ØDecreased permeability to gases, water and hydrocarbons thermocouples H 2 O Demands for a Phase Change Material Properties of nanocomposites substantially improved: 1/kchf = 1/kexp – d 1 / λ Amplifier interface Nano composites preparation Energy storage aims to reduce the conventional energy consumtion with a direct impact on CO 2 emissions. The advantages of phase change materials: A constant temperature domain for the phase transformation, chosen for each application. High storage density 70 -100 k. Wh/m 3 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). ▪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. Heat transfer coefficients determination Dimensional variation, d mm (L, B, W) -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 Tempera Thermal ture conductivity 0 C W/(m. K) 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 m 2/s 8. 43 10 -8 6. 55 10 -8 Specific heat , c, k. J/(kg. K) 2. 64 2. 65 2. 70 2. 84 3. 20 2. 72 2. 31 2. 32 2. 36 2. 52 2. 65 2. 39 qexp = ccc. Dc(Tint - Ties)/Ac *Ac = 0. 001 m 2 is the surface of the interface between PEG and transfer fluid, Dc = 0. 5 l/min is the flow rate, c = 998. 2 Kg/m 3 is the density and cc = 4183 J/Kg. K 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 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) 70 wt% 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 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 CO 2 emissions.