P.M.Pavel and M.Constantinescu. ICF-AR “Ilie Murgulescu” Bucuresti Romanian Academy of Science Institute of Physical Chemistry “Ilie Murgulescu” Spl. Independentei 202, Bucharest, Physico-chemical: -Phase change temperature in the required domain -High latent heat of phase change and caloric capacity -High thermal conductivity addition of C or Al powder -Low undercooling -Low volume changes -Reversible phase transition -Good physical and chemical stability Kinetical : -High nucleation and crystal grow velocity Economical : -low cost -Reciclability -Non-toxicity Material characterization and testing DSC Glauber-epoxy+ad SEM micrographs for Glauber –epoxy Importance of energy storage in PCM and objectives: Energy storage aims to reduce the conventional energy consumtion with a direct impact on CO 2 emissions. In order to achieve this it is necessary:  to find new materials with superior performances  to eliminate the existent material disadvantages -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. -Modeling the heat transfer in the obtained nanocomposites PCM-epoxi in order to dimensionate the real buildings. -Taking into account the application in a passive or active heating or cooling and their needs, the suitable material and its geometry will be used. Geometric form of the material is application dependant. CONCLUSIONS 1.These materials present good mechanical, thermal and chemical properties suitable for building materials. They 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. 2.The thermal transfer coefficients at loading/discharging in air with convection have close values for both TESM proving that they have a similar thermal behavior. 3. The loading times in the experiments of loading at constant temperature are similar for both TESM, leading to the same conclusion regarding the thermal behavior. 4.The mathematical model and the obtained solution gives the possibility to correlate the variables with the dimensionless criteria and approximate in acceptable limits the experimental values. HEAT TRANSFER OF A NANOCOMPOSITE PCM- EPOXY HEAT STORE Advantages of using PCM-epoxy materials In experiments were used: 1. TES tixotropic module; TESMt 88% Na 2 SO 4 -10H 2 O  5% Na 2 B 4 O 7 -10H 2 O  7% SiO 2 (encapsulated in a polyethylene sphere) 2. TES reticulated module;(PCM-epoxy) TESMr 66% Na 2 SO 4 -10H 2 O  3,7% Na 2 B 4 O 7 -10H 2 O  30%(epoxy resin)+1% Carbon black+1%CaCO 3 ) Starting with the experimental heat transfer results concerning the heat transfer in a PCM-epoxy module, a theoretical model for heat transfer in a spherical geometry has been developed using the Megerlin and Goodmann methods. An approximate formula for the solidification time was deduced and used on the experimental data. This applies satisfactory to heat transfer with phase change in a cross-linked three dimensional polymer structure. Thermal Transfer Experiments with Fusion for TES with PCM 1. Thermal loading experiments in air at constant temperature for TESM DSC Glauber Thermal loading set-up for TESM at constant temperature. The heat transfer coefficient at thermal loading in air with convection is: h =  a c a D a (T in - T out )/{4  r w 2[T w -(T in + T out )/2]} where: r w and T w are the radius and the temperature at the surface of TESM  a, c a, D a, are the density, specifical heat and the air flow rate, and T in and T out the air temperatures at the entrance and respectively out of. T in [°C]D a [l/min]h r [w/m 2 °C]h t [w/m 2 °C] Experimental results 1.Experimental cell 2.Spherical module 3.Termocouple 4. Data taker 5. Resistance for air heating 6.Measure instrument (A) 7.Electrical source 8.Compressor 9.Air flow meter 1 2 Thermal cycling setup of the TES modules in air with convection TESM r T w external, T c internal, T a =50 o C TESM t T w external, T c internal T a =50 o C TESM r ; 1.external; 2. internal. TESM t ; 1.external; 2. internal Thermal loading for TESM. T in, °C D a [l/min] Transfer coefficient, h, w/m 2 °C TESM r Transfer coefficient,h, w/m 2 °C TESM t Thermal cycling in air with convection Model and Solution for Inward Fusion of TESM One dimensional spherical geometry for inward fusion Assumptions 1. The composite medium is isotropic and homogeneous. 2. The composite medium is at the fusion temperature at initial moment. 3. Overall volume change due to phase change is negligible. 4. Physical properties are independent of temperature. 5. The solid-liquid interface is clearly defined; the PCM has a well-defined fusion temperature. 6. Heat conduction is the only mode of heat-transfer in the liquid phase; natural convection is assumed to be absent. Model Equations Ste  l  R,R f  R f    2  l  R,R f  R 2   2  R  l  R,R f  R   l  1,R f   0  l  R=R f,R f   1   dR f  d    l  R,R f  R  R  Rf  = Ste  Fo R = r/r w R f = r f /r w  = (T  T w )/ (T f  T w ) Fo =  l t/r 2 w Ste = c l (T f  T w )/  Perturbation Solution  l  R,Rf, Ste)   0  R,Rf   Ste  1  R,Rf   Ste2  2  R,Rf  ...  Rf, Ste)   0  Rf   Ste  1  Rf   Ste2  2  Rf  + … Method of strained coordinates for Perturbation Solution  =  (R,Rf)  =  (Rf,Rf) R =  +  i=1  Stei  i( ,  )Rf =  +  i=1  Stei  i( ,  ) After change variables (R,Rf)  ( ,  ) on obtain from  lorry, Ste):  1( ,  )  0,  2( ,  )  0,  3( ,  )  0… from extern boundary condition, R=1:  (R=1,Rf) = 1  i(1,  ) = 0  (Rf=1) = 1  i(1, 1) = 0  /  R  R=1 = 1  i/  =1 = 0 from inward boundary s-l conditions, R= Rf:  0  = ,  = 1  1  = ,  = 0  2  = ,  = 0  dRf  d  d  d  =  (  )(  R)  =  and from heat conduction equation in liquid phase: Ste  (  )(d  /dRf)  (  )(  Rf)  (  )(  R)  =  = = (  2  2)(  R)2   (  2  R2)  2  R  R  Yields for non-dimensional position of inward boundary s-l Rf: Rf =  – Ste(1 –  )/(6  ) + Ste2(22  – 3)(1 –  )/(360  3) and for the energy balance at inward boundary s-l form: d  /d  =  1  Ste  d  1( ,  )  d   Ste  1( ,  )   Ste2  d  2( ,  )  d   Ste2  2( ,  )   Ste2  d  1( ,  )  d  1( ,  )   0 ,  The non-dimensional time of fusion are obtained by integred last equation:  =  3(1 –  )2 – 2(1 –  )3  /6  Ste(1 –  )2/3 – Ste2(1 –  )2/(180  2) with  a solution of Rf equation. TESMr 1 at50 o C; 2 at 46 o C TESMt 1at50 o C; 2 at 46 o C PC Results for Inward Fusion of TESM solidification times Thermal loading in air at T=ct T int [°C]D a [l/min]h r [w/m 2 °C]h t [w/m 2 °C] Discharging in air with convection Thermal loading in air with convection.