Experimental dynamic thermal properties determination of EPDM/NBR panels with a shape stabilized Phase Change Material based on summer daily temperatures of four cities in Italy

In this work, the evaluation of E-PCM panels based on an elastomeric matrix containing a shape-stabilized paraffinic phase change material with a melting point of 28 °C was carried in a climatic chamber, simulating the summer daily temperature profile of four geographical locations in Italy at different latitudes. The characterization, carried out on testing boxes insulated using the E-PCM panels, allowed the determination of the delay (time lag) and of the dampening (decrement factor) in the propagation of the heat wave when passing from the outer to the inner surface of the walls; the results were correlated to two important parameters, the characteristic admittance and the heat capacity. From the difference between the heat fluxes on the outer and inner surface of the panels it was also possible to quantify the amount of stored energy and to do a comparison with a reference insulating panel (aerogel). Aerogel panels, despite the low thermal conductivity but due to the limited heat capacity and characteristic admittance, were unable to provide an effective insulation during summer conditions while E-PCM panels led to excellent outcomes. Results showed that with a peak of 33 °C in the external temperature, the phase change material limited the internal one at 27 °C with a maximum delay in the peak temperature of 6 h, an overall decrement factor of 0.4, time lag of 3 h and stored energy of 740 kJ/m2 per day. Finally, also the influence of the testing speed on the response of the E-PCM was evaluated through repetition of heating/cooling cycles in the temperature range 19–35 °C, highlighting the necessity of improving the thermal conductivity of the system in case of fast-response applications (cycle length < 3.5 h) and/or to optimize the PCM amount in the panel depending on the energy to be absorbed.