Thermo-physical characterization of some paraffins used as phase change materials for thermal energy storage

Three phase change paraffinic materials (PCMs) were thermophysically (phase-transition temperatures, latent heat, heat capacity at constant pressure, density, and thermal conductivity) investigated in order to be used as latent heat storage media in a pilot plant developed in Plovdiv Bulgaria. Raman structural investigation probes aliphatic character of the E53 sample, while the E46 and ECP samples contain also unsaturated components due to their Raman features within 1,500–1,700 cm−1 range. Orthorhombic structure of the three PCMs was evidenced by the Raman modes at the 1,417 cm−1. The highest latent heat value, ΔH, of phase transitions among the three materials was represented by summation of a solid order–disorder, and melting latent heat was encountered by the E53 paraffin, i.e., 194.32 J g−1 during a μ-DSC scan of 1 °C min−1. Conversely, the ECP composite containing ceresin component shows the lowest latent heat value of 143.89 J g−1 and the highest thermal conductivity of 0.46 W m−1 K−1 among the three phase change materials (PCMs). More facile melt-disordered solid transition with the activation energy of 525.45 kJ mol−1 than the lower temperature transition of disorder–order (E a of 631.73 kJ mol−1) during the two-step process of solidification for the E53 melt are discussed in terms of structural and molecular motion changes.

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