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In this study, an inorganic mixture of 40 wt% MgCl2·6H2O and 60 wt% Mg(NO3)2·6H2O was impregnated into two types of the expanded graphite (EG): EG flakes and EG matrix. Different methods of preparation usually used in the organic composite preparation, such as direct blending, vacuum impregnation, ultrasonic impregnation and immersion were applied in this work. Considering the samples with EG matrix, it can be concluded that the optimal result of the encapsulation and ΔH ratio can be reached with the experimental time of 1, 3 and 4 h using the vacuum, ultrasound and immersion methods, respectively. Moreover, the percentage of encapsulation increases with the experimental time and with the EG percentage for the EG matrix and for the EG flakes, respectively. Concerning the supercooling phenomena, the results show that the presence of EG reduces the difference between fusion and crystallization temperature for up to 65%, acting as а nucleating agent. The resulting composite samples (CPCM) were proved to have good latent heat and a significant reduction of the supercooling effect, which eliminates the need to use nucleating agents, that are essential for pure PCM of 40 wt% MgCl2·6H2O and 60 wt% Mg(NO3)2·6H2O. Moreover, using EG suppresses significantly the melting time which indicates the heat transfer enhance of the mixture. This circumstance could allow to empower the utilization of the mentioned mixture in different fields of thermal energy storage at low temperature.
Authors from Universidad de Antofagasta thank CONICYT/FONDAP N° 15110019, ERANET-LAC 2015–2016, project ELAC2015/T06-0988 and CONICYT/FONDECYT/REGULAR N° 1170675 for the financial support. Yana Galazutdinova would like to acknowledge for her doctorate scholarship to the CONICYT-PCHA/Doctorado Nacional para Estudiantes Extranjeros 2014/Folio 63140052. The work was partially funded by the Spanish government (ENE2015-64117-C5-1-R (MINECO/FEDER)). Dr. Luisa F. Cabeza would like to thank the Catalan Government for the quality accreditation given to her research group (2014 SGR 123). GREA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. This project has received funding from the European Commission Seventh Framework Programme (FP/2007–2013) under Grant agreement N°PIRSES-GA-2013-610692 (INNOSTORAGE) and from the European Union's Horizon 2020 research and innovation programme under grant agreement No 657466 (INPATH-TES). |
