Preparation and characterization of an inorganic magnesium chloride/nitrate/graphite composite for low temperature energy storage

Abstract

In this study, an inorganic mixture of 40 wt.% MgCl 2 •6H 2 O and 60 wt.% Mg(NO 3) 2 •6H 2 O 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 hours 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.% MgCl 2 •6H 2 O and 60 wt.% Mg(NO 3) 2 •6H 2 O. 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.

The use of ultrasound in the South Cone region. Advances in organic and inorganic synthesis and in analytical methods

“…In 2018, a Chilean group from Universidad de Antofagasta, led by Galazutdinova in collaboration with Vega (Universidad Mayor de San Simón, Bolivia), and Cabeza (University of Lleida, Spain), reported the synthesis and characterization of an inorganic magnesium chloride/nitrate/graphite composite for low temperature energy storage [67] . For this study, the authors impregnated an inorganic mixture of 40 wt% MgCl 2 ·6H 2 O and 60 wt% Mg(NO 3 ) 2 ·6H 2 O into two types (flakes and matrix) of the expanded graphite (EG).…”

Development and Results from Application of PCM-Based Storage Tanks in a Solar Thermal Comfort System of an Institutional Building—A Case Study

“…Thus, the replacement strategy was applied, and the proposed novel low-cost mixture based on Mg(NO 3 ) 2 •6H 2 O/bischofite had a melting temperature of 58.2 • C and the heat of fusion of 116.9 kJ•kg −1 . The details of their thermal and physical properties, as well as their characterization and optimization can be found in [27,28]. This waste material was studied as a possible PCM at different scales, from laboratory to pilot plant [25,26], demonstrating that bischofite has similar thermophysical characteristics to synthetic MgCl2•6H2O, but a lower cost.…”

“…Thus, the replacement strategy was applied, and the proposed novel low-cost mixture based on Mg(NO3)2•6H2O/bischofite had a melting temperature of 58.2 °C and the heat of fusion of 116.9 kJ•kg −1 . The details of their thermal and physical properties, as well as their characterization and optimization can be found in [27,28].…”

Thermal characteristics of hydrated salt blended with Tio2 for thermal energy storage

“…Yana Galazutdinova et al 16 used a mixture of MgCl 2 · 6H 2 O and Mg(NO 3 ) 2 · 6H 2 O in the ratio of 40% and 60% by weight respectively with the graphite vacuum impregnation technique. Preparation time and expanded graphite proportion lead to an increment in percentage encapsulation.…”