Effect of solvent on specific heat capacity enhancement of binary molten salt-based carbon nanotube nanomaterials for thermal energy storage

Abstract

a b s t r a c tThe specific heat capacity of a binary molten salt-based carbon nanotube nanomaterial was experimentally measured in both solid and liquid phases. The effect of the solvent on the specific heat capacity was examined for a wide range of chemical compositions for a binary carbonate salt mixture. The binary salt mixture consisted of lithium carbonate and potassium carbonate. Multi-walled carbon nanotubes were dispersed in the solvent to synthesize the nanomaterials. A surfactant, gum arabic, at 1% mass concentration with respect to the solvent was added to disperse the carbon nanotubes homogeneously in the salt mixture. The results indicated that the specific heat capacity of the carbonate salt mixtures was significantly enhanced by adding the carbon nanotubes in the solid and liquid phases. Moreover, the enhanced specific heat capacity was affected by the chemical composition of the salt mixtures. Furthermore, molecular dynamics simulations were used to examine the effects of different chemical compositions of the binary salt mixtures with nanotubes on the specific heat capacities of the nanomaterials.

Anomalous Increase in Specific Heat of Binary Molten Salt-Based Graphite Nanofluids for Thermal Energy Storage

“…Recently, Jo and Banerjee reported that the specific heat of carbonate salt mixtures in the liquid phase changes drastically with the molar fraction of the two salts [31]. As mentioned previously, the base fluid (chemical composition of two salts in a binary salt mixture) affects the enhancement of the specific heat of the salt mixtures as well [28]. For this reason, five different salt compositions were chosen for the base fluid of the nanofluid tested in this study.…”

“…However, the reason for the increase in the specific heat of molten salt nanofluids has not been clearly investigated. According to previous studies [20,28], the increase of the specific heat of nanofluids is not solely a result of the nanoparticles, but is closely associated with interactions between the nanoparticles and the base fluids. For effectively harnessing thermal energy storage media, such as molten salt mixtures, it is important to understand their specific heat-enhancing mechanism.…”

“…All the chemical agents were used as received. Figure 2 shows the procedures for synthesizing the molten salt-based graphite nanofluids [20,28]. First, graphite nanoparticles were dispersed into distilled water with the GA (1 wt %).…”

“…After the water was completely evaporated, the dry power of the molten salt nanofluids was scraped from the entire whole petri dish, and lastly, a grinding and mixing process was performed to obtain a uniform chemical composition of the base fluid. Pure salt mixtures were prepared though the same procedures but were subjected to sonication only once, for 2 h. Figure 2 shows the procedures for synthesizing the molten salt-based graphite nanofluids [20,28]. First, graphite nanoparticles were dispersed into distilled water with the GA (1 wt %).…”

“…Chieruzzi et al enhanced the specific heat of a binary nitrate (NaNO 3 -KNO 3 ) by dispersing various nanoparticles (Al 2 O 3 , SiO 2 , TiO 2 , and SiO 2 -Al 2 O 3 ) [23,24]. The enhanced specific heat of the molten salt nanofluids was explained in various ways, e.g., electron microscope images and molecular dynamics simulation [25][26][27][28][29][30]. Furthermore, a fundamental experimental study into thermal property variations of carbonate salt mixtures was performed using a differential scanning calorimeter (DSC) [31].…”