Enhanced Specific Heat Capacity of Molten Salt-Based Carbon Nanotubes Nanomaterials

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Byeongnam Jo ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Capacity ◽  
Liquid Phase ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Sodium Dodecyl ◽  
Base Material ◽  
Molar Ratio ◽  
Sem Images ◽  
Carbonate Salt

This study aims to investigate the specific heat capacity of a carbonate salt eutectic-based multiwalled carbon nanomaterial (or high temperature nanofluids). The specific heat capacity of the nanomaterials was measured both in solid and liquid phase using a differential scanning calorimetry (DSC). The effect of the carbon nanotube (CNT) concentrations on the specific heat capacity was examined in this study. The carbonate molten salt eutectic with a high melting point around 490 °C, which consists of lithium carbonate of 62% and potassium carbonate of 38% by the molar ratio, was used as a base material. Multiwalled CNTs were dispersed in the carbonate salt eutectic. A surfactant, sodium dodecyl sulfate (SDS) was utilized to obtain homogeneous dispersion of CNT into the eutectic. Four different concentrations (0.1, 0.5, 1, and 5 wt.%) of CNT were employed to explore the specific heat capacity enhancement of the nanomaterials as the concentrations of the nanotubes varies. In result, it was observed that the specific heat capacity was enhanced by doping with the nanotubes in both solid and liquid phase. Additionally, the enhancements in the specific heat capacity were increased with increase of the CNT concentration. In order to check the uniformity of dispersion of the nanotubes in the salt, scanning electron microscopy (SEM) images were obtained for pre-DSC and post-DSC samples. Finally, the specific heat capacity results measured in present study were compared with the theoretical prediction.

Effect of Dispersion Homogeneity on Specific Heat Capacity Enhancement of Molten Salt Nanomaterials Using Carbon Nanotubes

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Byeongnam Jo ◽  
Debjyoti Banerjee
Keyword(s):  
Carbon Nanotubes ◽  
Heat Capacity ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Mass Concentration ◽  
Sodium Dodecyl ◽  
Base Material ◽  
Capacity Enhancement ◽  
Carbonate Salt

The specific heat capacity of a carbonate salt eutectic-based carbon nanotube nanomaterial was measured in present study. Differential scanning calorimeter (DSC) was used to measure the specific heat capacity of the nanomaterials. The specific heat capacity value in liquid phase was compared with that of a pure eutectic. A carbonate salt eutectic was used as a base material, which consists of lithium carbonate and potassium carbonate by 62:38 molar ratio. Multiwalled carbon nanotubes (CNT) at 1% mass concentration were dispersed in the molten salt eutectic. In order to find an appropriate surfactant for synthesizing molten salt nanomaterials, three surfactants, sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), and gum arabic (GA), at 1% mass concentration with respect to the salt eutectic were added. In preparation of dehydrated nanomaterials, water was evaporated by heating vials on a hot plate. Three different temperature conditions (120, 140, and 160 °C) were employed to investigate the effect of dispersion homogeneity of the nanotubes in the base material on the specific heat capacity of the nanomaterials. It is expected that the amount of agglomerated nanotubes decreases with increase of evaporation temperature (shorter elapsed time for evaporation). The results showed that the specific heat capacity of the nanomaterials was enhanced up to 21% in liquid phase. Additionally, it was found that the specific heat capacity enhancement of the nanomaterials, which contained SDS, was more sensitive to the evaporation time. Also, it can be decided that GA is the most appropriate to disperse CNT into the aqueous salt solution. Finally, CNT dispersion was confirmed with scanning electron microscope (SEM) images for pre-DSC and post-DSC samples. Furthermore, theoretical predictions of the specific heat capacity were compared with the experimental results obtained in present study.

scholarly journals The Effects of Nanoparticles on the Specific Heat Capacity of Molten Salts

2018 ◽  
Vol 5 ◽  
pp. 56-65
Author(s):  
Alexander Foldi ◽  
Duy Khang Simba Nguyen ◽  
Yeong Cherng Yap
Keyword(s):  
Heat Capacity ◽  
Thermal Properties ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Molten Salts ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Efficiency Increase ◽  
Solar Power Plants

The desire to increase the efficiency of existing renewable energy sources has been thoroughly researched over the past years. This meta study aimed to investigate existing methods used by previous researchers to increase the Specific Heat Capacity of Molten Salt used for Concentrated Solar Power Plants. Investigations into nanoparticles were explored because of the effect of particle size and concentration can potentially increase the specific heat capacity of the molten salt. Numerous nanoparticles have shown to improve the thermal properties such as Silica (SiO2), Alumina (Al2O3), Titania (TiO2). Our summation was that the addition of nanoparticles into Molten Salts shows an increase in desired thermal properties of the Molten Salts. An efficiency increase of up to 28% was noted in the SHC (Cp) of the Molten Salts when Nanoparticles of 60nm were introduced.

scholarly journals The Effect of In Situ Synthesis of MgO Nanoparticles on the Thermal Properties of Ternary Nitrate

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5737
Author(s):  
Zhiyu Tong ◽  
Linfeng Li ◽  
Yuanyuan Li ◽  
Qingmeng Wang ◽  
Xiaomin Cheng
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Ternary Eutectic ◽  
Mgo Nanoparticles ◽  
Nitrate System

The multiple eutectic nitrates with a low melting point are widely used in the field of solar thermal utilization due to their good thermophysical properties. The addition of nanoparticles can improve the heat transfer and heat storage performance of nitrate. This article explored the effect of MgO nanoparticles on the thermal properties of ternary eutectic nitrates. As a result of the decomposition reaction of the Mg(OH)2 precursor at high temperature, MgO nanoparticles were synthesized in situ in the LiNO3–NaNO3–KNO3 ternary eutectic nitrate system. XRD and Raman results showed that MgO nanoparticles were successfully synthesized in situ in the ternary nitrate system. SEM and EDS results showed no obvious agglomeration. The specific heat capacity of the modified salt is significantly increased. When the content of MgO nanoparticles is 2 wt %, the specific heat of the modified salt in the solid phase and the specific heat in the liquid phase increased by 51.54% and 44.50%, respectively. The heat transfer performance of the modified salt is also significantly improved. When the content of MgO nanoparticles is 5 wt %, the thermal diffusion coefficient of the modified salt is increased by 39.3%. This study also discussed the enhancement mechanism of the specific heat capacity of the molten salt by the nanoparticles mainly due to the higher specific surface energy of MgO and the semi-solid layer that formed between the MgO nanoparticles and the molten salt.

A Literature Review on Novel Nitrate Molten Salt for Heat Storage

2021 ◽  
Vol 881 ◽  
pp. 87-94
Author(s):  
Jin Hua Chen
Keyword(s):  
Thermal Stability ◽  
Heat Capacity ◽  
Melting Point ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Molten Salts ◽  
Heat Storage ◽  
Stability Limit ◽  
Capacity Enhancement

Reducing the melting point, in creasing the thermal stability limit, and enhancing the specific heat capacity of molten salt are the research hotspots in the field of medium and high temperature energy storage in recent years. From the perspectives of the melting point, thermal stability limit, and specific heat capacity of nitrates, we summarize the melting point, thermal stability limit, and specific heat capacity enhancement of molten salts with different compositions and ratios. The melting points of molten salt with different compositions and ratios are compared. Furthermore, the enhancing effect of various nanomaterials on molten salt is elucidated. The application of nitrate molten salt is also summarized to provide a reference for the research and application of novel molten salts. Keywords: Nitrate Molten Salt; Melting Point; Thermal Stability Limit; Specific Heat Capacity; Application

Experimental Investigation of Molten Salt Nanofluid for Solar Thermal Energy Application

2011 ◽  
Author(s):  
Donghyun Shin ◽  
Debjyoti Banerjee
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Thermal Energy ◽  
Molten Salts ◽  
Solar Power ◽  
Solar Thermal ◽  
Wide Range

The overall efficiency of a Concentrated Solar Power (CSP) system is critically dependent on the thermo-physical properties of the Thermal Energy Storage (TES) components and the Heat Transfer Fluid (HTF). Higher operating temperatures in CSP result in enhanced thermal efficiency of the thermodynamic cycles that are used in harnessing solar energy (e.g., using Rankine cycle or Stirling cycle). Particlularly, high specific heat capacity (Cp) and high thermal conductivity (k) of the HTF and TES materials enable reduction in the size and overall cost of solar power systems. However, only a limited number of materials are compatible for the high operating temperature requirements (exceeding 400°C) envisioned for the next generation of CSP systems. Molten salts have a wide range of melting point (200°C∼500°C) and are thermally stable up to 700°C. However, thermal property values of the molten salts are typically quite low (Cp is typically less than ∼2J/g-K and k is typically less than ∼1 W/m-K). To obviate these issues the molten salts can be doped with nanoparticles — resulting in the synthesis / formation of nanomaterials (nanocomposites and nanofluids). Nanofluids are colloidal suspensions formed by doping with minute concentration of nanoparticles. Nanofluids were reported for anomalous enhancement in their thermal conductivity values. In this study, molten salt-based nanofluids were synthesized by liquid solution method. A differential scanning calorimeter (DSC) was used to measure the specific heat capacity values of the proposed nanofluids. The observed enhancement in specific heat is then compared with predictions from conventional thermodynamic models (e.g. thermal equilibrium model or “simple mixing rule”). Transmission Electron Microscopy (TEM) is used to verify that minimal aggregation of nanoparticles occurred before and after the thermocycling experiments. Thermocycling experiments were conducted for repeated measurements of the specific heat capacity by using multiple freeze-thaw cycles of the nanofluids/ nano-composites, respectively. This study demonstrates the feasibility for using novel nanomaterials as high temperature nanofluids for applications in enhancing the operational efficiencies as well as reducing the cost of electricity produced in solar thermal systems utilizing CSP in combination with TES.

scholarly journals Synthesis and Characterization of Molten Salt Nanofluids for Thermal Energy Storage Application in Concentrated Solar Power Plants—Mechanistic Understanding of Specific Heat Capacity Enhancement

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2266
Author(s):  
Binjian Ma ◽  
Donghyun Shin ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Capacity ◽  
Energy Storage ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solar Power ◽  
Alumina Nanoparticles ◽  
Concentrated Solar Power

Molten salts mixed with nanoparticles have been shown as a promising candidate as the thermal energy storage (TES) material in concentrated solar power (CSP) plants. However, the conventional method used to prepare molten salt nanofluid suffers from a high material cost, intensive energy use, and laborious process. In this study, solar salt-Al2O3 nanofluids at three different concentrations are prepared by a one-step method in which the oxide nanoparticles are generated in the salt melt directly from precursors. The morphologies of the obtained nanomaterials are examined under scanning electron microscopy and the specific heat capacities are measured using the temperature history (T-history) method. A non-linear enhancement in the specific heat capacity of molten salt nanofluid is observed from the thermal characterization at a nanoparticle mass concentration of 0.5%, 1.0%, and 1.5%. In particular, a maximum enhancement of 38.7% in specific heat is found for the nanofluid sample prepared with a target nanoparticle mass fraction of 1.0%. Such an enhancement trend is attributed to the formation of secondary nanostructure between the alumina nanoparticles in the molten salt matrix following a locally-dispersed-parcel pattern. These findings provide new insights to understanding the enhanced energy storage capacity of molten salt nanofluids.

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