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.

Experimental Study of Thermal Performance Enhancement of Molten Salt Nanomaterials

2018 ◽  
Author(s):  
Amirhossein Mostafavi ◽  
Vamsi Kiran Eruvaram ◽  
Donghyun Shin
Keyword(s):  
Heat Capacity ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Thermal Performance ◽  
Thermal Energy ◽  
Molten Salts ◽  
Elevated Temperatures ◽  
Performance Enhancement ◽  
Heat Transfer Fluid

Concentrating solar power (CSP) plants are one of the main technologies harvesting solar energy indirectly. In CSP systems, solar radiant light is concentrated into a focal receiver, where heat transfer fluid (HTF) as the energy carrier absorbs solar radiation. Thermal energy storage (TES) is the key method to expand operational time of CSP plants. Consequently, thermo-physical properties of the HTF is an important factor in transferring thermal energy. One of the promising chemicals for this purpose is a mixture of molten salts with stable properties at elevated temperatures. However, low thermal properties of molten salts, such as specific heat capacity (cp) around 1.5 kJ/kg°C, constrain thermal performance of CSP systems. Recently, many studies have been conducted to overcome this shortcoming, by adding minute concentration of nanoparticles. In this work, the selected molten salt eutectic is a mixture of LiNO3–NaNO3 by composition of 54:46 mol. % plus dispersing Silicon Dioxide (SiO2) nanoparticles with 10nm particle size. The results from the measured specific heat capacity by modulated differential scanning calorimeter (MDSC) shows a 9% cp enhancement. Moreover, the viscosity of the mixture is measured by a rheometer and the results show that the viscosity of molten salt samples increases by 27% and this may result in increasing the pumping energy of the HTF. Consequently, overall thermal performance of the selected mixture is investigated by figure of merit (FOM) analysis. The interesting results show an enhancement of the thermal storage of this mixture disregard with the viscosity increase effect.

Investigation of Molten Salt Nanomaterial as Thermal Energy Storage in Concentrated Solar Power

2012 ◽  
Author(s):  
Bharath Dudda ◽  
Donghyun Shin
Keyword(s):  
Heat Capacity ◽  
Energy Storage ◽  
Specific Heat ◽  
Molten Salt ◽  
Specific Heat Capacity ◽  
Thermal Energy ◽  
Molten Salts ◽  
Oxide Nanoparticles ◽  
Concentrated Solar Power ◽  
Mineral Oils

It is a known fact that the solar energy is the most abundant form of renewable source of energy available abundantly in most of the areas. It is relatively the most promising form of renewable energy through which many developed countries like US, Spain are generating electricity using CSP, PV, and other forms of solar cells. This paper mainly focuses on the Concentrated Solar Power (CSP) and about the method of enhancing the Thermal Energy Storage (TES) capacity. Here, we use molten salt as the Heat Transfer Fluid (HTF) as an alternative to mineral oils and other commonly used HTF. The reasons behind using molten salts have also been listed in the paper. The major disadvantage in molten salts as a HTF is their low specific heat capacity compared to mineral oils. The low specific heat capacity of molten salt can be enhanced by dispersing oxide nanoparticles. In this paper, we synthesized molten salt nanomaterials by dispersing oxide nanoparticles in to selcte4d molten salts. Specific heat capacity measurement was performed using a modulated differential scanning calorimeter (MDSC). Hence, we evaluated the use of molten salt nanomaterials as HTF in CSP.

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.

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

scholarly journals Effectiveness of Thermal Properties in Thermal Energy Storage Modeling

2021 ◽  
Vol 7 ◽  
Author(s):  
Law Torres Sevilla ◽  
Jovana Radulovic
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Energy Storage ◽  
Specific Heat ◽  
Melting Temperature ◽  
Latent Heat ◽  
Specific Heat Capacity ◽  
Thermal Energy ◽  
Thermal Energy Storage

This paper studies the influence of material thermal properties on the charging dynamics in a low temperature Thermal Energy Storage, which combines sensible and latent heat. The analysis is based on a small scale packed bed with encapsulated PCMs, numerically solved using COMSOL Multiphysics. The PCMs studied are materials constructed based on typical thermal properties (melting temperature, density, specific heat capacity (solid and liquid), thermal conductivity (solid and liquid) and the latent heat) of storage mediums in literature. The range of values are: 25–65°C for the melting temperature, 10–500 kJ/kg for the latent heat, 600–1,000 kg/m3 for the density, 0.1–0.4 W/mK (solid and liquid) for the thermal conductivity and 1,000–2,200 J/kgK (solid and liquid) for the specific heat capacity. The temperature change is monitored at three different positions along the tank. The system consists of a 2D tank with L/D ratio of 1 at a starting temperature of 20°C. Water, as the heat transfer fluid, enters the tank at 90°C. Results indicate that latent heat is a leading parameter in the performance of the system, and that the thermal properties of the PCM in liquid phase influence the overall heat absorption more than its solid counterpart.

Study on specific heat capacity and thermal conductivity of uranium nitride

Kerntechnik ◽  
2021 ◽  
Vol 86 (6) ◽  
pp. 400-403
Author(s):  
M. Gokbulut ◽  
G. Gursoy ◽  
Ş. Aşcı ◽  
E. Eser
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Nuclear Material ◽  
Nuclear Materials ◽  
Wide Range ◽  
Calculation Results ◽  
Uranium Nitride ◽  
Einstein Approximation

Abstract In this study, we have proposed an analytical method for calculating the specific heat capacity of uranium nitride nuclear material. The specific heat capacity results have obtained by the use of the Debye-Einstein approximation. The thermal conductivity of nuclear material has been obtained by using the experimental data of thermal diffusivity and the calculation results of specific heat capacity. This method shows that our results are satisfactory for the wide range temperature variations. The proposed approach can be easily applied to determine the thermodynamic properties of the other nuclear materials.

Review of Molten Salt Nanofluids

2016 ◽  
Author(s):  
Farzam Mortazavi ◽  
Debjyoti Banerjee
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Specific Heat ◽  
Molten Salt ◽  
Silica Nanoparticles ◽  
Specific Heat Capacity ◽  
Nuclear Power ◽  
Power Production ◽  
Dense Layer ◽  
The Cost

Literature review of molten salt nanofluids is performed in this study with focus on the thermo-fluidic properties and performance in thermal management applications. The colloidal mixture of nanoparticles in a base liquid phase is called nanofluid. Molten salts such as alkali nitrate eutectics, alkali carbonate eutectics and alkali chloride eutectics have high melting temperatures. These materials are suitable for various high temperature applications, including as Heat Transfer Fluid (HTF), Thermal Energy Storage (TES), Concentrated Solar Power (CSP) plants, nuclear power, etc. The major drawback of molten salt materials is their low thermal conductivity and specific heat capacity. Enhancing the thermo-physical properties of molten salt materials can lower the cost of power production involving these materials (e.g., as HTF and/ or TES in CSP or nuclear power plants. Mixing molten alt eutectics with nanoparticles (e.g., molten salt nanofluids) can provide a cost-effective technique for enhancing the specific heat capacity and thermal conductivity which in turn can enable the reduction in the cost of power production. In this review - the following topics involving molten salt nanofluids were explored: thermo-physical property measurements, numerical modeling (e.g., Molecular Dynamics/ MD simulations), materials characterization (e.g., using electron microscopy techniques — such as SEM and TEM). For example, SEM studies in conjunction with MD simulation results confirm the formation of a dense layer of fluid molecules on the surface of nanoparticles that can enhance the specific heat capacity of these molten salt nanomaterials. Subsequently the concepts of nanofins was explored (which involves the study of interfacial thermal impedance, such as resistance, capacitance and diodicity). The contribution of these interfacial thermal impedances to the enhancement of specific heat capacity and thermal conductivity are also explored. Specific heat enhancement as high as 100% has been observed for various molten salt eutectics when doped with 1.5% (weight) silica nanoparticles. Various synthesis protocols such as one-step, two-step and three-step methods as well as conventional experimental methods used for specific heat capacity measurement are compared and examined. A review of the effects of concentration, nanoparticle size, temperature, base fluid, and nanofluid chemical properties is also performed. Other topics of interest are the anomalous enhancement of thermal conductivity in molten salt nanofluids which contradict typical predictions obtained from using the effective medium theory. The available data in literature shows enhancement in thermal conductivity by as much as 35–45% for carbonate eutectics doped with silica nanoparticles at 1% mass fraction. The possible mechanisms suggested for this improvement are briefly discussed and compared with experimental observations (e.g., using SEM). In addition, nanofluids often display non-Newtonian rheological behavior. This necessitates a rigorous study, since the applications of nanofluids will impact the required pumping power. Studies show that the rheological properties of molten salt nanofluids are a function of base salt composition, shape of nanoparticles selected, chemical formula of nanoparticles, concentration of nanoparticles, size of nanoparticles, temperature, shear rate and synthesis protocol of the nanofluid. Several models are introduced to predict the viscosity variation along with their advantageous and disadvantages. SEM results show agglomeration of nanoparticles can be reduced by doping the nanofluids with very small values of mass fractions of additives such as Gum Arabic.

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