Investigation of Nanofluids for Solar Thermal Storage Applications

2009 ◽  
Author(s):  
Donghyun Shin ◽  
Debjyoti Banerjee
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Transport Properties ◽  
Experimental Studies ◽  
Thermal Storage ◽  
Nano Particles ◽  
Solar Thermal ◽  
Optimum Performance ◽  
Solar Thermal Applications

Nanofluids are synthesized by doping solvents with nano-particles at minute concentrations (typically less than 1 percentage by volume). Experimental studies have shown that nano-particles can dramatically enhance the specific heat of various liquid solvents. This is also associated with enhancement of other transport properties (e.g., viscosity, thermal conductivity, diffusivity, etc.). Hence, nanofluids are attractive materials for solar thermal applications. The objective of this study is to investigate the optimum performance of various nanofluids for solar thermal storage applications. Dimensional analyses and similitude techniques will be used to theoretically estimate the enhancement of transport properties of various nanofluids to predict their efficacy for solar thermal storage applications.

Enhanced Thermal Properties of PCM Based Nanofluid for Solar Thermal Energy Storage

2010 ◽  
Author(s):  
Donghyun Shin ◽  
Debjyoti Banerjee
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Transport Properties ◽  
Experimental Studies ◽  
Thermal Storage ◽  
Nano Particles ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
Heat Diffusivity ◽  
Solar Thermal Applications

Nanofluids are synthesized by doping solvents with nano-particles at minute concentrations (typically less than 1 percentage by volume). Experimental studies have shown that nano-particles can dramatically enhance thermal conductivity of various liquid solvents. This is also associated with enhancement of other transport properties (e.g., viscosity, specific heat, diffusivity, etc.). Hence, nanofluids are attractive materials for solar thermal applications. The objective of this study is to investigate the optimum performance of various nanofluids for solar thermal storage applications. Dimensional analyses and similitude techniques will be used to theoretically estimate the enhancement of transport properties of various nanofluids to predict their efficacy for solar thermal storage applications.

scholarly journals Comparative Analysis of Thermohydraulic Properties of Nano-Refrigerants

2018 ◽  
Vol 7 (4.12) ◽  
pp. 34
Author(s):  
Jai Parkash ◽  
Sanjeev Saini ◽  
Ankush Kohli ◽  
Balkar Singh
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Volume Concentration ◽  
Constant Pressure ◽  
Experimental Models ◽  
Nano Particles ◽  
Refrigeration System ◽  
Volumetric Concentration ◽  
Overall Performance ◽  
Compressor Work

The nano-particles achieved the focus of the researchers in the field of refrigeration, due to its capability to change the properties of refrigerants upto a large extent. Nanofluids based on refrigerant is known as nano refrigerants and provided an improvement in thermophysical properties of various refrigerants in different terms. Different theoretical and experimental models are provided by the researchers have been used for the evaluation of different properties of refrigerant in terms of thermal conductivity, density, specific heat and viscosity of the refrigerants. In this effort, a number of models, and correlations have been used to result in the improvement in these properties of nano refrigerants. This is achieved by the addition of nanoparticles with varying volume concentration of 1% to 5 %. The analyses have been made within a temperature range of 190K- 269K at a constant pressure of 0.3 MPa. The study is elaborated to compare the various refrigerants which are R11, R12, R22, R134a and R141b with the addition of different nano-particles which are TiO2, Al2O3, ZnO and CuO at evaporator conditions. The addition of ZnO has given a good impact on the thermal conductivity of refrigerants. Effective viscosity of nano refrigerants depends upon the viscosity of refrigerants and volumetric concentration of nano-sized particles. Specific Heat shows the negative variation with the addition of nanoparticles but increased with the rise in temperature. The density of nano refrigerants depends upon the density of base refrigerant, Density of nanoparticles, volumetric concentration of nanoparticles. In future, the study can be elaborated in terms of compressor work, power consumption and overall performance of refrigeration system.  

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.

Evaluation of Key Design Parameters of an Encapsulated Latent Heat Thermal Storage Unit

2016 ◽  
Vol 852 ◽  
pp. 652-658
Author(s):  
N. Lakshmi Narasimhan ◽  
P. Karthik
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Latent Heat ◽  
Thermal Response ◽  
Thermal Storage ◽  
Heat Transfer Fluid ◽  
Design Parameters ◽  
Inlet Temperature ◽  
Storage Unit ◽  
Melting Temperatures

The present work numerically investigates for a latent heat thermal storage (LHTS) unit, the effect of key design parameters such as the inlet temperature of the heat transfer fluid (HTF), initial and melting temperatures of the PCM, thermophysical parameters such as specific heat, thermal conductivity etc., on its performance. A numerical model has been developed considering the discharging mode of operation and solved employing finite difference technique. The parametric study reveals that the effect of HTF inlet temperature on the unit's thermal response is more compared to initial temperature of the PCM and the influence of thermal conductivity of the PCM is very strong compared to specific heat capacity of the solid PCM

Heat Transfer Characterization and Optimization of Latent Heat Thermal Storage System Using Fins for Medium Temperature Solar Applications

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Asmita Shinde ◽  
Sankalp Arpit ◽  
Pramod KM ◽  
Peddy V C. Rao ◽  
Sandip K. Saha
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Latent Heat ◽  
Optimum Design ◽  
Thermal Performance ◽  
Storage System ◽  
Thermal Storage ◽  
Solar Thermal ◽  
Medium Temperature ◽  
Fin Thickness

While solar thermal power plants are increasingly gaining attention and have demonstrated their applications, extending electricity generation after the sunset using phase change material (PCM) still remains a grand challenge. Most of the organic PCMs are known to possess high energy density per unit volume, but low thermal conductivity, that necessitates the use of thermal conductivity enhancers (TCEs) to augment heat transfer within PCM. In this paper, thermal performance and optimization of shell and tube heat exchanger-based latent heat thermal energy storage system (LHTES) using fins as TCE for medium temperature (<300 °C) organic Rankine cycle (ORC)-based solar thermal plant are presented. A commercial grade organic PCM, A164 with melting temperature of 168.7 °C is filled in the shell side and heat transfer fluid (HTF), Hytherm 600 flows through the tubes. A three-dimensional numerical model using enthalpy technique is developed to study the solidification of PCM, with and without fin. Further, the effect of geometrical parameters of fin, such as fin thickness, fin height, and number of fin on the thermal performance of LHTES, is studied. It is found that fin thickness and number of fin play significant role on the solidification process of PCM. Finally, the optimum design of the fin geometry is determined by maximizing the combined objective of HTF outlet temperature and solid fraction of PCM at the end of the discharging period. The latent heat thermal storage system with 24 fins, each of 1 mm thickness and 7 mm height, is found to be the optimum design for the given set of operating parameters.

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