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.

Enhanced thermal performance analysis of buried heat transfer tubes thermal storage system filled with microcapsule particles

2020 ◽  
Vol 44 (13) ◽  
pp. 10414-10429
Author(s):  
Yun Liu ◽  
Tian‐tian Chen ◽  
Yue Dong ◽  
Yong‐Hua Li ◽  
Da‐Wen Zhong
Keyword(s):  
Heat Transfer ◽  
Performance Analysis ◽  
Thermal Performance ◽  
Storage System ◽  
Thermal Storage

Effect of Natural Convection on Thermal Energy Storage in Supercritical Fluids

2013 ◽  
Author(s):  
Reza Baghaei Lakeh ◽  
Adrienne S. Lavine ◽  
H. Pirouz Kavehpour ◽  
Gani B. Ganapathi ◽  
Richard E. Wirz
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Energy Storage ◽  
Supercritical Fluid ◽  
Supercritical Fluids ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Thermal Storage

Heat transfer to the storage fluid is a critical subject in thermal energy storage systems. The storage fluids that are proposed for supercritical thermal storage system are organic fluids that have poor thermal conductivity; therefore, pure conduction will not be an efficient heat transfer mechanism for the system. The current study concerns a supercritical thermal energy storage system consisting of horizontal tubes filled with a supercritical fluid. The results of this study show that the heat transfer to the supercritical fluid is highly dominated by natural convection. The buoyancy-driven flow inside the storage tubes dominates the flow field and enhances the heat transfer dramatically. Depending on the diameter of the storage tube, the buoyancy-driven flow may be laminar or turbulent. The natural convection has a significant effect on reducing the charge time compared to pure conduction. It was concluded that although the thermal conductivity of the organic supercritical fluids are relatively low, the effective laminar or turbulent natural convection compensates for this deficiency and enables the supercritical thermal storage to charge effectively.

Investigation of Using Dispersed Particle and Branching Heat Exchnager in Medium Temperature Thermal Energy Storage System to Achieve Maximum Utilization of Solar Power

2013 ◽  
Author(s):  
A. M. M. G. Hasib ◽  
Rambod Rayegan ◽  
Yong X. Tao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Power Generation ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Energy Storage System ◽  
Medium Temperature ◽  
Change Material

Maximum utilization of solar energy is very critical to achieve, because a significant portion of solar energy is lost in the form of heat. In that case Thermal Energy Storage (TES) can play a significant role by capturing the energy in the form of heat and later on can be used as a backup source of energy for utilizing it in critical time. On the other side, from the view point of conservation of energy, energy cannot be created or destroyed, but surprisingly a significant amount of energy cannot be utilized due to the instantaneous nature of conventional power generation. So storing Energy is the most unique idea that can act as a strong backup for the instantaneous nature of power generation as it not only adds up to the power generation capacity but also serves to be the most reliable medium of supplying power when the energy demand is at peak. In the authors’ previous work a phase change material (molten solar salt comprised of 60% NaNO3+40%KNO3) and a system design for thermal energy storage (TES) system integrated with a solar Organic Rankine Cycle (ORC) has been proposed. The associated research problems investigated for phase change material (PCM) are the low thermal conductivity and low rate of heat transfer from heat transfer fluid to PCM. In this study a detailed numerical modeling of the proposed design using MATLAB code and the relevant calculation and results are discussed. The numerical model is based on 1-D finite difference explicit technique using the fixed grid enthalpy method. To overcome the research problem highly conductive nano-particle graphite is used to enhance the effective thermal conductivity of the PCM material in theoretical calculation. In the later part of the study results from the numerical computation have been utilized to demonstrate a comparison between a conventional heating system (with a simple single tube as a heat exchanger) and a branching heat exchanger in PCM thermal energy storage system using NTU-Effectiveness method. The comparison results show a significant amount of improvement using branching network and mixing nano-particle in terms of heat transfer, thermal conductivity enhancement, charging time minimization and pressure drop decrease. The results of this study can convince us that the proposed medium temperature TES system coupled with solar ORC can be a stepping-stone for energy efficient and sustainable future in small-scale power generation as the system proves to be better in terms of enhanced heat transfer, increased thermal conductivity and overall sustainability.

scholarly journals Solar Salt Latent Heat Thermal Storage for a Small Solar Organic Rankine Cycle Plant

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Sol-Carolina Costa ◽  
Khamid Mahkamov ◽  
Murat Kenisarin ◽  
Mohammad Ismail ◽  
Kevin Lynn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Latent Heat ◽  
Storage System ◽  
Organic Rankine Cycle ◽  
Heat Pipes ◽  
Rankine Cycle ◽  
Thermal Storage ◽  
Thermal Bonding ◽  
Solar Salt ◽  
Computational Fluid Dynamics Analysis

Abstract The design of the latent heat thermal storage system (LHTESS) was developed with a thermal capacity of about 100 kW h as a part of small solar plant based on the organic Rankine cycle (ORC). The phase change material (PCM) used is solar salt with the melting/solidification temperature of about 220 °C. Thermophysical properties of the PCM were measured, including its phase transition temperature, heat of fusion, specific heat, and thermal conductivity. The design of the thermal storage was finalized by means of the 3D computational fluid dynamics analysis. The thermal storage system is modular, and the thermal energy is delivered with the use of thermal oil, heated by Fresnel mirrors. The heat is transferred into and from the PCM in the casing using bidirectional heat pipes, filled with water. A set of metallic screens are installed in the box with the pitch of 8–10 mm to enhance the heat transfer from heat pipes to the PCM and vice-versa during the charging and discharging processes, which take about 4 h. This work presents a numerical study on the use of metallic fins without thermal bonding as a heat transfer enhancement method for the solar salt LHTESS. The results show that the absence of the thermal bonding between fins and heat pipes (there was a gap of 0.5 mm between them) did not result in a significant reduction of charging or discharging periods. As expected, aluminum fins provide better performance in comparison with steel ones due to the difference in the material conductivity. The main advantage observed for the case of using aluminum fins was the lower temperature gradient across the LHTESS.

Conjugate Heat Transfer in Latent Heat Thermal Storage System With Cross Plate Fins

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Rajesh Alayil ◽  
C. Balaji
Keyword(s):  
Heat Transfer ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Storage System ◽  
Thermal Storage ◽  
High Heat ◽  
Heat Fluxes ◽  
Isothermal Conditions ◽  
Latent Heat Capacity ◽  
Composite Heat

Latent heat thermal storage systems (LHTS) utilize their latent heat capacity to dissipate high heat fluxes while maintaining quasi-isothermal conditions. Phase change materials (PCMs) absorb a large amount of energy during their phase transformation from solid to liquid, maintaining quasi-isothermal conditions. However, they are often beset with low thermal conductivities which necessitate the use of a thermal conductivity enhancer (TCE) as it is impossible to design a device that can completely avoid sensible heat in the premelting or postmelting phase. In this study, the heat transfer performance of LHTS with cross plate fins as a TCE is numerically investigated for different values of fin thicknesses and fin numbers along the length and breadth. A hybrid artificial neural network coupled genetic algorithm (ANN–GA) is then used to obtain the optimized dimensions for the composite heat sink with cross plate fins as TCE for a fixed volume and a specific heat flux input. The numerically optimized configuration is finally validated with in-house experiments.

Numerical Investigation of Charging and Discharging Processes of a Shell and Tube Nano-Enhanced Latent Thermal Storage Unit

2020 ◽  
Vol 12 (2) ◽  
Author(s):  
Khaoula Nedjem ◽  
Mohamed Teggar ◽  
Kamal Adbel Radi Ismail ◽  
Driss Nehari
Keyword(s):  
Thermal Conductivity ◽  
Numerical Model ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Control Volume ◽  
Thermal Storage ◽  
Solar Thermal ◽  
Melting Time ◽  
Storage Unit ◽  
Shell And Tube

Abstract Phase change materials (PCMs) generally suffer from low thermal conductivity which limits their application in thermal systems. The effective thermal conductivity may be improved by including fins, metallic powders, fine wires, and nanoparticles. The objective of this study is to investigate the thermal performance of graphene nanoplatelets (GNPs) dispersed in small quantities in 1-tetradecanol (C14H30O) PCM. This nano-enhanced PCM (NPCM) is placed in the annular space of a shell and tube in a solar thermal storage unit. The numerical simulations have been carried out using a numerical model based on the enthalpy-porosity and the control volume methods. The numerical model has been successfully validated by comparison with experimental data available in the literature. The numerical results showed that the higher the GNPs concentration, the lower the stored energy. The higher the GNPs concentration the shorter the discharging time. But, during the charging process, though the reduction in the melting time by 9.5% for GNPs concentration increase from 0 to 1 wt%, the melting time increased in contrast by 10.5% for GNPs content increasing from 1 to 3 wt%. For the GNPs concentration of 3 wt%, the heat transfer rate enhancement was limited by an undesirable increase in viscosity which led to weak natural convection and hence a longer charging time. Thus, the GNPs concentration of 1 wt% showed better thermal performance than that of 3 wt% concentration. These results may guide the improvement of solar thermal storage by dispersing GNPs in PCM.

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