scholarly journals Enhanced Thermal Characteristics of NG Based Acetamide Composites

2019 ◽  
Vol 8 (10) ◽  
pp. 4227-4231 ◽  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Storage System ◽  
Thermal Characteristics ◽  
Energy Storage System ◽  
Melting Time

Fatty acids are a distinguished category of phase change materials (PCM). However, their inferior thermal conductivity value restricts their potential for thermal energy storage system. Carbonaceous nanomaterials have emerged as promising thermal conductivity enhancer materials for organic PCMs. The present study focuses on preparing a novel PCM nanocomposite comprising of small amount of nanographite (NG) in molten acetamide, an organic PCM, for elevation of the thermal characteristics and examining the trend of the nanocomposite through the course of charging / discharging process. These PCM-nanocomposites are prepared by dispersing NG in molten acetamide with weight fractions of 0.1, 0.2, 0.3, 0.4 and 0.5 %. The scanning electronic microscopic (SEM) analysis was conducted for the characterization of PCM nanocomposite. The energy storage behaviour of the prepared nanocomposites were analyzed with the help of differential scanning calorimeter instruments, which showed that there is no observable variation in the melting point of the nanocomposite, and a decline in the latent heat values. Furthermore, thermal conductivity trend of the nanocomposites caused by NG addition was investigated, which indicated enhancement of thermal conductivity with increasing NG concentration. Further, nanocomposites with a 0.4 wt. % of NG, displayed appreciable increase in rate of heat transfer, reducing melting time and solidification time by 48 and 47 %, respectively. The prepared PCM nanocomposites displayed superior heat transfer trend, permitting substantial thermal energy storage.

scholarly journals A Numerıcal Investıgatıon of The Thermal Behavıor of Dıfferent Phase Change Materıals In Thermal Energy Storage Systems

2021 ◽  
Author(s):  
Mehmet Kan
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Behavior ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Storage System ◽  
Energy Storage System ◽  
Thermal Energy Storage System ◽  
Thermal Energy Storage Systems

Abstract Phase change materials (PCM) are widely used in thermal energy storage systems due to their high heat storage properties. However, due to the low thermal conductivity of PCMs, different surface areas are employed in order to increase the amount of energy. One of these methods is to use fins with high thermal conductivity. This study numerically investigated the thermal behavior of different PCMs (paraffin, paraffin wax, polyethylene glycol 6000) during the melting process in a thermal energy storage system with 15 fins. A FOX 50 heat flow meter was used for thermal conductivity measurements of these PCMs, and TA DSC Q200 (Differential Scanning Calorimetry) devices were used for specific heat measurements. The thermal property data of these measured PCMs were used in a time-dependent analysis. With the PCM data obtained, time-dependent thermal analyses were carried out using the Ansys-Fluent program based on the Computational Fluid Dynamics (CFD) method. The effect of these different PCMs on the melting processes was investigated by using water at 75oC in a 15-fin thermal storage system by observing their thermal behavior in the thermal energy storage system. In addition, cost analyses were conducted by determining the required amount of PCMs for the thermal storage system.

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.

Computational Modeling of Latent Thermal Energy Storage System With Embedded Heat Pipes

2010 ◽  
Author(s):  
Karthik Nithyanandam ◽  
Ranga Pitchumani
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Heat Pipes ◽  
Energy Storage System ◽  
High Energy ◽  
Thermal Energy Storage System

Due to the intermittent nature of solar energy availability, storing sun’s energy in the form of latent thermal energy of a phase change material (PCM) is an effective technique that is widely used in energy storage and load management applications. In a Latent Thermal Energy Storage System (LTES), a heat transfer fluid (HTF) exchanges energy with a PCM. The advantages of an LTES include its isothermal operation and high energy storage density. However, the low thermal conductivity of PCM poses a significant disadvantage due to reduction in the rate at which the PCM can be melted (charging) or solidified (discharging). This paper explores an approach to reducing the thermal resistance of PCM in a LTES through embedded heat pipes. A heat pipe is a passive heat transfer device that efficiently transfers large amount of energy between the PCM and HTF thus indirectly amplifying the effective thermal conductivity of PCM. A transient computational analysis of a shell and tube LTES embedded with heat pipes is performed for charging to determine the position of melt front and energy stored as a function of time. The influence of the number and orientation of heat pipes and design configuration of the system is analyzed to identify configurations that lead to improved effectiveness.

Solid/Liquid Phase Change Heat Transfer in Latent Heat Thermal Energy Storage

2009 ◽  
Author(s):  
D. Zhou ◽  
C. Y. Zhao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Calcium Chloride ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Metal Foams ◽  
Chloride Hexahydrate

Phase change materials (PCMs) have been widely used for thermal energy storage systems due to their capability of storing and releasing large amounts of energy with a small volume and a moderate temperature variation. Most PCMs suffer the common problem of low thermal conductivity, being around 0.2 and 0.5 for paraffin and inorganic salts, respectively, which prolongs the charging and discharging period. In an attempt to improve the thermal conductivity of phase change materials, the graphite or metallic matrix is often embedded within PCMs to enhance the heat transfer. This paper presents an experimental study on heat transfer characteristics of PCMs embedded with open-celled metal foams. In this study both paraffin wax and calcium chloride hexahydrate are employed as the heat storage media. The transient heat transfer behavior is measured. Compared to the results of pure PCMs samples, the investigation shows that the additions of metal foams can double the overall heat transfer rate during the melting process. The results of calcium chloride hexahydrate are also compared with those of paraffin wax.

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