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.

The Optimum Design of Stratified Thermal Energy Storage Systems—Part II: Completion of the Analytical Model, Presentation and Interpretation of the Results

1992 ◽  
Vol 114 (3) ◽  
pp. 204-208 ◽  
Author(s):  
R. J. Krane ◽  
M. J. M. Krane
Keyword(s):  
Energy Storage ◽  
Heat Exchanger ◽  
Analytical Model ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Energy Storage System ◽  
Thermal Energy Storage System ◽  
Thermal Energy Storage Systems ◽  
Performance Gains

This investigation is presented in two parts. The basic analytical model is developed in Part I. Part II includes the completion of the analytical model and the results of an optimization study performed with this model. The results show that: 1) Significant performance gains, that is, reductions in the entropy generation number on the order of 10 percent, are possible by employing perfectly stratified thermal energy storage systems that are designed on the basis of the second law of thermodynamics. 2) These performance gains are mainly due to the complete elimination of the entropy generation due to heat transfer through finite temperature differences within the storage element. 3) In general, the optimum design of a perfectly stratified thermal energy storage system requires the use of a very large heat exchanger; however, it is possible to employ a much smaller than optimum heat exchanger without seriously degrading the superior performance of the system. 4) The operation of a stratified system is quite flexible because it has no optimum storage time. 5) The optimum values of the capacity rate ratios, (φR)opt and (φR)opt, for a perfectly stratified thermal energy storage system are in general not equal to unity; however, this finding is shown to be in concert with Bejan’s theory of “remanent” irreversibilities for a heat exchanger.

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.

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