scholarly journals Optimization of Nano-Additive Characteristics to Improve the Efficiency of a Shell and Tube Thermal Energy Storage System Using a Hybrid Procedure: DOE, ANN, MCDM, MOO, and CFD Modeling

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3235
Author(s):  
Mohammed Algarni ◽  
Mashhour A. Alazwari ◽  
Mohammad Reza Safaei
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Specific Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Hybrid Procedure ◽  
Stored Energy ◽  
Shell And Tube ◽  
Nano Additives ◽  
Change Material

Using nano-enhanced phase change material (NePCM) rather than pure PCM significantly affects the melting/solidification duration and the stored energy, which are two critical design parameters for latent heat thermal energy storage (LHTES) systems. The present article employs a hybrid procedure based on the design of experiments (DOE), computational fluid dynamics (CFD), artificial neural networks (ANNs), multi-objective optimization (MOO), and multi-criteria decision making (MCDM) to optimize the properties of nano-additives dispersed in a shell and tube LHTES system containing paraffin wax as a phase change material (PCM). Four important properties of nano-additives were considered as optimization variables: volume fraction and thermophysical properties, precisely, specific heat, density, and thermal conductivity. The primary objective was to simultaneously reduce the melting duration and increase the total stored energy. To this end, a five-step hybrid optimization process is presented in this paper. In the first step, the DOE technique is used to design the required simulations for the optimal search of the design space. The second step simulates the melting process through a CFD approach. The third step, which utilizes ANNs, presents polynomial models for objective functions in terms of optimization variables. MOO is used in the fourth step to generate a set of optimal Pareto points. Finally, in the fifth step, selected optimal points with various features are provided using various MCDM methods. The results indicate that nearly 97% of the Pareto points in the considered shell and tube LHTES system had a nano-additive thermal conductivity greater than 180 Wm−1K−1. Furthermore, the density of nano-additives was observed to be greater than 9950 kgm−3 for approximately 86% of the optimal solutions. Additionally, approximately 95% of optimal points had a nano-additive specific heat of greater than 795 Jkg−1K−1.

Enhanced thermal conductivity of phase change materials with ultrathin-graphite foams for thermal energy storage

2014 ◽  
Vol 7 (3) ◽  
pp. 1185-1192 ◽  
Author(s):  
Hengxing Ji ◽  
Daniel P. Sellan ◽  
Michael T. Pettes ◽  
Xianghua Kong ◽  
Junyi Ji ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Specific Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Heat Of Fusion ◽  
Change Material ◽  
Enhanced Thermal Conductivity

Embedding continuous ultrathin-graphite foams (UGFs) with volume fractions as low as 0.8–1.2 vol% in a phase change material (PCM) can increase the effective thermal conductivity by up to 18 times, with negligible change in the melting temperature or mass specific heat of fusion.

scholarly journals Si3N4 nanofelts/paraffin composites as novel thermal energy storage architecture

2020 ◽  
Vol 56 (2) ◽  
pp. 1537-1550
Author(s):  
Francesco Valentini ◽  
Andrea Dorigato ◽  
Alessandro Pegoretti ◽  
Michele Tomasi ◽  
Gian D. Sorarù ◽  
...  
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Composite Structures ◽  
Liquid Paraffin ◽  
Stored Energy ◽  
Storage Efficiency ◽  
Novel Material ◽  
Energy Storage Efficiency ◽  
Change Material

Abstract The environmental problems associated with global warming are urging the development of novel systems to manage and reduce the energy consumption. An attractive route to improve the energy efficiency of civil buildings is to store the thermal energy thanks, during heating, to the phase transition of a phase-change material (as paraffin) from the solid to the liquid state and vice versa. The stored energy can be then released under cooling. Herein, we developed a novel material (nanofelt) constituted by Si3N4 nanobelts able to absorb huge amounts of liquid paraffin in the molten state and to act as an efficient shape stabilizer. The nanofelt manufacturing technology is very simple and easy to be scaled-up. The effect of the Si3N4 nanofelts density and microstructure on the paraffin sorption and leakage and on the thermal properties of the resulting composite structures is investigated. It is shown that the produced Si3N4/paraffin composites are able to retain enormous fractions of paraffin (up to 70 wt%) after 44 day of desorption test on absorbent paper towel. The thermal energy storage efficiency measured through calorimetric tests is as high as 77.4% in heating and 80.1% in cooling.

Experimental Characterization of the Thermal Diffusivity of Paraffin Phase Change Material Embedded With Herringbone Style Graphite Nanofibers

2012 ◽  
Author(s):  
Ronald J. Warzoha ◽  
Anthony Rao ◽  
Rebecca Weigand ◽  
Amy S. Fleischer
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Diffusivity ◽  
Phase Change ◽  
Specific Heat ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Melt Temperature ◽  
Graphite Nanofibers

Phase change materials (PCMs) are promising candidates for thermal energy storage due to their intrinsically high values of latent heat. However, PCMs are unable to effectively utilize all of their energy storage capacities due to their poor thermophysical properties. In this study, the effect of graphite nanofibers (diameter = 2 to 1000 nm, length = 100μm) on the bulk thermal properties of paraffin PCM (Tmelt = 56 °C) is investigated. Material properties including effective thermal conductivity, specific heat, latent heat, melt temperature and thermal diffusivity are measured using a Differential Scanning Calorimeter (DSC) and comparative reference bar apparatus. Results suggest that the addition of nanostructures not only increases thermal conductivity by up to 180%, but also reduces the specific heat capacity and density of nano-enhanced paraffin, leading to improved thermal diffusivity and thus greater utilization of its latent heat for transient thermal energy storage.

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