Thermodynamic Optimization of Phase-Change Energy Storage Using Two or More Materials

1992 ◽  
Vol 114 (1) ◽  
pp. 84-90 ◽  
Author(s):  
J. S. Lim ◽  
A. Bejan ◽  
J. H. Kim
Keyword(s):  
Energy Storage ◽  
Melting Point ◽  
Phase Change ◽  
Phase Change Material ◽  
Finite Thickness ◽  
Melting Process ◽  
Two Phase ◽  
In Series ◽  
Optimal Melting ◽  
Change Material

This paper documents the relative merits of using more than one type of phase-change material for energy storage. In the case of two phase-change systems in series, which are melted by the same stream of hot fluid, there exists an optimal melting point for each of the two materials. The first (upstream) system has the higher of the two melting points. The second part of the paper addresses the theoretical limit in which the melting point can vary continuously along the source stream, i.e., when an infinite number of different (and small) phase-change systems are being heated in series. It is shown that the performance of this scheme is equivalent to that which uses an optimum single phase-change material, in which the hot stream remains unmixed during the melting process. The time dependence, finite thickness and longitudinal variation of the melt layer caused by an unmixed stream are considered in the third part of the paper. It is shown that these features have a negligible effect on the optimal melting temperature, which is slightly higher than (T∞Te)1/2.

scholarly journals Numerical investigation on the phase change process of different shaped macro encapsulated PCM

2018 ◽  
Vol 7 (4.5) ◽  
pp. 587
Author(s):  
Jay R. Patel ◽  
Manish K. Rathod
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Melting Process ◽  
Complex Flow ◽  
Ansys Fluent ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Convection Dominated ◽  
Change Material

Latent heat energy storage using macro encapsulated phase change material is an emerging technique for thermal energy storage applica- tions. The main aim of the present investigation is to investigate the melting process of phase change material filled in different shaped configurations. The selected different cavities are square, circular and triangular. A mathematical model based on convection dominated melting is required to be developed, especially in view of the complex flow geometries encountered in such problems. Thus, an attempt has been made to develop a model using ANSYS Fluent 16.2 to investigate the heat transfer rate and solid-liquid interface visualization of PCM filled in different shapes of cavity. It is found that triangular shaped macro encapsulated PCM melts faster than square and circu- lar shaped encapsulated PCM.   

scholarly journals Phase Change Material Melting Process in a Thermal Energy Storage System for Applications in Buildings

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3254 ◽  
Author(s):  
Túlio Nascimento Porto ◽  
João M. P. Q. Delgado ◽  
Ana Sofia Guimarães ◽  
Hortência Luma Fernandes Magalhães ◽  
Gicelia Moreira ◽  
...  
Keyword(s):  
Heat Flux ◽  
Energy Storage ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Melting Process ◽  
Average Heat ◽  
Change Material

The development of thermal energy storage systems is a possible solution in the search for reductions in the difference between the global energy supply and demand. In this context, the ability of some materials, the so-called phase change materials (PCMs), to absorb and release large amounts of energy under specific periods and operating conditions has been verified. The applications of these materials are limited due to their low thermal conductivity, and thus, it is necessary to associate them with high-conductivity materials, such as metals, to make the control of energy absorption and release times possible. Bearing this in mind, this paper presents a numerical analysis of the melting process of a PCM into a triplex tube heat exchanger (TTHX) with finned copper tubes, which allowed for the heat transfer between a heating fluid (water) and the phase change material to power a liquid-desiccant air conditioning system. Through the analysis of the temperature fields, liquid fractions, and velocities, as well as the phase transition, it was possible to describe the material charging process; then, the results were compared with experimental data, which are available in the specialized literature, and presented mean errors of less than 10%. The total required time to completely melt the PCM was about 105.5 min with the water being injected into the TTHX at a flow rate of 8.3 L/min and a temperature of 90 °C. It was observed that the latent energy that accumulated during the melting process was 1330 kJ, while the accumulated sensitive energy was 835 kJ. The average heat flux at the internal surface of the inner tube was about 3 times higher than the average heat flux at the outer surface of the TTHX intermediate tube due to the velocity gradients that developed in the internal part of the heat exchanger, and was about 10 times more intense than those observed in the external region of the equipment.

scholarly journals The Use of Eutectic Fe-Si-B Alloy as a Phase Change Material in Thermal Energy Storage Systems

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2312 ◽  
Author(s):  
Jianmeng Jiao ◽  
Bettina Grorud ◽  
Caroline Sindland ◽  
Jafar Safarian ◽  
Kai Tang ◽  
...  
Keyword(s):  
Energy Storage ◽  
Melting Point ◽  
Phase Change ◽  
Phase Change Material ◽  
Refractory Material ◽  
Thermal Energy ◽  
Eutectic Alloy ◽  
Thermal Energy Storage ◽  
Graphite Crucible ◽  
Change Material

Fe-26.38Si-9.35B eutectic alloy is proposed as a phase change material (PCM) as it exhibits high latent heat, high thermal conductivity, moderate melting point, and low cost. For successful implementation of it in the latent heat thermal energy storage (LHTES) systems, we investigate the use of graphite as a refractory material that withstands long-term melting/solidification in contact with the Fe-26.38Si-9.35B alloy. The PCM has been thermally cycled up to 1–4 times below and above its melting point at the temperature interval of 20 °C or 100 °C. It is observed that this eutectic alloy shows good thermal stability over a small temperature range of 1057–1257 °C. Some SiC and B4C solid precipitation will be formed at the top of the alloy. However, it does not seem to increase with time. The graphite crucible as a refractory material will produce a protective layer of SiC and B4C that will hinder the interaction between the PCM and the crucible. The small volume change during solidification will not break the graphite crucible during cycling. The chemical wear or dissolution of the crucible is negligible. It demonstrates the viability of Fe-26.38Si-9.35B alloy as a heat storage material in this type of container.

scholarly journals Melting of a phase change material in a horizontal annulus with discrete heat sources

2015 ◽  
Vol 19 (5) ◽  
pp. 1733-1745 ◽  
Author(s):  
Hooshyar Mirzaei ◽  
Abdolrahman Dadvand ◽  
Mohammad Mastiani ◽  
Seyed Sebti ◽  
Sina Kashani
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Liquid Fraction ◽  
Outer Cylinder ◽  
Melting Process ◽  
Cylinder Wall ◽  
Heat Sources ◽  
Discrete Heat Sources ◽  
Change Material

Phase change materials have found many industrial applications such as cooling of electronic devices and thermal energy storage. This paper investigates numerically the melting process of a phase change material in a two-dimensional horizontal annulus with different arrangements of two discrete heat sources. The sources are positioned on the inner cylinder of the annulus and assumed as constant-temperature boundary conditions. The remaining portion of the inner cylinder wall as well as the outer cylinder wall is considered to be insulated. The emphasis is mainly on the effects of the arrangement of the heat source pair on the fluid flow and heat transfer features. The governing equations are solved on a non-uniform O type mesh using a pressure-based finite volume method with an enthalpy porosity technique to trace the solid and liquid interface. The results are obtained at Ra=104 and presented in terms of streamlines, isotherms, melting phase front, liquid fraction and dimensionless heat flux. It is observed that, depending on the arrangement of heat sources, the liquid fraction increases both linearly and non-linearly with time but will slow down at the end of the melting process. It can also be concluded that proper arrangement of discrete heat sources has the great potential in improving the energy storage system. For instance, the arrangement C3 where the heat sources are located on the bottom part of the inner cylinder wall can expedite the melting process as compared to the other arrangements.

Thermodynamics of Energy Storage by Melting Due to Conduction or Natural Convection

1990 ◽  
Vol 112 (2) ◽  
pp. 110-116 ◽  
Author(s):  
M. De Lucia ◽  
A. Bejan
Keyword(s):  
Energy Source ◽  
Natural Convection ◽  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Melting Process ◽  
Absolute Temperature ◽  
Design Parameters ◽  
Environment Temperature ◽  
Change Material

This paper describes the most basic thermodynamic aspects of the process of energy storage by melting of a phase change material when the energy source is a stream of hot single-phase fluid. The first part of the paper considers the melting process ruled by pure conduction across the liquid phase, and the second part deals with the quasi-steady melting dominated by natural convection. The paper establishes the relationship between the total irreversibility of the melting process and design parameters such as the number of heat transfer units of the heat exchanger placed between the energy source and the phase change material, the duration of the melting process, and the position of the energy storage process on the absolute temperature scale. It is shown that the exergy transfer to the melting material is maximized when the melting temperature (Tm) equals the geometric average of the environment temperature (Te) and the temperature of the energy source (T∞), in other words when Tm=(TeT∞)1/2. This conclusion holds for both conduction-dominated melting and convection-dominated melting.

scholarly journals On the Melting Process of the Phase Change Material in Horizontal Rectangular Enclosures

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3100 ◽  
Author(s):  
Duan ◽  
Xiong ◽  
Yang
Keyword(s):  
Energy Storage ◽  
Aspect Ratio ◽  
Phase Change ◽  
Phase Change Material ◽  
Liquid Fraction ◽  
Melting Process ◽  
Energy Storage Devices ◽  
Rectangular Enclosure ◽  
Aspect Ratios ◽  
Change Material

Phase change material (PCM) is one of the most important ways to store and manage energy. The melting process of PCM in a rectangular enclosure with the different aspect ratio is frequently related to some thermal energy storage devices. In this work, the melting of PCM in the horizontal rectangular enclosures heated from the different sides and the influence of aspect ratio of the rectangle are carefully studied. The enthalpy porosity technique and the finite volume method (FVM) are used to simulate the melting process numerically. The results show that the melting process of PCM can be dominated by conduction or natural convection due to the different heated sides. The melting of PCM in the enclosure heated from the bottom side is firstly affected by conduction and then mostly influenced by convection. In addition, the aspect ratio of the rectangular enclosure is found to play an important role in the melting process. Finally, a series of fitting correlations of the liquid fraction, Nusselt number and the energy storage are presented with the influence of aspect ratios in order to provide the reference for designing the rectangular container of PCM. This study is helpful for the selection of an appropriate aspect ratio and heating method to achieve the desired energy storage performance of encapsulated PCM.

NUMERICAL STUDY OF A SOLAR GREENHOUSE DRYER WITH A PHASE-CHANGE MATERIAL AS AN ENERGY STORAGE MEDIUM

2018 ◽  
Vol 49 (6) ◽  
pp. 509-528 ◽  
Author(s):  
Orawan Aumporn ◽  
Belkacem Zeghmati ◽  
Xavier Chesneau ◽  
Serm Janjai
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Numerical Study ◽  
Storage Medium ◽  
Solar Greenhouse ◽  
Change Material
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