A General Model for Analyzing the Thermal Performance of the Heat Charging and Discharging Processes of Latent Heat Thermal Energy Storage Systems*

2001 ◽  
Vol 123 (3) ◽  
pp. 232-236 ◽  
Author(s):  
Yinping Zhang ◽  
Yan Su ◽  
Yingxin Zhu ◽  
Xianxu Hu
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Latent Heat ◽  
Thermal Performance ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
General Model ◽  
Phase Change Materials ◽  
Melting Process ◽  
Specific System

During melting of phase change materials (PCM) encapsulated in a container, the solid PCM sinks to the bottom or floats to the top of the container according to the gravitational force and buoyancy resulting from the difference between solid and liquid densities. Compared with the solidification process, the melting process has a quite different behavior. Although the heat transfer characteristics of melting processes in various typical kinds of containers have been studied, the general model for analyzing the thermal performance of both melting and solidification processes of latent heat thermal energy storage (LHTES) systems composed of PCM capsules has not been presented in the literature. The present paper describes such a model which can be used to analyze the instantaneous temperature distribution, instantaneous heat transfer rate, and thermal storage capacity of a LHTES system. For solidification, the model is validated with the results in the literature. The thermal performance during melting of a LHTES system composed of PCM spheres is analyzed as an example. The model is not limited to a specific system or a specific PCM, so it can be used to select and optimize system design and to simulate the thermal behavior of various typical LHTES systems.

A General Model for Analyzing the Thermal Characteristics of a Class of Latent Heat Thermal Energy Storage Systems

1999 ◽  
Vol 121 (4) ◽  
pp. 185-193 ◽  
Author(s):  
Kang Yanbing ◽  
Zhang Yinping ◽  
Jiang Yi ◽  
Zhu Yingxin
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Latent Heat ◽  
Thermal Performance ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
General Model ◽  
Thermal Characteristics ◽  
System Structure ◽  
Heat Transfer Fluid

The present study describes and classifies latent heat thermal energy storage (LHTES) systems according to their structural characteristics. A general model is developed for analyzing the thermal characteristics of the various typical LHTES systems to simulate thermal characteristics such as instantaneous heat transfer rate, instantaneous thermal storage capacity, etc. of the various typical LHTES systems. The model can calculate some important but difficult to measure system parameters for monitoring the charging or discharging processes of the systems. The model is verified using experimental data in the literature. Results from the model can be used to discuss the influence of the characteristic geometric parameters of LHTES units, the physical properties of the phase change material (PCM), the flow type and the velocity of heat transfer fluid (HTF) on the system thermal performance and to identify the key factors influencing the system thermal performance. The general model can be used to select and optimize the system structure and to simulate the thermal behavior of various typical LHTES systems.

Effect of Geometric Configurations on the Thermal Performance Of Encapsulated PCMs

2021 ◽  
Author(s):  
Mohammad Reza Mohaghegh ◽  
Shohel Mahmud ◽  
Syeda Tasnim
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Performance ◽  
Thermal Energy ◽  
Phase Change Materials ◽  
Mechanical Stability ◽  
Melting Process ◽  
Transport Processes ◽  
Melting Time

Abstract The integration of thermal energy storage (TES) systems with Phase Change Materials (PCMs) is a promising technique not only for storing thermal energy, also for thermal management applications. Encapsulation is a safe and efficient integration technique of using PCM, which has various advantages such as PCM protection, mechanical stability, leakage prevention and, diversified shapes and sizes. The thermal performance of these systems is heavily dependent on the form and geometry of the encapsulating PCM. Various literature has investigated PCM encapsulation for different applications; however, they were limited to just a few common geometries, i.e., rectangular, spherical, and cylindrical. The present research is aimed to investigate the effect of shape/geometry on the thermal performance of encapsulated PCMs and visualize the PCM melting process to a further improvement in the thermal performance of TES systems for different applications. For this purpose, transient heat transfer and the melting process of the same volume of PCM encapsulated in four different geometrical configurations of the capsules, including the common encapsulation shapes such as spherical, cubical, cylindrical, and conical shape as less studied and new proposed shape, are studied. A mathematical model is developed and numerically solved to study the energy transport processes inside the enclosures. The melting process is visualized numerically to track the solid-liquid interface during the phase change. Moreover, the heat transfer characteristics such as melting fraction and energy stored in the system and their temporal variation during the phase change process are determined. A comparison of the four cases in terms of melting rate and energy storage is carried out, as well. The results show that the conical capsule exhibits the best thermal performance with a total melting time of 72 minutes. While the cubical capsule requires 111 minutes to complete the melting process.

scholarly journals Latent Heat Phase Change Heat Transfer of a Nanoliquid with Nano–Encapsulated Phase Change Materials in a Wavy-Wall Enclosure with an Active Rotating Cylinder

2021 ◽  
Vol 13 (5) ◽  
pp. 2590
Author(s):  
S. A. M. Mehryan ◽  
Kaamran Raahemifar ◽  
Leila Sasani Gargari ◽  
Ahmad Hajjar ◽  
Mohamad El Kadri ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Wavy Wall ◽  
Governing Equations ◽  
Stefan Number ◽  
Change Material

A Nano-Encapsulated Phase-Change Material (NEPCM) suspension is made of nanoparticles containing a Phase Change Material in their core and dispersed in a fluid. These particles can contribute to thermal energy storage and heat transfer by their latent heat of phase change as moving with the host fluid. Thus, such novel nanoliquids are promising for applications in waste heat recovery and thermal energy storage systems. In the present research, the mixed convection of NEPCM suspensions was addressed in a wavy wall cavity containing a rotating solid cylinder. As the nanoparticles move with the liquid, they undergo a phase change and transfer the latent heat. The phase change of nanoparticles was considered as temperature-dependent heat capacity. The governing equations of mass, momentum, and energy conservation were presented as partial differential equations. Then, the governing equations were converted to a non-dimensional form to generalize the solution, and solved by the finite element method. The influence of control parameters such as volume concentration of nanoparticles, fusion temperature of nanoparticles, Stefan number, wall undulations number, and as well as the cylinder size, angular rotation, and thermal conductivities was addressed on the heat transfer in the enclosure. The wall undulation number induces a remarkable change in the Nusselt number. There are optimum fusion temperatures for nanoparticles, which could maximize the heat transfer rate. The increase of the latent heat of nanoparticles (a decline of Stefan number) boosts the heat transfer advantage of employing the phase change particles.

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