scholarly journals Simulation of solidification process of phase change materials in a heat exchanger using branch-shaped fins

2021 ◽  
Vol 25 ◽  
pp. 100835
Author(s):  
M. Asgari ◽  
M. Javidan ◽  
M. Nozari ◽  
A. Asgari ◽  
D.D. Ganji
Keyword(s):  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Materials ◽  
Solidification Process

scholarly journals Designs of PCM based heat exchangers constructions for thermal energy storage tanks – examples and case study for selected design

2018 ◽  
Vol 70 ◽  
pp. 01010
Author(s):  
Marta Kuta ◽  
Dominika Matuszewska ◽  
Tadeusz Michał Wójcik
Keyword(s):  
Energy Storage ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
New Technologies ◽  
Tube Heat Exchanger ◽  
Change Material

Increasing energy consumption in residential and public buildings requires development of new technologies for thermal energy production and storage. One of possibilities for the second listed need is the use of phase change materials (PCMs). This work is focused on solutions in this area and consists of two parts. First one is focused on different designs of thermal energy storage (TES) tanks based on the phase change materials. The second part is the analysis of tests results for TES tank containing shelf and tube heat exchanger and filled with phase change material. Thermal energy storage tank is analyzed in order to use it in domestic heating and hot utility water installations. The aim of this research was to check the applicability of phase change material for mentioned purpose. Results show that using phase change materials for thermal energy storage can increase amount of stored heat. The use of properly selected PCM and heat exchanger enables the process of thermal energy storing and releasing to become more efficient.

Solidification of Phase Change Materials Infiltrated in Porous Media in Presence of Voids

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Mahmoud Moeini Sedeh ◽  
J. M. Khodadadi
Keyword(s):  
Phase Change ◽  
Porous Structure ◽  
Phase Change Materials ◽  
Solidification Process ◽  
Volume Shrinkage ◽  
Freezing Process ◽  
Infiltration Process ◽  
Noticeable Increase ◽  
Melting Characteristics ◽  
Micron Size

Infiltration of phase change materials (PCM) into highly conductive porous structures effectively enhances the thermal conductivity and phase change (solidification and melting) characteristics of the resulting thermal energy storage (TES) composites. However, the infiltration process contributes to formation of voids as micron-size air bubbles within the pores of the porous structure. The presence of voids negatively affects the thermal and phase change performance of TES composites due to the thermophysical properties of air in comparison with PCM and porous structure. This paper investigates the effect of voids on solidification of PCM, infiltrated into the pores of graphite foam as a highly conductive porous medium with interconnected pores. A combination of the volume-of-fluid (VOF) and enthalpy-porosity methods was employed for numerical investigation of solidification. The proposed method takes into account the variation of density with temperature during phase change and is able to predict the volume shrinkage (volume contraction) during the solidification of liquids. Furthermore, the presence of void and the temperature gradient along the liquid–gas interface (the interface between void and PCM) can trigger thermocapillary effects. Thus, Marangoni convection was included during the solidification process and its importance was elucidated by comparing the results among cases with and without thermocapillary effects. The results indicated that the presence of voids within the pores causes a noticeable increase in solidification time, with a sharper increase for cases without thermocapillary convection. For verification purposes, the amount of volume shrinkage during the solidification obtained from numerical simulations was compared against the theoretical volume change due to the variation of density for several liquids with contraction and expansion during the freezing process. The two sets of results exhibited good agreement.

Detailed Numerical Modeling of a Hybrid PCM-Air Heat Sink

2013 ◽  
Author(s):  
Y. Kozak ◽  
G. Ziskind
Keyword(s):  
Numerical Modeling ◽  
Phase Change ◽  
Heat Sink ◽  
Phase Change Materials ◽  
Void Formation ◽  
Solidification Process ◽  
Melting Process ◽  
Significant Rise ◽  
Air Interface ◽  
Vof Model

The ability of phase-change materials (PCMs) to absorb large amounts of heat without significant rise of their temperature during the melting process may be utilized in thermal energy storage and passive thermal management. This paper deals with numerical modeling of a hybrid PCM-air heat sink, in which heat may be either absorbed by the PCM stored in compartments with conducting walls, or dissipated to the air using fins, or both. Under the assumptions of perfect insulation (except for the air fins), identity and symmetry between all PCM channels, and negligible 3-D boundary effects, a 2-D model of the problem for half a PCM compartment of the heat sink is solved, saving calculation time and yet taking into account the essential physical phenomena. A commercial program, ANSYS Fluent, is used in order to solve the governing conservation equations. Phase-change is solved using the enthalpy-porosity method. PCM-air interface is modeled using the volume-of-fluid (VOF) approach. The model takes into account natural convection in the liquid PCM and air, volume change, phase- and temperature-dependence of thermal properties, and PCM-air interface interaction. Various scenarios for the hybrid heat sink operation are simulated and compared. The difference in the melting patterns is analyzed for the cases of heating with and without the fan operating. The solidification process with the fan operating is also simulated. It is shown that the VOF model enables simulating realistic void formation in the solidification process.

scholarly journals Evaluation and Improvement of Thermal Energy of Heat Exchangers with SWCNT, GQD Nanoparticles and PCM (RT82)

2020 ◽  
Vol 79 (1) ◽  
pp. 153-168
Author(s):  
Mohammadreza Hasandust Rostami ◽  
Gholamhassan Najafi ◽  
Ali Motevalli ◽  
Nor Azwadi Che Sidik ◽  
Muhammad Arif Harun
Keyword(s):  
Energy Storage ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Phase Change Materials ◽  
Single Wall Carbon Nanotubes ◽  
In Series

Today, due to the reduction of energy resources in the world and its pollutants, energy storage methods and increase the thermal efficiency of various systems are very important. In this research, the thermal efficiency and energy storage of two heat exchangers have been investigated in series using phase change materials (RT82) and single wall carbon nanotubes (SWCNT) and graphene quantum dot nanoparticles (GQD) In this research, two heat exchangers have been used in combination. The first heat exchanger was in charge of storing thermal energy and the second heat exchanger was in charge of heat exchange. The reason for this is to improve the heat exchange of the main exchanger (shell and tube) by using heat storage in the secondary exchanger, which has not been addressed in previous research. The results of this study showed that using two heat exchangers in series, the thermal efficiency of the system has increased. Also, the heat energy storage of the double tube heat exchanger was obtained using phase change materials in the single-walled carbon nanotube composition of about 3000 W. The average thermal efficiency of the two heat exchangers as the series has increased by 52%. In general, the effect of the two heat exchangers on each other was investigated in series with two approaches (energy storage and energy conversion) using fin and nanoparticles, which obtained convincing results.

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