scholarly journals Experimental thermal performance comparison of pure and metal foam-loaded PCMs

2021 ◽  
Vol 2116 (1) ◽  
pp. 012058
Author(s):  
M Silvestrini ◽  
M Falcone ◽  
F Salvi ◽  
C Naldi ◽  
M Dongellini ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Metal Foam ◽  
Melting Process ◽  
Metal Foams ◽  
Performance Comparison ◽  
Melting Time ◽  
Porous Metals

Abstract The thermal performance of latent heat thermal energy storage (LHTES) systems considerably depends on thermal conductivity of adopted phase change materials (PCMs). To increase the low thermal conductivity of these materials, pure PCMs can be loaded with metal foams. In this study, the melting process of pure and metal-foam loaded phase change materials placed in a rectangular shape case is experimentally investigated by imposing a constant heat flux at the top. Two different paraffin waxes with melting point of about 35°C are tested. The results obtained with pure PCM are compared with those achieved from the use of PCM combined with two different porous metals: a 10 PPI aluminum foam with 96% porosity and a 20 PPI copper foam with 95% porosity. The results demonstrate how metal foams lead to a significant improvement of conduction heat transfer reducing significantly the melting time and the temperature difference between the heater and PCM.

Melting of Phase Change Materials With Volume Change in Metal Foams

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Zhen Yang ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Phase Change ◽  
Volume Change ◽  
Phase Change Materials ◽  
Metal Foam ◽  
Melting Process ◽  
Metal Foams ◽  
Volume Shrinkage ◽  
Two Temperature

Melting of phase change materials (PCMs) embedded in metal foams is investigated. The two-temperature model developed accounts for volume change in the PCM upon melting. Volume-averaged mass and momentum equations are solved, with the Brinkman–Forchheimer extension to Darcy’s law employed to model the porous-medium resistance. Local thermal equilibrium does not hold due to the large difference in thermal diffusivity between the metal foam and the PCM. Therefore, a two-temperature approach is adopted, with the heat transfer between the metal foam and the PCM being coupled by means of an interstitial Nusselt number. The enthalpy method is applied to account for phase change. The governing equations are solved using a finite-volume approach. Effects of volume shrinkage/expansion are considered for different interstitial heat transfer rates between the foam and PCM. The detailed behavior of the melting region as a function of buoyancy-driven convection and interstitial Nusselt number is analyzed. For strong interstitial heat transfer, the melting region is significantly reduced in extent and the melting process is greatly enhanced as is heat transfer from the wall; the converse applies for weak interstitial heat transfer. The melting process at a low interstitial Nusselt number is significantly influenced by melt convection, while the behavior is dominated by conduction at high interstitial Nusselt numbers. Volume shrinkage/expansion due to phase change induces an added flow, which affects the PCM melting rate.

Influence of Pore Density and Porosity on the Melting Process of Bio-Based Nano-Phase Change Materials Inside Open-Cell Metal Foam

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Kumar Venkateshwar ◽  
Soroush Ebadi ◽  
Hari Simha ◽  
Shohel Mahmud
Keyword(s):  
Surface Temperature ◽  
Phase Change ◽  
Thermal Energy ◽  
Phase Change Materials ◽  
Metal Foam ◽  
Melting Process ◽  
Melting Time ◽  
Pore Density ◽  
Open Cell ◽  
Nanoparticles Concentration

In this paper, experimental investigations were carried out to observe the melting process of a bio-based nano-phase change materials (PCM) inside open-cell metal foams. Copper oxide nanoparticles with five different weight fractions (i.e., 0.00%, 0.08%, 0.10%, 0.12%, and 0.30%) were dispersed into bio-based PCM (i.e., coconut oil) to synthesize nano-PCMs. Open-cell aluminum foams of different porosities (i.e., 0.96, 0.92, and 0.88) and pore densities (i.e., 5, 10, and 20 pores per inch (PPI)) were considered. An experimental setup was constructed to monitor the progression of the melting process and to measure transient temperatures variations at different selected locations. Average thermal energy storage rate (TESR) was calculated, alongside the melting time was recorded. The effects of various nanoparticles concentration, metal foam pore densities, porosities, and isothermal surface temperature on the melting time, TESR, thermal energy distribution, and the melting behavior were studied. It was observed that the melting time significantly reduced by using metal foam and increasing the isothermal surface temperature. It was concluded that the effect of adding nanoparticles on the TESR depends on the characteristics of metal foam, as well as, the weight fractions of nanoparticles. The change in TESR varied from −1% to 8.6% upon addition of 0.10 wt % nanoparticles compared to pure PCM, whereas the increase in the nanoparticles concentration from 0.10% to 0.30% changed TESR by −10.6% to 4.5%. The results provide an insight into the interdependencies of parameters such as pore density and porosity of metal foam and nanoparticles concentration on the melting process of nano-PCM in metal foam.

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.

Solid/Liquid Phase Change Heat Transfer in Latent Heat Thermal Energy Storage

2009 ◽  
Author(s):  
D. Zhou ◽  
C. Y. Zhao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Calcium Chloride ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Metal Foams ◽  
Chloride Hexahydrate

Phase change materials (PCMs) have been widely used for thermal energy storage systems due to their capability of storing and releasing large amounts of energy with a small volume and a moderate temperature variation. Most PCMs suffer the common problem of low thermal conductivity, being around 0.2 and 0.5 for paraffin and inorganic salts, respectively, which prolongs the charging and discharging period. In an attempt to improve the thermal conductivity of phase change materials, the graphite or metallic matrix is often embedded within PCMs to enhance the heat transfer. This paper presents an experimental study on heat transfer characteristics of PCMs embedded with open-celled metal foams. In this study both paraffin wax and calcium chloride hexahydrate are employed as the heat storage media. The transient heat transfer behavior is measured. Compared to the results of pure PCMs samples, the investigation shows that the additions of metal foams can double the overall heat transfer rate during the melting process. The results of calcium chloride hexahydrate are also compared with those of paraffin wax.

scholarly journals New Equivalent Thermal Conductivity Model for Size-Dependent Convection-Driven Melting of Spherically Encapsulated Phase Change Material

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4752
Author(s):  
Feng Hou ◽  
Shihao Cao ◽  
Hui Wang
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
Matrix Material ◽  
Melting Process ◽  
Melting Time ◽  
Equivalent Thermal Conductivity ◽  
Melting Front ◽  
Conductivity Model ◽  
Thermal Conductivity Model

Spherically encapsulated phase change materials (PCMs) are extensively incorporated into matrix material to form composite latent heat storage system for the purposes of saving energy, reducing PCM cost and decreasing space occupation. Although the melting of PCM sphere has been studied comprehensively by experimental and numerical methods, it is still challenging to quantitatively depict the contribution of complex natural convection (NC) to the melting process in a practically simple and acceptable way. To tackle this, a new effective thermal conductivity model is proposed in this work by focusing on the total melting time (TMT) of PCM, instead of tracking the complex evolution of solid–liquid interface. Firstly, the experiment and finite element simulation of the constrained and unconstrained meltings of paraffin sphere are conducted to provide a deep understanding of the NC-driven melting mechanism and exhibit the difference of melting process. Then the dependence of NC on the particle size and heating temperature is numerically investigated for the unconstrained melting which is closer to the real-life physics than the constrained melting. Subsequently, the contribution of NC to the TMT is approximately represented by a simple effective thermal conductivity correlation, through which the melting process of PCM is simplified to involve heat conduction only. The effectiveness of the equivalent thermal conductivity model is demonstrated by rigorous numerical analysis involving NC-driven melting. By addressing the TMT, the present correlation thoroughly avoids tracking the complex evolution of melting front and would bring great convenience to engineering applications.

scholarly journals Preparation and Thermal Performance Enhancement of Low Temperature Eutectic Composite Phase Change Materials Based on Na2SO4·10H2O

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2230 ◽  
Author(s):  
Pumin Hou ◽  
Jinfeng Mao ◽  
Fei Chen ◽  
Yong Li ◽  
Xian Dong
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Performance Enhancement ◽  
Expanded Graphite ◽  
Nucleating Agent ◽  
Thermal Reliability ◽  
Composite Phase Change Materials ◽  
Mass Fractions

In this paper, a series of Na2SO4·10H2O–KCl eutectic mixtures were prepared by adding different mass fractions of KCl (1 wt.%, 3 wt.%, 5 wt.%, or 7 wt.%) to Na2SO4·10H2O. Polyacrylamide (PAM) was proposed as the thickener, sodium tetraborate decahydrate (STD) was proposed as the nucleating agent, and expanded graphite (EG) was proposed as the high thermal conductivity medium for Na2SO4·10H2O–5 wt.% KCl eutectics. The results showed that in Na2SO4·10H2O–5 wt.% KCl eutectics with 5 wt.% PAM and 5 wt.% STD, almost no phase separation occurred, and the degree of supercooling was reduced to 0.4 °C. The thermal performance of Na2SO4·10H2O–5 wt.% KCl composite phase change materials (CPCMs) with varying contents of EG was explored. The results showed that EG could improve the thermal conductivity effectively and that the mass fraction of EG should be no more than 3%, otherwise the crystallization value and supercooling would deteriorate. The thermal reliability of the Na2SO4·10H2O–5 wt.% KCl eutectic CPCMs containing 5 wt.% PAM, 5 wt.% STD, and 3 wt.% EG was investigated, mainly through the ambient temperature, thermal cycling test, and TGA analysis. The results demonstrated that these CPCMs showed perfect thermal reliability.

Thermal performance analysis of phase change materials (PCMs) embedded in gradient porous metal foams

2020 ◽  
Vol 179 ◽  
pp. 115731 ◽  
Author(s):  
Ali Ghahremannezhad ◽  
Huijin Xu ◽  
Mohammad Reza Salimpour ◽  
Pei Wang ◽  
Kambiz Vafai
Keyword(s):  
Performance Analysis ◽  
Phase Change ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Porous Metal ◽  
Metal Foams
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