An Effective Thermal Conductivity Model for Architected Phase Change Material Enhancer

2020 ◽  
Author(s):  
Romain Hubert ◽  
Olivier Bou-Matar ◽  
Jerome Foncin ◽  
Philippe Coquet ◽  
Dunlin Tan ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Source ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
Phase Change Materials ◽  
Heated Surface ◽  
Analytical Investigation ◽  
Heat Of Fusion ◽  
Conductivity Enhancement ◽  
Thermal Conductivity Model

Abstract Phase Change Materials (PCM) have been widely used for thermal energy storage due to their high latent heat of fusion. However, PCMs suffer from their very low thermal conductivity which limits heat spreading around the heat source. Without proper thermal conductivity enhancement, melting would mainly occur at the interface between the heated surface and the PCM, and would slowly spread in the bulk of the PCM, greatly reducing its performance. Metallic foams are usually used as thermal conductivity enhancer, yet recent progress in additive manufacturing have allowed architected structures to be used and optimized. We present here an analytical investigation of the effective thermal conductivity of porous architected structures and emphasize is made on the effect of thermal constriction at the interface with a heat spreader in contact with the heat source.

Numerical Evaluation of Multiple Phase Change Materials for Pulsed Electronics Applications

2016 ◽  
Author(s):  
David Gonzalez-Nino ◽  
Lauren M. Boteler ◽  
Dimeji Ibitayo ◽  
Nicholas R. Jankowski ◽  
Pedro O. Quintero
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Source ◽  
Phase Change ◽  
Phase Change Materials ◽  
High Energy ◽  
Heat Of Fusion ◽  
Maximum Temperature ◽  
Conductivity Enhancement ◽  
Fast Transient

A simple and easy to implement 1-D heat transfer modeling approach is presented in order to investigate the performance of various phase change materials (PCMs) under fast transient thermal loads. Three metallic (gallium, indium, and Bi/Pb/Sn/In alloy) and two organic (erythritol and n-octadecane) PCMs were used for comparison. A finite-difference method was used to model the transient heat transfer through the system while a heat integration or post-iterative method was used to model the phase change. To improve accuracy, the material properties were adjusted at each iteration depending on the state of matter of the PCM. The model assumed that the PCM was in direct contact with the heat source, located on the top of the chip, without the presence of a thermal conductivity enhancement. Results show that the three metallic PCMs outperform organic PCMs during fast transient pulses in spite of the fact that two of the metallic PCMs (i.e. indium and Bi/Pb/Sn/In) have considerably lower volumetric heats of fusion than erythritol. This is due to the significantly higher thermal conductivity values of metals which allow faster absorption of the heat energy by the PCM, a critical need in high-energy short pulses. The most outstanding case studied in this paper, Bi/Pb/Sn/In having only 52% of erythritol’s heat of fusion, showed a maximum temperature 20°C lower than erythritol during a 32 J and 0.02 second pulse. This study has shown thermal buffering benefits by using a metallic PCM directly in contact with the heat source during short transient heat loads.

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 Investigation of Thermal Properties of Novel Phase Change Material Mixtures (Octadecane-Diamond) with Laser Flash Analysis

2019 ◽  
Vol 26 (4) ◽  
pp. 211-218
Author(s):  
Mateusz Sierakowski ◽  
Wojciech Godlewski ◽  
Roman Domański ◽  
Jakub Kapuściński ◽  
Tomasz Wiśniewski ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Phase Change ◽  
Power Plants ◽  
Large Scale ◽  
Phase Change Materials ◽  
Heat Dissipation ◽  
Electronics Cooling ◽  
Diamond Powder ◽  
Heat Of Fusion

AbstractPhase change materials (PCMs) are widely used in numerous engineering fields because of their good heat storage properties and high latent heat of fusion. However, a big group of them has low thermal conductivity and diffusivity, which poses a problem when it comes to effective and relatively fast heat transfer and accumulation. Therefore, their use is limited to systems that do not need to be heated or cooled rapidly. That is why they are used as thermal energy storage systems in both large scale in power plants and smaller scale in residential facilities. Although, if PCMs are meant to play an important role in electronics cooling, heat dissipation, or temperature stabilization in places where the access to cooling water is limited, such as electric automotive industry or hybrid aviation, a number of modifications and improvements needs to be introduced. Investigation whether additional materials of better thermal properties will affect the thermal properties of PCM is therefore of a big interest. An example of such material is diamond powder, which is a popular additive used in abradants. Its thermal diffusivity and conductivity is significantly higher than for a pure PCM. The article presents the results of an analysis of the effect of diamond powder on thermal conductivity and diffusivity of phase change materials in the case of octadecane.

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 Improvement of Phase Change Materials (PCM) Used for Solar Process Heat Applications

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1260
Author(s):  
Cristina Prieto ◽  
Anton Lopez-Roman ◽  
Noelia Martínez ◽  
Josep M. Morera ◽  
Luisa F. Cabeza
Keyword(s):  
Thermal Conductivity ◽  
Solar Energy ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
High Temperatures ◽  
Phase Change Materials ◽  
Material Selection ◽  
Inert Atmosphere ◽  
Enhancement Effect ◽  
Process Heat

The high intermittency of solar energy is still a challenge yet to be overcome. The use of thermal storage has proven to be a good option, with phase change materials (PCM) as very promising candidates. Nevertheless, PCM compounds have typically poor thermal conductivity, reducing their attractiveness for commercial uses. This paper demonstrates the viability of increasing the PCM effective thermal conductivity to industrial required values (around 4 W/m·K) by using metal wool infiltrated into the resin under vacuum conditions. To achieve this result, the authors used an inert resin, decoupling the specific PCM material selection from the enhancement effect of the metal wools. To ensure proper behavior of the metal wool under standard industrial environments at a broad range of temperatures, a set of analyses were performed at high temperatures and an inert atmosphere, presenting a thorough analysis of the obtained results.

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