An Experimental Study of Inward Solidification of Nano-Enhanced Phase Change Materials (NePCM) Inside a Spherical Capsule

2016 ◽  
Author(s):  
Min-Jie Liu ◽  
Zi-Qin Zhu ◽  
Li-Wu Fan ◽  
Zi-Tao Yu
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Phase Change Materials ◽  
Classical Problem ◽  
Transient Phase ◽  
Graphite Nanoplatelets ◽  
The Matrix ◽  
Thermally Conductive ◽  
Spherical Capsule ◽  
Enhanced Thermal Conductivity

Nano-enhanced phase change materials (PCM), referred to as NePCM, have been proposed by doping highly thermally-conductive nanofillers into matrix PCM to prepare composites that have enhanced thermal conductivity. The classical problem of inward solidification of PCM inside a spherical capsule, with applications to thermal energy storage, was revisited in the presence of nanofillers. In this work, the model NePCM samples were prepared with 1-tetradecanol (C14H30O) possessing a nominal melting point of 37 °C as the matrix PCM. Graphite nanoplatelets (GNPs) were synthesized and utilized as the nanofillers at loadings up to 1% by weight. The transient phase change and heat transfer during solidification were characterized by means of an indirect method that is based on the knowledge of transient volume shrinkage of the PCM. The experimental results showed that the total solidification time becomes shorter with increasing the loading of GNPs, in accordance to the increased effective thermal conductivity of the NePCM samples.

Heat Transfer During Constrained Melting of Nano-Enhanced Phase Change Materials in a Spherical Capsule: An Experimental Study

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Li-Wu Fan ◽  
Zi-Qin Zhu ◽  
Min-Jie Liu ◽  
Can-Ling Xu ◽  
Yi Zeng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Phase Change ◽  
Phase Change Materials ◽  
Classical Problem ◽  
Dominant Mode ◽  
Graphite Nanosheets ◽  
Melting Experiments ◽  
Spherical Capsule

The classical problem of constrained melting heat transfer of a phase change material (PCM) inside a spherical capsule was revisited experimentally in the presence of nanoscale thermal conductivity fillers. The model nano-enhanced PCM (NePCM) samples were prepared by dispersing self-synthesized graphite nanosheets (GNSs) into 1-dodecanol at various loadings up to 1% by mass. The melting experiments were carried out using an indirect method by measuring the instantaneous volume expansion upon melting. The data analysis was performed based on the homogeneous, single-component assumption for NePCM with modified thermophysical properties. It was shown that the introduction of nanofillers increases the effective thermal conductivity of NePCM, in accompaniment with an undesirable rise in viscosity. The dramatic viscosity growth, up to over 100-fold at the highest loading, deteriorates significantly the intensity of natural convection, which was identified as the dominant mode of heat transfer during constrained melting. The loss in natural convection was found to overweigh the decent enhancement in heat conduction, thus resulting in decelerated melting in the presence of nanofillers. Except for the case with the lowest heating boundary temperature, a monotonous slowing trend of melting was observed with increasing the loading.

Inward Solidification Heat Transfer of Nano-Enhanced Phase Change Materials in a Spherical Capsule: An Experimental Study

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Zi-Qin Zhu ◽  
Min-Jie Liu ◽  
Nan Hu ◽  
Yuan-Kai Huang ◽  
Li-Wu Fan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Materials ◽  
Classical Problem ◽  
Solidification Time ◽  
Graphite Nanoplatelets ◽  
Practical Applications ◽  
Retrieval Rate ◽  
Microscale Transport ◽  
Spherical Capsule

The classical problem of inward solidification heat transfer inside a spherical capsule, with an application to thermal energy storage (TES), was revisited in the presence of nano-enhanced phase change materials (NePCM). The model NePCM samples were prepared by dispersing graphite nanoplatelets (GNPs) into 1-tetradecanol (C14H30O) at loadings up to 3.0 wt %. The transient phase change, energy retrieval, and heat transfer rates during solidification of the various NePCM samples were measured quantitatively using a volume-shrinkage-based indirect method. The data reduction and analysis were carried out under single-component, homogeneous assumption of the NePCM samples without considering the microscale transport phenomena of GNPs. It was shown that the total solidification time becomes monotonously shorter with increasing the loading of GNPs, in accordance with the increased effective thermal conductivity. The maximum relative acceleration of solidification was found to be more than 50% for the most concentrated sample, which seems to be appreciable for practical applications. In addition to enhanced heat conduction, the possible effects due to the elimination of supercooling and viscosity growth were elucidated. The heat retrieval rate was also shown to be increased monotonously with raising the loading of GNPs, although the heat storage capacity is sacrificed. Despite the remarkable acceleration of the solidification time, the use of a high loading (e.g., 3.0 wt %) was demonstrated to be possibly uneconomical because of the marginal gain in heat retrieval rate. Finally, correlations for the transient variations of the melt fraction and surface-averaged Nusselt number were proposed.

Optimization of thermal conductivity in composites loaded with the solid-solid phase-change materials

2018 ◽  
Vol 25 (6) ◽  
pp. 1157-1165
Author(s):  
Taoufik Mnasri ◽  
Adel Abbessi ◽  
Rached Ben Younes ◽  
Atef Mazioud
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Phase Change Materials ◽  
Solid Phase ◽  
Spherical Inclusions ◽  
First Case ◽  
The Matrix ◽  
Composite Conductivity ◽  
First Time

AbstractThis work focuses on identifying the thermal conductivity of composites loaded with phase-change materials (PCMs). Three configurations are studied: (1) the PCMs are divided into identical spherical inclusions arranged in one plane, (2) the PCMs are inserted into the matrix as a plate on the level of the same plane of arrangement, and (3) the PCMs are divided into identical spherical inclusions arranged periodically in the whole matrix. The percentage PCM/matrix is fixed for all cases. A comparison among the various situations is made for the first time, thus providing a new idea on how to insert PCMs into composite matrices. The results show that the composite conductivity is the most important consideration in the first case, precisely when the arrangement plane is parallel with the flux and diagonal to the entry face. In the present work, we are interested in exploring the solid-solid PCMs. The PCM polyurethane and a wood matrix are particularly studied.

Enhanced thermal conductivity of PEG/diatomite shape-stabilized phase change materials with Ag nanoparticles for thermal energy storage

2015 ◽  
Vol 3 (16) ◽  
pp. 8526-8536 ◽  
Author(s):  
Tingting Qian ◽  
Jinhong Li ◽  
Xin Min ◽  
Weimin Guan ◽  
Yong Deng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Ag Nanoparticles ◽  
Phase Change Materials ◽  
Enhanced Thermal Conductivity

The thermal conductivity was 0.82 W m−1 K−1 for 7.2% AgNPs in PEG/diatomite, which was enhanced by 127% compared to PEG/diatomite.

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