Graphene Modified Montmorillonite Based Phase Change Material for Thermal Energy Storage with Enhanced Interfacial Thermal Transfer

Abstract Thermal energy storage technology plays a crucial role in the thermal management system. Clay based organic phase change material has considerable advantages in the application of thermal energy storage due to low cost and high energy storage capacity. However, the low thermal conductivity of clay, especially poor interfacial thermal transfer, limits its thermal energy storage efficiency. Herein, stearic acid/reduced graphene oxide modified montmorillonite composites (SA/RGO-MMT) were prepared by the vacuum impregnation of stearic acid into graphene modified montmorillonite matrix, which was obtained via the in situ reduction of graphene oxide on the surface of montmorillonite. Stearic acid is assembled in the porous structures of RGO-MMT with the physical interactions. SA/RGO-MMT possesses high melting enthalpy of 159 J/g, low extent of supercooling of 1.4 oC and excellent thermal reliability after 100 thermal cycling. Energy storage and release rates of SA/RGO-MMT were significantly improved due to the enhanced interfacial thermal transfer by graphene. Therefore, SA/RGO-MMT is a promising form-stable phase change material for applications in solar heat storage fields. The strategy in this study highlights the importance of enhancing interfacial thermal transfer for the efficient thermal energy storage materials.

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EFFECT OF CONTAINER ASPECT RATIO ON THE MELTING PROCESS OF A NANO-ENHANCED PHASE CHANGE MATERIAL IN LATENT HEAT THERMAL ENERGY STORAGE SYSTEMS

10.1615/tfec2020.est.32011 ◽

2020 ◽

Author(s):

Mahboobe Mahdavi ◽

Saeed Tiari ◽

Carley Sawyer

Keyword(s):

Energy Storage ◽

Aspect Ratio ◽

Phase Change ◽

Phase Change Material ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Storage Systems ◽

Melting Process ◽

Thermal Energy Storage Systems ◽

Change Material

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Thermal Energy Storage Through Melting of a Commercial Phase Change Material in an Annulus with Radially Divergent Longitudinal Fins

International Journal of Thermofluid Science and Technology ◽

10.36963/ijtst.20070102 ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Tonny Tabassum Mainul Hasan ◽

Latifa Begum

Keyword(s):

Energy Storage ◽

Phase Change ◽

Phase Change Material ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Storage System ◽

Operating Conditions ◽

Melting Time ◽

Bottom Part ◽

Change Material

This study reports on the unsteady two-dimensional numerical investigations of melting of a paraffin wax (phase change material, PCM) which melts over a temperature range of 8.7oC. The PCM is placed inside a circular concentric horizontal-finned annulus for the storage of thermal energy. The inner tube is fitted with three radially diverging longitudinal fins strategically placed near the bottom part of the annulus to accelerate the melting process there. The developed CFD code used in Tabassum et al., 2018 is extended to incorporate the presence of fins. The numerical results show that the average Nusselt number over the inner tube surface, the total melt fraction, the total stored energy all increased at every time instant in the finned annulus compared to the annulus without fins. This is due to the fact that in the finned annulus, the fins at the lower part of the annulus promotes buoyancy-driven convection as opposed to the slow conduction melting that prevails at the bottom part of the plain annulus. Fins with two different heights have been considered. It is found that by extending the height of the fin to 50% of the annular gap about 33.05% more energy could be stored compared to the bare annulus at the melting time of 82.37 min for the identical operating conditions. The effects of fins with different heights on the temperature and streamfunction distributions are found to be different. The present study can provide some useful guidelines for achieving a better thermal energy storage system.

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