Thermal Energy Storage and Heat Transfer of Nano-Enhanced Phase Change Material (NePCM) in a Shell and Tube Thermal Energy Storage (TES) Unit with a Partial Layer of Eccentric Copper Foam

Abstract

Thermal energy storage units conventionally have the drawback of slow charging response. Thus, heat transfer enhancement techniques are required to reduce charging time. Using nanoadditives is a promising approach to enhance the heat transfer and energy storage response time of materials that store heat by undergoing a reversible phase change, so-called phase change materials. In the present study, a combination of such materials enhanced with the addition of nanometer-scale graphene oxide particles (called nano-enhanced phase change materials) and a layer of a copper foam is proposed to improve the thermal performance of a shell-and-tube latent heat thermal energy storage (LHTES) unit filled with capric acid. Both graphene oxide and copper nanoparticles were tested as the nanometer-scale additives. A geometrically nonuniform layer of copper foam was placed over the hot tube inside the unit. The metal foam layer can improve heat transfer with an increase of the composite thermal conductivity. However, it suppressed the natural convection flows and could reduce heat transfer in the molten regions. Thus, a metal foam layer with a nonuniform shape can maximize thermal conductivity in conduction-dominant regions and minimize its adverse impacts on natural convection flows. The heat transfer was modeled using partial differential equations for conservations of momentum and heat. The finite element method was used to solve the partial differential equations. A backward differential formula was used to control the accuracy and convergence of the solution automatically. Mesh adaptation was applied to increase the mesh resolution at the interface between phases and improve the quality and stability of the solution. The impact of the eccentricity and porosity of the metal foam layer and the volume fraction of nanoparticles on the energy storage and the thermal performance of the LHTES unit was addressed. The layer of the metal foam notably improves the response time of the LHTES unit, and a 10% eccentricity of the porous layer toward the bottom improved the response time of the LHTES unit by 50%. The presence of nanoadditives could reduce the response time (melting time) of the LHTES unit by 12%, and copper nanoparticles were slightly better than graphene oxide particles in terms of heat transfer enhancement. The design parameters of the eccentricity, porosity, and volume fraction of nanoparticles had minimal impact on the thermal energy storage capacity of the LHTES unit, while their impact on the melting time (response time) was significant. Thus, a combination of the enhancement method could practically reduce the thermal charging time of an LHTES unit without a significant increase in its size.

Investigation the thermal performance of Nano-Enhanced Phase Change Material (NEPCM) in an enclosure

“…However, their study focused primarily on the position of the heat source, leaving room for additional research into the influence of temperature variations on the thermal performance of NEPCM in an enclosure. Similarly, Ghalambaz et al [11] investigated the thermal energy storage and heat transfer of NEPCM in a shell-and-tube thermal energy storage unit, taking into account a partial layer of eccentric copper foam. The findings of this study highlighted the significant impact of temperature on the thermal properties of NEPCM and emphasized the need for further research into the effects of temperature variation.…”

Enhancing the Melting Process of Shell-and-Tube PCM Thermal Energy Storage Unit Using Modified Tube Design

“…The results suggested that using nanoparticles accelerated the charging process and that platelet-shaped nanoparticles provide the fastest pace. More recently published papers, those considering using NePCM for enhancing thermal performance of TES units, can be found in [ 40 , 41 , 42 , 43 ].…”

Numerical simulation of geothermal‐PVT hybrid system with PCM storage tank

“…Furthermore, they found that copper nanoparticles had more effective performance in raising heat transfer in comparison with graphene oxide particles. 10 Although the PVT-assisted heat pumps have been the center of interest for researchers, there are still many obscure parts to reach an almost ideal and economical system. In the previous studies, many researchers concentrated on covering the thermal or electrical aspects of the system separately by using renewable energies.…”