Experimental and numerical investigation of melting and solidification enhancement using Fibonacci-inspired fins in a latent thermal energy storage unit

Date

2023-08-15

Author

Baghaei Oskouei, Seyedmohsen
Bayer, Özgür

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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The major challenge with phase change materials (PCMs) is their low thermal conductivity, eventuating long melting (charging) and solidification (discharging) times in latent thermal energy storage (LTES) units. Using extended surfaces (fins) is a popular method to resulve this issue, with recent developments in novel designs such as tree-like and fractal fins. The complex fin configurations improve the conduction while decreasing the natural convection effects by introducing additional shear stress to the melted PCM. The current work proposes a new fin design based on the Fibonacci sequence in a vertical LTES unit to improve the charging/discharging characteristic. The finned geometry is manufactured out of a solid block of aluminum using the wire-cutting technique. Based on the volume expansion method, an experimental setup is designed to observe the charging/discharging behavior. The PCM under study is RT42 and its density, volumetric thermal expansion coefficient and solid-state thermal conductivity are measured in house. Water is the chosen heat transfer fluid (HTF) set to a constant mass flow rate of about 99 kg/h and 96 kg/h for the melting and solidification processes, respectively. The water charging temperature is 61.5 °C while the water discharge temperature is 21.5 °C. A numerical model based on the enthalpy-porosity method is implemented to investigate the physics behind melting/solidification. A careful investigation of the mushy zone constant is performed based on comparing the experimental and numerical results for melting and solidification. The average liquid PCM velocity on the melt front is studied to evaluate the natural convection behavior. The effects of secondary flows and mixing on the melting process in the new geometry are studied by investigating the liquid PCM flow behavior during the charging. The proposed fin performed 20% better in total melting time than longitudinal fins by introducing more dispersed natural convection dominated regions. The reduction of 45% in solidification time is also established for the novel fin.

Subject Keywords

Energy storage, Natural convection, Nature-inspired, Phase change material

URI

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85152125235&origin=inward
https://hdl.handle.net/11511/102894

Collections

Department of Mechanical Engineering, Article