Performance improvement in a vertical latent thermal energy storage tank with crossing heat transfer tubes

Date

2024-05-30

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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In a vertical latent thermal energy storage (LTES) tank, the lack of natural convection and domination of conduction results in a slow charging rate. On the other hand, due to large thermal resistances between the cold surfaces and liquid phase change material (PCM), the discharge process is also hindered. The current work suggests using multi-tube configurations for LTES tanks to address non-uniform melting and solidification in a vertical LTES unit. These tubes cross each other in the middle of the tank to reach the locations that struggle to melt and solidify. The motivation originates from studies that report a better natural convective heat transfer in titled tubes and that using titled tubes decreases the distance between the locations where PCM struggles to melt/solidify and the heated/cooled surface. A set of numerical simulations is performed to understand the effects of crossing heat transfer tubes on the charging and discharging process by keeping the total volume of the PCM constant. The mentioned numerical simulations utilize the enthalpy-porosity method which are validated using an experimental setup where a singular heat transfer fluid (HTF) tube was present. The study found that increasing the angle between the tubes enhances melting in double-tube configurations. Compared to a conventional LTES unit with one heat transfer fluid (HTF) tube, double-tube cases with 30°, 40°, and 50° angles between the tubes experience faster melting by 16 %, 23 %, and 39 %, respectively. Increasing the number of tubes does not necessarily correspond to faster melting due to hindrance in natural convection when three tubes are used. However, when the number of tubes is increased to four, the melting hastens, and the total melting time decreases up to 47 %. The suggested designs also enhance the solidification performance significantly. Four HTF tubes reduce the solidification time by up to 53 % compared to the conventional one-tube LTES.

Subject Keywords

Melting, Natural convection, Solar energy, Solidification

URI

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85190433429&origin=inward
https://hdl.handle.net/11511/109249

Collections

Department of Mechanical Engineering, Article