Evaluation of multi-branch fin inserts for improved thermal response in latent heat storage systems: A numerical approach

Abstract

Latent heat thermal energy storage (LHTES) offer a promising solution, but the inherently low thermal conductivity of their storage materials, known as phase change materials (PCMs), impedes thermal response rates. This study numerically explores the impact of multi-branch fin configurations on melting and solidification performance in a fixed-volume LHTES system, aiming to optimize the trade-off between increased fin surface area for improved heat transfer and potential flow constraints from excess fins obstructing convective PCM motion. A transient Two-dimensional (2D) model using the enthalpy-porosity approach simulates the phase change of the PCM around cylindrical tube-fin arrangements. Four cases are compared: plain fins, two-branch fins, four-branch fins, and five-branch fins, all with constant total fin volumes. Results show that multi-branch fins initially enhance melting rates due to increased heat transfer area, but declining returns arise beyond a threshold. At 325 K inlet temperature, the PCM with two-branch, three-branch, and four-branch fins melted completely within 60 min versus 90 min for plain fins, reducing melting time by 33.9 %, 37.1 %, and 44.9 %, respectively. However, the five-branch case provided marginal further improvement due to excessive fin crowding restricting molten PCM flow. Similar trends occurred during solidification, with multi-branch fins reducing solidification times by 18.3–29.0 %. This work guides identifying an optimal fin configuration that balances heat transfer enhancement and unimpeded convection. This approach prevents diminishing returns typically observed when implementing excessive fin volume arrangements.