Experimental evaluation of the use of fins and metal wool as heat transfer enhancement techniques in a latent heat thermal energy storage system

This paper experimentally studies and compares the addition of fins and the addition of metal wool in a latent heat thermal energy storage (TES) system as heat transfer enhancement techniques. Despite the well-known suitability of fins as enhancement technique, their implementation cost in the TES system is one of its main drawbacks. Therefore, the objective of this study is to evaluate the potential of adding a cheap and commercially available metallic wool in order to overcome the abovementioned drawback. In particular, four different latent heat TES systems based on the shell-and-tube heat exchanger concept were designed using n-octadecane as phase change material (PCM). One of them was used as a reference, while in the remaining configurations the heat transfer surface was increased by means of seventeen rectangular fins and by means of metallic wool arbitrarily distributed within the PCM and compacted in a finned shape. Charging and discharging processes with constant heat transfer fluid temperature and flow rate were evaluated from the temperature and heat transfer points of view. Results were focused on the metal wool because is a cheap and handmade solution which can be implemented in an already made heat exchanger. The addition of metal wool showed an enhancement, during the charge, higher than 10% when it was arbitrarily distributed, while compacting the metal wool in a finned shape showed practically no improvement. During the discharge, both metal wool configurations allowed minimal improvements.