Experimental study on the role of metal foams in a vertical PCM-based thermal energy storage tube.

In this work an aluminum foam is proposed and studied to increase the thermal conductivity of a commercial paraffin wax having a melting temperature of around 40 °C and to decrease the charging and discharging times. Two samples were experimentally tested. Both are tube-in-tube heat exchangers where water flows in the tube and there is Phase Change Material (PCM) in the annulus. In one sample there is a 40PPI aluminum foam inside the PCM, while the reference sample contains only PCM. Experimental tests were carried out by running charging/discharging cycles feeding the tube with hot and cold water, respectively. The influence of water flow rate and inlet water temperature were investigated. The use of the aluminum foam was demonstrated to speed up both the charging and the discharging processes of the latent thermal storage, and to make the temperature field more uniform.