3D printed lattice metal structures for enhanced heat transfer in latent heat storage systems

The low thermal conductivity of Phase Change Materials (PCMs), e.g., paraffin waxes, is one of the main drawbacks of latent heat storage, especially when fast charging and discharging cycles are required. The introduction of highly conductive fillers in the PCM matrix may be an effective solution; however, it is difficult to grant their stable and homogeneous dispersion, which therefore limits the resulting enhancement of the overall thermal conductivity. Metal 3D printing or additive manufacturing, instead, allows to manufacture complex geometries with precise patterns, therefore allowing the design of optimal paths for heat conduction within the PCM. In this work, a device-scale latent heat storage system operating at medium temperatures (similar to 90 celcius) was manufactured and characterized. Its innovative design relies on a 3D Cartesian metal lattice, fabricated via laser powder bed fusion, to achieve higher specific power densities. Numerical and experimental tests demonstrated remarkable specific power (approximately 714 +/- 17 W kg-1 and 1310 +/- 48 W kg-1 during heat charge and discharge, respectively). Moreover, the device performance remained stable over multiple charging and discharging cycles. Finally, simulation results were used to infer general design guidelines to further enhance the device performance. This work aims at promoting the use of metal additive manufacturing to design efficient and responsive thermal energy storage units for medium-sized applications, such as in the automotive sector (e.g. speed up of the engine warm up or as an auxiliary for other enhanced thermal management strategies).