Thermal Analysis of a High-Temperature Heat Pipe-Assisted Thermal Energy Storage System With Nano-Enhanced Phase Change Material

In this study, the thermal characteristics of a high-temperature latent heat thermal energy storage system assisted by highly conductive nanoparticles and finned heat pipes are investigated numerically. A transient two-dimensional model is developed using the commercial CFD package of ANSYS-FLUENT18.2 to analyze the thermal performance of the storage unit during the charging process. Copper oxide (CuO) and aluminum oxide (Al₂O₃) are the nanoparticles introduced to enhance the thermal conductivity of the phase change material (PCM) which is potassium nitrate (KNO₃) with melting temperature of 335°C. The effects of different types and volume fractions of nanoparticles, as well as the quantities of embedded heat pipes have been studied. The results revealed that increasing the volume fraction of nanoparticles leads to the increase of the melting rate and input heat flux of the system. It was also found that the dispersion of aluminum oxide in the PCM provides a faster charging process in comparison to the case with copper oxide nanoparticles. In addition, the results showed that the quantity of heat pipes has a significant impact on the thermal performance of the storage unit.