The thermal performance and heat transfer augmentation of paraffin wax as a phase change material (PCM) throughout discharging process within a triplex tube heat storage have been examined using a combined experimental and numerical analysis. The efforts of this research are focused on using a blend of two different types of highly conductive nanoparticles (Al2O3/CuO hybrid nano additives) to enhance the thermal characteristics of paraffin and improve the overall performance of TTHS, which is the originality of this study. Various volume concentrations (0.4, 0.8, 1.6, 3.2%) of hybrid nanoparticles were explored. Besides that, A set of tests were carried out to evaluate the impact of changing inlet temperature and mass flow rate of the heat transfer fluid (HTF) on the phase change phenomenon of the paraffin. The mass flow rates of HTF ranges from 3 kg/min to 12 kg/min while the temperatures of HTF varies from 30 °C to 40 °C. The calculations are included an iterative, finite-volume numerical technique that involves a domain enthalpy porosity model to simulate the phase transition process. The agreement between the experimental data and the numerical simulation is good. According to the results, reducing inlet temperature and/or increase the inlet mass flow rate of HTF speed up solidification rate. However, HTF inlet temperature has more impact on solidification rate than inlet mass flow rate. Moreover, the reduction in freezing duration caused by implementing hybrid nanoparticles has been observed for all volume concentrations investigated. However, adding 3.2% volume percentage of hybrid nanoparticles results in the highest overall freezing time reduction (about 23%).