Based on the structure of bilayer tube energy storage unit (ESU), the study investigates the effects of physical parameters and arrangement combinations of phase change materials (PCMs) on the heat storage and exothermic performance of the ESU. The control variable method is used to focus on a single physical parameter of the phase change material to analyze its influence on the heat storage and exothermic performance. Use of experimental and numerical modelling, we firstly analyze the influence of the thermal conductivity of PCMs on the thermal storage and discharge performance, and then study the influence of the latent heat value of PCMs on the thermal storage and discharge performance, and compare and analyze its thermal performance parameters with those of traditional ESUs. Studies have shown that the thermal conductivity of the bilayer ESU can be minimized by up to 26.9% and the heat release time can be increased by up to 23.8% compared with the conventional ESU. The latent heat value of the bilayer ESU can be minimized by up to 28.1% and the heat release time can be increased by up to 35.3% as opposed to the conventional ESU. Obviously, the selection of PCMs must be considered for each parameter, and the selection of PCMs with appropriate parameters plays a crucial role for different energy storage conditions.