Enhancing thermal performance of heat storage using optimization of double helix tube coil structure

To optimize the performance of the heat storage unit, the double helix tube phase change storage unit filled with the novel composite phase change material is considered as the research object. A phase change heat storage system was constructed, and the heat transfer process was emulated through numerical simulation. The validity of the numerical model was verified by comparing the experimental and simulation outcomes. Based on the heat storage, complete melting time, and average heat flux, the enhanced heat transfer attributes of the coil diameter and compression ratio, as well as the influence of the carbon nanotube ratio on the melting process were analyzed. The results reveal that when the coil diameter is 88 mm, the heat storage unit manifests superior heat storage performance, with the heat storage reaching 4399 kJ, the complete melting time being reduced by 32.6 %, and the optimal ratio between the coil diameter and the heat storage unit diameter ranging from 0.59 to 0.72. When the compression ratio is 21:10:21, the heat transfer process of the heat storage unit is more rapid and uniform, the complete melting time is shortened by 71.3 %, and the average heat flux is augmented by 42.5 %. When the heat storage unit is filled with A9+3, the maximum heat storage attains 4733 kJ. When the heat storage unit is filled with A9+8, the complete melting time is decreased to 9703 s and the average heat flux ascends to 3023 W/m². These structural parameters offer guidelines for enhancing the thermal performance and optimizing the design of the double helix tube heat storage unit.