It is a central challenge for energy self-supplied underwater vehicles converting the huge ocean thermal energy to electrical energy effectively. However, the energy storage efficiency of ocean thermal energy storage (OTES) unit limits the conversion efficiency. Fins are proposed for OTES unit to improve energy storage efficiency in this paper. Firstly, this paper develops a non-stationary model of solidification heat transfer for OTES unit and uses FLUENT to accomplish its numerical analysis. Then, the influence of radial fin and fractal fin on the solidification behavior of phase change material (PCM) are compared. Finally, several fractal fins with different fractal levels, bifurcation angles and ambient temperature are analyzed for the evolution of the liquid phase rate and temperature distribution of PCM. The results show that fractal fins can reduce the solidification time of PCM by 34.46% compared with radial fins. Furthermore, the solidification rate of PCM can be improved by increasing the number of fractal levels and choosing a proper bifurcation angle. However, the solidification behavior of PCM changes slightly when the fractal level increases to 3. The bifurcation angle of 90° is appropriate for practical applications. Furthermore, keeping the temperature difference above 10K can achieve faster solidification.

将巨大的海洋热能有效地转化为电能是能源自给式水下航行器面临的核心挑战。然而，海洋热能储存（OTES）单元的储能效率限制了转换效率。本文提出了 OTES 单元的鳍片以提高储能效率。首先，本文建立了OTES单元凝固传热的非平稳模型，并利用FLUENT对其进行了数值分析。然后，比较了径向翅片和分形翅片对相变材料（PCM）凝固行为的影响。最后，分析了不同分形水平、分叉角和环境温度的几种分形鳍片，以了解相变材料液相速率和温度分布的演变。结果表明，与径向翅片相比，分形翅片可使相变材料的凝固时间缩短34.46%。此外，可以通过增加分形层数和选择合适的分叉角来提高相变材料的凝固速度。然而，当分形水平增加到 3 时，PCM 的凝固行为略有变化。90°的分叉角适合实际应用。此外，保持10K以上的温差可以实现更快的凝固。90°的分叉角适合实际应用。此外，保持10K以上的温差可以实现更快的凝固。90°的分叉角适合实际应用。此外，保持10K以上的温差可以实现更快的凝固。