The phase change process is of significant importance in the application of phase change material (PCM). In this paper, the natural convection melting in a square cavity was investigated and the enthalpy-based lattice Boltzmann model (TLBM) combined with the pseudo-potential LB model was developed to trace the solid–liquid interface. Four cases with different boundary conditions were calculated and the corresponding temperature contours, velocity vectors and average liquid fraction at various time were compared.

Results show that TLBM has good accuracy in simulating the solid-liquid phase transition process. Variation in boundary conditions has appreciable impact on the natural convection process and melting behavior. Comparing model.1 (single heating wall) with model.2 (double adjacent heating walls with cold wall), the maximum liquid fraction is increased 16.7% in model.2 and the additional top heating wall acts to accelerate the average melting rate by 16.7%. The comparison between model.3 (double opposite heating walls) and model.4 (double adjacent heating walls without cold wall) shows that the natural convection heat transfer is intensive in model.3 and resulting in a 280% faster melting rate than that in model.4. Comparing the melting rate between the model.5 (all heating walls) and model.3, the increase of 54% due to the more heating walls in model.5 is observed.

相变过程在相变材料（PCM）的应用中非常重要。在本文中，研究了方腔中自然对流熔化，并开发了基于焓的格子玻尔兹曼模型（TLBM）和拟势LB模型，以追踪固液界面。计算了四种边界条件不同的情况，并比较了不同时间的相应温度轮廓，速度矢量和平均液体分数。

结果表明，TLBM在模拟固液相变过程中具有良好的精度。边界条件的变化会对自然对流过程和融化行为产生明显影响。将模型1（单加热壁）与模型2（双相邻的带冷壁的加热壁）进行比较，模型2中的最大液体分数增加了16.7％，附加的顶部加热壁起到了将平均熔化速率提高16.7的作用。 ％。模型3（两个相对的加热壁）和模型4（两个相邻的无冷壁的加热壁）之间的比较表明，模型3的自然对流传热很强，熔化速度比模型3快了280％。模型4。比较模型5（所有加热壁）和模型3之间的熔化速率，