The effects of geometry, Stefan number based on melting temperature differential, and subcooling of a phase change material (PCM) on the onset of natural convection have been reported in Part I of this paper. In this second part, the effects of Fourier, Grashof, and Rayleigh numbers are reported. The melting of n-octadecane and dodecanoic acid in horizontal cylindrical enclosures heated from the center-tubes with diameters of 18, 27, and 36 mm was studied experimentally. The PCMs were initially subcooled by 2.5, 7.5, 15, and 22.5 °C. The melting temperature differentials (the difference between the melting temperature of the PCMs and the heating temperature) were 8.44, 16.9, 25.3, 33.8, and 42.2 °C for n-octadecane and 8.44, 25.3, and 42.2 °C for dodecanoic acid. The experimental results show that the melt volume at the onset of natural convection decreases nonlinearly as the Grashof number increases. Also, the Fourier number at the onset of convection decreases nonlinearly as the ΔT_m-based Stefan number increases. Correlations were developed for the Fourier and Rayleigh numbers at the onset of natural convection. These correlations would allow an estimation of the elapsed time or melt volume at the onset of natural convection for a given geometry and operating temperature.

本文的第一部分报告了几何形状、基于熔化温差的 Stefan 数以及相变材料 (PCM) 过冷对自然对流开始的影响。在第二部分中，报告了傅立叶数、格拉肖夫数和瑞利数的影响。实验研究了正十八烷和十二烷酸在从直径为 18、27 和 36 毫米的中心管加热的水平圆柱形外壳中的熔化。PCM 最初过冷度分别为 2.5、7.5、15 和 22.5 °C。熔融温度差（该相变材料的熔化温度和加热温度之间的差）为8.44，16.9，25.3，33.8，和42.2℃，Ñ-十八烷，十二烷酸为 8.44、25.3 和 42.2 °C。实验结果表明，随着格拉肖夫数的增加，自然对流开始时的熔体体积呈非线性减小。此外，随着基于Δ T _m的 Stefan 数增加，对流开始时的傅立叶数非线性地减少。在自然对流开始时为傅立叶数和瑞利数建立了相关性。对于给定的几何形状和操作温度，这些相关性将允许在自然对流开始时估计经过的时间或熔体体积。