赤藓糖醇/碳纳米管复合相变材料热特性模拟研究

在“碳达峰、碳中和”的大背景下，能源结构从一次能源向新能源转变刻不容缓。由于新能源具有间歇性、波动性的特点，储能技术可以有效解决上述问题而得到了广泛的关注。相变材料作为储能技术的关键，其热导率低的问题亟需解决。赤藓糖醇作为中低温区常用的高焓值相变材料，热导率仅为0.7 W?m–1?K–1，严重制约了实际应用中的能量利用效率。本文以赤藓糖醇作为主要研究对象，采用具有超高导热系数的单壁碳纳米管作为导热增强材料，借助分子动力学模拟的方法探究了碳纳米管长度、质量分数以及分布方式对赤藓糖醇/碳纳米管复合相变材料热导率的影响规律。当碳纳米管轴向长度小于其声子平均自由程时，复合相变材料热导率随碳纳米管轴向长度增加而增大，同时随碳纳米管质量分数增加而增大，但表现出显著的各向异性。由于引入赤藓糖醇–碳纳米管界面，复合相变材料径向热导率相比纯赤藓糖醇反而降低。当碳纳米管在赤藓糖醇中随机分布时，热导率的各向异性得到了显著改善且各方向热导率均得到了提升。通过对比复合前后赤藓糖醇与碳纳米管的声子振动态密度发现，由于两者间的相互作用，碳纳米管的声子振动受到抑制，而赤藓糖醇中声子热输运得到激发，从而提高了热导率。 

Simulation of thermal properties of erythritol/carbon nanotube composite phase change materials

In the area of “carbon peaking and carbon neutralization,” changing energy structure from primary energy to new energy is an extremely important issue. Due to the intermittent and fluctuating characteristics of new energy, energy storage technology has proven a viable solution to this issue thus has attracted extensive attention. As a key to energy storage technology, the problem of the low thermal conductivity of phase change materials (PCMs) requires immediate attention. Erythritol is a high enthalpy phase change material commonly used in low-to-medium temperature processes. Its thermal conductivity of only 0.7 W?m–1?K–1 seriously hinders its energy utilization efficiency in practical application. In this paper, erythritol is the main research focus, and single-walled carbon nanotubes (CNTs) of ultra-high thermal conductivity are used as thermal conductivity reinforcements. The effects of length, mass fraction, and the distribution of CNTs on the thermal conductivity of erythritol/CNT composite PCMs were studied by means of molecular dynamics simulation. When the axial lengths of the CNTs were less than their phonon mean free paths, the thermal conductivity of the composite PCMs increased with increasing CNT axial length and mass fraction, although clear anisotropy was exhibited. Due to the introduction of erythritol–CNTs interfacial thermal resistance, the radial thermal conductivity of the composite materials was lower than that of pure erythritol. When CNTs were randomly distributed in erythritol, the anisotropy of thermal conductivity was significantly improved, as was thermal conductivity in all directions. Comparing the phonon vibration densities of the states of erythritol and CNT before and after recombination, it was found that, due to the interaction between the two, the phonon vibration of CNT was suppressed, and the phonon heat transport in erythritol was excited, thus improving thermal conductivity.