Comparison of molecular heat transfer mechanisms between water and ammonia in the liquid states
Comparison of molecular heat transfer mechanisms between water and ammonia in the liquid states
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DOI：
10.1016/j.ijthermalsci.2020.106762
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发表时间：
2021-03
影响因子：
4.5
通讯作者：
H. Matsubara;G. Kikugawa;T. Ohara
中科院分区：
文献类型：
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作者：
H. Matsubara;G. Kikugawa;T. Ohara
水和氨都是具有高导热性的缔合液体，但它们的分子缔合程度分别以强氢键和弱氢键为特征。本文采用非平衡态分子动力学模拟方法对水和氨的高导热性的分子机理进行了研究和比较。使用原子热路径分析[J. Heat Mass Transf. 108，749（2017）]分析了与分子构型相关的分子尺度传热，其中将单个货车德瓦尔斯（vdW）相互作用和单个库仑相互作用视为热路径，并量化了它们对传热的贡献。水和氨都表明，高热导率的主要因素是通过库仑相互作用的大量热传递，这是由高密度的热路径实现的。这些杰出的库仑传热的热路径不仅包括氢键，但也更远的库仑相互作用。另一方面，氢键的重要作用是形成实现高热路径密度的分子的特定配位结构。这种配位结构在水和氨之间不同，因为氢键的强度不同，这反过来又导致了不同的传热分子图像。因此，水和氨在分子尺度上使用稍微不同的机制来实现高热导率。
Water and ammonia are both associated liquids with high thermal conductivity, but their degrees of molecular association are characterized differently by strong and weak hydrogen bonds, respectively. Here, we employed non-equilibrium molecular dynamics simulation to clarify and compare the molecular mechanisms of high thermal conductivity of water and ammonia. The molecular-scale heat transfer was analyzed in relation to molecular configuration using the atomistic heat path analysis [J. Heat Mass Transf. 108, 749 (2017)], where a single van der Waals (vdW) interaction and a single Coulomb interaction were considered as a heat path and their contributions to heat transfer were quantified. Both water and ammonia showed that the primary factor of high thermal conductivity is a large amount of heat transfer via Coulomb interaction, which was enabled by a high density of heat paths. These heat paths for outstanding Coulomb heat transfer included not only hydrogen bonds, but also more distant Coulomb interactions. On the other hand, an important role of hydrogen bond was to form a specific coordination structure of molecules that realizes the high heat path density. Such coordination structures differed between water and ammonia because of different strengths of hydrogen bond, which in turn led to different molecular pictures of heat transfer. Thus, water and ammonia achieve high thermal conductivity using somewhat different mechanisms at the molecular scale.