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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

SIZE EFFECT ON THE THERMAL CONDUCTIVITY OF OCTADECANOIC ACID: A MOLECULAR DYNAMICS STUDY

Hanying Zou
School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China; Beijing Key Laboratory of Energy Saving and Emission Reduction for Metallurgical Industry, University of Science and Technology Beijing, Beijing 100083, China

Lin Qiu
School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China; Beijing Key Laboratory of Energy Saving and Emission Reduction for Metallurgical Industry, University of Science and Technology Beijing, Beijing 100083, China

Yanhui Feng
School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China; Beijing Key Laboratory of Energy Saving and Emission Reduction for Metallurgical Industry, University of Science and Technology Beijing, Beijing 100083, China

Xinxin Zhang
School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing 100083, China; Beijing Key Laboratory of Energy Saving and Emission Reduction for Metallurgical Industry, University of Science and Technology Beijing, Beijing 100083, China

DOI: 10.1615/IHTC16.tpm.024018
pages 8919-8925


KEY WORDS: Thermophysical properties, Nano/Micro, Numerical simulation, octadecanoic acid, molecular dynamics, phase change materials

Abstract

Octadecanoic acids (OA) is a well-known phase change materials (PCMs) of thermal storage owing to their high energy density and narrow phase change temperature. Composite PCMs now is the mainstream. In the application of PCMs, OA often be filled in the substrate, like porous, framework and microencapsulated matrix, in nanoscale form. Although, OA greatly influenced by size effect, its macro thermal properties usually used in the composite's design. In order to further develop efficient composite PCMs based on OA, it is essential to study OA's thermal properties in nanoscale. In this study, we performed the atom-scale simulation through a top-down approach based on equilibrium molecular dynamics (EMD) to calculated the thermal conductivity(k) of OA with bulk, nanowire and nanochain. Vibrational density of states(VDOS) and phonon overlap energy were used to explore size scale of k. There is the greatest k of nanochain in 3 form and the smallest is nanowire. Size effect limit atoms vibration and weaken phonon match level of nanowire that results its k lower than bulk. But for nanochain, the effect of better nanostructure for heat transfer is much greater than attenuate by nanosize, with the VDOS peak shifting to lower frequency and phonon overlap energy enhancing. For the composite materials, especially for multilevel porous structure, it is better for materials design to choose appropriate k of filled OA. Our findings can provide a viable guidance for high-efficient thermal management designs of composite phase change materials.

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