Directional enhancement and potential reduction of thermal conductivity induced by one-dimensional nanoparticle addition in pure PCMs

To increase the thermal conductivity of organic phase change material (PCM), One-dimensional materi-als are often used as an additive due to their excellent thermal performance. Many experiments have shown that micro effects have a great influence on the thermal conductivity of composite materials. To clarify the micro effect, numerous molecular dynamics simulations (MD) have been carried out. Previ-ous research has entirely overlooked the thermal conductivity changes of pure PCM in composite sys-tems. Neglecting the thermal conductivity changes of pure PCM is unreasonable, as the mass fraction of nanoparticles is often small. We took paraffin wax (PW) with carbon nanotube (CNT) as an example, and successfully reproduced the phase transition of composite PCM. Then we optimized the details of simulating thermal conductivity, and two processes of replication and movement were taken to get a stable thermal conductivity. A disassembly of thermal conductivity based on heat flux was actualized to investigate the thermal conductivity of pure PCM in composite systems. We investigated the difference in thermal conductivities between solids and liquids and analyzed the underlying mechanism through vibrational changes. The change of thermal conductivity in solids is contributed by CNT itself and the structure of PW; the change of thermal conductivity in liquids is contributed by CNT itself and the inter-action of CNT. Among these factors, structure change wouldn't always be beneficial. CNT always induces an axial enhancement of thermal conductivity in pure PCMs. At last, verification was carried out to prove the importance of structure. Our study brought a new view to understanding the behavior of thermal conductivity in composite PCM. & COPY; 2023 Elsevier Ltd. All rights reserved.

Automated summary

Studied the methods to increase the thermal conductivity of organic phase change materials (PCM) and found that one-dimensional materials as additives have excellent thermal properties. Molecular dynamics simulations showed that nanoparticles have an impact on the thermal conductivity of pure PCM. Investigated the thermal conductivity changes of composite PCM using paraffin wax (PW) and carbon nanotube (CNT) as an example.