Transient thermal response of multi-walled carbon nanotube phase change materials in building walls

Abstract

The low thermal conductivity of organic phase change materials has hindered their widespread use in building applications. In this study, it is attempted to overcome this limitation by investigating the transient thermal performance of adding multi-walled carbon nanotube (MWCNT) to n-octadecane. As such, this macroencapsulated, nano-enhanced phase change material (NePCM) was located within a multi-layer wall and its heat transfer was simulated through to the roof and wall sides. The panel’s interior wall temperature distribution, the daily/seasonal charging/discharging cycle, and the effect of the MWCNT’s aspect ratio variation on thermal performance were analysed for a range of weather conditions. The acquired results showed that increasing the PCM’s thermal conductivity, by MWCNT addition, yields a preferable outcome regarding thermal comfort in the selected winter and autumn days, but not on the summer days. By adding 3 wt% of MWCNT, the panel’s latent heat activation increased by 50.1%, 18.5%, and 39.7% for summer, autumn, and winter days, respectively. Furthermore, increasing the MWCNT’s aspect ratio showed a noticeable enhancement effect on the thermal conductivity, until a limit for NePCMs, with a higher nanotube concentration.