In order to investigate the size effects of two-dimensional nanoparticles on the energy storage property of composite PCMs

graphite nanosheets (GNS-10

GNS-30

GNS-90) with different sizes were prepared by exfoliating expanded graphite with the assistance of ultra-sonication for different time and dispersed into hexadecanol. The prepared PCMs were characterized with SEM

XRD and Hot Disk

and the thermal conductivity was predicted by Maxwell

Bruggeman and Nielsen models. Results reveal that the graphite nanosheets presenting larger aspect ratios can achieve better thermal conductivity enhancement

because relatively large nanofiller contributes to the formation of heat transfer network in PCM matrix. An enhancement of thermal conductivity up to 517% has been achieved by GNS-10 at the loading of 10% (mass). The prediction of Nielsen model fits the experimental value better with the shape factor of A as 100 to 180. Compared to the great increase in thermal conductivity after the addition of graphite nanosheets

the changes in melting/solidification temperature and enthalpy of composite PCMs are negligible. Furthermore

the increased freezing rate of composited PCMs is clearly presented as a consequence of enhanced thermal conductivity.