Enhancement on thermal properties of paraffin/calcium carbonate phase change microcapsules with carbon network

For latent heat storage with phase change materials (PCM), heat transfer rate and energy storage efficiency are often limited by the low PCM thermal conductivity. Therefore, this paper develops a sort of new phase change composites (PCC) with double-layer network to enhance the thermal conductivity and thermal stability. Different mass fractions of expanded graphite (EG) as heat transfer promoter were added in the spindle microencapsulated phase change materials (MicroPCM). The relationship between the PCC thermal conductivity and carbon network structure was investigated. The thermal conductivity was measured by transient plane source method. The carbon network structure of PCC was detected by energy dispersive spectroscopy. Temperature-regulated property was captured by infrared imager. As a result, distinct carbon network structure in PCC was observed with 20% mass fraction of EG, the corresponding thermal conductivity was increased up to 7.5 times of the pristine paraffin. Negligible change in thermal properties of the PCC was confirmed after 100 times thermal cycling and 7 days serving durability tests. The enhancement on thermal properties of the PCC is a promising route to achieve high energy storage efficiency targets of numerous thermal applications.