Simultaneous decrease in supercooling and enhancement of thermal conductivity of paraffin emulsion in medium temperature range with graphene as additive

Highlights: • Better supercooling and thermal conductivity of emulsion obtained simultaneously. • Using graphene as additive for paraffin emulsion in medium temperature range. • The thermal conductivity of paraffin emulsion increased by 20.22%. • Reducing the supercooling degree of paraffin emulsion from 14.23 to 0.27 °C. - Abstract: As a promising functional latent-heat fluid, phase change emulsion suffers from high supercooling and low thermal conductivity, yet no satisfactory solution for both problems has been reported. We firstly proposed a solution to the problems of 20 wt% paraffin emulsion(PE) in medium temperature range (40–80 °C) with graphene as additive. After adding graphene, the supercooling degree dropped from 14.23 to 0.27 °C, while the latent heat changed by less than 2J g⁻¹(3%), and the thermal conductivity increased by 20.22%. The size of the emulsion particles with or without graphene, which was originally between 200 and 1500 nm, only changed within 5% after 300 melting/freezing cycles. DSC test showed the graphene-added composite PE(GPE) had good stability with only changed 1.53%, 3.14% in latent heat and 1.45% in phase change temperature after 300 cycles. Therefore, this new emulsion with high heat storage capacity, good thermal performance, and high stability, will exhitat remarkable potential in thermal energy storage.