Preparation and thermal properties of low-temperature composite phase-change materials based on a binary eutectic mixture with expanded graphite: Effect of particle size and mass fraction

Abstract

Considering the low thermal conductivity (λ) of organic phase-change materials (PCMs), a 1-dodecanol–tetradecane binary eutectic mixture (BEM) with a mass ratio of 26.3:72.7 was modified with expanded graphite (EG). BEM/EG low-temperature composite phase-change materials (LTCPCMs), with an EG mass fraction of 5 to 8 % and an EG particle size of 20 to 60 mesh, were prepared and characterised using various analysis techniques. Based on the results, 7 % EG with a size of 20 mesh (20-LTCPCM-7) was selected to enhance the λ of the BEM. Compared with that of the BEM, the λ of 20-LTCPCM-7 had a substantial enhancement of up to 3.2060 W/(m·K). The melting and solidification temperatures (Tm and Ts) of 20-LTCPCM-7 were measured to be 3.45 and 7.02°C, respectively. In addition, the latent heats of melting and solidification (∆Hm and ∆Hs) of 20-LTCPCM-7 were −197.90 and 193.71 J/g, respectively. In addition, the range of the phase-change temperatures (∆T) broadened. The LTCPCMs with different EG particles sizes also had notably higher thermal degradation temperatures of up to ~180°C. The results show that these LTCPCMs are appropriate for applications in solar air conditioning systems and cold chain logistics.