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In this study, a series of binary mixtures of stearic acid (SA) and acetanilide (AA) at various mass fractions were prepared. A novel binary mixture of SA and AA in the ratio of 81.0:19.0 mol% is shown to be an eutectic mixture with melting temperature of 342.45 ± 0.25 K, melting latent heat of 220.04 ± 10.02 J·g-1. In order to improve the thermal properties of SA-AA eutectic mixture so as to obtain a better composite phase change materials (CPCM) with high thermal conductivity, large heat storage capacity, good thermal stability and reliability for heat energy storage, expanded graphite (EG) at different mass fractions is added into SA-AA eutectic mixture. The results exhibited it remarkable energy storage capacity with a latent heat of CPCM of 176.14 J·g-1 compared to most of the organic eutectic mixture composite. The thermal conductivity of the CPCM was enhanced by 14.5 times comparing to SA-AA eutectic mixture. And the thermo-physical properties of the SA-AA/EG CPCM after 100 accelerated thermal cycles were slightly decreased which did not distinct influence on heat storage. Thus, the prepared SA-AA/EG CPCM is a promising material for latent heat storage systems.

The thermal properties of the binary system composed of lauric acid (LA) and nonanoic acid (NA) and its binary phase diagram were studied. To put this binary system into practice, the mixture with 96wt% of LA was selected, and it has a phase change temperature of 41oC and a latent heat of 163 J g-1, which is suitable for domestic water heating application. Besides, its thermal and chemical structure stability, thermal conductivity, degree of supercooling and thermal reliability were investigated by thermogravimetric analyzer (TGA), fourier transform infrared (FT-IR) spectrophotometer, thermal conductivity apparatus (TCA), T-history method and accelerated thermal cycle test for 1000 melt/freeze cycles, separately. The results of above tests indicated that the mixture has a remarkable thermal stability, a good chemical structure stability, no supercooling and an excellent thermal reliability. Therefore, the mixture can be a potential PCM used for thermal energy storage.

An adipic acid/boric acid (AA–BA) binary eutectic mixture containing 80 wt % adipic acid and 20 wt % boric acid was investigated as a new phase change material (PCM) with high latent heat, high thermal stability, and low cost. The material′s thermophysical properties and thermal stability were studied using differential scanning calorimetry (DSC), X-Ray Diffraction (XRD), and thermogravimetric analysis (TGA). The thermal stability was investigated in situ over 100 cycles using DSC. The phase change temperature of the AA–BA binary eutectic mixture was 135.04 °C and the latent heats of the melting and crystallization process were 283.42 and 272.16 J g−1, respectively. The latent heat of melting only dropped 4.94 % after in situ 100 cycles using DSC. Following comparison of thermal properties and price of the AA–BA eutectic mixture PCM with those of some composite PCMs, the results indicate that the newly prepared AA–BA eutectic mixture is a potential phase change material for thermal storage tanks.