Preparation and characteristics optimization of octadecanoic acid/octadecanol/expanded graphite based composite phase change materials for energy storage

Abstract

The thermal energy storage (TES) based on latent heat technique with outstanding thermal performance is required to boost the development of the field thermal management application. Hence, this research proposes a solid-liquid composite phase change materials (CPCMs) based on octadecanoic acid (C18-acid), octadecanol (C18-OH) and expanded graphite (EG). The CPCMs structural and thermal properties were analyzed using the spectroscopy and calorimetry techniques. The X-ray diffractometer (XRD), Scanning electron microscope (SEM) and Fourier transformation infrared spectroscopy (FTIR) were utilized for the morphological and structural characterization of the CPCMs. Accordingly, the results revealed that the three components combined in the CPCMs were successfully mixed by physically combination. The CPCMs thermal performance was determined by using differential scanning calorimetry (DSC) and thermal conductivity analyzer (TCA) instruments. As a result, the CPCMs latent heats were in the area of 135.2 to 143.5 J/g in the melting process for the temperature range of 45.5 to 47 °C and −149.0 to −189.6 J/g during the crystallization phase transition in the temperature range of 37.1 to 37.8 °C. It is worth mentioning that the addition of several mass fractions (1 %, 3 %, 5 %, 7 % and 9 %) of EG in the binary C18-acid/C18-OH has significantly enhanced the CPCMs thermal conductivity from 0.066 W/(m·K) up to 3.38 W/(m·K), hence, leading to optimize the heat transfer rate in the CPCMs medium. Moreover, the thermal degradation and leakage experiments were performed to evaluate the CPCMs operating performance. Based on results, the solid-liquid CPCMs as prepared with great thermal properties is a suitable PCMs for the thermal energy management application.