A capric-palmitic-stearic acid ternary eutectic mixture/expanded graphite composite phase change material for thermal energy storage

This paper demonstrated a capric acid-palmitic acid-stearic acid ternary eutectic mixture/expanded graphite (CA-PA-SA/EG) composite phase change material (PCM) for low-temperature heat storage. The CA-PA-SA ternary eutectic mixture with a mass ratio of CA:PA:SA = 79.3:14.7:6.0 was prepared firstly, and its mass ratio in the CA-PA-SA/EG composite can reach as high as 90%. The melting and freezing temperatures of CA-PA-SA/EG composite were 21.33 °C and 19.01 °C, and the corresponding latent heat were 131.7 kJ kg−1 and 127.2 kJ kg−1. The CA-PA-SA/EG composite powders can be formed into round blocks by dry pressing easily, with much higher thermal conductivity than CA-PA-SA. Thermal performance test showed that the increasing thermal conductivity of CA-PA-SA could obviously decrease the melting/cooling time. Thermal property characterizations after 500 heating/cooling cycles test indicated that CA-PA-SA/EG composite PCM had excellent thermal reliability. Based on all these results, CA-PA-SA/EG composite PCM is a promising material for low-temperature thermal energy storage applications.