Experimental study of metal‐oxide nanoparticles on the thermal properties of erythritol for thermal energy storage

Abstract Erythritol has attracted wide attention due to high latent heat of 297.2 kJ/kg and excellent chemical stability as a medium‐ to low‐temperature thermal energy storage (TES) material. However, low thermal conductivity leads to extended charging and discharging time and severely affects its large‐scale application. In this article, three cheap nanoparticles (CuO, Al 2 O 3 , and Fe 2 O 3 ) and triethanolamine (TEA) were used as heat transfer enhancers and dispersant to improve the TES performance of erythritol. Sedimentation of nanoparticles in erythritol indicates that TEA is an effective dispersant in erythritol for three kinds of nanoparticles. The experimental results show that the thermal conductivity increased from 0.671 W/(m·K) of erythritol to 0.722 W/(m·K) and 0.761 W/(m·K) of 1.5 wt% CuO and Fe 2 O 3 nano‐enhanced phase change materials (NePCMs), respectively. Based on the DSC results, the melting temperature and heat of fusion of NePCMs stayed stable with nanoparticles but increased significantly after adding TEA. Furthermore, the charging/discharging cyclic behaviors of NePCMs were tested in the cycle test platform. During the cycle test, the melting time of 1.5 wt% CuO NePCM decreased from 657.9 s for pure erythritol to 615.8 s but increased to 757 s and 680.6 s for 1.5 wt% Al 2 O 3 and 1.5 wt% Fe 2 O 3 NePCMs. The solidification time decreased from 311.2 s for erythritol to 179.3 s, 198.5 s, and 132.4 s for 1.5 wt% CuO, 1.5 wt% Al 2 O 3 , and 1.5 wt% Fe 2 O 3 NePCMs. Interestingly, the supercooling degree of NePCMs we got from the test was much lower than that from the DSC curves, indicating that the supercooling is related to the sample size. These results testify that CuO and Fe 2 O 3 nanoparticles can improve the thermal conductivity of erythritol effectively.