Temperature-dependent growth kinetic and crystallization behavior of the supercooled erythritol as a phase change material in long-term heat storage

Abstract

Along with the development of long-term heat storage, the utilization of sugar alcohol with large supercooling has been valued in recent years. However, the heat release rate is not easy to control, and the supercooling would be easily influenced by accident factors. Different from the research of directly developing the composites to control the heat release rate and keep stable supercooling, this paper investigated the temperature-dependence crystal growth of erythritol coupled with diffusion-limited kinetics to find the mechanism for better understanding the utilization of supercooling upon different heat needs. The mean crystal growth rate (vm) on supercooled erythritol and the thermodynamic parameters were characterized experimentally. A nucleation factor J* was proposed to improve the modern Wilson-Frenkel equation, which enables a more accurate reflection of the nucleation effect on the practical vm. The sensitivity analysis indicates that the diffusion coefficient (D) and liquid–solid interfacial free energy (IFE1) have a great impact on vm, with 62% and 37% correlations. To verify this result, 0.1 wt% PVA was added to erythritol, which resulted in a significant reduction in the vm maximum by 33.3%. An oil seal was added to reduce the liquid–air interfacial free energy (IFE2) of erythritol, which significantly extended the supercooling duration to 5 days with a 12% cumulative crystallization fraction. Moreover, the crystal morphology analysis revealed that the maximum growth rate had preferred orientations of (2 1 1), the largest grain boundary size of 9.2 mm, and exhibited three-dimensional growth. This work can aid in the creation of a dependable heat release model for sugar alcohols in long-term heat storage systems.