Analysis on the Improvement of Thermal Performance of Phase Change Material Ba (OH)2·8H2O

Abstract

Benefitting from the characteristics of a high latent heat capacity and stable phase change behavior, phase change materials have widely received concerns in the field of thermodynamic management. Ba(OH)2·8H2O is an ideal phase change material (PCM) in the mid-to-low temperature range, but its large-scale application is still limited by severe supercooling during the nucleation process. In this paper, the experimental analysis and comparison are performed via an Edisonian approach, where Ba(OH)2·8H2O is adopted as an original substrate; BaCO3, CaCl2, NaCl, KH2PO4, and NaOH are selected as nucleating agents; and graphite is used as a heat-conducting agent. The results show that Ba(OH)2·8H2O containing 1.2% BaCO3 and 0.2% graphite powder has the best performance. Compared with pure Ba(OH)2·8H2O, the supercooling degree is reduced to less than 1 °C, the phase change latent heat duration is extended, and the thermal conductivity is significantly improved. Therefore, this study not only provides a reference for the application of Ba(OH)2·8H2O, but can also be used as a guidance for other material modifications.

Development of a New Modified CaCl2·6H2O Composite Phase Change Material

“…At present, the commonly used method is to add a nucleating agent, which can effectively reduce the subcooling degree. Luo et al [31] used barium carbonate as a nucleating agent to effectively reduce the subcooling of Ba(OH) 2 • 8H 2 O to less than 1 • C. The selection of nucleating agent should be based on the following two principles: (1) the nucleating agent does not react with the original substrate; (2) the phase transition temperature of a nucleating agent should be higher than that of the original substrate to avoid polluting the original substrate and affecting the heat storage and release performance. After consulting the literature, it was found that barium salt can effectively reduce the subcooling of CaCl 2 •6H 2 O and improve the cycle stability of the CaCl 2 •6H 2 O system [32].…”