Thermal behavior of a sodium acetate trihydrate-based PCM: T-history and full-scale tests

Abstract

Latent heat thermal energy storage (LHTES) has been receiving increasing attention from researchers and engineers. A practical LHTES installation requires a deep understanding of phase change material’s (PCM’s) thermal behavior under thermal property testing and realistic operating conditions. To enrich this understanding, an experimental study on a commercial sodium acetate trihydrate-based PCM (Climsel C58) is presented in this article. C58 was characterized with two test methods: T-history tests and full-scale LHTES tests. The results are presented and discussed to exhibit the thermal behavior of C58 with these two test methods and the variations between them. With T-history tests, the thermal properties of C58 such as melting/solidification temperature range (57–61 °C/55–50 °C) and latent heat of fusion (216 kJ/kg) were determined. In full-scale LHTES tests, a parametric study was conducted to investigate the effects of heat transfer fluid flowrate and operating temperature range on the thermal performance of a 0.38 m3 storage prototype containing cylindrically macro-encapsulated C58. Moreover, longitudinal and radial PCM temperature distributions in full-scale tests were analyzed, suggesting the presence of phase separation. In general, C58 behaved differently between the two test methods regarding phase separation (negligible in T-history tests), supercooling effects (within 3 K in full-scale but up to 10 K in T-history tests), and thermal energy storage capacity (10% lower in full-scale tests). When using C58 or other salt hydrate-based PCMs for large-scale heat storage, these thermal behavior differences between the property-measurement and the application-oriented environments should be properly addressed in the design stage to ensure performance.