A physics-based 0D model for unsteady prediction of shell-and-tube latent heat thermal energy storage systems

A physics-based reduced-order model is developed to predict the performance of latent heat thermal energy storage (LHTES) systems. The well-established vertical shell-and-tube configuration is considered, consisting of a storage vessel filled with phase change material (PCM) and crossed by a representative tube through which the heat transfer fluid flows. The modelling of LHTES systems is inherently challenging due to the strong nonlinear coupling between phase change, heat conduction, and natural convection phenomena. To address this complexity, the proposed approach adopts a multi-zone lumped heat-transfer formulation derived from physical phenomenology and informed by experimental and high-fidelity numerical studies. The PCM domain is approximated using different zonal decompositions depending on the operating mode. During charging, vertical stratification is represented by upper and lower regions, while during discharging, a radial partition is adopted to account for dominant heat-transfer pathways. Although the model does not explicitly track the solid–liquid interface, it retains the key physical mechanisms governing the coupled heat-transfer and storage dynamics. Comparison with low- and high-temperature experimental datasets demonstrates accurate prediction of the measured PCM-temperature evolution over complete charging and discharging cycles. The model also provides internally consistent predictions of heat-transfer rates and stored thermal energy. Due to its low computational cost and general formulation, the proposed model is particularly suitable for integration into system-level simulations of energy systems incorporating thermal storage.