Experimental and numerical investigation of a laboratory-scale shell-and-tube latent heat storage

Thermal energy storage plays a key role in balancing energy supply and demand, thus improving the reliability and efficiency of energy systems. Latent heat thermal energy storages are particularly promising due to their higher energy density and ability to provide a substantial amount of heat over small temperature differences. In this work, an experimental shell-and-tube latent heat storage is assembled with stearic acid, which has a peak melting temperature of 69.95 °C, as a phase change material. Two modelling approaches are employed to study the melting and solidification of stearic acid during the storage's charging and discharging phases: detailed computational fluid dynamics simulations and simplified process modelling. The experimental data is used for model validation and comparison. The results demonstrate that the computational fluid dynamics model can accurately predict the temperature distribution within the phase change material when natural convection is included, achieving a root-mean-square error relative to the experiments of 3.7 °C compared to 6.2 °C in the process model. Meanwhile, the process model shows excellent agreement with the experimental data in the unit's overall performance, reducing the root-mean-square error in charging power to 4 W, compared to 13 W in the computational fluid dynamics model, by allowing for more flexible modifications to the modelled system. The paper also discusses the causes of the discrepancies between the numerical and experimental data and suggests ways to minimize them. © 2024 The Authors