Experimental validation of a novel modelling technique for packed bed thermal storage systems containing non-spherical phase change material capsules

Abstract

This work presents a novel modeling technique for non-spherical capsule-shaped latent heat packed bed storage (PBS) systems aiming for resource efficiency in iterative optimization and design. The current simulation methods for such systems are resource-intensive and not suitable for iterative design. To address this, it is proposed to combine an efficient approach of detailed simulations of a single capsule during the phase change process with a one-dimensional (1D) model. Finite element simulations are used to capture local phenomena and characterize heat transfer rates from the capsules. The resulting heat flux dataset is integrated into a finite volume model to simulate the entire PCM-PBS system effectively. By combining these approaches, the computational resources needed are significantly reduced while maintaining accuracy. Experimental validation was conducted using a PCM-PBS setup with steel cans containing stearic acid and water as the heat transfer fluid. The results were able to reproduce the temperature history measured at four locations within the packed bed as well as the outlet temperature and total energy remove from the system during discharge for six separate experiments. These confirm the effectiveness of this simulation technique and provide validation. It addresses a knowledge gap in both experimental and numerical aspects, offering potential improvements in charge/discharge rate, energy density, and cost-effectiveness of PCM-PBS systems.