Numerical Modeling of Thermal Storage Performance of Encapsulated PCM Particles in an Unstructured Packed Bed

In this work, a numerical model to study phase transition in unstructured packed beds of phase change particles for latent heat thermal energy storage is presented and implemented into the open-source CFDEM(R) coupling program. The governing equations for both fluid and solid particles are discussed. The presented model is validated using experimental data. The validated model is used to study the effect of bed structure (e.g., using multiple sizes of particles and mixing of multiple configurations of particles) on the charging and discharging of PCM bed. It is found that using smaller particles leads to faster charging and discharging of the bed. A decrease of 26% was achieved by changing half the bed into particles with half the diameter. Furthermore, it is observed that placing small particles downstream has more effect on increased charging speed than placing them upstream when charging the bed fully. A decrease of 20% in charging time and a decrease of 13% in discharging time were observed in the configurations that were tested.