Numerical studies on the performance enhancement of an encapsulated thermal storage unit

This paper investigates numerically the performance of an encapsulated latent heat thermal storage (LHTS) unit containing a phase change material (PCM) dispersed with high conductivity particles. A temperature based numerical model that incorporates the effect of particles via an effective thermal conductivity model has been developed considering the energy discharging (solidification) process. The system of governing equations has been solved using finite difference scheme employing Gauss-Seidel iteration technique. The results have shown a significant reduction in the time taken for complete solidification of the PCM due to the addition of high conductivity particles. It has been found that the time taken for complete solidification of the PCM decreased by about 26% with a particle fraction of about 30%. Compared to thermal conductivity of particles, the influence of particle fraction (ζ) on the performance enhancement of the unit has been found to be significant. For a given particle fraction, the performance enhancement obtained was almost the same for particle-PCM thermal conductivity ratio (kc/kpl) between 10 and 100 for the Pe, St and Ste studied in this work. The enhancement in energy discharge rate was found to be remarkable due to the addition of high conductivity particles to the PCM.