Behaviour of phase change material during discharge stage in a thermal energy storage system: an experimental and numerical study.

In this work, an investigation of the discharge stage of Phase Change Material (PCM) based Thermal Energy Storage (TES) system is carried out. Particle Image Velocimetry (PIV) technique is used for velocity measurement during the PCM solidification process and various real-time characteristics (flow, interface, mushy zone) are captured using High-Speed Imaging technique. Thermal stratification phenomenon led by gravity-driven convective cells is observed and analyzed. An interesting phenomenon of the detachment of dendrite particles from the developing mushy zone is also observed. The detached dendritic particles provide many nucleation sites for the initiation of the solidification in the domain. A numerical simulation is also performed using a one-domain continuum formulation based on finite volume method with an in-house developed code. The numerical prediction of the flow field and the solidified PCM thickness are compared with the related experimental measurements.