Modeling of PCM melting: Analysis of discrepancy between numerical and experimental results and energy storage performance

• Published in: Energy (Oxford) 2018-05, Vol.150, p.190-204
• Main Authors: Soni, Vikram, Kumar, Arvind, Jain, V.K.
• Format: Article
• Language: English
• Subjects: Computational fluid dynamics; Computer simulation; Density; Energy; Energy consumption; Energy density; Energy equation; Energy storage; Fluid flow; Heat storage; Heated water; Mathematical models; Melt flow; Melting; Phase change material; Phase change materials; Research methodology; Simulation; Thermal energy; Thermal energy storage; Thermal performance; Thermal plumes; Variation
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2018.02.097

In this work, a comprehensive analysis of constrained melting of phase change material (PCM) is performed to identify the reasons for the discrepancy of numerical predictions. To identify this, models are proposed by accounting various experimental geometrical details. The predictions are compared and validated with the available experimental results. The results indicated a substantial influence of accounting geometrical details for reducing the difference between the numerical predictions and the experimental data. Further, the global and the local thermal and flow behavior during PCM melting, and their influence on heat storage is described. It is observed that the thermally induced flow patterns followed by formation of stratified layers aid in achieving improved heat storage. Moreover, undulations in the melting front and temperature fluctuations are observed due to thermal plumes and multiple counter-rotating vortices in the capsule. For evaluating the thermal performance, the stratified and the total energy storage densities, along with the thermal energy storage (TES) effectiveness, are also analyzed. At the end, for accounting different solid and liquid phase properties, a new physically consistent mathematical formulation of the conservative form of the energy equation is proposed. Simulation using this advanced model has shown further improvement in the predictions. •The reasons for the failure of numerical predictions performed in the literature are identified.•A detailed local and global analysis on transient phase fraction, fluid flow and thermal response is performed.•Thermal performance in terms of Energy Storage Density, Specific Energy and Energy Effectiveness of the system is analyzed.•A new model with different solid and liquid phase material properties is proposed.•It is important to consider exact geometrical conditions with appropriate material properties in simulations.