Numerical Study on Melting Dynamics and Heat Transfer Enhancement of Micro‐Encapsulated Phase Change Material–Water Slurry in Natural Convection Enclosure Using Eulerian–Eulerian Model

Abstract

The two‐phase Eulerian–Eulerian solver is developed to analyze natural convection within a differentially heated square enclosure with water‐based micro‐encapsulated phase change material (MEPCM) slurry. The model solves the conservation equations for the liquid and MEPCM phases separately, with coupling between them is done through interfacial momentum and energy exchanges. Finite difference techniques, along with sixth‐order accuracy compact schemes for the nonlinear terms, are employed to discretise the equations. The MEPCM particles are considered in such a way that they melt close to the hot wall and solidify adjacent to the cold wall to make use of the latent heat benefits. After validating the solver with numerical and experimental data, the study analyses the transient evolution of the melting front, offering insights into phase transition behavior and underlying heat transfer mechanisms. This study also examines the effects of MEPCM volume fraction, hot wall temperature, and different phase change materials (n‐Octadecane and n‐Eicosane) on melting dynamics, flow fields and heat transfer. The MEPCM particles suspended in water enhance heat transfer by increasing the effective heat capacity through latent heat. At a temperature difference of ΔT=6$$ \Delta T=6 $$ K ( Gr=9.9×105$$ Gr=9.9\times {10}^5 $$ ) and volume fraction, ϕs$$ {\phi}_s $$ = 15% the heat transfer improves by 54.55% compared to water. However, at a higher temperature difference of ΔT=12$$ \Delta T=12 $$ K ( Gr=1.98×106$$ Gr=1.98\times {10}^6 $$ ), the enhancement drops to approximately 35.08%, indicating that at larger temperature differences, the stronger buoyancy forces dominate, increasing heat transfer, limiting the impact of MEPCM particles. Notably, heat transfer enhancement occurs only if the MEPCM particles undergo phase change within the cavity. If the hot wall temperature is too low to cause MEPCM melting, the lack of phase change reduces the slurry's overall thermal conductivity, thereby decreasing heat transfer.