Analysis of surface tension and EHD effects on differentially heated cavity filled with NEPCMs nanofluids

This paper aims to investigate the coupled interactions between electrohydrodynamic (EHD) forces, Marangoni convection and buoyancy-driven flow within a square cavity filled with a nanofluid containing nano-encapsulated phase change materials (NEPCMs). The study seeks to elucidate how the triple coupling of active electric forcing, interfacial thermocapillary stresses and latent heat storage influences flow morphology, thermal distribution and overall heat transfer performance.

A comprehensive numerical model is developed based on the stream function-vorticity formulation. The governing equations are solved using a finite difference method with second-order accurate spatial discretization and the resulting algebraic systems are iteratively solved via the successive over-relaxation (SOR) technique. The parametric study encompasses variations in the Marangoni number (⁠$−4000≤Ma≤4000$⁠), electric Rayleigh number (⁠$200≤RaE≤400$⁠), gravitational Rayleigh number (⁠$103≤Rag≤105$⁠), fusion temperature (⁠$0.1≤ΘF≤0.3$⁠) and NEPCM volume fraction (⁠$0.0≤ϕ≤0.05$⁠).

Systems with negative Marangoni numbers (⁠$Ma<0$⁠) consistently exhibit superior heat transfer due to synergistic thermocapillary shear reinforcing the primary buoyant-EHD circulation. The average Nusselt number displays a characteristic V-shaped dependence on Ma, with a distinct minimum near $Ma=1000$⁠. Crucially, the electric field actively restructures the flow and relocates the NEPCMs melting region.

The numerical model assumes a two-dimensional, steady-state flow, which may not capture the three-dimensional instabilities and transient plume behaviors characteristic of high electric Rayleigh numbers. Furthermore, the hybrid nanofluid is treated as a homogeneous medium, neglecting potential particle migration due to electrophoretic or thermophoretic forces.

The findings provide predictive design guidelines for developing efficient, controllable thermal management systems, including high-power electronics cooling, advanced energy storage and aerospace thermal control applications.

To the best of the authors’ knowledge, this work presents the first integrated analysis of triple-coupled enhancement strategies combining active EHD forcing, interfacial Marangoni convection and passive latent heat storage within NEPCM nanofluids.