Entropy generation of double-diffusive natural convection of a hybrid nano-encapsulated phase change materials in a partially porous biconcave cavity

This study aims to numerically explore double-diffusive natural convection and entropy generation of nano-encapsulated phase change materials (NEPCMs) mixed hybrid nanofluid within a partitioned biconcave cavity. This research also studies the effects of the width of the central porous layer and the top wall.

The momentum conservation in the porous region is described on the basis of Darcy–Brinkman–Forchheimer formulation. The governing equations are made dimensionless by defining some variables and parameters. The resulting equations are then solved numerically using the Galerkin finite element method.

Results reveal that the hybrid NEPCM mixture yields 7% and 0.62% improved heat and mass transport than that of NEPCM suspension with $φNEPCM$ = 3%. The Lewis number (Le) exhibits a nonmonotonic influence on the Nusselt number (Nu), with $Le=0.3$ being optimal for buoyancy ratio number $Nz≤3$⁠. Hybrid NEPCM suspension yields improved heat and mass transport compared to pure NEPCM suspension. The optimal $θfusion$ is identified as 0.4 for heat transfer and 0.2 for species transport. Both widening the adiabatic top wall and increasing porous layer thickness suppress Nu and Sherwood number (Sh). The entropy generation analysis shows that increasing $φNEPCM$ from 0.005 to 0.025 reduces total entropy generation (⁠$Ntotal$⁠) by 6%, while increasing volume fraction of $Al2O3$ (⁠$φSNP$⁠) elevates $Ntotal$ by 3.6%.

To the best of the authors’ knowledge, this work provides the first comprehensive numerical analysis of coupled heat and mass transport and second-law thermodynamic efficiency inside a partitioned enclosure with a hybrid nanofluid comprising NEPCMs and alumina.