Lattice Boltzmann simulation of magnetohydrodynamic double-diffusive convection hybrid nanofluid flow through solid blocks in a porous H-shaped enclosure

Background

Efficient heat transfer is vital in cooling systems to prevent overheating and maintain optimal performance. This study explores an H-shaped enclosure design incorporating conducting solid blocks and hybrid nanofluids (HNFs) based on a water-ethylene glycol (60:40) mixture. This coolant composition improves thermal stability by lowering the freezing point and raising the boiling point. The research focuses on magnetohydrodynamic double-diffusive natural convection (MHD-DDNC), analyzing the interactions between porous media, conducting blocks, and HNFs in the presence of a magnetic field.

Methods

Numerical analysis was performed using the non-orthogonal multi-relaxation time lattice Boltzmann method (NMRT-LBM). The D2Q9 scheme was applied for density and velocity, while D2Q5 was used for temperature and concentration fields. Key parameters such as Darcy number (Da), nanoparticle volume fraction (ϕ), buoyancy ratio (Br), Soret (S_r) and Dufour (D_r) numbers, thermal conductivity ratio (R_k), and mass transfer coefficient ratio (R_d) were analyzed to understand their impact on heat and mass transfer within the enclosure.

Significant findings

The results demonstrate that increasing ϕ and Br significantly enhances both heat and mass transfer rates, with improvements of up to 16.65% in the average Nusselt number ($\overline{Nu}$) and 12.45% in the average Sherwood number ($\overline{Sh}$). Increasing Da intensifies horizontal velocity and enhances nanofluid circulation, leading to a 12.91% improvement in $\overline{Nu}$ and a 9.59% increase in $\overline{Sh}$ at ϕ = 4%. The Soret number reduces $\overline{Nu}$ by 1.01% but rises $\overline{Sh}$ by 26.65%, while the Dufour number yields the opposite. Varying R_k from 0.1 to 10 at ϕ = 4% increases thermal performance by 33.53% and mass transfer by 9.61%. Increasing R_d from 0.1 to 10 improves $\overline{Nu}$ by 8.07% and $\overline{Sh}$ by 31.53%, demonstrating the strong influence of these parameters on heat and mass transfer performance. These results highlight the potential applications for optimizing automotive cooling systems, regenerative exchangers, and HVAC heat exchangers.