Thermodynamic evaluation and particle migration of hybrid nanofluids flowing through a complex microchannel with porous fins

A compound method is established by adding Al2O3-TiO2/Water (W) nanofluids and porous media in a microchannel to reduce pressure drop and enhance heat transfer in the limited heat dissipated area. Effects of porosity and hybrid nanofluids are numerically investigated in the laminar region. Pressure drop, Nusselt number, velocity and temperature fields are used as indicators to evaluate the characteristics of flow and heat transfer. Furthermore, the analytical methods including thermodynamic evaluation and nanoparticle migration were performed to reveal the essential mechanism of heat transfer enhancement. Compared with non-porous microchannels, the maximum reduction of porous microchannels is 9.73% (epsilon = 0.5), 8.3% (epsilon = 0.6) and 6.8% (epsilon = 0.7) for pressure drop, while the maximum agument is 23.53% (epsilon = 0.5), 20.59% (epsilon = 0.6) and 16.67% (epsilon = 0.7) for Nusselt number. The permeability of fluid reduces pressure drop and enhances heat transfer in the porous region. The maximum heat transfer irreversibility reduces up to 64%, and exergy efficiency reaches 88% by adding nanofluids and porous media. Nanoparticle migration originating from thermophoresis affects the concentration distribution near the wall, and cold-hot fluids fully mix in the porous region, thereby increasing heat transfer. The effect of thermophoretic diffusion of dilute nanofluids in micro-scale convective heat transfer is higher than that in the macro-scale one.

Automated summary

This study investigates the use of nanofluids and porous media in microchannels to reduce pressure drop and enhance heat transfer. Numerical simulations and analytical methods are used to evaluate the effects of porosity and hybrid nanofluids on flow and heat transfer. The results show that porous media can reduce pressure drop and enhance heat transfer, and nanoparticle migration affects heat transfer. The effect of thermophoretic diffusion is higher in micro-scale convective heat transfer.