Abstract:
Due to rapid development in the technology of electronic devices and improved performance of thermoelectric
materials, thermal management is one of the significant issues to be dealt with. Hence, the conventional heat
transfer methods are not responsive anymore, especially in micro-electric applications. In this work, the application
of nanofluid, instead of pure fluids, in the microchannel heat sink with sudden explanation and insertion
of ribs and dimples inside the backward-facing step microchannel is studied numerically. Lattice Boltzmann
method is applied to study the heat transfer and laminar flow behaviour of 4% concentration of Al2O3-water
nanofluids in Reynolds numbers ranging 40–100 through the backward-facing step microchannel. Microchannel
size is 60 μm (H) × 60 μm (W) × 336 μm (L), and the height of the microchannel’s step is 27 μm, and located 108
μm from the entrance. The bottom wall of the microchannel, downstream of the step is exposed to constant heat
flux. Ribs and hemispherical dimples are located on this wall section as vortex generators. A few studies focus on
curved boundaries in Lattice Boltzmann Method due to some complexities in curved boundaries, especially
spherical ones. So, the main novelty of this work is inserting hemispherical dimples in backward-facing step
microchannel and combining them with ribs as proposed turbulators. The results showed that increasing the
number of ribs from 4 to 8 (100% growth) leads to a 63.64 and 64.65% augmentation in the average Nusselt
number at Re = 40 and 100, respectively. Also, increasing the ribs heights from 0.5H to 2H (300% growth)
caused average Nusselt number augmentation of about 54.54 and 40.91% at Re = 40 and 100, respectively. In
some cases, with lower numbers or shorter ribs, the effects of adding ribs on the Nusselt number are either minor
or undesirable.
