Numerical investigation of nanofluid particle migration and convective heat transfer in microchannels using an Eulerian–Lagrangian approach

Abstract

An Eulerian–Lagrangian modelling approach was employed in order to investigate the flow field, heat transfer and particle distribution in nanofluid flow in a parallel-plate microchannel, with a focus on relatively low Reynolds numbers ($Re\leqslant 100$). Momentum and thermal interactions between fluid and particle phases were accounted for using a transient two-way coupling algorithm implemented within an in-house code that tracked the simultaneous evolution of the carrier and particulate phases while considering timescale differences between the two phases. The inaccuracy of assuming a homogeneous particle distribution in modelling nanofluid flow in microchannels was established. In particular, shear rate and thermophoresis were found to play a key role in the lateral migration of nanoparticles and in the formation of particle depletion and accumulation regions in the vicinity of the channel walls. At low Reynolds numbers, nanoparticle distribution near the walls was observed to gradually flatten in the streamwise direction. On the other hand, for relatively higher Reynolds numbers, higher particle non-uniformities were observed in the vicinity of the channel walls. Furthermore, it was established that convective heat transfer between channel walls and the bulk fluid can either improve or deteriorate with the addition of nanoparticles, depending on whether the flow exceeded a critical Reynolds number of enhancement. It was also established that Brownian motion and thermophoresis had a major role in nanoparticle deposition on the channel walls. In particular, Brownian motion was the main deposition mechanism for nano-sized particles, whereas due to thermophoresis, nanoparticles were repelled away from channel walls. The result of the competition between the two is that deposition gradually increased along the streamwise direction.

Numerical investigation of nanoparticles slip mechanisms impact on the natural convection heat transfer characteristics of nanofluids in an enclosure

“…The latter can be also subdivided into; single-phase approach, two-phase approach based on the Eulerian–Lagrangian method (see for example the work of Sharaf et al . 9 ), or two-phase approach based on the Eulerian-Eulerian method, which is the focus of the present study. Considering this, a brief review of the evolution of Eulerian-Eulerian based models used for the prediction of nanofluid heat transfer features in the square cavity is presented here.…”

Conjugate buoyant convective transport of nanofluids in an enclosed annular geometry

“…Roy 33 examined nanofluid buoyant motion in the annular section between a square geometry and three distinct interior geometries, such as circular or elliptical or rectangular cylinder and found the inner shapes has profound impacts on thermal dissipation rates compared to a square geometry. Using combined Lagrangian and Eulerian modeling, Sharaf et al 34 investigated the convective motion and nanoparticle dissemination in a microchannel formed by parallel plates and brought out inaccuracies in the existing nanofluid model. The impacts of three different arrangements of conductive baffles on nanofluid motion and associated thermal behavior in a square geometry has been performed by Bendaraa et al 35 and noticed that the fin location has vital role in effective controlling of the flow movement and thus thermal dissipation rates.…”

A numerical comparison of circular and corrugation heat sink for laminar CuO–water nano-fluid flow and heat transfer enhancement

“…The thermal performance of CuO-H 2 O nanofluids was better as compare to water. Sharaf et al (2019) investigated numerically convective heat transfer of nanofluid in a parallel-plate microchannel, at low Reynolds numbers (Re ≤ 100). It is found the convective heat transfer between channel walls and the bulk fluid can either improve or deteriorate with the addition of nanoparticles, depending on whether the flow exceeded a critical Reynolds number of enhancement.…”