Influence of particle deposition on heat transfer characteristics for nanofluid free impinging jet: A numerical study

Abstract

Based on the two-body collision model, a nanoparticle collision, deposition and peeling model is established to describe the nanoparticle deposition process during SiO2-water nanofluid jet impinging on a heated copper column. The model is loaded with the Euler-Lagrange multiphase model in Ansys Fluent 19.1, and its accuracy is verified by comparing with the experimental data. Then the nanoparticle deposition processes during nanofluid jet impinging are studied with different inlet Reynolds numbers (Re), nanofluid volume fractions and impact heights (H/D). Result shows that the amount of nanoparticle deposition increases with the increasing nanofluid volume fraction, and it has a tendency of first increasing and then decreasing with the increasing inlet Reynolds number and the impact height, which reaches a maximum value when Re = 8849 and H/D = 4. Result also shows that it is easier to deposit at the junction between the impact zone and the wall jet zone with a deposition amount approximately 2 times of that at the outlet. A nanoparticle thermal resistance layer and a high-density nanofluid layer are formed in the near-wall region, and velocity slip between phases in the layer could reach 2.824m/s, which significantly enhance the base-fluid’s micro-flow intensity and the particles’ movement, thus strengthening the momentum exchange and energy exchange between phases and wall. The maximum heat transfer coefficient could reach 27857.4 W/(K·m2), and the average heat transfer coefficient has a 67.9% increment with 3% SiO2-water nanofluid volume fraction.