An Eulerian-Lagrangian model for analyzing the flow of nanofluids was developed and the effects of trap and reflect wall boundary conditions for nanoparticles were investigated. The discrete nature of particles was accounted for the two-way coupled model and the approach was applied to simulate the laminar AL2O3-water nanofluids inside a duct. The influence of the particle boundary conditions, solid volume fractions on concentration distribution and depositions of nanoparticles were investigated. For a fixed values of Reynolds number Re=100 and nanoparticle diameter dp=30nm, series of simulations were performed at a range of solid volume fraction 0 ≤ ϕ ≤ 0.05 for both trap and reflect boundary conditions for nanoparticle-wall interactions. It was found that for a reflecting wall, the concentration near the wall increased slightly that could cause a slight diffusion away from the wall. For the trapping wall, there was a sharp concentration gradient near the wall and the particles diffused toward the wall.

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