Pore-scale simulation of nanoparticle transport and deposition in a microchannel using a Lagrangian approach

The application of nanoparticles to a fluid improves heat transfer and hydrodynamics, especially in porous media. To analyze the flow of nanoparticles and heat transfer in porous media at the pore scale, simulation in micro-scale channels of porous media is necessary. One concern is the deposition of nanoparticles to solid surfaces, which reduces the amount of material available in the bulk fluid. Also, in porous media, the nanoparticle deposition increases the surface roughness of pore surfaces, affecting the volumetric flow rate of nanofluid. Nanoparticle transport and deposition in a microchannel (as a representation of pore) are investigated numerically. The open-source library of OpenFOAM is used, and the Eulerian-Lagrangian (EL) approach is employed to simulate nanoparticles interacting with the base fluid and the surfaces of the microchannel. Integration of all forces exerted on nanoparticles, from base fluid and also microchannel’s surfaces are considered simultaneously. Brownian motion, drag, buoyancy, gravity, and Saffman lift forces are considered between nanoparticles and the base fluid. Van der Waals and electrostatic double-layer forces based on DLVO theory are considered between nanoparticles and microchannel surfaces. The deposition ratio of nanoparticles (the fraction of nanoparticles that deposit on the solid surface) is analyzed by the variation of nanoparticle diameter, fluid velocity, temperature, surface potentials, and double-layer thickness. It is assumed that the nanofluid is dilute, and the collisions between the nanoparticles are neglected. The results of nanoparticle deposition ratio are validated through comparison with available data in the literature. It has been shown that the nanoparticle deposition ratio decreases from 0.98 to 0.4 when the nanoparticle diameter increases from 30 to 150 nm. The effect of Van der Waals force on the enhancement of nanoparticle deposition ratio is about 1.6 %. Next, the deposition of nanoparticles is studied for different Reynolds number values, surface potential, nanoparticle radius, and double-layer thickness. Brownian motion dominates the behavior; increasing temperature and decreasing nanoparticle diameter will increase nanoparticle deposition. The magnitude of the nanoparticle and surface potentials and the double layer thickness are the two essential parameters that control the electrostatic double-layer force; its effect on deposition is also investigated. It has been concluded that the rise of the surface potential value decreases the deposition ratio.