Thermophoresis and Brownian Motion Effects on Nanoparticle Deposition Inside a 90° Square Bend Tube

Eulerian CFD model of direct absorption solar collector with nanofluid

“…Although there have not been many computational studies of nanofluid flow in DASCs, a number of papers consider flow and heat transfer of nanofluids in thermal systems of other type. Yin et al [84] investigated how aerosol nanoparticles were affected by forces. The main forces acting are drag-, Brownian-and thermophoretic forces.…”

“…Their simulation results show that the distribution of nanoparticles inside the channel is unsteady and nonuniform. Yin et al [84] discovered that the Brownian force takes the particles in the opposite direction of the particle concentration gradient, in an attempt to make the particle more homogeneous. The diffusivity was investigated to determine the primary mechanism of particle mitigation.…”

“…The resulting conclusion was that the Brownian force has a more significant impact on nanoparticle deposition with smaller particles and lower air temperatures. In comparison, the thermophoretic force is higher with a high temperature gradient [1,14,84].…”

“…Momentum coupling between phases occurs as a result of these mechanisms. For nanoparticles, the Brownian force, thermophoretic force, and the flow drag force are the dominating mechanisms [84]. As the number of particles is high, direct simulation of inter-particle collisions is not practicable because of high computational cost and large storage requirements.…”

“…For nanosized particles, the force magnitude is very high. The particle diffusion is much higher than for large particles, and leads to a high particle deposition rate [84]. Brownian motion can be considered as a macroscopic picture of a particle influenced by many microscopic random effects (as seen in Figure 4.1).…”