Numerical and experimental analysis of nanoparticle deposition within geometrically varied microchannels

Solving deposition problems in nanofluid-microchannel cooling systems is the key to bringing this technology from the laboratory to industry. Despite numerous simulation studies on particle deposition in bent microchannels, the mechanisms controlling deposition patterns and the debated role of secondary flow remain unresolved, largely due to a lack of experimental results. In order to solve these problems, this study combines a discrete phase model (DPM) with real-time visualization experiments to investigate nanoparticle deposition in various microchannel shapes. The results indicate that straight microchannels in either vertical or horizontal orientations did not influence deposition numbers along the channel. However, the study of sharp bend 90° microchannels revealed two recirculation zones: one at the outer radius of the corner was only affected by geometry, while one at the inner radius of the downstream increased with increasing fluid velocity. In sharp bend microchannels, the particle deposition number increased in corners, and the particle deposition downstream of the corner was higher than that observed upstream. In round bend 90° microchannels, the highest deposition of nanoparticles was observed at the corner but was slightly higher downstream than in the upstream of the microchannel. Overall, 90° corners with a larger radius were found to perform better than a sharp bend in terms of reducing particle deposition. Furthermore, particle deposition at the corner can be minimized by employing larger particles, along with a greater bend angle and radius.