Investigations of thermal and flow behavior of bifurcations and bends in fractal-like microchannel networks: Secondary flow and recirculation flow

In this work, the secondary flow and recirculation flow motions initiated at the bifurcations and bends in symmetric fractal-like microchannel networks with two branching levels were studied through three-dimensional simulations. The effects of Reynolds number and aspect ratio on the vortices generation were investigated. And the influences of these flow behaviors on the hydrodynamic and thermal characteristics of the fractal-like microchannel networks were demonstrated. It was found that for a fractal-like microchannel network, both the flow rate and the aspect ratio have large influences on the evolution of the vortices which therefore promoted the fluid mixing and enhanced the efficiency of the heat transfer greatly. As a result, the fractal-like microchannel network with a smaller aspect ratio of 0.333 was verified to have the lowest pressure drop and highest heat transfer performance compared with the other microchannel networks under investigation in our study.