Numerical study of nanofluid forced convection flow in channels using different shaped transverse ribs

A numerical investigation is performed to study the effects of different rib shapes and turbulent nanofluid flow on the thermal and flow fields through transversely roughened rectangular channels with Reynolds number ranging from 5000 to 20000 and uniform heat flux of 10 kW/m2. Considering single-phase approach, the two-dimensional continuity, Navier-Stokes, and energy equations were solved by using the finite volume method (FVM). The optimization was carried out by using various rib shapes (rectangular shape, triangular shape, wedge pointing upstream, and wedge pointing downstream) in two arrangements (in-line and staggered) and three different aspect ratios (w/e = 0.5, 2, and 4) to reach the optimal geometry with maximum performance evaluation criterion (PEC). The main aim of this study is to analyze the effects of nanoparticle types (Al2O3, CuO, SiO2, and ZnO), concentration (1-4%), and nanoparticle diameter (30-80 nm), on the heat transfer and fluid flow characteristics. Simulation results show that the ribbed channels' performance was greatly influenced by rib shapes and their geometrical parameters. The highest PEC was obtained for the in-line triangular ribs with w/e = 4 at Re = 5000. It is found that the water-SiO2 shows the highest heat transfer enhancement compared with other tested nanofluids. The Nusselt number through the ribbed channels was enhanced with the increase of the particle volume fraction and Reynolds number, and with the decrease of nanoparticle diameter.