Numerical investigation of multi walled carbon nanotubes- water nanofluid turbulent flow in a tube with 180° bent and selection of optimum turbulency model

Common fluids such as water, ethylene glycol and oil have low thermal conductivity compared to metals and metal oxides. Hence, in recent decades, use of nanofluids has received significant interest. These fluids are colloidal of a base fluid (such as water or oil) with metal, ceramic or polymer nanoparticles. In this study, multi walled carbon nanotubes/water nanofluid in a forced convection heat transfer was investigated numerically in turbulent flow through a curved tube (180°) with constant wall temperature. Effects of Reynolds number and nanoparticles volume fraction on convection heat transfer were considered. Results showed that with increase in Reynolds number from 4000 to 6000, convection heat transfer coefficient was enhanced by 24%. Also, with increasing the volume friction of nanoparticles up to 0.01, convection heat transfer coefficient increased by 21% compared to the base flow.