In tube convection heat transfer enhancement: SiO₂ aqua based nanofluids

In this paper, an experimental investigation is carried out on internal convective heat transfer of SiO₂/water nanofluids in a copper tube for a fully turbulent regime. Nusselt number and convective heat transfer coefficients of nanofluid at three different volumetric concentration (0.001%, 0.003%, 0.007%) of nanoparticles were estimated. Local convective heat transfer coefficient at different locations along the tube at varying Reynolds number was also observed. With volumetric concentration of 0.001% of SiO₂ nanoparticles, maximum enhancement observed was 8–9%. Whereas at 0.007% volumetric concentration of SiO₂ nanoparticles, a 27% enhancement in convective heat transfer coefficient was observed. The decrease in the heat transfer rate was observed in axial direction. Particle migration, chaotic movement of the nanoparticles and fluctuations in the fluid and increased thermal conductivity of the nanofluid are considered the possible reasons for this enhancement.