Experimental investigation of convective heat transfer and friction factor of Al2o3/water nanofluid in helically corrugated tube

The effect of nanoparticles and helical corrugation on turbulent heat transfer and dimensionless friction factor were experimentally investigated. Thermal conductivity and viscosity of nanofluids with various volume fractions were experimentally measured at different temperatures. Reynolds number and nanoparticle concentration varied from 5000 to 20,000 and 0% to 1% by volume, respectively. Nusselt number and friction factor of nanofluids were obtained for different concentrations as well as various Reynolds and Prandtl numbers. Results show that the heat transfer and friction factor increase by increasing nanofluid concentrations in plain and helical corrugated tube while its effect are more significant in helical corrugated tubes. The effect of nanoparticles on heat transfer is intensified at higher corrugation height and smaller corrugation pitch. Heat transfer enhancement at same pumping power, heat transfer performance, have been improved by increasing the nanoparticles concentration not as well as by increasing the corrugation height or reducing the corrugation pitch.