LAUSR

Abstract The turbulent convective heat transfer behavior of CaCO3/TiO2/CuO nanocomposite dispersions in water/ethylene glycol is investigated experimentally in horizontal pipe-lines at constant heat flux at various in the Reynolds number range of 2900–18200 at 30°C, heat flux of 800 kW/m2, and nanocomposite concentration of 0.01-0.1 Vol. %. The results showed considerable enhancement of convective heat transfer using the nanofluids. The enhancement was particularly significant in the entrance region, and was much higher than that solely due to the enhancement on thermal conduction. The Nusselt number and friction factor at 0.1 vol. % is greater than that values of water/ethylene glycol about 34.5 % and 18.9 %, respectively. The pressure drop increased with the concentration more than 3.6 % and decreased thereafter. Also, heat transfer coefficient in rough pipe-lines was higher than that in smooth pipe-lines at the same Reynolds number and it enhanced as the diameter decreased. Eventually, the greatest thermal performance factor of the nanofluid was 1.28 at 0.1 vol. % and Reynolds number of 4800.