Nanofluids are liquid suspensions containing nanoparticles that are smaller than 100 nm. There is an increased interest in nanofluids as thermal conductivity of nanofluids is significantly higher than that of the base liquids. ZnO-water nanofluids with volume concentration of ZnO particles varying from 0.0001 to 0.1% were prepared using ultrasonic vibration mixer. Thermal conductivity of the ZnO-water fluids was investigated for different sonication time using thermal property analyzer (KD2 Pro). Thermal conductivity of nanofluids for a given concentration of nanoparticle varies with sonication time. Heat transfer coefficient and pressure drop in an annular test section with variable pressure (1–2.5 bar) and heat flux (0–400 kW/m2) at constant mass flux of 400 kg/m2s were studied for samples having maximum thermal conductivity. Surface roughness of the heating rod was also measured before and after the experimentation. The study shows that heat transfer coefficient increases beyond the base fluid with pressure and concentration of ZnO.

No abstract

Nanofluids are suspensions of metallic or nonmetallic nanopowders in base liquid and can be employed to increase heat transfer rate in various applications. In this work turbulent flow forced convection heat transfer of Al 2 O 3-water nanofluid inside an annular tube with variable wall temperature was investigated experimentally. The Nusselt numbers of nanofluid were obtained for various heat flux, Reynolds numbers and nanoparticle concentrations at atmospheric pressure. The addition of nanoparticle in water enhances heat transfer coefficient and enhancement increases with increase in the nanoparticle concentration, heat flux and flow rate. Experimental results emphasize the enhancement of heat transfer due to the nanoparticle presence in the fluid.

No abstract

Anofluids are suspensions of metallic or nonmetallic nanopowders in base liquid and can be employed to increase heat transfer rate in various applications. In this work turbulent flow forced convection heat transfer of Al2O3-water nanofluid inside an annular tube with variable wall temperature was investigated experimentally. The Nusselt number of nanofluid was obtained for various Reynolds numbers and nanoparticle concentrations at atmospheric pressure. The addition of nanoparticles in water enhances heat transfer coefficient and the enhancement increases with increase in the nanoparticle concentration and flow rate. Experimental results emphasize the enhancement of heat transfer due to nanoparticles presence in the fluid.