Experimental studies on the heat transfer and pressure drop characteristics of Cu-water and Al-water nanofluids in a spiral coil

This study presents the heat transfer coefficient and friction factor of the Al-water and Cu-water nanofluids flowing in a spiral coil in the laminar flow regime with constant wall temperature condition. The experiments were done for water and two types of nanofluids with different volumetric concentrations (0.55%, 1.12%, and 223%) and various operational conditions. The effect of different parameters such as Gz number, wall temperature and nanofluid particle concentration on the heat transfer coefficient and pressure drop of the flow were studied. Thermal Conductivities of the fluids are measured experimentally and results show that the thermal conductivity of Cu-water nanofluid is about 18% higher than Al-water nanofluid in 2.23 vol% concentration. Nusselt number oscillations can be seen for different nanofluids which are caused by the secondary flow. Finally, applying spiral coil is much effective in enhancing the thermal performance. (C) 2013 Elsevier Inc. All rights reserved.