Experimental convective heat transfer studies in a turbulent flow regime using alumina-water nanofluids

The present work investigates forced convective heat transfer characteristics of alumina-water nanofluids in a turbulent flow regime. Nanofluids are dilute colloidal suspensions with nano-sized particles ( < 100 nm) dispersed in a basefluid. The thermal conductivity values are measured by a steady state method, using a guarded hot plate (GHP) apparatus customized for liquids. The forced convective heat transfer characteristics are evaluated with the help of a test loop maintained in a constant heat flux condition. Controlled experiments under a turbulent flow regime are carried out using four particle concentrations (0.5vol%, 1vol%, 2vol% and 4vol %). The experimental results show that, the thermal conductivity of nanofluids increases with an increase in particle concentration and closely follow effective medium theories. However, the enhancement of heat transfer coefficients in the turbulent regime is observed to be within the measurement uncertainty.