Experimental investigation of forced convective heat transfer enhancement of γ-Al2O3/water nanofluid in a tube

Abstract

The effect of nanofluids on heat transfer inside circular tubes under uniform constant heat flux boundary condition was investigated. The working nanofluid was a suspension of γ-Al2O3 nanoparticles of average diameter 20 nm. The heat transfer coefficients were calculated experimentally in the range of 1057 < Re < 2070 with different particle volume concentrations of 0.1%, 0.3% and 0.9%. Increasing the particle volume fraction led to enhancement of the convective heat transfer coefficient. The results show that the average heat transfer coefficient increased 16.8% at 0.9% volume concentration and Reynolds number of 2070 compared with distilled water. In addition, the enhancement of the convective heat transfer was particularly significant in the entrance region and decreased with axial distance. Finally, an empirical correlation for Nusselt number has been proposed for the present range of nanofluids. The mean deviation between the predicted Nusselt number and experimental values for the new correlation is 3.57%.