Turbulent heat transfer of Al2O3–water nanofluid inside helically corrugated tubes: Numerical study

Turbulent heat transfer in heated helically corrugated tube was investigated numerically for pure water and water–alumina nanofluid using two phase approach. The study was carried out for different corrugating pitch and height ratios at various Reynolds numbers ranging from 10,000 to 40,000. The effect of nano-particles in heat transfer augmentation for smooth tube and helically corrugation tubes (HCT) was discussed and their relative Nusselt number was compared. Results show that the heat transfer enhancement is promoted extremely by increasing the volume fraction of nano-particles. Adding 2% and 4% nano-particles by volume to water enhances the heat transfer by 21% and 58%, respectively. Also, the overall enhancement in heat transfer using two mechanisms simultaneously compared to using pure fluid within smooth tube exceeds over 330%. A correlation is given based on curve fitting from numerical data. Results indicate that using nano-particles yields different enhancement in heat transfer of tube for different corrugation height and pitch.