Thermo-hydraulic investigation of Al2O3/water nanofluid flow in an oval tube fitted with dual conical twisted-tape inserts: parametric studies

This work presents the thermo-hydraulic performance of water-Al2O3 nanofluid flow in an oval tube fitted with two parallel conical twisted strips in different alignments including staggered with four wings (S-4), staggered with five wings (S-5), non-staggered with 4 wings (NS-4), and non-staggered with five wings (NS-5). A detailed parametric study is carried out to evaluate the impact of different arrangements of conical strip insert, Reynolds number, and volume fraction of nanoparticles (phi) on the heat transfer and pressure drop of the oval tube. It is found out that the highest Nusselt number is obtained in the case of NS-5 at Re=250 and phi =3-86.9% higher than that of the plain tube. To investigate the effectiveness of conical twisted strips in terms of heat transfer enhancement, the intensity of the secondary flow generated by two parallel conical strips is represented by the vorticity isosurfaces. The NS-5 configuration generates stronger secondary flow at the vicinity of the heated wall. The increase in Nusselt number comes at the expense of a much higher friction factor relative to other configurations. Performance evaluation criterion (PEC) is calculated to identify a configuration with higher heat transfer performance at the lowest friction factor. The maximum PEC of 1.52 is obtained in the case of S-5 at Re=250 and phi =3%.

Automated summary

This study investigates the thermo-hydraulic performance of water-Al2O3 nanofluid flow in an oval tube with different configurations of conical twisted strips. It is found that the NS-5 configuration achieves the highest Nusselt number, indicating enhanced heat transfer performance at the expense of a higher friction factor.