Heat Transfer Enhancement in Laminar Pipe Flow Using Al2O3-Water Nanofluid and Twisted Tape Inserts

In this study, an attempt has been made to carry out a numerical investigation using water based Al2O3 nanofluid, flowing through a circular tube under constant inlet temperature and constant heat flux condition in a laminar flow regime. The water-based Al2O3 nanofluid is used in a circular plane tube first and then this process is repeated for the same tube with a twisted tape inserted having twist ratio (H/w) of 1.85 at Reynolds number ranging from 680 to 2030. For the numerical analysis, ANSYS FLUENT is used to solve 3-dimensional conservation equations of mass, momentum and energy. The simulated results indicate that when twisted tape is used, heat transfer rates increase significantly with the use of nanofluid. In case of nanofluid with the plane tube, only 10-24% enhancement in heat transfer rate is noted. On the other hand, almost 27-45% increase in heat transfer is observed compared to that with only water when twisted tape is inserted into it. It is also noticed that the friction factor value increases with the increase in volume fraction. But the effect of heat transfer is more significant than the other factors. The best thermo-hydraulic performance factor achieved is 2.1 using nanofluids with 5% volume fraction at high Reynolds number when twisted tape is also inserted.