Nanofluid heat transfer between concentric independently rotating tubes with axial flow

Nanofluid heat transfer behaviour between concentric independently rotating tubes with an axial flow was numerically investigated. Co-rotating and counter-rotating of the inner and outer tubes was simulated at a fixed rotation number. Flow inside the annulus was turbulent with Reynolds number of 5000 and 10000. k-epsilon turbulent model was used and the current work is in agreement with published experimental work. Mixture-multiphase model was used to model the multiphase flows of the TiO2/water nanofluid. Results show that the Nusselt number increases with the Reynolds number. At a constant Reynolds number, different Nusselt number distribution along the hotted tube for co-rotating and counter-rotating tube was observed. The counter-rotating tube was found to be more efficient in enhancing the heat transfer rate in comparison to the co-rotating tube.