Heat transfer of laminar non-Newtonian fluid flow through pipes boosted by inlet swirl

Introducing swirling velocity at the inlet is one of the best ways to enhance the transport properties of flow through the pipes. Flow of fluids in small tubes have important applications involving fluid mixing or heat transfer and the flow in these small devices appears to be laminar in nature. Non-Newtonian fluids have wide variety of applications in small pipes ranging from heat-pipes to micro heat exchangers. Hence, it becomes very important to enhance the transport properties of fluids flowing through small devices. To enhance the transport characteristics, the method of introducing swirling of fluid at the inlet of the pipe is chosen. Further, the effect of important dimensionless parameters such as the power-law index of the fluid (characterizes fluid rheology), Reynolds number, the inlet swirl velocity profile shape (transition radius) and the inlet swirl number on the heat transfer characteristics is investigated. The qualitative and quantitative aspects of the heat transfer problem are discussed with particular focus on temperature contours and determination of Nusselt number. Results from the present study show that the power-law index of the fluid and Reynolds number plays an important role in enhancing the heat transfer. Increase in the flow Reynolds number and decrease in the power-law index tend to increase heat transfer strongly. It is also revealed that the inlet swirl number and the profile shape (transition radius) have a weak effect on the augmentation of heat transfer. A correlation is proposed to determine the heat transfer in the form of Nusselt number based on the flow Reynolds number and power-law index.