The effects of chaotic advection on mixing and heat transfer in coiled tube heat exchangers

The propose of this work is to analyze the feasibility of using chaotic mixing as a mean of enhancing the intube convective heat transfer in a coiled tube heat exchanger and point out that is possible to increase the heat transfer by suitably designing the coils to alter the secondary pattern and induce chaotic mixing. In order to assess the enhancement of heat transfer by chaotic advection, we compared two different shell-and-tube heat exchangers having the same heat-transfer area and the same tube length, but different configurations: one is a convectional helical coil with a fixed axis which produces regular mixing, while the other one is a new configuration in which there is a periodic change in helical coils paths. Velocity vectors and temperature field are computed. Furthermore, the Liaapounov exponents are used to identify the presence of chaos in particle path lines. By means of Lagrangian tracing of fluid particles in the flow field and fluid elements stretching calculations, it is shown that mixing and heat transfer is increased significantly due to change advection mechanism to chaotic advection. Furthermore, a higher Nusselt number indicates an enhanced heat transfer and a more uniform temperature distribution for the fluid flow in the chaotic coil.

Keywords:

Chaotic advection , Helical coiled Tube , Heat exchanger , Heat transfer