The relationship between efficiency and flow regimes for a chaotic heat exchanger.

Helical coiled tubes offer a combination of enhanced mixing and improved heat transfer, making them a subject of significant interest in various heat transfer applications. In these configurations, the fluid within the core undergoes a unique flow pattern where it moves toward the outer wall and then returns to the core, generating a secondary flow. However, due to the stabilizing influence of the secondary flow within helical coils, laminar flow can persist at significantly higher Reynolds numbers compared to flow in a straight pipe. Consequently, this leads to reduced streamwise mixing, which in turn hampers the attainment of high rates of convective heat transfer. To address this issue, several studies have focused on disrupting the orderly laminar flow and introducing chaos into the system. Creating chaotic fluid trajectories within the laminar flow regime is an effective passive method for improving heat transfer, commonly referred to as chaotic advection. In this study, we generates chaotic advection within an alternating Dean flow. In the latter, every bend undergoes a 90∘^{\circ} rotation in relation to its neighboring bend. This rotation causes the roll-cells to regenerate in a plane perpendicular to the preceding one, prompted by the centrifugal forces’ realignment. This geometric disturbance primarily induces chaotic advection. The objective of this research is to characterize the chaotic heat exchanger in comparison to the helical one. A dedicated experimental setup was developed to assess the heat transfer characteristics. Computational fluid dynamics (CFD) simulations were validated versus the experimental data. Direct Numerical Simulation (DNS) were employed to investigate the flow and heat transfer characteristics within both configurations. The open-source continuum mechanics suite OpenFOAM was used. To comprehend the performance of both geometries, we first analyzed the pressure drop and the global Nusselt number. Additionally, the study delves into the flow structure and behavior, exploring the laminar flow and it’s eventual transition to turbulent flow across a Reynolds number range of 200 to 30,000. Exploring the effect of chaotic advection on the enhancement of mixing efficiency.

Work In Progress