Investigation of Heat Transfer Enhancement Using Coil Inserts in Circular Tubes
A Computational Fluid Dynamics model has been developed to improve heat transfer analysis and design, specifically for photon absorbers in the Advanced Photon Source. This model can be extrapolated to other heat transfer situations, so its impact is much deeper than its original purpose. Coil inserts have been used for over 25 years in photon absorber applications, but the possibility for heat transfer improvement based on simple coil inserts exists. Empirical data for various coil geometries exists from a study completed by Jeff Collins and William O’Brien, Heat Transfer Optimization For APS High-Heat-Load/Flux Components, in 2008. The model developed in this research was used to duplicate those results digitally for model validation and to use the most impactful parameters to improve on the coil geometries. The model developed allows for insight into the flow around these coils and gives the opportunity to increase their effectiveness by characterizing their behavior. Of particular interest is the appearance of a primary and secondary flow around the coil inserts may allow future designs to exploit this behavior. Primary flow is defined as the flow that follows the coil around the tube, while secondary flow is the flow inside the coil, passing with a different spatial period than the spatial period of the coil through the center of the tube. Additionally, the onset of turbulence was investigated, as that was expected to be a defining factor of the heat transfer improvement made by a coil insert. We were surprised to find even at low Reynolds numbers, the benefit of the coil inserts was seen as there seemed to be no laminar regime present while a coil is inserted. Further research is expected to characterize the flow around the coils and to develop new geometries tailormade to take advantage of the phenomenon present in these tubes.
