Friction stir channeling: An innovative technique for heat exchanger manufacturing

Friction stir processing (FSP) is an emerging processing technique based on the principles of friction stir welding (FSW), which is a relatively new solid-state metal joining process developed by The Welding Institute, UK. Some of the unique features of FSW such as the low amount of heat generated, extensive plastic deformation and controlled flow of material is being exploited to develop new material modification and manufacturing processes. Friction stir channeling (FSC) is one such adaptation of FSP that can produce continuous and stable internal channels for application in heat exchanging equipment. Friction stir channeling produces these channels if the defect formation and material flow are controlled during the FSW/P. Channel formation is also affected by other factors, including the process parameters, tool design, and material properties. A good understanding of the process forces, material flow, and metallurgy is therefore necessary to control and optimize the channel formation for use in heat exchangers.;The process forces acting on the tool during channeling were analyzed to study the channel formation mechanism and correlate the channel features to the process parameters and geometric features of the pin. A mechanistic model of the process specific energy was then developed and correlated to the channel size. Finally, the performance of the channels was experimentally determined by measuring the pressure drop across the channels and calculating the friction factor and heat transfer coefficient for different flow rates. These results will help develop the manufacturing process that will enable better control of the channel profile.