Joining by forming technology for thermal applications: A case study of finned tube heat exchanger

Heat exchangers are essential for various thermal applications, and their performance could be improved by optimization of layout/operating conditions or materials. The layout/operating conditions optimization has been widely subjected to research and development, while the implementation of different materials has been limited to the available joining solutions. Joining by forming allows to circumvent the existent limitations, since it utilizes plastic deformation to produce multi-material mechanical joints between thin sheets and thin-walled tubes. Here, joining by forming is adopted for the first time, to manufacture multi-material transversal finned tube heat exchangers. The numerical-experimental analysis explores the production of tube compression beads obtained by plastic instability to fix and support fins, and therefore manufacture a novel design of finned heat exchanger with improved performance. A case study is carried out with the help of computational fluid dynamics simulations to find an optimal layout. Then, finite element simulations are employed to analyse the joining by forming process. A prototype model of transversal finned tube heat exchangers was finally manufactured and experimentally tested. Results show considerable gains in comparison with conventional finned tube heat exchangers made from steel tubes and fins, being the multi-material heat exchanger effectiveness doubled with respect to traditional designs.