Numerical Approach to Model a Novel Electrohydraulic Incremental Forming Process for the Manufacture of Pillow Plate Heat Exchangers

Pillow plate heat exchangers (PPHE) represent a promising alternative to conventional heat exchangers. The manufacturing process of the heat exchangers often consists of two processes. In the first step, two plane sheets are positioned and spot-welded over the entirety of their surface. The edges are sealed, such as by roll seam welding. In the second step, the inner channels are formed by hydroforming. This construction method does, however, offer enormous potential for optimization. According to [2], a secondary-structured surface, in which the sheets are dimpled, leads to an improvement in heat transfer. This is because the fluid mechanics are positively influenced by these dimples. This sheet modification also leads to an increase in surface area and stiffness. One approach to manufacturing this secondary structure is by using a new electrohydraulic incremental forming process (EHIF) [3]. The topic of this research is the development of a numerical model that can predict the manufacturing process using EHIF. The model is developed in two steps. In this paper, the free forming process using a drawing ring is modeled and validated. Based on the validation tests, it can be stated that the simulation model represents the electrohydraulic forming process in a good way. Both the drawing depths and the displacement-time curves of the free forming showed a high level of agreement for the charging energy of 1.5 to 4.5 kJ. In future work, the simulation model will be adapted in such a way that incremental structuring of a sheet metal can be carried out.