Numerical analysis of tube expansion process for heat exchangers production

This work analyses two different aspects of the mechanical process of tubes expansion used for the production of heat exchangers. In particular, the influences on the expansion process due to mandrel geometry and geometrical errors in tubes, caused by production tolerances, were studied and analyzed using finite element (FE) models. A 2D axisymmetric model was used to study the influence of mandrel geometry, whereas a 3D solid model was adopted to investigate the influence of geometrical errors in tubes. Experimental tests were carried out on actual materials in order to set up and validate the FE models. Force required for expansion, and variation in tube dimensions due to expansion were investigated and a good agreement was found between experimental and FE results. Additionally, the obtained results showed that the fillet radius is the most important geometrical factor of the mandrel in order to reduce the expansion force. A great influence of the tube geometrical errors was observed on the tube expansion process, which can compromise the performance of the heat exchanger. Finally, it is worth mentioning that the present study provides useful information that might be used to improve tubes expansion processes in general and heat exchangers production in particular.