Design of plate-fin surfaces for multi-fluid heat exchanger applications

Amidst the various design approaches available for the design of plate-fin heat exchangers for multi-fluid applications, are those based on the segmentation of the exchanger length into blocks that correspond to the enthalpy intervals in the Composite Curves. Such methods are characterized by three main features: identification of exchanger sections, surface selection from among the available types, and reconciliation of dimensions by pressure drop relaxation. The work presented in this paper introduces new concepts and removes some limitations in earlier approaches. In the first place, it reduces the number of block sections when the space between them is too short to fit intermediate headers along the length of the exchanger. Additionally, it introduces the concept of surface design as an aid to fulfil the heat transfer duties. Finally, it allows the design to meet fixed dimensions as design objective together with the heat duty within the limitations imposed by the pressure drop. The approach is demonstrated using a case study solved by different authors in the open literature. It is shown that the number of block sections is reduced from 3 to 2.