Design for Performance and Manufacturability of Additively Manufactured Heat Exchangers

Minimal surfaces minimize the total surface area subject to boundary or volume constraints. In nature, we can find captivating examples of minimal surfaces such as soap bubbles, catenoidal soap-film surfaces, and gyroids on butterfly wings.
Recent advances in CAD systems and additive manufacturing enable designers to design and manufacture these amazing designs. Minimal surfaces such as Gyroids, Schwarz, Lidinoid, and Diamond have remarkable strength, heat transfer, and manufacturability properties. When a volume is infilled with a minimal surface, it is subdivided into two separate, continuous, intermingled volumes. This property makes minimal surface geometries ideal for heat exchangers. In addition, these geometries can be 3D printed without supports.
We need to conduct a conjugate heat transfer analysis to assess and improve these designs. The simulation process is challenging because the minimal surface geometries are not the typical B-Rep geometry; implicit or voxel-based modelers generate them. This presentation will showcase the steps to address these challenges using an aircraft heat exchanger design as an example. In this case, the hot fluid is the transmission oil, while the cold fluid is the jet fuel. We will cover the conceptual design process, parametric geometry generation, real-time preliminary simulation, and final CFD validation. In designing for additive manufacturing, a “manufacturing process simulation” must be performed to evaluate the residual stress levels, the surface accessibility, and the distortion sensitivity. The manufacturing process simulation dictates design changes to reduce residual stress and distortion. Design modifications to improve manufacturability, as suggested by the fabrication team, will also be presented. The digital thread from concept to design to simulation to additive manufacturing and postprocessing, with subtractive manufacturing, will be demonstrated. The heat exchanger has been produced using additive manufacturing and will be available during the presentation.