3D topology optimization and additive manufacturability of two-fluid heat exchangers

This paper presents a topology optimization approach aiming at enhancing the performance of two-fluid heat exchangers. The study focuses on optimizing three types of material distributions: the hot fluid, the cold fluid, and the solid material, with the objective of maximizing heat transfer efficiency. A formulation using two density fields is developed to optimize the distribution of the three materials. Two manufacturability constraints, the thickness of the solid layer and the self-supported overhang angle, are imposed to ensure practicality and feasibility. Controlling the solid layer thickness is crucial for ensuring that the thinnest wall can be fabricated using additive manufacturing. Overhang angle control is important for creating self- supported solid components that can be printed without support structures. A numerical example compares the performance of the optimized heat exchanger with a benchmark straight channel design, demonstrating a remarkable 2.3 times increase in heat transfer rate for the optimized configuration. The topologically optimized design improves the heat transfer rate by disrupting the thermal boundary layer and enhancing heat convection. Even when compared to the straight channel heat exchanger with a 1.9 times higher surface area, the optimized design still demonstrates a 12% higher heat transfer rate and achieves a power density 5.3 times higher than that of the straight channel heat exchanger. An additive manufacturing process is employed to validate the manufacturability of the optimized design, resulting in the successful fabrication of heat exchangers in three different sizes. This study underscores the effectiveness of topology optimization with manufacturability constraints in producing heat exchangers that are manufacturable and have superior heat transfer performance.