Main Results

Compact heat exchangers (HEX) are used in many areas. Examples include HVAC systems, aerospace, vehicles, compact energy conversion systems, integrated industrial processes, and cooling of micro- and power electronics. In all these application areas, a good design is crucial to achieve high overall energy efficiency and reduce costs. The IAMHEX project achieved technological improvements in compact heat exchangers by pushing the boundaries of both current design methods and production processes, and developed a hybrid time-resolved micro-PIV/LIF technique to experimentally validate flow features within some of the designs.

While experimentally testing prototypes is very cumbersome, design based on detailed numerical simulations is also too time-consuming and expensive. Simplified simulation models or design methods, on the other hand, are too inaccurate to achieve a significantly improved design. In the IAMHEX project, we therefore combine advanced heat transfer models with efficient optimization methods to automatically determine the best possible shape within limited computational time.

In this project large scale shape optimizations were realized for both laminar and turbulent flows around repetitive fin structures in evaporators and condensers. Methodologically multiscale models were derived both for evaporators/condensers and for balanced heat exchangers. Improved optimization formulations were assessed against full array simulations. It was shown that depending on the constraints and operating conditions significant improvements could be achieved for finned evaporators and condensers. However, more drastic limitations were found to apply to the base plates of balanced counterflow heat exchangers, where the optimal sizing showed that the use of materials with high thermal conductivity not necessarily lead to the best designs as manufacturing and fouling constraints strongly affect the heat exchanger performance. In particular the plate thickness and lower bounds on the channel spacing turned out to be important factors. With respect to topology optimized manifold designs significant reduction in flow maldistribution by up to 90% compared to conventional designs was achieved.

These innovative computer-generated designs pushed the limits of what can be achieved through Additive Manufacturing (AM). The IAMHEX project focused on improving the capabilities of AM processes for thermally conductive materials (copper and aluminum alloys) through two complementary technologies: Laser Powder Bed Fusion (LPBF) and 3D micro-extrusion. 

Finally, the development of new measurement techniques will allow us to verify the models and their improved designs.