The use of 3D printing to manufacture thermal dissipation devices has become the focus of several investigations addressing both thermal and hydrodynamic behavior. However, experimental studies involving metallic prototypes have consistently reported pressure losses higher than those predicted by analytical and numerical models. In this context, this work presents a comprehensive experimental investigation of pressure drop in compact heat exchangers manufactured by additive manufacturing, focusing on the influence of channel geometry, surface roughness, geometric deviations, and manufacturing process on hydrodynamic behavior. Two core geometries with 2 mm diameter circular channels arranged in straight and zigzag flow paths were designed and fabricated using two additive manufacturing techniques: LCD photopolymerization with an ABS-like resin and selective laser melting, with AISI 316 L stainless steel, resulting in four prototypes. Geometric characterization and internal surface roughness measurements were performed for both materials. Pressure drop experiments were conducted using air and water in two experimental facilities, covering Reynolds numbers from 2000 to 15,000. The present study introduced an original experimental methodology in which pressure taps were directly integrated into the heat exchanger core, allowing the pressure drop to be measured within the flow channels rather than only between the inlet and outlet nozzles. This approach enabled a clear separation between channel friction losses and inlet–outlet losses. This research also applied the minor losses method to describe the pressure drop in zigzag heat exchangers. For polymeric heat exchangers, the theoretical model exhibited deviations below 35%. In contrast, for metallic SLM heat exchangers, the experimental results demonstrate that surface roughness alone cannot explain the elevated pressure losses observed. As a result, the analysis revealed that geometric non-uniformity along the channel length, originating from the SLM manufacturing process, played a dominant role in the elevated pressure losses. Additional experiments with redesigned cores reveal that geometric nonuniformities along the channel length, inherent to the SLM process, dominate the hydrodynamic behavior, increasing flow resistance and leading to pressure losses that exceed conventional rough-pipe predictions. • Novel methodology measures ΔP in channels, separating internal losses. • Non-uniformities dominate ΔP in SLM, not just roughness. • Critical evaluation of friction correlations for zigzag channels. • Approach with local losses improving prediction in zigzag channels. • Comparison of the hydrodynamic performance of straight and zigzag heat exchangers.
Baraldi et al. (Fri,) studied this question.