PIV visualization and CFD analysis of thermal-hydraulic performance in printed circuit heat exchangers with zigzag channels

Printed circuit heat exchangers (PCHEs) are manufactured using chemical etching and diffusion bonding. The internal microchannels formed through chemical etching provide high heat transfer performance, while diffusion bonding ensures excellent mechanical strength. Due to these advantages, PCHEs have gained attention as next-generation heat exchanger in various industrial applications. Their thermal-hydraulic performance can be further improved by optimizing microchannel geometry. Among various configurations, zigzag channels cause significant pressure drop due to abrupt flow direction changes, but also promote fluid mixing, enhancing heat transfer performance. In this study, thermal-hydraulic characteristics of PCHEs with different zigzag bending angles were analyzed experimentally and numerically. Experimentally, water was used as the working fluid, and flow patterns inside the zigzag channels were observed using particle image velocimetry (PIV) within a Reynolds number (Re) range of 300-2500. Additionally, computational fluid dynamics (CFD) simulations were validated against experimental results to ensure numerical reliability, followed by analysis of thermal-hydraulic performance for different bending angles. Furthermore, the performance factor (η) was analyzed based on both experimental and numerical results to determine the optimal bending angle corresponding to different Reynolds numbers. The results indicate that at Re ≈ 300-900, 40° zigzag channel exhibited the highest performance factor. However, at Re ≈ 1200-2,500, the pressure drop in 40° zigzag channel increased exponentially, leading to a lower performance factor than that of 20° zigzag channel. Finally, based on these findings, new correlations related to heat transfer and pressure drop were developed to optimize PCHE design.