Numerical and experimental study of jet chamber designs for enhancing convective heat transfer in mini-tube heat exchangers

With growing demand for energy-efficient cooling systems, compact heat exchangers have become increasingly important, yet their performance is often constrained by persistent thermal boundary layers within mini-tubes. While numerous studies have explored various insert designs to enhance heat transfer in mini-tubes, the persistence of boundary layers remains a significant challenge for achieving high-performance heat exchange. This study introduces a novel jet chamber insert that disrupts thermal boundary layers by generating sequential, wall-impinging jets from the core flow. We systematically examine how variations in jet chamber length influence flow behavior, jet dynamics, and the resulting convective heat transfer characteristics in miniature heat exchangers. Numerical and experimental analyses were conducted to investigate the influence of jet chamber length on the thermal–hydraulic performance of miniature heat exchangers. The results reveal that chamber length plays a dominant role in shaping the internal flow structure and convective heat transfer behavior. As the length increases, a larger number of jet orifices contribute to fluid ejection toward the tube walls, enhancing near-wall mixing and promoting more effective boundary-layer disruption. The mini tube equipped with a 15 mm jet chamber insert achieved a Nusselt number 6.27 times higher than that of the smooth tube at Re = 1200, with a corresponding performance evaluation criterion (PEC) of 2.16. These findings highlight the strong potential of jet chamber inserts to enhance the thermal efficiency of compact mini-tube heat exchangers for energy-efficient thermal management applications.