Numerical investigation on thermal-hydraulic performance of hybrid TPMS heat exchangers under cryogenic conditions

Traditional two-dimensional enhanced surfaces in cryogenic channels often face bottlenecks due to prohibitive pressure drop penalties under high-velocity conditions. To address this fundamental trade-off, a Triply Periodic Minimal Surfaces (TPMS)-based heat exchanger was investigated to achieve a more efficient and compact cryogenic system. Hybrid TPMS structures with varying mixing ratios were designed by extracting the optimal flow and heat transfer characteristics from pure Diamond, Gyroid, and Primitive structures. Accordingly, Computational Fluid Dynamics (CFD) simulation was conducted to evaluate the thermal-hydraulic performance of hybrid TPMS structures with cryogenic conditions. Numerical results reveal that a 50% mixing ratio maximizes heat transfer enhancement, while it incurs a severe pressure drop penalty. Based on the integration of the volumetric heat transfer capacity Q/V and the Performance Evaluation Criterion (PEC), the Diamond-Gyroid type HX with a 25% mixing ratio was identified as the optimal balance. This structure achieves a peak PEC of 1.733 and outperforms the pure Gyroid HX. Furthermore, the heat transfer enhancement analysis with the Field Synergy Principle (FSP) reveals that the hybrid topological transitions induce potent secondary flows and disrupt thermal boundary layers, effectively optimizing the synergy between the velocity and temperature gradient fields. This study substantiates the immense potential of hybrid TPMS structures, offering critical guidance for the design and optimization of heat exchangers operating under cryogenic conditions.HighlightsCryogenic convective heat transfer in hybrid TPMS is numerically uncovered.Proposed hybrid Diamond-Gyroid type HXs enhance comprehensive performance.The 25% hybrid structure cuts pressure drop by 33.9% with a peak PEC of 1.733.Topological transitions induce secondary flows to disrupt thermal boundary layers.