Experimental and numerical investigation of TPMS heat exchangers in precooler of combined engine under large temperature difference

Cylindrical TPMS (Triple Periodic Minimal Surface) structures, characterized by high thermal-hydraulic performance, structural compactness, and geometric compatibility with engine outline, are regarded as potential configurations for next-generation precoolers. This research designed three cylindrical TPMS heat exchanger structures (Diamond, Gyroid, SplitP) and constructed a large-temperature-difference experimental platform utilizing high-temperature air (∼550 K) on the hot side and cryogenic nitrogen (∼110 K) on the cold side. The Diamond structure was employed to validate the operational stability of thin-walled TPMS structures fabricated by additive manufacturing under large-temperature-difference conditions, and detailed thermal-hydraulic performance data were acquired. Based on experimental validation, numerical simulations were conducted under actual flight conditions, and a novel evaluation metric WPEC (Weight-aware Performance Evaluation Criterion) was proposed to assess lightweight and high-efficiency heat exchangers for aerospace applications. The results demonstrate that the total heat transfer coefficient k of TPMS structures reaches 250 W·m⁻²·K⁻¹ under experimental conditions and exceeds 1600 W·m⁻²·K⁻¹ under actual flight conditions. The SplitP structure exhibits total heat transfer rates 27% and 54% higher than those of the Diamond and Gyroid structures, respectively. However, this is accompanied by air-side pressure drops increased by 70% and 80%, and helium-side pressure drops increased by 3.5 and 4.6 times, respectively. Comprehensive performance analysis indicates that Diamond achieves a higher WPEC value of 1.33 when the power-to-weight ratio is incorporated, establishing its superior suitability for precooler applications in combined-cycle engines with stringent lightweight requirements.