Multi-objective optimization of the TPMS-Fin three-fluid heat exchanger for vehicles using RSM-NSGA-III

A novel TPMS-Fin three-fluid heat exchanger was developed by integrating TPMS with fins. The TPMS enables three isolated flow paths for simultaneous heat exchange between air and two liquid streams, while fins enhance air-side performance. The heat exchanger was fabricated using 3D printing and experimentally tested. A validated CFD model was established, and response surface methodology (RSM) combined with Non-dominated Sorting Genetic Algorithm III (NSGA-III) was employed for multi-objective optimization. Five design variables—hydraulic diameter (d), volume fraction (V), fin area percentage (Fs), fin pitch ratio (w) and inlet velocity (u)—were investigated with respect to unit length pressure drop (ΔP/L), volumetric heat transfer rate (Qv) and j/f. The manufacturing and testing parameters were established, including scanning speed of 1400 mm/s and fill area offset of 0.13 mm. The design variables exhibit nonlinear and strongly coupled spatial synergistic effects on the flow and heat transfer performance. Based on NSGA-III and TOPSIS, the optimal design achieved ΔP/L = 2.038 kPa/m, Qv = 2271 kW/m³ and j/f = 0.1032, corresponding to d = 6.11 mm, V = 11.16 %, Fs = 51.06 %, w = 0.16 and u = 4.04 m/s. Compared to the orginal design, Qv and j/f increased by 7.4 % and 6 %, respectively. The results offer insights into variable interactions and support future development of multi-fluid heat exchangers.