Exploration and numerical study of new structures for high-efficiency and low-resistance vehicle-mounted plate-fin heat exchanger based on the three-field synergy principle

As the power density of the power transmission device increases, heat exchangers are required to dissipate more heat and provide better flow resistance in the limited space of the vehicle. In this study, the synergy mechanism of the temperature field, pressure field, and velocity field in the serrated fin channel of the plate-fin heat exchanger (PFHX) was thoroughly analyzed under the guidance of the three-field synergy principle. This study also quantitatively revealed the distribution of the angle θ between the temperature gradient and velocity, and the angle α between the pressure gradient and velocity. For the regions in the channel where θ was too large (i.e., poor synergy between temperature and velocity fields) and α was too small (i.e., poor synergy between pressure and velocity fields), high-efficiency and low-resistance fin structures were proposed. The performance improvement of the new structures was quantified using the comprehensive heat transfer and flow resistance performance evaluation plot in the three-field synergy standard. The results indicate that the new structures improve the synergy of the three fields in the channel. When the air velocity is 15 m s⁻¹, the average synergy angle θ_m between the temperature gradient and the velocity of the two structures, changing the inlet flow direction and the slotted fin, decreases from 83.4° to 80.3° and 82.8°, respectively. The outlet temperature increases by 2.3 and 1.6 K, respectively, compared to the basic structure, indicating enhanced the heat transfer of the PFHX. By changing the shape of the fin cross-section, the average synergy angle α_m between the pressure gradient and the velocity increased from 143.6° to 150.8°, while θ_m increased by only 0.6°. The pressure loss was reduced by 15.2% compared to the basic structure, resulting in a significant decrease in pressure drop while maintaining essentially the same heat transfer performance. Meanwhile, the optimized PFHX can increase the heat transfer rate by 0.2%–8% under identical pump power. This work provides guidance on selecting high-efficiency and low-resistance vehicle-mounted PFHXs.