Flow and Heat Transfer Performance Analysis of Plate-Fin Heat Exchanger in Electric Vehicles

In driving condition, the electric drive system of electric vehicles generates significant heat, which increases temperature of the motor, leading to reduced performance and energy loss. To manage the motor temperature and recover energy, a plate-fin heat exchanger (PFHE) is used to facilitate heat exchange between the electric drive system and the vehicle's thermal management system. In this study, Computational Fluid Dynamics (CFD) method was used to investigate the fin structure on thermal flow performance within the PFHE. A CFD simulation model was developed for a local heat exchange unit, considering the generic boundary conditions and temperature-dependent properties of the coolant and oil in the PFHE. The pressure drop and heat transfer rate of the local heat exchange unit were calculated under different boundary conditions, and an empirical formula for the friction factor was derived. The Wilson plot method was applied to separate convective heat transfer resistance from the total thermal resistance, enabling the calculation of the convective heat transfer coefficient and the derivation of an empirical formula for the Colburn factor. The simulated results of the local heat exchange unit were compared with experimental data to verify the model's accuracy. Alumped parameter model was established to estimate temperature changes in the flow direction of the PFHE, and its predictions were compared with experimental results. A response surface model was created to analyze the effects of fin height, spacing, thickness, inclination angle, and pitch on the flow and heat transfer performance. The results show that, within certain ranges, fin pitch and spacing significantly impact the friction factor, while fin spacing has the greatest effect on the Colburn factor. This research provides valuable insights into optimizing the fin structure of PFHE.