Flow Analysis and Design Improvement of a Heat Sink of an Integrated Starter Generator

Abstract

Due to the limitation in volume and size of vehicles’ integrated starter generators (ISGs), an effective cooling mechanism has to be considered while designing the ISGs. The main purpose of this research is to improve the fins of heat sink design of the ISG to enhance the cooling performance and fan efficiency. To do this, conjugate heat transfer simulations have been performed using the realizable k-ε turbulence model. Also, the MRF method is employed for simulation of the rotating parts. Base on the analysis of the simulation result of the baseline model, the modified models are suggested and investigated. The rotation speed of the fan is 2000 rpm and the number of blades is 11 and 9 for the front and rear fans, respectively. By assuming that the flow in narrow gap between the rotor and stator is negligible, only the rear part which includes the heat sink is simulated. Firstly, conjugate heat transfer simulation is conducted for the baseline model and the heat transfer characteristics are observed. Then, from the observation, modified heat sink model with wider fin spacing is suggested and compared. In order to have more uniformly distributed flow field, a heat sink model with radially arranged fins is also made and simulated. As a result, it is concluded that increasing the air passages between the fins increases the heat transfer. In addition, it is observed that the optimized fan had better performance. Furthermore, radial fin structure is turned out to have advantage for cooling compare to the original heat sink structure. In a radial model, more uniform distribution of the flow is observed, both of flowrate and fan efficiency are higher and temperature of the coil is lower.