Raffreddamento di macchine elettriche con refrigeranti avanzati

The aim of this research is to investigate the adaption of advanced coolants and phase change materials for electric machines in electric/hybrid vehicle applications. The study uses Al2O3 nanoparticles to enhance the heat transfer ability of liquid cooling systems employing the commonly used cooling jacket approach. Employing advanced coolants to improve the heat transfer performance of cooling systems with minimal changes in their structure can be considered as a cost-effective and practical approach to meet the requirements of vehicle applications. In line with this goal, in this research, both heat transfer and fluid flow behaviors of cooling systems employing nanofluids are investigated. In this way, the feasibility and effectiveness of the cooling system can be justified by taking practical criteria into account. Results of the study are used to find the trade-off between the heat transfer and fluid flow behaviors of the under-study nanofluid coolant to achieve the best possible overall performance. 3D CFD analyses are used to evaluate the cooling systems proposed in this research. Since the applications considered in this research are electric machines used in electric vehicles, the losses of the electric machine were calculated under standard driving cycles. From the results, it was found that there are frequent peak power demands resulting in several peak losses. Also, it was observed that the values of peak losses are several times the mean value of electric machine losses. Considering this property of heat production in electric machines used in electric vehicle applications and the prominent property of phase change materials that have a high latent heat capacity, in this research a hybrid cooling system consisting of a passive cooling part based on phase change materials and an active cooling part based on liquid cooling method was designed. The results of the analyses showed that the phase change material is able to properly store excess thermal energy and the active cooling part assists the passive cooling part by rejecting the stored thermal energy to prepare the phase change material for the next peak heating cycle.