Experiment And Simulation On Heat Dissipation Of Ni-mh Battery Packs For Hybrid Electric Vehicle

Nickel-hydrogen (Ni-MH) battery, which influences the performance of Hybrid Electric Vehicle (HEV) directly, with its characteristics of high specific energy,high specific power,long cycle life,small environmental pollution and high safety,is widely applied and becomes the core component in HEV. The rise of battery temperature and temperature difference among the battery modules in charge-discharge period will affect the performance and even safety and service life of Ni-MH battery.In order to improve the performance of reliability and consistency of battery, not only the battery temperature is required to maintained below a certain critical temperature, but also the small temperature difference among the battery modules is required, and the temperature difference will not cause significant difference in battery performance, which will affect performance of battery packs. Therefore, it is great significance to establish the theoretical model of battery temperature field, simulate the temperature distribution under conditions specified, optimize the cooling system structure and predict the thermal performance of battery packs, so as to improve the battery performance.The main works in this thesis include:â‘ With regard to problems of charge-discharge characteristics and service life of Ni-MH battery packs caused by high temperature rise and large temperature difference among the battery modules during vehicle running, a three-dimensional, transient heat dissipation model was built for Ni-MH battery packs, based on the mass, momentum and energy conservation equations. The thesis analyzed the heat generation theory and component of the heat load.â‘¡The model was applied to simulate flow field and temperature field of the initial Ni-MH battery packs ,and researched the influence of flow rate of cooling air and driving cycle to the heat dissipation, with the help of computational fluid dynamics (CFD) software.â‘¢An optimal scheme of heat dissipation was proposed and its simulation results of thermal performance were obtained. It indicates that the optimal scheme improves the thermal performance, decreases the temperature rise and temperature difference among the battery modules effectively, thus show that the optimal heat dissipation scheme of the battery packs can satisfy the application requirements in HEV. â‘£A temperature measurement experiment of the battery packs of hybrid electric vehicle (HEV) during charge and discharge periods was carried out under the driving cycle to confirm accuracy of simulation analysis. And the simulation results consist well with the experimental data, which confirms the rationality of the model of the flow field and temperature field.