| Because of the large capacity, low operating costs, no direct pollution and other advantages, Modern trams are favored by all over the world. As one of the components of the modern tram power system,the performance of lithium titanate batteries directly affects the development of trams. However, the lithium titanate battery will produce heat in the charge and discharge. When the battery temperature is too high or the battery temperature difference is too large, not only the battery performance and service life will be reduced, and even the battery will fire, explosion. Therefore, it is great significance for the development of trams to take steps to control the temperature of battery pack so that the battery work in a suitable temperature range. Therefore, according to the modern tram car lithium titanate battery, a temperature control system of coupled phase change materials - air is designed,and through theoretical analysis, experimental research and numerical calculation method,the PCM-air coupled temperature control system is analysed. The research results can provide a reference for the thermal design of modern tram car lithium titanate. The main research contents are as follows:In this paper, the basic structure and heat generation principle of lithium ion battery are briefly described, and the heat generation model of lithium titanate batteries is assumed and simplified. Then, the physical parameters and the heat generation rate of the lithium titanate battery were calculated, and the reliability of the thermal model of the lithium titanate single cell was verified by the comparison between the experimental and the numerical calculation,which provides a theoretical basis for the research and analysis of the thermal management system of the battery pack.Aiming at the shape and size of the lithium titanate battery and combining the advantages of the common cooling mode of the power battery, the foamed copper / paraffin composite phase change material was selected as the cooling medium, and the PCM-air coupling temperature management system was designed. Then, according to the experimental study, the control effect of the PCM-air coupling temperature management system on the battery temperature is analyzed when the battery charge/discharge ratio is 1C and 2C.The numerical simulation model of PCM-air coupling temperature management system was established by Fluent software, and the reliability of numerical calculation method was verified by experimental data. Then, the influence of the factors such as the charge/discharge ratio, the composite phase change material, the height of the convective heat transfer zone and the cooling air on the thermal management effect of the PCM-air coupling temperature management system were analyzed by using the numerical method and model.Finally, the correlation formula of the Nuyshar number in the convective heat transfer zone of the PCM-air coupling temperature management system is obtained by using the multiple linear regression analysis method. On this basis, the relationship between the heat dissipation and the height of the heat transfer plate, the inlet temperature of the cooling air and the flow velocity of the cooling air are obtained. The relational expression can provide a reference for the design of PCM-air coupling temperature management system. |
