Enhanced Heat Transfer On Thermal Management Of Hydronic Battery Packing

With increasingly stricter requirements of sustainable energy development and environmental protection, the EV Thermal Management has become a mainstream trend. As the power source of electric vehicles, the battery packing is much more sensitive to temperature changes. Thermal Management and temperature consistency of battery packing are the essential guarantee of performance, reliability and life spans of EV. As for electrical vehicle battery research of thermal characteristics and thermal management, in order to ensure the stability of the battery performance, it is necessary to maintain the appropriate operation temperature and control the internal temperature difference within a certain range for battery packing. Therefore, with the increasing focus on battery packing enhanced heat transfer structure and high efficiency BTMS,battery system with large capacity and high-power has become the core technique.Based on the conclusion of the application and status for electric vehicle battery packing and thermal management, this article inductively analyzes the domestic and overseas research and application of BTMS. Large capacity and high power of battery packing are the foundation to prolong EV mileage, the method of BTMS evolved from traditional air cooling to liquid cooling. It’s an optimum solution for efficient cooling that liquid cooling can enhance heat transfer efficiency. It’s beneficial for preheating in the cold weather and integrating multi-thermos dynamic systems with liquid circulation.This article concerns liquid cooling method of BTMs and designs the four typical battery packing heat transfer structure and pattern. Based on existing battery packing, to lighten up,enhance heat transfer and ensure optimum performance of BTMS as much as possible, this article concentrates on fluid flow pattern and heat transfer of battery packing, including physical models, numerical simulation, calculation, analysis and evaluation and etc.As for columnar battery pack, this article designs heat transfer enhancing structure with soft contacting and high thermal conductivity piece for the battery packing. As for flake batteries, this article develops the flat sheet bundle stacked structure and high thermal conductivity sheet-like battery group non-flow type heat transfer within the sandwich structure.This article applies battery packing heat transfer structure CFD simulation and calculation to analyze the basic properties performance of BTM, temperature distribution, temperature consistency and thermal performance under various conditions, additionally, to ascertain the battery packing heat transfer structure for further design.The simulation and experimental results show great consistency with comparison and analysis, emphasizing that the adopted methods effective and feasible.Concerning columnar battery pack,the enhanced heat transfer structure with soft contacting can ensure the surface temperature thermal control and the operation performance in the processes of charging and discharging with medium and low rate. Non-flow pattern within the high thermal conductivity of the heat transfer sheet structure characterizes light weighting for reducing internal flow pattern,with the increase of the heat conducting sheet thickness, its heat transfer ability enhances. In virtue of the high- conducting sheet inserting battery surface, the thermal control capability become more powerful, the consistency of battery surrounding temperature get improved. This article also proves that the effect of heat conducting sheet thickness reaches up to a certain extent, the battery temperature consistency impact is limited. As the coolant flow rate increased to some extend,its influence on thermal transfer is limited. Thus,the liquid cooling BTMS characterizes low flow rate and small flow resistance. The lower the cooling fluid inlet temperature is, the faster the battery temperature decrease. Nevertheless,with the decease of inlet temperature,the battery packing temperature consistency deteriorates. Thus,battery packing inlet temperatures control strategy must take both temperature consistency and high-efficacy heat transfer structure into consideration.For flake battery pack, temperature control of basic structure of the tube bundle is reliable,but with charging rate increases, surface temperature will be higher after balanced. What’s more,it does easily tend to form large temperature difference, worsening the battery temperature consistency. Winding effective conductive sheets on the surface of the battery can effectively improve heat transfer efficiency and promote its temperature consistency. Similarly, Non-flow pattern within the high thermal conductivity of the heat transfer sheet structure characterizing light weighting and reducing internal flow pattern performs favorable thermal control ability.With the conducting sheet thickness increasing, the temperature consistency gets more satisfactory. The influence rules and thermal control characteristics of flow rate and inlet temperature are similar to the columnar battery backing structures.