Discussion on new energy vehicle battery thermal management technology
Battery cooler Electronic expansion valve Electronic water pump Heat exchanger Power battery is the main power source of new energy vehicles. The battery generates a large amount of heat during vehicle operation, and accumulates in a relatively small space over time. Due to the battery pack The dense stacking of internal battery cells also makes it more difficult to dissipate heat in the middle area to a certain extent, exacerbating the temperature inconsistency between battery cells. As a result, the charging and discharging efficiency of the battery will be reduced, and the power of the battery will be affected; in severe cases, it will also cause Thermal runaway affects the safety and life of the system, especially in terms of temperature management. Thermal runaway of the battery may cause fires and performance degradation. Therefore, research on new energy vehicle battery thermal management technology is very important for the development of new energy vehicles. meaning.
1. Basic components of vehicle thermal management system
The thermal management system of new energy vehicles includes four major parts: battery system, motor system, air conditioning system, and other components. Compared with traditional thermal management of fuel vehicles, the thermal management system of new energy vehicles is more complex. The battery system is crucial to new energy vehicles. To design a complete vehicle thermal management system, engineers need to start with the thermal management of the battery system.
2. Common heat dissipation methods for new energy vehicle battery thermal management
Since the birth of new energy vehicles, experts and scholars in related industries have conducted a lot of research on battery heat dissipation issues, and a lot of results have been achieved. The mainstream cooling method of battery thermal management has changed from air cooling to liquid cooling and phase change material cooling. Heat dissipation and heat pipe cooling. Cooling technologies such as air cooling, liquid cooling, phase change material cooling and heat pipe cooling are analyzed below.
Air cooling
Air cooling is a heat dissipation method that uses air as the medium and uses heat convection in the air to directly exchange heat between the battery and the air, thereby reducing the battery temperature. Air cooling can be divided into natural cooling and forced cooling according to whether a fan is used. Not used The fan is natural air cooling; the fan is forced air cooling. Models using forced air cooling include BAIC New Energy, Toyota Prius, etc. A large number of studies have shown that the heat dissipation effect of forced air cooling is much higher than that of natural air cooling. Effect.
Air cooling is currently a relatively mature cooling solution. It has the advantages of low cost, low energy consumption, mature technology, and is easier to control. Since the structure of the entire cooling system is not complicated, subsequent maintenance is easy and cheap. The disadvantage is that The cooling effect is greatly affected by the ambient temperature. In hot summer, the heat dissipation efficiency is low. In winter, if the battery needs to be heated, an additional heating system is also required, such as installing an electric heating film between the batteries. In addition, the air cooling method is not suitable for It is difficult to ensure the uniformity of heat dissipation in large-scale battery packs. There are problems that some batteries generate large amounts of heat and have very low heat dissipation efficiency, which affects the safety of the entire power battery pack [4]. Air cooling plays an important role in new energy vehicle battery thermal management. It is not the best cooling method in the industry.
Liquid cooling
Power battery liquid cooling technology is a type of thermal management technology. This technology usually uses coolant with a high heat transfer coefficient to allow heat exchange between the battery and the coolant, thereby reducing the battery temperature. Akbarzadeh et al. conducted simulation analysis on air A comparative analysis of the heat dissipation performance of cooled and liquid-cooled battery packs shows that the maximum temperature of the battery pack is lower and the temperature consistency is better in the liquid-cooled system. Liquid cooling is an extremely effective heat dissipation method, which is similar to the air Compared with cooling, the heat transfer coefficient is higher. The liquid cooling system of electric vehicles can be divided into direct contact and indirect contact according to the contact form between the insulating liquid and the battery. The form of immersing the battery cells or modules in the liquid for heat exchange is Direct contact form; in addition, cooling channels can also be set up between battery modules, or a cooling plate can be used at the bottom of the battery. The heat of the power battery is transferred to the coolant through the cooling plate. This form of liquid cooling is indirect contact. These two forms The liquid cooling system has high air tightness requirements. In addition, the mechanical strength requirements are high, and the vibration resistance and life requirements of the cooling system need to be ensured.
The liquid cooling system of electric vehicles is mainly composed of coolant, cooling plate, electronic water pump, temperature sensor, radiator, etc. The compressor, as the power starting point for refrigeration, determines the heat exchange of the entire system. Capacity. The Chiller (cooling device) plays the role of exchanging refrigerant and coolant, and the amount of heat exchange directly determines the temperature of the coolant. The water pump determines the flow rate of the coolant in the pipeline. The faster the flow rate, the faster the coolant. The thermal performance will be better and vice versa.
