The main difference between new energy vehicles and traditional vehicles lies not only in the newly added core component "three electric", but also in the significantly increased importance of the thermal management system. The thermal management system of traditional cars mainly includes the cooling system of the engine and transmission, and the car air conditioning, while the thermal management system of new energy vehicles covers almost all the components of new energy vehicles, including power batteries, drive motors, vehicle electronic control, etc. The complexity is higher, so it has become a key focus of development for car companies

From the perspective of thermal management requirements, the thermal management system of new energy vehicles mainly includes battery pack environment, power electrical components, motor cooling, automotive air conditioning, etc. The most important ones are the air conditioning system and battery thermal management system. Let's take a look at the changes and development trends of thermal management technology for new energy vehicles:

Secondly, the battery system of new energy vehicles has stricter temperature requirements for the working environment, and excessively high or low ambient temperatures will significantly affect the vehicle's range and battery life. At present, new energy passenger vehicles widely adopt battery liquid cooling technology. Liquid cooling technology takes away the heat generated by the battery through liquid convection heat transfer. Liquid has a high heat transfer coefficient, large heat capacity, and fast cooling speed, which is more effective in reducing the maximum temperature and maintaining the consistency of the battery pack temperature. Compared with air-cooled liquid cooling solutions, it is easier to achieve waste heat recovery. According to relevant research data, 100% of PHEVs produced in China in 2017 have adopted battery liquid cooling solutions, while only 6% of pure electric vehicles use liquid cooling. It is expected that the penetration rate of liquid cooling for pure electric vehicles will exceed 60% in 2018.

In terms of motor cooling, there are also certain differences between new energy vehicles and traditional fuel vehicles. The traditional engine cooling method uses a water ethylene glycol mixture to cool the outer wall surface of the motor stator (cooling water jacket), which is also the simplest cooling method. However, a more efficient way is to spray oil onto the main heating components inside the motor for direct contact cooling. The current best solution is to combine the above two schemes for hybrid cooling.

In terms of electronic control, according to relevant data statistics, electronic components accounted for 5% of the total vehicle cost in 1970, this proportion had reached 35% in 2010, and may reach 50% by 2030. In the future, with the improvement of intelligence, the number and types of electronic components loaded on new energy vehicles will become more diverse, ranging from LED chips with a power of only a few tens of watts to power electronics of several hundred kilowatts. Xu Kunhao pointed out that liquid cooling will be the main cooling solution for high-power electronic components. The heat dissipation of low-power electronic components requires innovative low-cost air cooling solutions, and in this regard, Grangis is exploring.

With the emergence of new thermal management technologies, it is necessary to develop new heat exchangers for different functions, which also means that the number of heat exchangers will continue to increase, bringing significant growth potential to related industries.

Challenges and innovative solutions faced by heat exchanger materials under the new trend of automotive thermal management
Opportunities and challenges have always coexisted, with increasing electrification and new architectures and operating environments posing significant challenges to heat exchangers and materials.

Challenge 1: Higher intensity requirements.
In recent years, due to the trend of energy conservation and emission reduction, governments around the world have begun advocating the use of environmentally friendly refrigerants to replace the original R134a. The current EU Directive 2006/40/EC has come into effect. According to the directive, starting from January 2017, all air conditioners used in new M1 and N1 vehicle models must use refrigerants with a GWP<150. Germany has also introduced a series of national standards related to R744 automotive air conditioning. It is reported that if R744 is used as the refrigerant, the internal working pressure of the entire refrigeration system will significantly increase. Although the heat exchanger can achieve sufficient pressure bearing capacity through structural design optimization by reducing the volume of the inner cavity and thickening the material, an increase in wall thickness will inevitably lead to an increase in the weight of the heat exchanger.

In addition, in other fields such as intercoolers, the inlet pressure on the pressurized air side may continue to increase with the demand for further improvement of the compression ratio inside the turbine. The battery casing also requires higher strength to resist thermal expansion at high temperatures, which puts higher strength requirements on the aluminum material of heat exchangers.

Challenge 2: Higher temperature and corrosion resistance requirements.

With the application and upgrading of new technologies, the working temperature of heat exchangers gradually increases, and heat exchangers that come into contact with exhaust gas in the inner chamber will face corrosion problems caused by low pH condensation products, which brings new challenges to heat exchanger materials.

Challenge 3: Residual flux.
The brazing process of aluminum heat exchangers is complex, including processes such as flux coating, drying, thermal degreasing, and cleaning. The traditional brazing process not only causes losses in time, manpower, and chemicals, but also generates flux residues, which are time-consuming to clean. In addition, the residual flux in the coolant system may react slightly with the coolant, which may accelerate corrosion if used excessively.

Challenge 4: The demand for material thinning.
In order to reduce the weight and cost of heat exchangers, there is a continuous demand for material thinning. However, this will bring new challenges to the reliability and even heat transfer performance of heat exchangers, which will also be solved through material optimization in the future.

In summary, automotive thermal management technology not only helps to improve power distribution efficiency and extend driving range, but also faces more opportunities and development space with the rapid development of new energy vehicle technology in the context of energy conservation and emission reduction. At the 10th Grangis Technology Symposium, it was learned that multiple heat exchanger manufacturers and related enterprises are accelerating the research and development of new energy vehicle heat exchangers, promoting the upgrade of thermal management systems from traditional solutions to new solutions, in order to improve the performance of heat exchangers, better cope with higher pressures and more severe corrosive environments, and further reduce the size of heat exchangers. I believe that with the joint promotion of the industry, the thermal management technology of new energy vehicles will enter a new stage of development.