Battery thermal management system liquid cooling and air cooling
Currently, there are two mainstream thermal management methods for lithium battery units, air cooling and liquid cooling. Many engineers are also studying hybrid modes of phase change materials and liquid cooling or air cooling, but they are not yet mature. Air cooling and liquid cooling each have their own characteristics. The density of antifreeze is 1,000 times that of air, and its specific heat is 4 times that of air. Therefore, as a heat carrier, compared with air cooling, liquid cooling inherently has the characteristics of large heat carrying capacity, low flow resistance, and high heat exchange efficiency. It is widely used in situations where battery packs have high energy density, fast charging and discharging speeds, and large changes in ambient temperature. . The liquid cooling system can be highly integrated with the battery pack. It is easy to install on site and occupies a small area. There is no need to worry about dust, water vapor condensation and other issues. When there are signs of thermal runaway, the liquid cooling solution can rely on a large flow of cooling medium to force the battery pack to dissipate heat and redistribute heat between battery modules, which can quickly inhibit the continued deterioration of thermal runaway and reduce the risk of runaway.
The air cooling system has the characteristics of simple system, low manufacturing cost and easy installation. There are still many applications in scenarios where battery energy density is low and charging and discharging speeds are slow.
From the perspective of cooling effect, air cooling has greater advantages than liquid cooling. The analysis is as follows:
NO.1 Battery pack temperature
Under the same inlet temperature and extreme wind speed and flow rate, the temperature of the liquid-cooled battery pack is 30-40 degrees Celsius, while the temperature of the air-cooled battery pack is 37-45 degrees Celsius. Liquid cooling has better temperature stability.
Air Cooling
Liquid Cooling
NO.2 Operational energy consumption
After experimental research, in order to achieve the same average battery temperature, air cooling needs 2-3 times higher energy consumption than liquid cooling. The maximum temperature of the battery pack with the same power consumption is 3-5 degrees Celsius higher with air cooling than with liquid cooling. Liquid cooling consumes less power.
NO.3 Battery thermal runaway risk
Due to the specific heat capacity of air, convection heat transfer coefficient is small and other factors, the battery air cooling technology heat transfer efficiency is low, the battery heat generation increases, which will lead to high battery temperature, there is a risk of thermal runaway; liquid cooling system can greatly reduce the risk of thermal runaway of the battery.
