Cooling systems are mainly divided into two categories: air cooling and water cooling. The air cooling system cools the high-temperature parts of the engine by directly dissipating the heat into the atmosphere; while the water cooling system first transfers the heat to the coolant, and then the coolant dissipates the heat into the atmosphere. The water cooling system is widely used in automobile engines because of its advantages such as uniform cooling, good effect and low engine running noise. In the water cooling system, the temperature of the coolant should be maintained between 80~90℃ to ensure the normal operation of the engine.
The air cooling system mainly relies on air as the cooling medium, and the heat of the heat sink is dissipated into the atmosphere through the air flow. The system is mainly composed of components such as fans, air guides, heat sinks, cylinder air guides and splitters, which together form an efficient heat dissipation system.
The cylinder block and cylinder head of the air-cooled engine are both equipped with heat sinks, and these two parts are usually cast separately and assembled together. The cylinder head is made of aluminum alloy and equipped with longer heat sinks because of its highest temperature. In order to enhance the cooling effect and ensure the uniformity of cooling, the air cooling system is also equipped with a air guide and a splitter. The position of the fan varies according to the design of the engine. It may be located in the middle of the front of the engine or installed at the front of the left and right rows of cylinders.
The advantages of the air cooling system are its simple structure, reliable operation, light weight, rapid heating and economical. This makes it particularly suitable for use in high temperature environments such as deserts and cold environments such as polar regions. However, it also has some disadvantages, such as the difficulty in accurately adjusting the cooling effect, high power consumption and noise during operation. Therefore, this cooling method is mainly used in some small-displacement automobiles and military automobile engines.
On the other hand, the water cooling system uses coolant (or water) as the cooling medium. During the operation of the engine, the coolant will circulate continuously, absorb excess heat from the engine's water jacket, and then dissipate it into the atmosphere. According to the circulation method of the coolant, the water cooling system can be divided into three types: evaporative, natural circulation and forced circulation. At present, the forced circulation water cooling system is commonly used in automobiles, which relies on the drive of the water pump to force the coolant to circulate in the engine.