In an air-cooling system, the outer surface of the cylinder and cylindrical head in reciprocating engine is cooled by air flowing over them. To increase the heat transfer rate from the surface, the metallic fins are cast on the cylinder and cylinder head. These fins increases the heat transfer area and thereby heat transfer rate.
Air cooling system is a very simple, reliable and maintenance-free cooling system, with no operating cost. It is very suitable for small engines of automobiles.
Applications of Air-cooling System:
- Air-cooling system is used in small engines, i.e., motor cycles, scooters, mopeds, airplanes and combat tanks, where speed of the vehicle gives a good velocity to the air to cool the engine.
- It is also used in small stationary engines used for agriculture and industries.
Advantages of Air-cooling System:
- The design of the engine becomes simpler with use of an air-cooling system.
- There is no cooling pipe radiator, fan pump and liquid cooling jacket and hence the engine has less weight.
- In an air-cooled engine, the cylinder wall temperature is relatively higher. Thus there is more power output from the engine.
- No danger of coolant leakage, coolant freezing, etc.
- Installation, assembly, dismantling of the engine are quick and simple.
- The weight per kW of air-cooled engine is less than that of a water-cooled engine.
- The engine is almost maintenance free.
Disadvantages of Air-cooling system:
- Engine is cooled non-uniformly.
- The compression ratio of the engine is limited due to high wall temperature.
- The volumetric efficiency of the engine is less than a water-cooled engine.
- It produces aerodynamic noise.
- It can be used for only small-sized engines due to its small capacity of heat dissipation.