Air-cooling System in Reciprocating Engine

In an air-cooling system, the outer surface of the cylinder and the cylindrical head in a reciprocating engine are 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 increase the heat transfer area and thereby the 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.

Air conditioning system in the Superjet. Image source: Flickr (Artem Katranzhi)

Applications of Air-cooling System:

1. Air-cooling system is used in small engines, i.e., motorcycles, scooters, mopeds, airplanes and combat tanks, where the speed of the vehicle gives a good velocity to the air to cool the engine.
2. It is also used in small stationary engines used for agriculture and industry.

Advantages of Air-cooling System:

1. The design of the engine becomes simpler with the use of an air-cooling system.
2. There is no cooling pipe, radiator, fan, pump and liquid cooling jacket, and hence the engine has less weight.
3. In an air-cooled engine, the cylinder wall temperature is relatively higher. Thus, there is more power output from the engine.
4. No danger of coolant leakage, coolant freezing, etc.
5. Installation, assembly, and dismantling of the engine are quick and simple.
6. The weight per kW of an air-cooled engine is less than that of a water-cooled engine.
7. The engine is almost maintenance-free.

Disadvantages of the air-cooling system:

1. The engine is cooled non-uniformly.
2. The compression ratio of the engine is limited due to high wall temperature.
3. The volumetric efficiency of the engine is less than that of a water-cooled engine.
4. It produces aerodynamic noise.
5. It can be used for only small-sized engines due to its small capacity for heat dissipation.