Engine Cooling System (page.1)

Cooling System:

A great deal of heat is produced by burning of fuel in an engine. A part of it is removed along with exhaust gases and by the lubrication system. Cooling system is required to remove the remaining portion of excess heat. Cooling system should be such that temperature is maintained within fairly close limits so that optimum compression ratio and maximum power is obtained.

If the engine temperature is too high:

* The engine will be overheated
* The film of lubrication oil will be burnt off which may damage cylinder walls, pistons and piston rings
* Detonation may be caused
* The engine may be ruined
If the engine is too cool:
* Uneconomical burning of fuel takes place
* Engine will lose power

It is to be noted that the engine is quite inefficient when it is cold and hence the cooling system is designed in such a way that it prevents cooling when the engine is warming up and till it attains to maximum efficient operating temperature, then it starts cooling. It is also to be noted that.

The advantages of air-cooling are:

* No radiator is required
 * No danger of freezing water
* Air-cooled engines are about 10% less in weight as compared to water-cooled ones.

The disadvantages of air-cooling are:

* Because of the greater heat to which the engine is
* About 20-25% of total heat generated is used for producing brake power (useful work).
* Cooling system is designed to remove 30-35% of total heat.
* Remaining heat is lost in friction and carried away by exhaust gases.

COOLING SYSTEMS

Two types of cooling systems are used:

* Air cooling: This system is used in engines of two and three wheeler's, aeroplanes and small stationary engines.

* Liquid cooling: This system is used for applications other than those mentioned for air cooling. Water is generally the liquid used in liquid cooling systems, in which additives are sometimes added.

Air Cooling: In this, air is passed over the cylinder and the cylinder head. (?In the picture) To obtain better cooling, fines are cast on hot areas, which provide large heat radiating surface.

In multi-cylinder air-cooled engines, a fan driven from crankshaft is provided which forces air through ducts so as to have uniform flow. Subjected, a little lower compression ratio is obtained

* Fan takes away 5% of the engine power

* It is difficult to maintain even cooling

* Air-cooled systems make more noise

Liquid Cooling: The majority of engines are water cooled because of the advantages:

* Mechanical noise is reduced

* Temperature of the various engine parts is more uniform.