ENGINE COOLING SYSTEM

Need

Engine is the device which converts heat energy generated from the combustion of fuel into useful mechanical work. Around 25% of whole heat energy generated from the fuel is utilized for generating the desired output. The rest of heat is either released in the form of exhaust gases or is absorbed by the  engine itself. This absorbed heat by the engine is required to be dissipated through engine cooling system otherwise engine will become overheated and result in burning of lubricant which further causes the engine seizure and damage to the engine components. Following is the distribution of heat loss in engine operation.

· Loss of heat through the cylinder walls/liners : 30%

· Loss of heat through exhaust gases : 35%

· Loss of heat in friction : 10%

Keeping in view the essential requirement of maintaining optimum operating temperature of the engine a suitable cooling system is required. However, the cooling beyond the desired limit, results into decrease in the engine efficiency because of the following reasons.

· Decrease in the thermal efficiency due to loss of heat

· Decrease in the combustion efficiency due to less vaporization of the fuel

· Decrease in mechanical efficiency due to increase in piston friction as the viscosity of lubricant increases with low temperature

The overheating of an engine is considered to be as serious and undesirable as over cooling. So, it is desired that the temperature of cooling system is to be maintained in the optimum operating temperature range ( 71⁰ to 82⁰C for petrol engines and 88⁰ to 90⁰C in diesel engines) to do the following ;

• Maintain optimum lubrication between the moving components of an engine
• Minimise the loss of power due to detonation
• Avoids burning of oil with fuel

Generally there are two types of cooling systems used in an engine;

• Air cooling system
• Water cooling system