COOLING SYSTEMS

IN INTERNAL COMBUSTION ENGINES

Mantosh Kumar

12BTMECH016

What is it?

It is a system which is used to keep engine from getting not too hot and at the same time not to keep it too cool either.

Reasons for Cooling

To promote a high volumetric efficiency.

To ensure proper combustion.

To ensure mechanical operation.

Effect for Over-cooling

The thermal efficiency is decreased due to more loss of heat carried by the coolant.

The vapourization of the fuel is less resulting in lower combustion efficiency.

Low temperature increases the viscosity of lubricant causing more loss due to friction.

Types of Cooling system

Air cooling (or direct cooling) system.

Liquid cooling (or indirect cooling) system.

Air cooling system

Air cooled engines depend on airflow across their external surfaces of the engine cylinders to remove the necessary heat. It is used for Small Engines

The amount of heat dissipated depends upon: The area of cooling surface in contact with the air. Mass flow rate of air Temperature difference between cylinder and air Conductivity of metal.

Air cooling system – Advantages No need of radiator, cooling jackets, coolant and

pumps. The engine can be operated in cold climate where

liquid may freeze. In places where water is scarce , air cooled engine is

an advantage. Less weight and low cost. Air cooled engines have no coolant leakage or

freezing problems.

Air cooling system - Disadvantages Large amount of power is used to drive the

cooling fan. Engines give low power output. Cooling fins under certain conditions may

vibrate and amplify the noise level. Cooling is not uniform.

Liquid cooling system

A liquid (coolant) is circulated around the cylinders and absorb heat from thecylinder walls and cylinder head.

It is used for large Engines

Liquid cooling systems - Types

Thermo-syphon system Forced circulation cooling system Evaporative cooling system Direct or non- return system

Thermo Siphon System

In this system the circulation of water is due to difference in temperature of water. So in this system pump is not required but water is circulated because of density difference only.

Evaporative cooling system

In this system , the engine will be cooled because of the evaporation of the water in the cylinders into steams. It is used for cooling of many types of industrial engines.

Forced circulation cooling systemThis system is used in a large number of vehicles like cars, buses , trucks and other heavy vehicles . Here, circulation of water takes place with convection currents helped by a pump.

Non-Return Water Cooling System

This is suitable for large installations and where plenty of water is available. The water from a storage tank is directly supplied to the engine cylinder. The hot water is not cooled for reuse but simply discharges.

Parts of Liquid System

Water Pump Cooling Fan Radiator

Types of Radiator

1 Gilled tube 2 Tubular3 Honey comb

Parts of cooling system Thermostat valve

Liquid cooling system- Advantages Uniform cooling of cylinder, cylinder head and

valves. fuel consumption of engine improves by using

water cooling system. The Engine need not be provided at the front end

of moving vehicle because of cooling system. Engine is less noisy as compared with air cooled

engines, as it has water for damping noise.

Disadvantages of Cooling system It depends upon the supply of water. The water pump which circulates water absorbs

considerable power. If the water cooling system fails then it will result

in several damage of engine. The water cooling system is costlier as it has

more number of parts. Also it requires more maintenance and care for

its parts.

Use of Anti- Freezers

During winter the water used in the radiator freezes because of cold climates, then ice formed has more volume and produces cracks in the cylinder blocks, pipes, and radiator. So, to prevent freezing antifreeze mixtures or solutions are added in the cooling water.

Normally following are used as antifreeze solutions : Methyl, ethyl alcohols. A solution of alcohol and water. Ethylene Glycol etc.

The ideal antifreeze solutions should have the following properties : It should dissolve in water easily. It should not evaporate. It should not have any harmful effect on any

part of cooling system. It should be cheap and easily available. It should not corrode the system.

Lubricating oil as coolant

The heat, generated by piston, cylinder, and bearings is removed by lubrication to a great extent. Lubrication creates cooling effect on the engine parts.

Conclusion

A cooling system must be provided not only to prevent damage to the vital parts of the engine (due to high temperature), but the temperature of these components must be maintained within certain limits in order to obtain maximum performance from the engine.

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