2. 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.
3. Reasons for Cooling
To promote a high volumetric efficiency.
To ensure proper combustion.
To ensure mechanical operation.
4. 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.
5. Types of Cooling system
Air cooling (or direct cooling) system.
Liquid cooling (or indirect cooling) system.
6. 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.
7. 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.
8. 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.
9. Liquid cooling system
A liquid (coolant) is circulated around the
cylinders and absorb heat from the
cylinder walls and cylinder head.
It is used for large Engines
10. Liquid cooling systems - Types
Thermo-syphon system
Forced circulation cooling system
Evaporative cooling system
Direct or non- return system
11. 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.
12. 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.
13. Forced circulation cooling system
This 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.
14. 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.
18. 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.
19. 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.
20. 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.
21. 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.
22. 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.
23. 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.
