Cooling System – Types, Functions, &
Requirements in IC Engines – Complete
Technical Overview
COOLING SYSTEM
A system, which controls the engine temperature, is known as a cooling system.
NECESSITY OF COOLING SYSTEM
The cooling system is provided in the IC engine for the following reasons:
The temperature of the burning gases in the engine cylinder reaches up to 1500 to
2000°C, which is above the melting point of the material of the cylinder body and head of
the engine. (Platinum, a metal which has one of the highest melting points, melts at
1750 °C, iron at 1530°C and aluminium at 657°C.) Therefore, if the heat is not dissipated,
it would result in the failure of the cylinder material.
Due to very high temperatures, the film of the lubricating oil will get oxidized, thus
producing carbon deposits on the surface. This will result in piston seizure.
Due to overheating, large temperature differences may lead to a distortion of the engine
components due to the thermal stresses set up. This makes it necessary for, the
temperature variation to be kept to a minimum.
Higher temperatures also lower the volumetric efficiency of the engine.
REQUIREMENTS OF EFFICIENT COOLING SYSTEM
The two main requirements of an efficient cooling system are:
1. It must be capable of removing only about 30% of the heat generated in the combustion
chamber. Too much removal of heat lowers the thermal efficiency of the engine.
2. It should remove heat at a fast rate when the engine is hot. During the starting of the
engine, the cooling should be very slow so that the different working parts reach their operating
temperatures in a short time.
TYPES OF COOLING SYSTEM
There are two types of cooling systems:
(i) Air cooling system and
(ii) Water-cooling system.
AIR COOLING SYSTEM
In this type of cooling system, the heat, which is conducted to the outer parts of the engine, is
radiated and conducted away by the stream of air, which is obtained from the atmosphere. In
,order to have efficient cooling by means of air, providing fins around the cylinder and cylinder
head increases the contact area. The fins are metallic ridges, which are formed during the
casting of the cylinder and cylinder head The amount of heat carried off by the air-cooling
depends upon the following factors:
(i) The total area of the fin surfaces,
(ii) The velocity and amount of the cooling air and
(iii) The temperature of the fins and of the cooling air.
Air-cooling is mostly tractors of less horsepower, motorcycles, scooters, small cars and small
aircraft engines where the forward motion of the machine gives good velocity to cool the engine.
Air-cooling is also provided in some small industrial engines. In this system, individual cylinders
are generally employed to provide ample cooling area by providing fins. A blower is used to
provide air.
1. Its design of air-cooled engine is simple.
2. It is lighter in weight than water-cooled engines due to the absence of water
jackets, radiator, circulating pump and the weight of the cooling water.
3. It is cheaper to manufacture.
4. It needs less care and maintenance.
5. This system of cooling is particularly advantageous where there are extreme climatic
conditions in the arctic or where there is scarcity of water as in deserts.
6. No risk of damage from frost, such as cracking of cylinder jackets or radiator water tubes.
, WATER COOLING SYSTEM
It serves two purposes in the working of an engine:
a) It takes away the excessive heat generated in the engine and saves it from over heating.
b) It keeps the engine at working temperature for efficient and economical
working. This cooling system has four types of systems:
(i) Direct or non-return system,
(ii) Thermo-Syphone system,
(iii) Hopper system and
(iv) Pump/forced circulation system.
Though the present tractor has a forced circulation system, it is still worthwhile to get
acquainted with the other three systems.
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. The low H.P. engine, coupled with the irrigation pump is an example.
Thermo-Syphone Water Cooling System
This system works on the principle that hot water being lighter rises up and the cold water being
heavier goes down. In this system the radiator is placed at a higher level than the engine for the
easy flow of water towards the engine. Heat is conducted to the water jackets from where it is
taken away due to convection by the circulating water. As the water jacket becomes hot, it rises
to the top of the radiator. Cold water from the radiator takes the place of the rising hot water
and in this way a circulation of water is set up m the system. This helps in keeping the engine at
working temperature. Disadvantages of Thermo-Syphone System
1 Rate of circulation is too slow.
2. Circulation commences only when there is a marked difference in temperature.
3. Circulation stops as the level of water falls below the top of the delivery pipe of the radiator.
For these reasons this system has become obsolete and is no more in use.
Hopper Water Cooling System
This also works on the same principle as the thermo-syphone system. In this there is a hopper on
a jacket containing water, which surrounds the engine cylinder. In this system, as soon as water
starts boiling, it is replaced by cold water. An engine fitted with this system cannot run for
several hours without it being refilled with water.
Force Circulation Water Cooling System
This system is similar in construction to the thermo-syphone system except that it makes use of a
centrifugal pump to circulate the water throughout the water jackets and radiator
Requirements in IC Engines – Complete
Technical Overview
COOLING SYSTEM
A system, which controls the engine temperature, is known as a cooling system.
NECESSITY OF COOLING SYSTEM
The cooling system is provided in the IC engine for the following reasons:
The temperature of the burning gases in the engine cylinder reaches up to 1500 to
2000°C, which is above the melting point of the material of the cylinder body and head of
the engine. (Platinum, a metal which has one of the highest melting points, melts at
1750 °C, iron at 1530°C and aluminium at 657°C.) Therefore, if the heat is not dissipated,
it would result in the failure of the cylinder material.
Due to very high temperatures, the film of the lubricating oil will get oxidized, thus
producing carbon deposits on the surface. This will result in piston seizure.
Due to overheating, large temperature differences may lead to a distortion of the engine
components due to the thermal stresses set up. This makes it necessary for, the
temperature variation to be kept to a minimum.
Higher temperatures also lower the volumetric efficiency of the engine.
REQUIREMENTS OF EFFICIENT COOLING SYSTEM
The two main requirements of an efficient cooling system are:
1. It must be capable of removing only about 30% of the heat generated in the combustion
chamber. Too much removal of heat lowers the thermal efficiency of the engine.
2. It should remove heat at a fast rate when the engine is hot. During the starting of the
engine, the cooling should be very slow so that the different working parts reach their operating
temperatures in a short time.
TYPES OF COOLING SYSTEM
There are two types of cooling systems:
(i) Air cooling system and
(ii) Water-cooling system.
AIR COOLING SYSTEM
In this type of cooling system, the heat, which is conducted to the outer parts of the engine, is
radiated and conducted away by the stream of air, which is obtained from the atmosphere. In
,order to have efficient cooling by means of air, providing fins around the cylinder and cylinder
head increases the contact area. The fins are metallic ridges, which are formed during the
casting of the cylinder and cylinder head The amount of heat carried off by the air-cooling
depends upon the following factors:
(i) The total area of the fin surfaces,
(ii) The velocity and amount of the cooling air and
(iii) The temperature of the fins and of the cooling air.
Air-cooling is mostly tractors of less horsepower, motorcycles, scooters, small cars and small
aircraft engines where the forward motion of the machine gives good velocity to cool the engine.
Air-cooling is also provided in some small industrial engines. In this system, individual cylinders
are generally employed to provide ample cooling area by providing fins. A blower is used to
provide air.
1. Its design of air-cooled engine is simple.
2. It is lighter in weight than water-cooled engines due to the absence of water
jackets, radiator, circulating pump and the weight of the cooling water.
3. It is cheaper to manufacture.
4. It needs less care and maintenance.
5. This system of cooling is particularly advantageous where there are extreme climatic
conditions in the arctic or where there is scarcity of water as in deserts.
6. No risk of damage from frost, such as cracking of cylinder jackets or radiator water tubes.
, WATER COOLING SYSTEM
It serves two purposes in the working of an engine:
a) It takes away the excessive heat generated in the engine and saves it from over heating.
b) It keeps the engine at working temperature for efficient and economical
working. This cooling system has four types of systems:
(i) Direct or non-return system,
(ii) Thermo-Syphone system,
(iii) Hopper system and
(iv) Pump/forced circulation system.
Though the present tractor has a forced circulation system, it is still worthwhile to get
acquainted with the other three systems.
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. The low H.P. engine, coupled with the irrigation pump is an example.
Thermo-Syphone Water Cooling System
This system works on the principle that hot water being lighter rises up and the cold water being
heavier goes down. In this system the radiator is placed at a higher level than the engine for the
easy flow of water towards the engine. Heat is conducted to the water jackets from where it is
taken away due to convection by the circulating water. As the water jacket becomes hot, it rises
to the top of the radiator. Cold water from the radiator takes the place of the rising hot water
and in this way a circulation of water is set up m the system. This helps in keeping the engine at
working temperature. Disadvantages of Thermo-Syphone System
1 Rate of circulation is too slow.
2. Circulation commences only when there is a marked difference in temperature.
3. Circulation stops as the level of water falls below the top of the delivery pipe of the radiator.
For these reasons this system has become obsolete and is no more in use.
Hopper Water Cooling System
This also works on the same principle as the thermo-syphone system. In this there is a hopper on
a jacket containing water, which surrounds the engine cylinder. In this system, as soon as water
starts boiling, it is replaced by cold water. An engine fitted with this system cannot run for
several hours without it being refilled with water.
Force Circulation Water Cooling System
This system is similar in construction to the thermo-syphone system except that it makes use of a
centrifugal pump to circulate the water throughout the water jackets and radiator
