ENGINE COOLING SYSTEM
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. Toomuch
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,The velocity
(ii)
and amount of the cooling air andThe
(iii
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.
Advantages of Air Cooled Engines
Air cooled engines have the following advantages:
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.
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. Toomuch
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,The velocity
(ii)
and amount of the cooling air andThe
(iii
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.
Advantages of Air Cooled Engines
Air cooled engines have the following advantages:
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.
