Necessity of Engine Cooling | Overcooling | Demerits of Overcooling | Undercooling | Demerits of Undercooling |
-: Necessity of Engine Cooling :-
In an I.C. engine , the temperature of the gases inside the engine cylinder may vary from 35⁰C or less to as high as 2750⁰C during a cycle . Due to this cooling system is provided on an engine for the following reasons -
1- If the cylinder head temperature is high the volumetric efficiency and hence the power output of the engine is reduced .
2- Physical and chemical changes may occur in lubricating oil which may cause sticking of piston rings and excessive wear of cylinder .
3- The even expansion of piston in the cylinder may result in seizure of the piston .
4- High temperature reduce strength of piston and cylinder liner .
5- Overheated cylinder may lead to pre-ignition of the fuel , in case of S.I. engines .
Note:- It must be noted that heat carried away by the coolant is a dead loss because not only no useful work can be obtained from it but a part of the engine power is also used to remove this heat .
-: Demerits of Overcooling :-
Overcooling is defined as - The cooling of engine above the desired level , is known as Overcooling .
Overcooling of the engine is harmful because of the following reasons :-
1- Due to Overcooling , engine life is reduced due to corrosion.
2- At very low temperature , starting of engine becomes difficult .
3- If the engine is overcooled some of the heat which could be used to expand the gases will be lost .
4- Due to Overcooling , lubricating oil not being warm enough to flow freely , results in greater frictional loss.
5- Due to Overcooling , the fuel will not vaporize properly and some of the gases produced by combustion will condense on the cylinder walls . This leads to dilution of the in the pump and the addition of harmful corrosive acids . Removal of the oil film from the cylinder wall by unvaporised fuel leads to increased cylinder bore wear .
Note:- In general , due to Overcooling the economy and life of the engine is reduced .
-: Demerits of Undercooling :-
Undercooling is defined as - When the cooling of engine is below the desired cooling then this is known as demerits of Undercooling .
The following are the demerits of Undercooling -
1- Undercooling can cause engine seizure , or at least - shorten valve life and possible distortion of the cylinder block head or gasket .
2- A hot-spot inside the combustion chamber may be sufficient to cause pre-ignition , i.e. to ignite the fuel before the spark plug does , thus causing loss of power and possible damage to the engine components .
3- Water in cooling system may boil and evaporate , and should the oil film burn away additional friction and wear will occur between cylinder and piston .
-: Necessity of Engine Cooling :-
In an I.C. engine , the temperature of the gases inside the engine cylinder may vary from 35⁰C or less to as high as 2750⁰C during a cycle . Due to this cooling system is provided on an engine for the following reasons -
1- If the cylinder head temperature is high the volumetric efficiency and hence the power output of the engine is reduced .
2- Physical and chemical changes may occur in lubricating oil which may cause sticking of piston rings and excessive wear of cylinder .
3- The even expansion of piston in the cylinder may result in seizure of the piston .
4- High temperature reduce strength of piston and cylinder liner .
5- Overheated cylinder may lead to pre-ignition of the fuel , in case of S.I. engines .
Note:- It must be noted that heat carried away by the coolant is a dead loss because not only no useful work can be obtained from it but a part of the engine power is also used to remove this heat .
-: Demerits of Overcooling :-
Overcooling is defined as - The cooling of engine above the desired level , is known as Overcooling .
Overcooling of the engine is harmful because of the following reasons :-
1- Due to Overcooling , engine life is reduced due to corrosion.
2- At very low temperature , starting of engine becomes difficult .
3- If the engine is overcooled some of the heat which could be used to expand the gases will be lost .
4- Due to Overcooling , lubricating oil not being warm enough to flow freely , results in greater frictional loss.
5- Due to Overcooling , the fuel will not vaporize properly and some of the gases produced by combustion will condense on the cylinder walls . This leads to dilution of the in the pump and the addition of harmful corrosive acids . Removal of the oil film from the cylinder wall by unvaporised fuel leads to increased cylinder bore wear .
Note:- In general , due to Overcooling the economy and life of the engine is reduced .
-: Demerits of Undercooling :-
Undercooling is defined as - When the cooling of engine is below the desired cooling then this is known as demerits of Undercooling .
The following are the demerits of Undercooling -
1- Undercooling can cause engine seizure , or at least - shorten valve life and possible distortion of the cylinder block head or gasket .
2- A hot-spot inside the combustion chamber may be sufficient to cause pre-ignition , i.e. to ignite the fuel before the spark plug does , thus causing loss of power and possible damage to the engine components .
3- Water in cooling system may boil and evaporate , and should the oil film burn away additional friction and wear will occur between cylinder and piston .
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