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COOLING SYSTEM
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Cooling System in IC Engine
1)Need for cooling system: A large portion of the heat formed due to combustion is
transferred to the cylinder head and walls, piston and valves.
Unless this excess heat is carried away and these parts are
adequate cooled, the engine will be damaged.
The duty of cooling system, is to keep the engine from getting
not too hot and at the same time not to keep it too cool either to
get maximum performance from engine.
2) Characteristics of efficient cooling system:
capable of removing about 30% of heat generated in the
combustion chamber
During starting of the engine the cooling should be minimum, so
that the working parts of engine reach their operating temperature
in short time
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Types of cooling system:
1) Liquid or indirect cooling system
2) Air or direct cooling system
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Liquid cooled systems:
Mainly water is used and made to circulate
through the jackets provided around the
cylinder, cylinder-head, valve ports
and seats
It consists of a long flat, thin-walled tube
with an opening, facing the water pump
outlet and a number of small openings
along its length that directs the water against the
exhaust valves.
The liquid becomes heated in its passage
through the jackets and is in turn cooled
by means of an air-cooled radiator system
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Water cooling can be carried out by any of the following
Methods:
1) Direct or non-return system
2)Thermosyphon system
3)Forced circulation cooling system
4)Evaporative cooling system
5)Pressure cooling system
1)Direct or non-return system:
useful for large installation where plenty of water is available.
Water is directly supplied through the inlet valve to the enginecooling jacket. The hot water is not cooled for reuse but simply
discharged.
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2)Thermosyphon system:
The fluid circulates through the system in the form of
convective current.
For engine application the tank A represent the cylinder jacket
while tank B represent a radiator and water act as a circulating
fluid
Fig. Principal of thermosyphon system
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3) Forced circulating cooling system
Used in large number of automobile like cars, buses and even
heavy trucksflow of water from radiators to water jacket is by convection
assisted by pump.
Fig. Principle of forced circulation cooling system using
thermostat
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water or coolant is circulated through jacket around the part of
engine, is kept in motion by a centrifugal pump .
The water is passed through the radiator where it is cooled by the
air, A thermostat is used to control the water temperature requiredfor cooling.
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4)Evaporative Cooling System
predominately used in stationary engine, cooling is because of
the evaporation the water in the cylinder jackets into the steam.
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Air cooled system is generally used in small enginessay up to 15-20 kW and in aero plane engines.
In this system fins or extended surfaces are providedon the cylinder walls, cylinder head, etc.
Heat generated due to combustion in the enginecylinder will be conducted to the fins and when theair flows over the fins, heat will be dissipated to air.
The amount of heat dissipated to air depends upon :
(a) Amount of air flowing through the fins.
(b) Fin surface area.
(c) Thermal conductivity of metal used for fins
AIR COOLED SYSTEM
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motor cycles
Air planes
Combat tanks
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Advantage of liquid cooling system
Compact design of engine
The fuel consumption of high compression liquidcooled engine is rather lower than for air cooled ones.
Because of the even cooling of the cylinder barrel and
due to jacketing makes it possible to reduce thecylinder head and valve seat temperature.
In case of water cooled engines, installation is notnecessarily at the front of the mobile vehicle, aircraft
etc. as the cooling system can be conveniently locatedwherever required. This is not possible in case of aircooled system.
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Limitation of liquid cooling system
This is a dependent system in which water circulation
in the jackets is to be ensured by additional.
Power absorbed by the pump for water circulation is
considerable and this affects the power output of theengine.
Cost of the system is considerably high.
System requires considerable maintenance of its
various parts.
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Limitations of Air-cooling System
Can be applied only to small and medium sizedengines.
Cooling is not uniform.
Higher working temperature compared to water-
cooling.
Produce more aerodynamic noise.
Specific fuel consumption is slightly higher.
Lower maximum allowable compression ratios.
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NEW INNOVATION
THERMODYNE
No need of mechanical moving parts like
belt, water pump , thermostat Utilize waste heat energy of engine
Less in cost
It is applicable in all gasoline and diesel carengine.
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THANK YOU