3. • Cylinder wall is usually kept below 200°C.
• To prevent high thermal stresses caused due to high
temperature.
• High cylinder head temperature may cause pre-ignition in
SI engine.
• Spark plug and valve must be cool to avoid knock and
pre-ignition.
4. • The cooling system serves to remove heat from the hot
engine components and maintain normal temperature
condition of the running engine.
• There are mainly two types of cooling system
air cooling system
liquid cooling system
5. • Air cooled system is generally used in small engines say up
to 15-25kw and in aero planes engines.
• In this system fins and extended surfaces are provided on
the cylinder walls , cylinder head , etc.
• Heat generated due to the combustion engine cylinder will
be conducted to the fins and when the air flows over the
fins ,heat will be dissipated to air.
6. Amount of heat dissipated to air depends upon
Amount of air flowing through the fins.
Fins surface area
Thermal conductivity of metal used for fins.
8. In this method, cooling water jackets are provided
around the cylinder, cylinder head, etc. The water when
circulated through the jackets, it absorbs heat of
combustion. This hot water will then be cooling in the
radiator partially by a fan and
partially by the flow developed by the forward motion of
the vehicle. The cooled water is again recirculated
through the water jackets.
9.
10.
11. • Radiator & pressure cap
• Cooling fan
• Water pump
• Water jackets
• Thermostat
• Hoses
• Coolant
12. • It mainly consists of an upper tank and lower tank and
between them is a core. The upper tank is connected to
the water outlets from the engines jackets by a hose
pipe and the lover tank is connect to the jacket inlet
through water pump by means of hose pipes.
• When the water is flowing down through the radiator
core, it is cooled partially by the fan which blows air and
partially by the air flow developed by the forward motion
of the vehicle.
13. • It is to be noted that radiators are generally made out of
copper and brass and their joints are made by soldering.
14.
15. • Serves the purpose of maintaining the cooling system
pressure at a definite level during engine operation and
equalizing it with atomspheric pressure when the engine
is cooled off.
16. • Driven by the engine and draws air though the radiator
to cool the coolant.
• Power is ab-sorbed from the engine even when it is not
required.
• Most cooling system use some type of cooling fan.
There are 3 types of fan.
• Electric fan
• Clutch type fan
• Flex fan
17. • It is used to pump the circulating water.Impeller type
pump will be mounted at the front end.
• Pump consists of an impeller mounted on a shaft and
enclosed in the pump casing. The pump casing has
inlet and outlet openings.
• The pump is driven by means of engine output shaft
only through belts. When it is driven water will be
pumped
19. • The thermostat's main job is to allow the engine to heat
up quickly, and then to keep the engine at a constant
temperature. It does this by regulating the amount of
water that goes through the radiator. At low temperatures,
the outlet to the radiator is completely blocked -- all of the
coolant is recirculated back through the engine.
• Once the temperature of the coolant rises to between
180 and 195 F (82 - 91 C), the thermostat starts to open,
allowing fluid to flow through the radiator. By the time the
coolant reaches 200 to 218 F (93 - 103 C), the
thermostat is open all the way.
21. • Coolant is a mixture of antifreeze and water. Antifreeze
lowers the freezing point and raises the boiling point.
• The ideal antifreeze solutions should have the following
properties :
(a) It should dissolve in water easily.
(b) It should not evaporate.
(c) It should not have any harmful effect on any part of
cooling system.
(d) It should be cheap and easily available.
Examples : Glycerin along with water, Ethylene Glycol , A
solution of alcohol and water. etc.
22. • Starting of the engine will be difficult at low temperatures.
• Reduced evaporation of the fuel at low temperatures.
• Lower average combustion gas temperature and
pressure reducing specific power and efficiency.
• Higher friction due to higher viscosity of lubricating oil at
lower temperatures.
