COOLING SYSTEMS
SISTEM ENGINE OTTO :
IN INTERNAL COMBUSTION ENGINES
What is it?
It is a system which is used to keep engine from
getting not too hot and at the same time not to
keep it too cool either.
Reasons for Cooling
To promote a high volumetric efficiency.
To ensure proper combustion.
To ensure mechanical operation.
Purpose of the Cooling system
Control temperature of hot combustion
4000 degree temps. Could seriously damage
engine parts
Provide heat for passenger compartment
Cool Trans fluid & Oil
Heat moves from warm to cold
Effect for Over-cooling
The thermal efficiency is decreased due to more
loss of heat carried by the coolant.
The vapourization of the fuel is less resulting in
lower combustion efficiency.
Low temperature increases the viscosity of
lubricant causing more loss due to friction.
Types of Cooling system
Air cooling (or direct cooling) system.
Liquid cooling (or indirect cooling) system.
Cooling System Parts
Air cooling system
Air cooled engines depend on airflow across their external
surfaces of the engine cylinders to remove the necessary
heat. It is used for Small Engines
The amount of heat dissipated depends upon:
The area of cooling surface in contact with the air.
Mass flow rate of air
Temperature difference between cylinder and air
Conductivity of metal.
Air cooling system –Advantages
No need of radiator, cooling jackets, coolant and pumps.
The engine can be operated in cold climate where liquid
may freeze.
In places where water is scarce , air cooled engine is an
advantage.
Less weight and low cost.
Air cooled engines have no coolant leakage or freezing
problems.
Air cooling system -
Disadvantages
Large amount of power is used to drive the
cooling fan.
Engines give low power output.
Cooling fins under certain conditions may vibrate
and amplify the noise level.
Cooling is not uniform.
Liquid cooling system
A liquid (coolant) is
circulated around the
cylinders and absorb heat
from the cylinder walls
and cylinder head.
It is used for large Engines
Liquid cooling systems -Types
Thermo-syphon system
Forced circulation cooling system
Evaporative cooling system
Direct or non- return system
Thermo Siphon System
In this system the circulation of water is due to
difference in temperature of water. So in this
system pump is not required but water is circulated
because of density difference only.
Evaporative cooling system
In this system , the engine will
be cooled because of the
evaporation of the water in
the cylinders into steams. It is
used for cooling of many types
of industrial engines.
Forced circulation cooling system
This system is used in a large
number of vehicles like cars,
buses , trucks and other heavy
vehicles . Here, circulation of
water takes place with
convection currents helped by a
pump.
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.
Parts of Cooling System
Parts of cooling system
Water Jackets
➢Surrounds the cylinders with
water passage.
➢Absorbs heat from the cylinder
wall.
➢Pump move water to radiator
where heat is exchanged to
the air.
Parts of cooling system
Water pump
➢Non-positive displacement
pump
which circulates coolant around
cooling system.
➢Simple impeller design.
➢Usually driven by drive belt
from crankshaft.
• Leakage
Weep hole
• Noise
bearing
Parts of cooling system
Radiators
➢A radiator is a heat exchanger.
➢Tube and fin style the most
popular.
➢Made of copper and brass or
aluminum and plastic.
➢3 (radiator, evaporator, heater
core)
Parts of cooling system
Radiators
Two types of radiator construction
✓Down-flow
- older
✓Cross-flow
- Aerodynamic
- Lower hood lines
(a) Down Flow (b) Cross Flow
Types of Radiator
1 Gilled tube
2 Tubular
3 Honey comb
Parts of cooling system
Radiators Fan
Two types of radiator
construction
✓Down-flow
- older
✓Cross-flow
- Aerodynamic
- Lower hood lines
Parts of cooling system
Thermostat valve
• Controls coolant
temperature.
• Uses a temperature
sensor and a valve.
• Usually opens around
195 degrees F.
Thermostat Failure
• If it fails in the open position engine
runs cold. No heat, poor gas mileage,
gunks up motor oil and engine insides.
• If it fails closed: look out! It creates
pressure in the engine well beyond
normal limits. Many types of damage
may occur.
Parts of cooling system
Radiator Cap
• The cap allows access to the
cooling system for filling and
testing.
• The cap has two valves: a
pressure relief valve set at
around 15 PSI and a vacuum
valve which is needed when
the engine cools down.
• Raises boiling point of fluid
• Able to take on more heat
Parts of cooling system
Radiator Cap
• Keeps the coolant level full in
the system at all times.
• Works in conjunction with the
radiator cap.
• When the engine heats up the
coolant expands and flows to
the recovery tank.
• When the engine coolant the
coolant contracts and creates a
vacuum and draws the fluid
back into the radiator.
• Reduces air in system
• Reduces rust
• Less need to open radiator
Parts of cooling system
Radiator Hose
• The upper and lower radiator hoses
direct the fluid from the engine to
the radiator and back.
• Radiator hoses are a special part for
each car.
- Radiator
- Heater
- Bypass
• Heater hoses do the same for the
heater core.
• Heater hoses are generic and come
in ½”,5/8”, and ¾” diameter sizes.
Liquid cooling system-
Advantages
Uniform cooling of cylinder, cylinder head and
valves.
fuel consumption of engine improves by using
water cooling system.
The Engine need not be provided at the front end
of moving vehicle because of cooling system.
Engine is less noisy as compared with air cooled
engines, as it has water for damping noise.
Disadvantages of Cooling system
It depends upon the supply of water.
The water pump which circulates water absorbs
considerable power.
If the water cooling system fails then it will result in
several damage of engine.
The water cooling system is costlier as it has more
number of parts.
Also it requires more maintenance and care for its
parts.
Use of Anti- Freezers
During winter the water used in the radiator freezes because of cold
climates, then ice formed has more volume and produces cracks in the
cylinder blocks, pipes, and radiator. So, to prevent freezing antifreeze
mixtures or solutions are added in the cooling water.
Normally following are used as antifreeze solutions :
Methyl, ethyl alcohols.
A solution of alcohol and water.
Ethylene Glycol etc.
The ideal antifreeze solutions
should have the following
properties :
It should dissolve in water easily.
It should not evaporate.
It should not have any harmful effect on any part
of cooling system.
It should be cheap and easily available.
It should not corrode the system.
Lubricating oil as coolant
The heat, generated by piston, cylinder, and bearings is removed by
lubrication to a great extent. Lubrication creates cooling effect on
the engine parts.
Conclusion
A cooling system must be provided not only to
prevent damage to the vital parts of the engine
(due to high temperature), but the temperature of
these components must be maintained within
certain limits in order to obtain maximum
performance from the engine.
TERIMA
KASIH
