Chapter 3 - Cooling System

8/2/2019 Chapter 3 - Cooling System

1/15

International Islamic University MalaysiaInternational Islamic University Malaysia

Introduction to Automotive EngineeringIntroduction to Automotive Engineering

Department of Mechanical Engineering, KulliyyahDepartment of Mechanical Engineering, Kulliyyahof Engineering, IIUMof Engineering, IIUM


2/15

Why does cooling system important for the IC engine ?Why does cooling system important for the IC engine ? The burning A/F mixture in the engine cylinder might reach 4000The burning A/F mixture in the engine cylinder might reach 400000FF

or higher.or higher.

Causes engine overheatedCauses engine overheated

While, the boiling temperature of the cylinder wall is 500While, the boiling temperature of the cylinder wall is 50000F.F.

4000400000F causes the cylinder wall to damage.F causes the cylinder wall to damage.

Higher temperature causes the lubricating may lose its lubricatingHigher temperature causes the lubricating may lose its lubricatingability.ability.

To prevent overheating, the cooling system is important whichTo prevent overheating, the cooling system is important which removes the excess heat,removes the excess heat,

prevent the cylinder wall from damaging,prevent the cylinder wall from damaging,

keep the lubricating viscosity index constant and so on.keep the lubricating viscosity index constant and so on.

Function of cooling system:Function of cooling system: Takes away heat from the engine body before it damageTakes away heat from the engine body before it damage Keeps the engine upto its normal operating temperatureKeeps the engine upto its normal operating temperature

Provides a source of heat for the passenger compartment heaterProvides a source of heat for the passenger compartment heater--andand airair--conditioner.conditioner.

Question: what is the other advantage could get from the cooling system ratherQuestion: what is the other advantage could get from the cooling system rather

than cooling the engine.than cooling the engine.


3/15

InternalInternal--combustion enginescombustion engines Burn Fuel hotterBurn Fuel hotterthan thethan the

melting temperaturemelting temperature of engine materials, and hot enoughof engine materials, and hot enough

to set fire to lubricants.to set fire to lubricants. Engine cooling removes energy fast enough to keep temperaturesEngine cooling removes energy fast enough to keep temperatures

low so the engine can survive.low so the engine can survive.

Some highSome high--efficiency engines run without explicit coolingefficiency engines run without explicit cooling

and with only accidental heat loss, a design calledand with only accidental heat loss, a design called

adiabaticadiabatic..

The term "adiabatic" literally means an absence ofThe term "adiabatic" literally means an absence ofheatheat

transfertransfer..

AnAn adiabatic processadiabatic process or anor an isocaloric processisocaloric process is ais athermodynamic processthermodynamic process in which noin which no heatheat is transferred to oris transferred to or

from the workingfrom the working fluidfluid..

Adiabatic coolingAdiabatic cooling occurs when the pressure of aoccurs when the pressure of a

substance is decreased as it does work on itssubstance is decreased as it does work on its

surroundings.surroundings.


4/15

Basic principleBasic principle Most internal combustion engines areMost internal combustion engines are fluidfluid cooled usingcooled using

either air (a gaseous fluid) or a liquid coolant run througheither air (a gaseous fluid) or a liquid coolant run througha heat exchanger (a heat exchanger (radiatorradiator) cooled by air.) cooled by air. A heat exchanger is a device in which energy is transferred fromA heat exchanger is a device in which energy is transferred from

one fluid to another across a solid surfaceone fluid to another across a solid surface Heat transferred from hot water to outside airHeat transferred from hot water to outside air

The water may be used directly to cool the engine, butThe water may be used directly to cool the engine, butoften has sedimentoften has sediment which can clog coolant passages, or chemicals, such as salt,which can clog coolant passages, or chemicals, such as salt,

that can chemically damage the engine.that can chemically damage the engine.

Thus, engine coolant may be run through a heat exchangerThus, engine coolant may be run through a heat exchangerthat is cooled by the body of water.that is cooled by the body of water.

Q.Why a heat exchanger is important for the cooling system of an ICQ.Why a heat exchanger is important for the cooling system of an ICengine?engine?


5/15

The Components of a Cooling SystemThe Components of a Cooling System The RadiatorThe Radiator

Radiator Cooling FansRadiator Cooling Fans Pressure Cap & Reserve TankPressure Cap & Reserve Tank

Water PumpWater Pump

ThermostatThermostat

Head Gaskets & Intake Manifold GasketsHead Gaskets & Intake Manifold Gaskets

Heater CoreHeater Core HosesHoses

Bypass SystemBypass System

Freeze PlugsFreeze Plugs


6/15

The RadiatorThe Radiator

The radiator is a heat exchangerThe radiator is a heat exchanger

Why does radiator call heat exchanger ?Why does radiator call heat exchanger ?

It has two sets of passages.It has two sets of passages.

One for coolant and other for outside airOne for coolant and other for outside air

Coolant losses heat to the passing air.Coolant losses heat to the passing air.

The radiator core is usually made of flattened aluminum tubes with aluminumThe radiator core is usually made of flattened aluminum tubes with aluminum

strips (fins) that zigzag between the tubes.strips (fins) that zigzag between the tubes.

These fins transfer the heat in the tubes into the air stream to be carried awayThese fins transfer the heat in the tubes into the air stream to be carried away

from the engine.from the engine.

On each end of the radiator core is a tank, usually made of plastic that coversOn each end of the radiator core is a tank, usually made of plastic that covers

the ends of the radiator,the ends of the radiator,


7/15

Water PumpWater Pump A water pump is a simple device that will keep the coolant moving asA water pump is a simple device that will keep the coolant moving as

long as the engine is running.long as the engine is running.

It is usually mounted on the front of the engine and turns whenever theIt is usually mounted on the front of the engine and turns whenever theengine is running.engine is running.

The water pump is driven by the engine through one of the following:The water pump is driven by the engine through one of the following:

A fan belt that will also be responsible for driving an additionalA fan belt that will also be responsible for driving an additionalcomponent like an alternator or power steering pumpcomponent like an alternator or power steering pump

A serpentine belt, which also drives the alternator, power steeringA serpentine belt, which also drives the alternator, power steering

pump and AC compressor amongpump and AC compressor among other things.other things. The timing belt that is also responsible for driving one or moreThe timing belt that is also responsible for driving one or more

camshafts.camshafts.


8/15

ThermostatThermostat The thermostat is simply a valve that measures the temperature of theThe thermostat is simply a valve that measures the temperature of the

coolant and control coolant flow and,coolant and control coolant flow and, If the coolant is not hot enough, the flow to the radiator is blockedIf the coolant is not hot enough, the flow to the radiator is blocked

fluid is directed to a bypass system that allows the coolant to return directly back tofluid is directed to a bypass system that allows the coolant to return directly back tothe engine.the engine.

This keeps all heat in engines so it warms up quicklyThis keeps all heat in engines so it warms up quickly

if it is hot enough, opens to allow the coolant to flow through the radiator.if it is hot enough, opens to allow the coolant to flow through the radiator.

The bypass system allows the coolant to keep moving through the engineThe bypass system allows the coolant to keep moving through the engineto balance the temperature and avoid hot spots.to balance the temperature and avoid hot spots. Because flow to the radiator is blocked, the engine will reach operatingBecause flow to the radiator is blocked, the engine will reach operating

temperature sooner and,temperature sooner and,

on a cold day, will allow the heater to begin supplying hot air to the interioron a cold day, will allow the heater to begin supplying hot air to the interiormore quickly.more quickly.

The thermostat is usually located in the front, top part of the engine in a water outletThe thermostat is usually located in the front, top part of the engine in a water outlet

housing that also serves as the connection point for the upper radiator hose.housing that also serves as the connection point for the upper radiator hose.


9/15

A thermostat is placed between the engine and the radiator to makeA thermostat is placed between the engine and the radiator to makesure that the coolant stays above a certain preset temperature.sure that the coolant stays above a certain preset temperature. If the coolant temperature falls below this temperature, the thermostatIf the coolant temperature falls below this temperature, the thermostat

blocks the coolant flow to the radiator, forcing the fluid instead through ablocks the coolant flow to the radiator, forcing the fluid instead through a

bypass directly back to the engine.bypass directly back to the engine. The coolant will continue to circulate like this until it reaches the designThe coolant will continue to circulate like this until it reaches the design

temperature, at which point,temperature, at which point, the thermostat will open a valve and allow the coolant back through thethe thermostat will open a valve and allow the coolant back through the

radiator.radiator.

The thermostat opens at a specified temperature or thermostatThe thermostat opens at a specified temperature or thermostat

rating.rating. This number is usually stamped on the thermostat.This number is usually stamped on the thermostat.

Two common ratings are 185Two common ratings are 18500F and 195F and 19500FF Thermostat fully open at 20Thermostat fully open at 2000F higher temperature than the ratingF higher temperature than the rating

temperaturetemperature

For example, thermostat starts to open at 195For example, thermostat starts to open at 19500 and fully open atand fully open at(195(19500F+20F+2000F) or 215F) or 21500FF


10/15

Pressure (Radiator) cap and reserve tankPressure (Radiator) cap and reserve tank As coolant gets hot, it expands.As coolant gets hot, it expands.

Since the cooling system is sealed, this expansion causes anS

ince the cooling system is sealed, this expansion causes anincrease in pressure in the cooling system, which is normal and partincrease in pressure in the cooling system, which is normal and partof the design.of the design.

When coolant is under pressure, the temperature where the liquidWhen coolant is under pressure, the temperature where the liquidbegins to boil is considerably higher.begins to boil is considerably higher.

This pressure, coupled with the higher boiling point of ethyleneThis pressure, coupled with the higher boiling point of ethyleneglycol, allows the coolant to safely reach temperatures in excess ofglycol, allows the coolant to safely reach temperatures in excess of250 degrees.250 degrees.

The radiator pressure cap is a simple device that will maintainThe radiator pressure cap is a simple device that will maintainpressure in the cooling system up to a certain point.pressure in the cooling system up to a certain point.

If the pressure builds up higher than the set pressure point, thereIf the pressure builds up higher than the set pressure point, thereis a spring loaded valve, calibrated to the correct Pounds peris a spring loaded valve, calibrated to the correct Pounds perSquare Inch (psi), to release the pressure.Square Inch (psi), to release the pressure.


11/15

Radiator CapRadiator Cap

In order to prevent the coolant from boiling, the coolingIn order to prevent the coolant from boiling, the cooling

system is designed to be pressurized.system is designed to be pressurized.

Under pressure, the boiling point of the coolant is raisedUnder pressure, the boiling point of the coolant is raised

considerably.considerably.

However, too much pressure will cause hoses and other parts toHowever, too much pressure will cause hoses and other parts to

burst,burst, so a system is needed to relieve pressure if it exceeds a certainso a system is needed to relieve pressure if it exceeds a certain

point.point.

The job of maintaining the pressure in the cooling system belongsThe job of maintaining the pressure in the cooling system belongs

to the radiator cap.to the radiator cap.

The cap is designed to release pressure if it reaches the specifiedThe cap is designed to release pressure if it reaches the specifiedupper limit that the system was designed to handle.upper limit that the system was designed to handle.

Since then, a system was added to capture any released fluid andSince then, a system was added to capture any released fluid and

store it temporarily in a reserve tank.store it temporarily in a reserve tank.

This fluid would then return to the cooling system after the engineThis fluid would then return to the cooling system after the engine

cooled down.cooled down.

This is called a closed cooling system.This is called a closed cooling system.


12/15


13/15

CirculationCirculation

The coolant follows a path that takes it from the water pump, through passages insideThe coolant follows a path that takes it from the water pump, through passages insidethe engine block where it collects the heat produced by the cylinders.the engine block where it collects the heat produced by the cylinders.

It then flows up to the cylinder head (or heads in a V type engine) where it collectsIt then flows up to the cylinder head (or heads in a V type engine) where it collectsmore heat from the combustion chambers.more heat from the combustion chambers.

It then flows out past the thermostat (if the thermostat is opened to allow the fluid toIt then flows out past the thermostat (if the thermostat is opened to allow the fluid topass), through the upper radiator hose and into the radiator.pass), through the upper radiator hose and into the radiator.

The coolant flows through the thin flattened tubes that make up the core of theThe coolant flows through the thin flattened tubes that make up the core of theradiator and is cooled by the air flow through the radiator.radiator and is cooled by the air flow through the radiator.

From there, it flows out of the radiator, through the lower radiator hose and back to theFrom there, it flows out of the radiator, through the lower radiator hose and back to thewater pump.water pump. By this time, the coolant is cooled off and ready to collect more heatBy this time, the coolant is cooled off and ready to collect more heatfrom the engine.from the engine.

The capacity of the system is engineered for the type and size of the engine and theThe capacity of the system is engineered for the type and size of the engine and thework load that it is expected to undergo.work load that it is expected to undergo.

Obviously, the cooling system for a larger, more powerful V8 engine in a heavyObviously, the cooling system for a larger, more powerful V8 engine in a heavyvehicle will need considerably more capacity then a compact car with a small 4vehicle will need considerably more capacity then a compact car with a small 4cylinder engine.cylinder engine.

On a large vehicle, the radiator is larger with many more tubes for the coolant to flowOn a large vehicle, the radiator is larger with many more tubes for the coolant to flow

through.through. The radiator is also wider and taller to capture more air flow entering theThe radiator is also wider and taller to capture more air flow entering thevehicle from the grill in front.vehicle from the grill in front.


14/15

Antifreeze and CoolantAntifreeze and Coolant The coolant that courses through the engine and associatedThe coolant that courses through the engine and associated

plumbing must be able to withstand temperatures well below zeroplumbing must be able to withstand temperatures well below zerowithout freezing.without freezing.

It must also be able to handle engine temperatures in excess ofIt must also be able to handle engine temperatures in excess of25025000C without boiling.C without boiling.

The fluid must also contain rust inhibiters and a lubricant.The fluid must also contain rust inhibiters and a lubricant.

The coolant in today's vehicles is a mixture of ethylene glycolThe coolant in today's vehicles is a mixture of ethylene glycol(antifreeze) and water.(antifreeze) and water. The recommended ratio is 50The recommended ratio is 50--50.50.

In other words, one part antifreeze and one part water.In other words, one part antifreeze and one part water.

This is the minimum recommended for use in automobile engines.This is the minimum recommended for use in automobile engines.

Less antifreeze and the boiling point would be too low.Less antifreeze and the boiling point would be too low.

In certain climates where the temperatures can go well below zero,In certain climates where the temperatures can go well below zero,

it is permissible to have as much as 75% antifreeze and 25% water, butit is permissible to have as much as 75% antifreeze and 25% water, butno more than that.no more than that.

Pure antifreeze will not work properly and can cause a boil over.Pure antifreeze will not work properly and can cause a boil over.


15/15

What are the problems could incurred in the engine if water simplyWhat are the problems could incurred in the engine if water simply

used as the coolant ?used as the coolant ?

The freezing point of water is 32The freezing point of water is 3200F (0F (000C). If only water uses as the coolant, itC). If only water uses as the coolant, it

would freeze if the temperature drop below 32would freeze if the temperature drop below 3200F.F.

This would stop coolant circulation and the engine would overheat.This would stop coolant circulation and the engine would overheat.

Water also expand about 9% if it freezeWater also expand about 9% if it freeze

could crack the cylinder block and head, and split the radiator.could crack the cylinder block and head, and split the radiator.

Chapter 3 - Cooling System

Documents

Transcript of Chapter 3 - Cooling System