DAV Public School, Hudco Bhilai

A
Project Report
On
“Diagrammatic Representation of Cooling System
Showing all parts of the system with
Proper labeling in a full size
Chart paper”
Subject: Automotive (804)

Submitted by
“D.Abhijay”
“11-A”
‘11106’
 Session: 2023 – 2024

Guided By:
Sandeep Saha Sir
Preface
The main objective of any Automotive student is to get as much of practical
knowledge as possible. Being able to have practical knowledge by developing a
project is a lifetime experience. As practical knowledge is important as theoretical
knowledge I am thankful of having this project.

Through the development of the project we had a great experience of various

strategies that can be applied in development of the project.

We are pleased to present this project. Proper care has been taken while organizing
the project so that it is to be comprehend in the best possible manner.
 Acknowledgement
I would like to express my sincere gratitude to my Automotive teacher
Mr Sandeep Saha for hs vital support, guidance and encouragement,
without which this project would not have come forth. I would also like
to express my gratitude to Principal Sir and Teachers of DAV Public
School, Hudco, Bhilai for their support during the making of this
project.
 Certificate
This is to certify that “D.Abhijay” of class 11th, DAV Public School,
Hudco, Bhilai, has completed the project titled “Diagrammatic
Representation of Cooling System Showing all parts of the system with
Proper labeling in a full size Chart paper”, during the academic year
2023-24 towards the partial fulfillment of credit for “Automotive (804)
Practical” evaluation of CBSE and submitted satisfactory report, as
compiled in the following pages, under my supervision.
Name of the student:
Roll no.
Signature of the student:

Signature of Internal
 ABSTRACT

The Following paper deals with the topic of Engine Cooling

System in Cars, these systems are used in the cooling of the
engine of the cars, was introduced around the early 1870s. It is
Mandatory in every Engine to have its own cooling mechanism
or system. The operation of cooling system is to remove the
excess heat from the engine. The removal of heat prevents the
damage to parts and also keeps the engine at its normal pressure.
The radiator is the main part of the cooling system. The paper
begins with a brief introduction of cooling mechanism. The next
part is about its components and its working. Then we study
about its various components in details and their uses. In the last
part we discuss about the fluids or coolant used in the system.
Then finally we sum up to the Conclusion.
 CONTENTS

ABSTRACT
CONTENTS
LIST OF FIGURES
1. Introduction

2. Literature Review

3. Working of a Cooling System

4. Components of Cooling System

4.1. Water Jacket

4.2. Water Pump

4.3. Engine Fan

4.4. Variable Speed Fan

4.5. Flexible Blade Fan

4.6. Electric Fan

4.7. Radiator

4.8. Expansion Tank

4.9. Thermostat

4.10. Cooling Bypass Passage

4.11. Radiator Cap

5. Antifreeze and Coolant

5.1. Antifreeze

5.2. Types of Antifreeze

6. Conclusion
REFERENCES

LIST OF FIGURES

Fig 1: Engine Cooling System………………………………

 1. Introduction
The burning air-fuel mixture in the engine cylinders may reach 4000°F [2200°C] or
higher. This means engine parts get hot. However, cylinder walls must not reach hotter
than about 500°F [260°C], higher temperature causes lubricating oil to break down and
lose its lubricating ability. Other engine parts are also damaged. To prevent overheating,
the cooling systems removes the excess heat. The cooling system keeps the engine at its
most efficient temperature at all speeds and operating conditions. It also helps bring the
engine up to normal operating temperature as quickly as possible. In addition, the cooling
system provides a source of heat for the passenger-compartment heater and air-
conditioner

Cooling system uses five basic parts :-

1. Water Jacket

2.Water Pump

3. Thermostat

4. Radiator
5. Fan

2. Literature Review
Oliet et al. (2007) studied different factors which influence radiator performance. It

includes air, fin density, coolant flow and air inlet temperature. It is catch that heat transfer

and performance of radiator strongly affected by air & coolant mass flow rate. As air and

coolant flow increases cooling capacity also increases. When the air inlet temperature

increases, the heat transfer and thus cooling quantity decreases. Smaller fin spacing and

greater louver fin angle have higher heat transfer. Fin density may be increased till it blocks

the air flow and heat transfer rate reduced.

Sulaiman et al. (2009) use the computational Fluid Dynamics (CFD) modeling

simulation of air flow distribution from the automotive radiator fan to the radiator. The task

undertook the model the geometries of the fan and its surroundings is the first step. The

results show that the outlet air velocity is 10 m/s. The error of average outlet air velocity is

12.5 % due to difference in the tip shape of the blades. This study has shown that the CFD

simulation is a useful tool in enhancing the design of the fan blade. In this paper this study

has shown a simple solution to design a slightly aerodynamic shape of the fan hub.

Chacko et al. (2005) used the concept that the efficiency of the vehicle cooling system

strongly rely on the air flow towards the radiator core. A clear understanding of the flow

pattern inside the radiator cover is required for optimizing the radiator cover shape to increase

the flow toward the radiator core, thereby improving the thermal efficiency of the radiator.

CFD analysis of the baseline design that was validated against test data showed that

indispensable area of re-circulating flow to be inside the radiator cover. This recirculation

reduced the flow towards the radiator core, leading to a reputation of hot air pockets close to

the radiator surface and subsequent disgrace of radiator thermal efficiency. The CFD make

able optimization led to radiator cover configuration that eliminated these recirculation area
and increased the flow towards the radiator core by 34%. It is anticipated that this increase in

radiator core flow would important to increase the radiator thermal efficiency.

Jain et al. (2012) presented a computational fluid dynamics (CFD) modeling of air

flow to divide among several from a radiator axial flow fan used in an acid pump truck Tier4

Repower. CFD analysis was executed for an area weighted average static pressure is variance

at the inlet and outlet of the fan.

Pressure contours, path line and velocity vectors were plotted for detailing the flow

characteristics for dissimilar orientations of the fan blade. This study showed how the flow of

air was intermittent by the hub obstruction, thereby resulting in unwanted reverse flow

regions. The different orientation of blades was also considered while operating CFD

analysis. The study revealed that a left oriented blade fan with counterclockwise rotation 5

performed the same as a right oriented blade fan with rotating the clockwise direction. The

CFD results were in accord with the experimental data measured during physical testing.

Singh et al. (2011) studied about the issues of geometric parameters of a centrifugal

fan with backward- and forward-curved blades has been inspected. Centrifugal fans are used

for improving the heat dissipation from the internal combustion engine surfaces. The

parameters studied in this study are number of blades, outlet angle and diameter ratio. In the

range of parameters considered, forward curved blades have 4.5% lower efficiency with 21%

higher mass flow rates and 42% higher power consumption compared to backward curved

fan. Experimental investigations suggest that engine temperature drop is significant with

forward curved blade fan with insignificant effect on mileage. Hence, use of forward fan is

recommended on the vehicles where cooling requirements are high. The results suggest that

fan with different blades would show same an action below highpressure coefficient. Increase

in the number of blades increases the flow coefficient follow by increase in power coefficient

due to better flow guidance and reduced losses.

 Kumawat et al. (2014) illustrated about the axial flow fans, while incapable of

increasing high pressures, they are well relevant for handling large volumes of air at

comparatively low pressures. In general, they are low in cost, possess good efficiency and

can have blades of airfoil shape. Axial flow fans show good efficiencies, and can to work at

high static pressures if such operation is necessary. The presentation of an axial fan was

simulated using CFD results were presented in the form of velocity vector and streamlines,

which provided actual flow characteristics of air around the fan for different number of fan

blades. The different parameters similar temperature, pressure, fan noise, turbulence and were

also considered while performing CFD analysis. The study exposed that a fan with an

optimum number of fan blades performed well as compared to the fan with less number of

fan blades. In general, as a compared between the efficiency and cost, five to 12 blades are

good practical solutions.

Barve et al. (2014) illustrated about design the fan and analyze it for its strength in

structure using the Finite Element Method (FEM) and the flow of air all side it using

Computational Fluid Dynamics (CFD) approach. The design of the fan was conducted in

phases, starting with calculating to need all dimensions followed by analytical models to

prove the concept. The results obtained from the analytical studies determined a potential for

a successful design that met greatest of the above outlined parameters. The calculations of the

Flow Rate, Static Pressure, Velocity Vectors, and Safety in Structural were made. The

structural analysis of the fan represents its strength structurally. The shear stress, Von-Misses

stresses approve the safety of the design in structural. Torque Optimization: The maximum

torque is optimized for the fan. Its value is 42.5 Nm.

Jama et al. (2014) The airflow distribution and non-uniformity across the radiator of a

full size Results from these tests have shown the best method for shielding the front end of
the vehicle in terms of airflow equality to be the horizontal way followed by the vertical

method. These shielding methods also produced the high average airflow velocity across the

radiator which is analogous to better cooling. The results showed that the method to shield

the front-end of a passenger vehicle would be to employ a flat method. This shielding method

produced the high uniform cooling airflow distribution matched to the other methods. By

extension it should also produce the lesser reduction in cooling capacity for a given intake

area.

Leong et al. (2010) described use of Nano fluids based coolant in the engine cooling

system and its effect on cooling capacity. It is found that Nano-fluid having higher thermal

conductivity than base coolant like 50% water and 50% ethylene glycol. It increases heat

transfer. So for same heat transfer, radiator core area can be decreased matched to base one. It

finds better solution to minimize area. Thermal performance of a radiator using Nano fluids is

increased with increase in pumping power required compared to same radiator using ethylene

glycol as coolant.

Sai et al. (2014) an experimental study of performance of A1203 Nano fluid in a car

radiator was studied in the present work. Nano fluids were tested in a car radiator by varying

the percentage of nanoparticles mix with the water. Pure water is used in a radiator and its

performance was studied. A1203 Nano particles are mixed with the water in 0.025%, 0.05%

and 0.1% volume concentration and the performance was studied. The performance

comparison has made between pure water and Nano fluids tested in a radiator.

The convective heat transfer performance and flow characteristics of A1203

nanofluids flowing in an automotive radiator have been experimentally investigated.

Impotent increase in heat transfer was observed with the used different volume foci of

nanoparticles mixed with water. The experimental result have shown that the heat transfer

enhancement was about 4.56% for 0.025% Al2O3 nanofluid at 80ºC and this is about 12.4%
for 0.1% A1203 nanofluid at 80°C.The results have shown that A1203 nanofluid has a high

potential for hydrodynamic flow and heat transfer enhancement in an automotive radiator.

Trivedi et al. (2012) illustrated the effect of pitch tube for best configured radiator for

optimum presentation. Heat transfer increases as the surface area of the radiator core is

increased. This leads to change the geometry by modifying the order of tubes in automotive

radiator to increase the surface area for greater heat transfer. The modification in order of

tubes in radiator is carried out by studying the effect of tube pitch by CFD analysis. Results

Shows that as the tube pitch this decreased or increased than optimum pitch of tubes, the heat

transfer rate increases. So it can suggest that optimum efficiency is coming at the pitch of 12

mm.

Yadav et al. (2011) presented parametric study on automotive radiator. In the action

evaluation, a radiator is installed into a test setup. The various parameters including inlet

coolant temperature, mass flow rate of coolant, and etc. are varied. Following remarks are

observed during learning. Influence of coolant mass flow cooling capacity of the radiator has

straightforward relation with the coolant flow rate. With an increase in the value of cooling

flow rate, corresponding increase in the value of the effectiveness and cooling capacity.

Influence of coolant inlet temperature is increase in the inlet temperature of the coolant the

cooling capacity of the radiator increases.

Bozorgan et al. (2012) This paper presented a numerical investigation of the use of

copper oxide water nanofluid as a coolant in a radiator of Chevrolet Suburban IC engine with

a given heat exchange and pumping power for Cuowater capacity. The local convective

overall heat transfer coefficients Nano fluid at different volume fractions (0.1% to 2%) was

of the coolant Reynolds number and the studied under turbulent flow conditions. Also the

effects automotive speed on the radiator performance are consider in the work. The

simulation results indicate that the total heat transfer coefficient of Nano fluid is better than
that of water alone and therefore the total heat transfer area of the radiator can be decrees.

Nguyen et al. (2007) studied we have experimentally studied the heat transfer

enhancement delivered by a particular nanofluid, Al2O3 water mixture, for a water closed

system that is destined for cooling of microprocessors and another heated electronic

components. Data obtained for distilled water and Nano fluid with various component

concentrations, namely 0.95% and 2.2% & 4.5% have eloquently shown that the use of such

a Nano fluid appears especially advantageous for cooling of heated component. For the

particular concentration of 4.5%, a heat transfer improvement as much as 23% with respect to

that of distilled water has been achieved.

Satyamkumar et al. (2006) in this cooling system of automotive engine the water is

evaporate at more temperature, so we need to add water and also water is low capacity of

absorb the heat. By using nano fluids in radiator alternative of water, we can improve the

thermal efficiency of the radiator. So cooling effect of the radiator is improve and the overall

efficiency of engine willpower increased. As heat transfer can be improving by nanofluids, in

Automotive radiators can be made energy efficient and compact.

Vajjha et al. (2010) have been numerically studied a 3D laminar flow and heat

transfer with two different nanofluid, Al2O3 and CuO, in the ethylene glycol/water mixture

circulating through the flat tubes of an automotive radiator to evaluate their control over the

base fluid. Convective heat transfer coefficient along the flat tubes with the nanofluid flow air

considerable improvement over the base fluid.

Peyghambarzadeh et al. (2011) have recently investigated the application of

A1203/water nanofluids in the radiator by calculating the tube side heat transfer co-efficient.

They have recorded the interesting enhancement of 45% contrasting with the pure water

application under highly turbulent flow condition. Peyghambarzadeh et al. have used diverse

base fluids including pure water, pure ethylene glycol and their binary mixtures with A1203
nanoparticles and once again it was proved that nanofluids enhances the cooling efficiency of

the car radiator extensively.

Kim et al. (2009) Investigated effect of nanofluids on the performances of convective

heat transfer coefficient of a circular straightforward tube having laminar and turbulent flow

with consistent heat flux. This studied have create that the convective heat transfer coefficient

of alumina nanofluids enhanced in comparison to base fluid by 15% & 20% in laminar and

turbulent flow, separately.

This showed that the thermal boundary layer played a dominant role in the laminar flow while

thermal conductivity played a dominant role in turbulent flow. Be that as it may no development

in convection heat transfer coefficient was noticed for amorphous molecule nanofluids.

Naraki et al. (2013) found that thermal conductivity of CuO/water nanofluids much

higher than that of base liquid water. Author found that the total heat transfer coefficient

increases with the improvement in the nanofluid focus from (0 - 0.4) vol. %. Conversely,

the enactment of nanofluid increases the overall heat exchange coefficient up to 8% at

nanofluid focus of 0.4 vol % incomparison with the base fluid.

 3. Working of a Cooling System
The cooling system is a system of parts and fluid that work together to control an engine's
operating temperature for optimal performance. The system is made up of passages inside the
engine block and heads, a water pump and drive belt to circulate the coolant, a thermostat to
control the temperature of the coolant, a radiator to cool the coolant, a radiator cap to control the
pressure in the system, and hoses to transfer the coolant from the engine to the radiator. The
liquid that flows through a cooling system, antifreeze, or commonly referred to as coolant,
withstands extreme hot and cold temperatures and contains rust inhibitors and lubricants to keep
the system running smoothly.

Coolant follows a circulation path that begins with the water pump. The water pump's
impeller uses centrifugal force to draw coolant from the radiator and push it into the engine
block. Pumps are usually fan, serpentine timing belt, or timing chain driven. Nowadays, they
may even be driven electrically. If the water pump experiences a leak from the seal, a cracked
housing, broken impeller or a bearing malfunction, it can compromise the entire cooling system,
causing the vehicle to overheat. As coolant flows through the system, it picks up heat from the
engine before arriving at the thermostat. The thermostat is a valve that measures the temperature
of the coolant and opens to allow hot fluid to travel to the radiator. If the thermostat becomes
'stuck' and quits working, it will affect the entire cooling system.

Once released by the thermostat, hot coolant travels through a hose to be cooled by the
radiator. The antifreeze passes through thin tubes in the radiator. It is cooled as air flow is passed
over the outside of the tubes. Depending upon the speed of the vehicle, airflow is provided by the
vehicle's movement down the road (ram air effect) and/or cooling fans. Radiator restrictions can
compromise its ability to transfer heat. These can be either external air flow or internal coolant
flow restrictions. A malfunctioning electric cooling fan or fan clutch can limit air flow across the
radiator. Check/replace the fan clutch...the life expectancy of water pumps and fan clutches are
about the same and share a common shaft. A failed fan clutch can cause severe damage to the
water pump.

As coolant temperature increases, so does the pressure in the cooling system. This
pressure is regulated by the radiator cap. Correct system pressure is required for proper water
pump seal lubrication. Increasing the cooling system pressure raises the boiling point of the
coolant. Each one pound of increased pressure raises the boiling point by 3°F. If the pressure
builds up higher than the set pressure point, a spring-loaded valve in the cap will release the
pressure. If an engine has overheated, the radiator cap and thermostat should be replaced. It is
important to regularly inspect the condition of your cooling system's belts and hoses. Soft hoses,
oil soaked belts or cracked belts and hoses can have dire effects on the entire cooling system.
Proper belt tension is also important.
 Always refer to your manufacturer's manual to determine the recommended coolant type
for your vehicle. This and the proper mixture of coolant and distilled water are the lifeblood
towards keeping your system running cool. Most parts retailers now offer a solution of premixed
coolant and distilled water. While it may seem like an unnecessary added expense, the
cleanliness of the premixed solution will pay off over time.

Mineral deposits and sediments from corroded or malfunctioning parts accumulate in the
cooling system. Before performing a cooling system repair, it is recommended to flush the
cooling system prior to installing any new parts. This is a task made even easier by using a flush-
fill kit. Failure to flush the system will contaminate the new parts being installed and could lead
to premature component failure.
 4. Components of Cooling System
4.1. Water jacket
The water jackets are open spaces between the cylinder walls and the outside
shell of the block and head. Coolant from the water pump flows first through the
block water jackets. Then the coolant flows up through the cylinder-head water
jackets and back to the radiator.

4.2. Water Pump

Water pumps are impeller pumps. They attach to the front of the engine and
are driven by a belt from the crankshaft pulley. The pump circulates as much as
7500 gallons (28,390 L) of coolant an hour. As the impeller rotates, the curved
blades draw coolant from the bottom of the radiator. They force the coolant
through the pump outlet to the water jackets. The impeller shaft is supported on
sealed bearings which never need lubrication. Seals prevent the coolant from
leaking past the bearings. The water pump is driven by the fan belt. The water
pump may also be driven by a single serpentine belt that also drives other
components.

4.3. Engine Fan

Engine Fan The radiator sometimes needs additional airflow through it to
prevent the engine from overheating. This usually occurs at idle and slow speed. At
higher vehicle speeds, the air rammed through the radiator by the forward motion
of the vehicle provides all the cooling that is needed. An engine fan or cooling fan
pulls the additional air through the radiator. The fan may be either a mechanical
fan or an electric fan.

Engines mounted longitudinally in rear-drive vehicles usually have a

mechanical fan that mounts to the water-pump shaft. The fan is made of sheet steel
or molded plastic. It has four to seven blades and turns with the waterpump
impeller. A fan shroud around the fan directs the airflow. This increases the
efficiency of the fan.
4.4. Variable Speed Fan
Many longitudinal engines use a variable-speed fan driven through a fan
clutch. The fan clutch is a temperature-controlled fluid coupling that mounts
between the water-pump pulley and the fan. The air passing through the radiator
strikes a thermostatic blade or spring on the front of the clutch. The temperature of
the air causes the thermostatic device to bend. This operates a valve that allows
silicone oil to enter or leave the fluid coupling. When the engine is cold, the fluid
coupling slips so the fan is not driven. This reduces noise and saves engine power.
As the engine warms up, the thermostatic device causes more oil to enter the fluid
coupling. Then the fan clutch begins to drive the fan.

4.5. Flexible Blade Fan

Fan Another way to reduce the power needed to drive the fan and reduce fan
noise is to use flexible blades on the fan. In operation, the blades slant or pitch of
the blades decreases as fan speed increases. Centrifugal force flattens the blades so
they take a smaller bite of air. This reduces noise and airflow, and the power
needed to turn the fan.

4.6. Electric Fan

Transverse engines in front-drive vehicles usually have an electric fan. An
electric motor turns the blades. A thermostatic switch turns on the fan only when
needed. For example, in one engine, the switch turns on the fan when the coolant
reaches 200°F [93°C]. It turns off the fan if the coolant drops below this
temperature. On vehicles with air conditioning, turning on the air conditioning
bypasses the thermostatic switch. The fan runs all the time when the air conditioner
is on. The fan is turned on and off by the electronic control module (ECM) in many
vehicles with an electronic engine control system.

Most fans, mechanical and electric, are pull-type fans. They mount behind
the radiator and pull air through it. Some cars also have a push-type fan. It mounts
in front of the radiator and pushes air through it. An electric fan drains less power
from the engine and creates less noise than a mechanical fan. Also, there is no fan
belt to inspect, adjust, or replace.
 4.7. Radiator
Radiator The radiator is a heat exchanger that removes heat from
engine coolant passing through it. The heat transfers from the hot coolant to the
cooler outside air. An automotive radiator has three main parts. These are a
radiator core, and inlet and outlet tanks. The cores are usually made of aluminum.
The tanks may be made of plastic or metal. The core has two sets of passages, a set
of tubes, and a set of fins attached to the tubes.

The tubes run from the inlet tank to the outlet tank. Coolant flows through
the tubes and air flows between the fins. The hot coolant sends heat through the
tubes to the fins. The outside air passing between the fins picks up and carries
away the heat. This lowers the temperature of the coolant. The coolant flows from
the upper tank down through the tubes to the lower tank. Most cars use a cross-
flow radiator. The tubes are horizontal so the coolant flows from the inlet tank
horizontally to the outlet tank. The cross-flow radiator takes up less space from top
to bottom. A car with a cross- flow radiator can have a lower hood line.

A typical radiator in a car with factory-installed air conditioning has seven

fins per inch [25.4 mm]. Heavy-duty radiators may have more fins and more rows
of tubes. These provide greater cooling capacity to handle additional heat loads
such as those caused by the air conditioner or turbocharger. On vehicles with an
automatic transaxle or transmission, the outlet tank has a transmission oil cooler.
Many radiators have a drain valve in the bottom. Radiators with filler neck in the
top seal the opening with a radiator pressure cap.

4.8. Expansion Tank

Expansion Tank Most cooling systems have a separate plastic reservoir or
expansion tank. It is partly filled with coolant and connected by an overflow or
transfer tube to the radiator filler neck. As the engine heats up, the coolant expands
and flows through the transfer tube into the expansion tank. When the engine is
turned off and cools, the coolant contracts. This creates a partial vacuum in the
cooling system. Then the vacuum siphons coolant from the expansion tank back
through the transfer tube and into the radiator.
 The cooling system with an expansion tank is a closed system. Coolant can
flow back and forth between the radiator and the expansion .tank as the engine
heats and cools, this keeps the cooling system filled for maximum cooling
efficiency. The expansion tank also eliminates air bubbles from the coolant.
Coolant without air bubbles can handle more heat.

4.9. Thermostat
The thermostat is a heat-operated valve that regulates coolant temperature. It
does this by controlling coolant flow from the engine to the radiator. The
thermostat is in the coolant passage between the cylinder head and the radiator.
The valve in the thermostat opens anti doses as coolant temperature changes. When
the engine is cold, the thermostat closes. As the engine warms up, the thermostat
opens. This prevents or allows coolant to flow through the radiator.

By closing the passage to the radiator when the engine, is cold, the engine
warms up more quickly. Engine heat stays in the engine instead of being carried to
the radiator. This shortens warmup time, wastes less fuel, and reduces exhaust
emissions. After warmup, the thermostat keeps the engine running at a higher
temperature than it would without a thermostat. The higher operating temperature
improves engine efficiency and reduces exhaust emissions.

There are several types of automotive thermostats. A heat-sensitive wax

pellet operates most thermostats; it expands with increasing temperature to open
the valve. The thermostat opens at a specific temperature or thermostat rating. This
number is usually stamped on the thermostat. Two common ratings are 185°F
[85°C] and 195°F 91°C], most thermostats begin to open at their rated temperature.
They are fully open about 20°F [11°C] higher. For example, a 195°F [91°C] starts
to open at that temperature. It is fully open about 215°F [102°C].

4.10. Cooling Bypass Passage

Most engines have a small coolant bypass passage. The bypass may be an
external bypass hose on the top of the water pump, or an internal passage. It
permits some coolant to circulate within the cylinder block and head when the
engine is cold and the thermostat closed. This provides equal warming of the
cylinders and prevents hot spots. Some engines use a blocking-bypass thermostat.
It has a bypass valve that restricts or closes the bypass passage as the thermostat
opens after engine warmup. This prevents coolant from continuing to flow through
the bypass.

4.11. Radiator Cap

Cooling systems are sealed and pressurized by a radiator pressure cup.
Sealing reduces coolant loss from evaporation and allows the use of an expansion
tank. Pressurizing raises the boiling temperature of the coolant, thereby increasing
cooling efficiency. At normal atmospheric pressure, water boils at 212°F [100°C],
if air pressure increases, the boiling point also increases. For example, if the
pressure is raised by 15 psi [103 kPa] over atmospheric pressure, the boiling point
is raised to about 260°F | 127°C], Every I psi [7 kPa] increase in pressure raises the
boiling point of water about 3 1/4°F [ 1,8°CJ]. This is the principle on which the
pressurized cooling system works.

As the pressure in the cooling system goes up, the boiling point of the
coolant goes higher than 212 F [100°C]. There is a greater difference between
coolant temperature and outside air temperature. The hotter the coolant, the faster
heat moves from the radiator to the cooler passing air. Pressurizing the cooling
system also increases water-pump efficiency. Normal pressure in the cooling
system is determined by the vehicle manufacturer. Less than normal pressure
allows coolant to be lost and may cause boiling. Too much pressure can damage
the radiator and blow off hoses.

The radiator cap has a pressure-relief valve (Fig. 25- 20) to prevent
excessive pressure. When the pressure goes too high, it raises the valve. Excess
pressure and coolant then escape into the expansion tank. The radiator cap also has
a vacuum-relief valve. It protects the system from developing a vacuum that could
collapse the radiator. When the engine is shut off and begins to cool, the coolant
contracts. Cold coolant takes up less space than hot coolant. As the volume of
coolant decreases, a vacuum develops in the cooling system. This pulls open the
vacuum valve. Coolant from the expansion tank then flows back into the cooling
system. The radiator pressure cap must seal tightly if the pressurized cooling
system is to work properly. When the cap is put on the filler neck, the locking lugs
on the cap fit under the filler-neck flange. The cam locking surface of the flange
tightens the cap as it is turned clockwise. This also preloads the pressure-relief
valve spring.
 5. Antifreeze and Coolant
5.1. Antifreeze
Antifreeze is a chemical additive which lowers the freezing point of a
waterbased liquid. An antifreeze mixture is used to achieve freezing-point
depression for cold environments and also achieves boiling-point elevation ("anti-
boil") to allow higher coolant temperature Most automotive engines are "water"-
cooled to remove waste heat, although the "water" is actually antifreeze/water
mixture and not plain water. The term engine coolant is widely used in the
automotive industry, which covers its primary function of convective heat transfer
for internal combustion engines. When used in an automotive context, corrosion
inhibitors are added to help protect vehicles' radiators, which often contain a range
of electrochemically incompatible metals (aluminium, cast iron, copper, brass,
solder, et cetera). Water pump seal lubricant is also added.

Antifreeze was developed to overcome the shortcomings of water as a heat

transfer fluid. In some engines freeze plugs (engine block expansion plugs) are
placed in areas of the engine block where coolant flows in order to protect the
engine from freeze damage if the ambient temperature drops below the freezing
point of the antifreeze/water mixture. These should not be confused with core
plugs, whose purpose is to allow removal of sand used in the casting process of
engine blocks (core plugs will be pushed out if the coolant freezes, though,
assuming that they adjoin the coolant passages, which is not always the case).

On the other hand, if the engine coolant gets too hot, it might boil while
inside the engine, causing voids (pockets of steam), and leading to localized hot
spots and the catastrophic failure of the engine. If plain water were to be used as an
engine coolant, it would promote galvanic corrosion. Proper engine coolant and a
pressurized coolant system can help obviate the problems which make plain water
incompatible with automotive engines. With proper antifreeze, a wide temperature
range can be tolerated by the engine coolant, such as −34 °F (-37 °C) to +265 °F
(129 °C) for 50% (by volume) propylene glycol diluted with water and a 15 psi
pressurized coolant system.
 Early engine coolant antifreeze was methanol (methyl alcohol), still used in
windshield washer fluid. As radiator caps were vented, not sealed, the methanol
was lost to evaporation, requiring frequent replenishment to avoid freezing of the
coolant. Methanol also accelerates corrosion of the metals, especially aluminium,
used in the engine and cooling systems. Ethylene glycol was developed, and soon
replaced methanol as an engine cooling system antifreeze. It has a very low
volatility compared to methanol and to water.

Fluid - Freezing Point - Boiling Point

Pure Water: 0 C/32 F 100 C/212 F

50/50 mix of C2H6O2/Water: -37 C/-35 F - 106 C/223 F

70/30 mix of C2H6O2/Water: -55 C/-67 F-113 C/235 F

5.2. Types of Antifreeze

There are two types of ethylene-glycol antifreeze, high silicate and low
silicate. This refers to the amount of silicone silicate inhibitor added to the ethylene
glycol. Most automotive engines use high-silicate antifreeze. It protects aluminium
parts. Without this protection, aluminium flakes from the water jackets of an
aluminium cylinder head may clog the radiator. Low-silicate antifreeze is used in
diesel or gasoline engines with cast-iron cylinder block and heads. The
recommended antifreeze is listed in the vehicle owner's manual.
 6. CONCLUSION
Cooling system is one of the most important parts of the
automobile; it dissipates the extra heat out of the engine which can
damage the various components of the engine. The temperature of the
engine reaches high enough to weld the piston with the cylinder which
can damages the engine. So there is a provision of cooling system which
keeps the various components of the engine cool and safe. Cooling
system is of two type: Air cooling and Liquid cooling system. Air
cooling system is mostly used in old cars and bikes. It is not suitable for
the engines which dissipates large amount of heat whereas liquid cooling
is the most reliable cooling system used mostly in modern cars. The
mixture of water and ethylene glycol is used in the system. Ethylene
glycol is mixed in water because water freezes in winters or in the region
having temperature below freezing point, so ethylene glycol increases
the freezing point of the water. So cooling system plays a vital role as a
part of an automobile to keep it working with full efficiency.
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