Cooling System

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LIST OF FIGURES

Figure 1: Internal combustion ... 2

Figure 2: Cooling system. ... 3

Figure 3: Cooling system components. ... 5

Figure 4: Liquid cycle In the system. ... 5

Figure 5: Engine liquid passageways. ... 6

Figure 6: Radiator drawing. ... 7

Figure 7:Cooling system components. ... 8

Figure 8: Radiator cooling fan. ... 9

Figure 9: The closed positions of a thermostat. ... 11

Figure 10: The open positions of a thermostat. ... 12

Figure 11: Natural (Free) Convection ... 14

Figure 12: Forced Convection ... 14

Figure 13: Current radiator. ... 18

Figure 14: Radiator core model ... 19

Figure 15:Radiator core model ( front view) ... 20

Figure 17: Radiator tube and fins model. ... 22

Figure 16: Radiator tube and fins model ... 21

Figure 18:Radiator lower cover. ... 23

Figure 19: Radiator upper cover. ... 23

Figure 20: Fan model. ... 24

Figure 21: Assembled drawing. ... 25

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Figure 23: Radiator tube. ... 29

Figure 24: Solid Mesh ... 30

Figure 25: Copper tube temp. distribution ... 31

Figure 26: Aluminum tube temp. distribution ... 32

Figure 27: Aluminum & Copper temp. distribution. ... 32

Figure 28:Aluminum temperature distribution contour. ... 33

Figure 29: Copper temperature distribution contour. ... 34

Figure 30: Modified design model. ... 35

Figure 31: Improved model maximum temperature ... 36

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AUTOMOTIVE COOLING SYSTEM IN INDUSTRY

CHAPTER 1: INTRODUCTION

1.1. Internal Combustion :

Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. [1]

The four strokes are illustrated in Figure 8. They are:

1. Intake stroke : The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest drop of gasoline needs to be mixed into the air for this to work.

2. Compression stroke: the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful.

3. Combustion stroke : When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down.

4. Exhaust stroke : Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe.

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Figure 1: Internal combustion

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1.2. Automotive Cooling Systems :

Modern automotive internal combustion engines generate a huge amount of heat. This heat is created when the gasoline and air mixture is ignited in the combustion chamber. This explosion causes the piston to be forced down inside the engine, levering the connecting rods, and turning the crankshaft, creating power. Metal temperatures around the combustion chamber can exceed 1000° F. In order to prevent the overheating of the engine oil, cylinder walls, pistons, valves, and other components by these extreme temperatures, it is necessary to effectively dispose of the heat.

It has been stated that a typical average-sized vehicle can generate enough heat to keep a 5-room house comfortably warm during zero degree weather (and I'm not talking about using the exhaust pipe). Approximately 1/3 of the heat in combustion is converted into power to drive the vehicle and its accessories.

Another 1/3 of the heat is carried off into the atmosphere through the exhaust system. The remaining 1/3 must be removed from the engine by the cooling system. Modern automotive engines have basically dumped the Air Cooled System for the more effective Liquid Cooled System to handle the job. In a liquid cooled system, heat is carried away by the use of a heat absorbing coolant that circulates through the engine, especially around the combustion chamber in the cylinder head area of the engine block. The coolant is pumped through the engine, then

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after absorbing the heat of combustion is circulated to the radiator where the heat is transferred to the atmosphere. The cooled liquid is then transferred back into the engine to repeat the process. Excessive cooling system capacity can also be harmful, and may affect engine life and performance. You must understand that coolant temperatures also affect oil temperatures and more engine wear occurs when the engine oil is below 190° F. An effective cooling system controls the engine temperature within a specific range so that the engine stays within peak performance.

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1.3. Cooling System Functions :

Temperatures in the combustion chamber of the engine can reach 4,500 F (2,500 C) [2], so cooling the area around the cylinders is critical. Areas around the exhaust valves are especially crucial, and almost all of the space inside the cylinder head around the valves that is not needed for structure is filled with coolant. If the engine goes without cooling ,the metal got hot enough for the piston to weld itself to the cylinder. This usually means the complete destruction of the engine. The cooling system removes enough heat to keep the engine at a safe temperature for best performance. A secondary function of the cooling system is to provide interior cabin heat during cold winter.

1.4. Cooling System Types :

1.4.1. Air Cooling:

Some older cars, motorcycle and very few modern cars, are air-cooled. Instead of circulating fluid through the engine, the engine block is covered in aluminum fins that conduct the heat away from the cylinder. A powerful fan forces air over these fins, which cools the engine by transferring the heat to the air.

Since most cars are liquid-cooled, we will focus on that system in this project.

1.4.2. Liquid Cooling System :

Figure 3 illustrates the cooling system components, and in these sections we'll talk about each part of the system in more detail. Figure 4 illustrates the liquid cycle in the system..

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Figure 3: Cooling system components.

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1.5. Engine :

The engine block and cylinder head have many passageways cast or machined in them to allow for fluid flow. These passageways direct the coolant to the most critical areas of the engine.

1.5.1. Method for protecting cylinder liner:

One interesting way to reduce the demands on the cooling system is to reduce the amount of heat that is transferred from the combustion chamber to the metal parts of the engine. Some engines do this by coating the inside of the top of the cylinder head with a thin layer of ceramic. Ceramic is a poor conductor of heat, so less heat is conducted through to the metal and more passes out of the exhaust.

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1.6. Radiator :

A radiator is a type of heat exchanger. It is designed to transfer heat from the hot

flows through it to the air blown through it by the fan. Most modern cars use aluminum radiators. These radiators are made by brazing thin aluminum fins to flattened aluminum tubes. The coolant flows from the inlet to the outlet through many t

conduct the heat from the tubes and transfer it to the air flowing through the radiator.

1.6.1. Pressure cap :

The radiator cap actually increases the boiling point of your coolant by about 45 F (25 C). How does this simple cap do this? The same way a pressure cooker increases the boiling temperature of water. The cap is actually a pressure release valve, and on ca

boiling point of water increases when the water is placed under pressure. When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can esc

pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the

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A radiator is a type of heat exchanger. It is designed to transfer heat from the hot

flows through it to the air blown through it by the fan. Most modern cars use aluminum radiators. These radiators are made by brazing thin aluminum fins to flattened aluminum tubes. The coolant flows from the inlet to the outlet through many tubes mounted in a parallel arrangement. The fins conduct the heat from the tubes and transfer it to the air flowing through the radiator.

Figure 6: Radiator drawing.

The radiator cap actually increases the boiling point of your coolant by about 45 F (25 C). How does this simple cap do this? The same way a pressure cooker increases the boiling temperature of water. The cap is actually a pressure release valve, and on cars it is usually set to 15 psi. The boiling point of water increases when the water is placed under pressure. When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the A radiator is a type of heat exchanger. It is designed to transfer heat from the hot coolant that flows through it to the air blown through it by the fan. Most modern cars use aluminum radiators. These radiators are made by brazing thin aluminum fins to flattened aluminum tubes. The coolant ubes mounted in a parallel arrangement. The fins conduct the heat from the tubes and transfer it to the air flowing through the radiator.

The radiator cap actually increases the boiling point of your coolant by about 45 F (25 C). How does this simple cap do this? The same way a pressure cooker increases the boiling temperature rs it is usually set to 15 psi. The boiling point of water increases when the water is placed under pressure. When the fluid in the cooling system heats up, it expands, causing the pressure to build up. The cap is the only place ape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the

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overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled.

1.7. Radiator Fan :

A radiator fan is used to draw the air towards the radiator and help in the cooling process. The radiator fan has four or more blades that spin rapidly to provide sufficient air that would cool the engine. It is usually mounted between the radiator and the engine so that the air can easily get to the radiator. Some cars have an additional fan in front of the radiator in order to draw more cool air into the engine. Especially when it is so hot and the vehicle isn’t moving fast enough, very little cool air reaches the radiator, and thus, the engine is not cooled properly. Fig(7,8) illustrates the radiator fan.

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Figure 8: Radiator cooling fan.

1.8. Water Pump :

The water pump is a simple centrifugal pump driven by a belt connected to the crankshaft of the engine. The pump circulates fluid whenever the engine is running. The water pump uses centrifugal force to send fluid to the outside while it spins, causing fluid to be drawn from the center continuously. The inlet to the pump is located near the center so that fluid returning from the radiator hits the pump vanes. The pump vanes fling the fluid to the outside of the pump, where it can enter the engine. The fluid leaving the pump flows first through the engine block and cylinder head, then into the radiator and finally back to the pump.[3]

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1.9. Plumbing :

The cooling system has a lot of plumbing. We'll start at the pump and work our way through the system. The pump sends the fluid into the engine block, where it makes its way through passages in the engine around the cylinders. Then it returns through the cylinder head of the engine. The thermostat is located where the fluid leaves the engine. The plumbing around the thermostat sends the fluid back to the pump directly if the thermostat is closed. If it is open, the fluid goes through the radiator first and then back to the pump. There is also a separate circuit for the heating system. This circuit takes fluid from the cylinder head and passes it through a heater core and then back to the pump.

1.10. Fluid :

Cars operate in a wide variety of temperatures, from well below freezing to well over 100 F (38 C). So whatever fluid is used to cool the engine has to have a very low freezing point, a high boiling point, and it has to have the capacity to hold a lot of heat. Water is one of the most effective fluids for holding heat, but water freezes at too high a temperature to be used in car engines. Pure Water 50/50 C2H6O2/Water 70/30 C2H6O2/Water Freezing Point 0 C / 32 F -37 C / -35 F -55 C / -67 F Boiling Point 100 C / 212 F 106 C / 223 F 113 C / 235 F

The fluid that most cars use is a mixture of water and ethylene glycol (C2H6O2), also known as antifreeze. By adding ethylene glycol to water, the boiling and freezing points are improved significantly. The temperature of the coolant can sometimes reach 250 to 275 F (121 to 135 C). Even with ethylene glycol added, these temperatures would boil the coolant, so something additional must be done to raise its boiling point. The cooling system uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of water is higher in a

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pressure cooker, the boiling temperature of coolant is higher if you pressurize the system. Most cars have a pressure limit of 14 to 15 pounds per square inch (psi), which raises the boiling point another 45 F (25 C) so the coolant can withstand the high temperatures.

1.11. Thermostat :

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.

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Figure 10: The open positions of a thermostat.

The secret of the thermostat lies in the small cylinder located on the engine-side of the device. This cylinder is filled with a wax that begins to melt at around 180 F (different thermostats open at different temperatures, but 180 F is a common one). A rod connected to the valve presses into this wax. When the wax melts, it expands significantly, pushing the rod out of the cylinder and opening the valve.

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1.12. Thermal Analysis

In general, there are three mechanisms of heat transfer. These mechanisms are conduction, convection and radiation.

Thermal analysis calculates the temperature distribution in a body due to some or all of these mechanisms. In all three mechanisms, heat energy flows from the medium with higher temperature to the medium with lower temperature. Heat transfer by conduction and convection requires the presence of an intervening medium while heat transfer by radiation does not.[4]

1.12.1. Convection Heat Transfer

Convection is the heat transfer mode in which heat transfers between a solid face and an adjacent moving fluid (or gas). Convection has two elements:

The mechanism of convection can be explained as follows: as the layer of the fluid adjacent to the hot surface becomes warmer, its density decreases (at constant pressure, density is inversely proportional to the temperature) and becomes buoyant. A cooler (heavier) fluid near the surface replaces the warmer fluid and a pattern of circulation forms.

The rate of heat exchange between a fluid of temperature Tf and a face of a solid of area A at temperature Ts obeys the Newton's law of cooling which can be written as:

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Where h is the convection heat transfer coefficient. The units of h are W/m2.K or Btu/s.in2.F. The convection heat transfer coefficient (h) depends on fluid motion, geometry, and thermodynamic and physical properties.

1.12.1.1. Modes of Convection Heat Transfer

1. Natural Convection : The motion of the fluid adjacent to a solid face is caused by buoyancy forces induced by changes in the density of the fluid due to differences in temperature between the solid and the fluid. When a hot plate is left to cool down in the air the particles of air adjacent to the face of the plate get warmer, their density decreases, and hence they move upward.

Figure 11: Natural (Free) Convection

2. Forced Convection :An external means such as a fan or a pump is used to accelerate the flow of the fluid over the face of the solid. The rapid motion of the fluid particles over the face of the solid maximizes the temperature gradient and increases the rate of heat exchange. In the

following image, air is forced over a hot plate.

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1.13. Introduction to Reverse Engineering (RE):

Reverse engineering is "the process of discovering the technological principles of a mechanical application through analysis of its structure, function and operation. That

Involves sometimes taking something apart and analyzing its workings in detail, usually with the intention to construct a new device or program that does the same thing without actually copying anything from the original." - Wikipedia

Reverse engineering of mechanical parts requires extraction of information about an instance of a particular part sufficient to replicate the part using appropriate manufacturing techniques. This is important in a wide variety of situations, since functional CAD models are often unavailable or unusable for parts which must be duplicated or modified. Computer vision techniques applied to 3–D data acquired using non-contact, three-dimensional position digitizers have the potential for significantly aiding the process. Serious challenges must be overcome, however, if sufficient accuracy is to be obtained and if models produced from sensed data are truly useful for manufacturing operations. This approach has two advantages over current practice. The resulting models can be directly imported into feature-based CAD systems without loss of the semantics and topological information inherent in feature-based representations.

1.14. Problem Definition:

In this project, an existing “ Daihatsu” Sirion’s cooling system will be studied and evaluated. In the designing stage, features and dimensions for the radiator will be fully defined and measured. Choosing the right radiator’s material and deciding if the material has been chosen is good enough to keep the radiator running without any overheating during the real conditions, is not an

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1.15. Project Objectives:

1. Studying a sub-module such as the cooling system in order to absorb its technology for the purpose of future technology transfer in auto industry.

2. Testing how the redesigned cooling system will work due to design and material properties restriction using finite element software.

3. Developing of a Finite-element model of a radiator to simulate different boundaries and loading conditions.

4. Using the developed model to simulate and evaluate the thermal loading on the radiator.

1.16. Methodology

1. Measuring all the radiator’s dimensions and features using reverse engineering tool system. 2. Developing the radiator’s solid model using Solid Works software.

3. Developing a finite-element model using COSMOS Works, considered at different loading and boundary conditions on the model.

4. Evaluate the radiator’s performance with Aluminum and Copper Finite-element models. 5. Modify the radiator tubes and fins design and evaluate its performance using Finite-element

model.

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1.17. CSMOS Work :

COSMOS Works Designer is a software used for the definition ,preparation and visualization of all the data related to a numerical simulation. This data includes definition of the material ,geometry, boundary conditions and other parameters. All material and conditions are defined by the user. The meshing is done by the program itself once the problem has been defined.

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CHAPTER 2: SOLID MODEL DEVELOPMENT

2.1. Radiator Solid Model Development:

The radiator consists of forty eight Aluminum tube, thin fins between the tubes and two plastic covers. The radiator consists of forty five aluminum tube, fins between tubes, upper & lower cover had been made from plastic, see figure (13). The overall dimensions of radiator assembly were obtained. Next, radiator disassembly is carried to measure and obtain the actual dimensions to be used in solid model development.

Figure 13: Current radiator.

To increase the performance of computer during solid model development, it is decided to reduce number of tubes to nine.

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2.1.1. The Radiator Core

It is made from Aluminum and consists of forty eight tubes. The general out dimensions of radiator core is : 17 * 323 * 422 mm, see figures (14-15).

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2.1.2. Radiator Tubes and Fins Dsign

To decrease the computational time and due to symmetry, It is decided to model one tube with two side fines, see figure (16). Figure(17) shows the outer dimension of the developed solid model. The Tube shape is assumed to be square.

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Figure 17: Radiator tube and fins model.

2.1.3. Radiator Upper and Lower Covers

The Radiator covers are made from plastic and crimped to radiator core. The outer dimensions of both upper and lower covers are shown in solid model illustrated in figures (18-19).

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Figure 18:Radiator lower cover.

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2.1.4. Radiator Fan Solid Model Development

Fig (20) shows the developed model including the outer dimensions.

2.1.5. Assembly Solid Model Development

Figures(21-22) shows the solid model assembly drawings of radiator assembly system.

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Figure 21: Assembled drawing.

Radiator core Lower radiator cover Fan Motor Upper radiator cover Fan cover

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CHAPTER 3: FINITE- ELEMENT ANALYSIS

3.1. Solid Model Development

The solid model development has shown in chapter two. Radiator tube and fins will be used through the finite-element analysis in this chapter.

3.2. Material Properties

Two different material will be evaluated and compared :

3.2.1. Aluminum Alloy: 1060 Alloy

Specifications:

Description Value Units

Elastic modulus 6.90E+10 N/m^2 Poisson ratio 0.33

Shear modulus 2.70E+10 N/m^2 Mass density 2700 Kg/m^3 Tensile strength 68935600 N/m^2

Yield strength 274200 N/m^2 Thermal expansion

coefficient 2.40E-05 /Kelvin Thermal conductivity 200 W/(m.K)

Specific heat 900 J/(kg.K)

3.2.2. Copper Alloy :

Specifications:

Description Value Units

Elastic modulus 1.10E+11 N/m^2

Poisson ratio 0.37

Shear modulus 4 E+10 N/m^2

Mass density 8900 Kg/m^3

Tensile strength 394380000 N/m^2 Yield strength 258646000 N/m^2 Thermal expansion

coefficient 2.40E-005 /kelvin

Thermal conductivity 390 W/(m.K)

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3.3. Boundary and Loading Conditions

One tube and its fins is being studied and evaluated. The engine provides 40 KW power [5], and assuming that the cooling system load is one third of the engine power which is equal to 13.34 KW. So, the load per tube is [(13.34*1000)/48]= 277 W.

The tube model is shown in figures (16-17).

In the analysis, due to some limitation of the finite element software, the following assumptions has been used :

The tube height has been reduced from 400 mm to 100 mm.

The power per tube equals to 70 W, which is simulates the hot water flow per tube.

Heat power source is distributed along the internal faces of the tube which is equal to 70 W per tube .

Forced convection condition is applied on all the external faces of the tube and the fins.

Heat Transfer coefficient = 75 W/m2.K. (This is based on several trials with other values between 3 and 80 W/m2.K.)

Ambient Temperature = 353 K

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Figure 23: Radiator tube.

Forced convection

70 W heat power source is applied to the internal faces

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3.4. Mesh Generation

Solid mesh has been generated using Tetrahedral elements. Fig (24) shows the solid mesh. Total number of Nodes = 1154165

Total number of Elements = 75974. The mesh has been done by COSMOS Works software.

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3.5. Computation:

Steady State Analysis has been done using a desktop computer with specification: P4, CPU 3.2 GHz and 512 GB of RAM. The computation running time is 30 minutes. Fig (25-27) shows the temperature for Aluminum and Copper tube temperature. The figures show that the Cooper radiator has dropped the water temperature by (3.56 %.) comparing with the Aluminum radiator. Fig.(28) shows the contour of temperature distribution in the Aluminum radiator, The figure demonstrate that the temperatures is higher in the upper section of the radiator and lower in the bottom section due to the water flow and the effect of forced convection induced by the fan. Fig.(27) shows that the Copper radiator is more efficient than aluminum one. Since, it resulted in reducing the radiator water temperature by 3.56% .It’s recommended to use Copper radiator rather than Aluminum radiator due to higher temperature drop.

Figure 25: Copper tube temp. distribution

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Figure 26: Aluminum tube temp. distribution

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3.6. Improving the Radiator Aluminum Model

In current investigation, the depth of radiator tube is increased from 20 mm to 40 mm to increase the area which will increase the rate of heat transfer to the air as well .The dimensions are shown in figure (30).

Material : Aluminum Alloy :1060 Alloy

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The improved design has reduced the maximum temperature by 3.9 % as shown in fig.(31)

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Figure 31: Improved model maximum temperature

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CHAPTER 4: RESULTS AND DISCUSION

1. The reverse engineering has been implemented throughout the present work, in order to achieve design analysis and improvement for the car radiator element.

2. A comparison has been carried out in chapter three between Aluminum and Copper alloy radiator models.

3. It is found that Copper radiator is more efficient when compared with the Aluminum radiator due to higher temperature drop (3.56 %.). However, The Aluminum radiator is much cheaper.

4. A new design of the radiator has been proposed. The radiator dimensions were changed by increasing the width from 20 mm to 40 mm. And this change has reduced in reducing the maximum temperature by 3.9 %.

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CHAPTER 5: CONCLUSION AND RECOMMENDATION

The efficiency of the internal combustion engine cooling system depends mainly on the performance of its units. The main unit in this system is the radiator.

It is reported that Copper radiator is more efficient when compared with the Aluminum radiator due to higher temperature drop. However, The Aluminum radiator is much cheaper.

It’s recommended to use Copper radiator rather than Aluminum radiator due to higher temperature drop .Aluminum radiator is recommended due to lower cost.

Also the modified design is preferred due to low temperature where as the old model is preferred due to low cost and low weight.

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REFRENCES :

[1]. William H. C. and Donald L. A,1981. Automotive Fuel, Lubricating, and Cooling Systems. [2]. Randy Rundle, 1999. Automotive Cooling System Basics.

[3]. Ray T. Bohacz,2007.

Engine Cooling Systems

[4]. Yunus A. Cengel and Robert H. Turner, 2005. Fundamental of Thermal-Fluid Sciences. [5] Daihatsu Sirion Owner Manual, 2008.