System of Cooling

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INSTITUTO SUPERIOR TECNOLOGICO

CENTRAL TECHNICAL

NAME: RUTH MALDONADO H.

LEVEL: FIRST

Item:SYSTEM OF COOLING

PERIOD: MARCH - AUGUST

2012


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SYSTEM OF COOLING

Mission of the cooling systemWhen talking about engine explosion mentioned that part of the chemical

energy in a fuel exploited in its operation and that is transformed into

mechanical energy.

The transformation was done by inflammation of the mixture which produced an

explosion. This explosion is carried out an extraordinary heat, to the point that

most of the energy that is not used, it gives rise to global warming and

consequently to very high temperatures in the elements and parts of the House

of explosion, mainly during the time of escape.

This temperature, which at the time of the explosion close to 2,000 degrees

(instant temperature), would produce such a dilation that the pieces would come

to agarrotar, on the other hand giving rise to a breakdown of the lubrication oil.Now, not only is produces heat in the compression Chamber, but also in the

cylinders, because even though in them the explosion does not take place and

they are not subject to the instantaneous temperature that it causes, they are so

gases during the time of explosion and on the other hand the heat produced by

continual rubbing of the piston on its walls.

To partly eliminate the heat and avoid the damages that may cause resorted to

the cooling of parts or elements of the engine which receive more heat. This isaccomplished with the cooling system.


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This absorbed heat should not be either very short (because that would produce

dilatations) or very high (since fall of the engine performance significantly).

Approximately 30% of the heat produced in the explosion or combustion will be

removed by the cooling system.

In addition to these large dilatations, high temperatures produced engines make

the amount of mixture reaches the cylinders to be small, so it is necessary to

increase engine performance, to provide it with a cooling system. It also

happens that you due to high temperatures, lubricating oil loses its lubricating

properties. The parties that will require more cooling, are those subjected to

higher temperatures. These are: the butt (especially areas in proximity to the

exhaust valve), the valves (with their seats and guides) and cylinders (due to

the friction with the piston).Coolingsystems

Systemsof cooling that are usedtodayThey are: Cooling by air.

Cooling by liquid.

Cooling by air

Air cooling is achieved by exposing the warmest parts of the motor (cylinder

head and outside cylinders) to the flow of air that is produced by the vehicle or

by a turbine to be renewing the air continuously and rapidly absorbs heat from

above surfaces.

The heat produced in the engine it evacuates directly to air, for which the

engine is constructed of light alloy (with good thermal conductivity coefficient)

and increase you the surface of contact with the air, giving him a series of fins.

These fins will be higher the greater the heat to evacuate. Thus the greater be

the closer to the butt (Chamber of explosion).

The exchange of heat between the cylinders and the air will be greater the more

slender are the walls of the fins, must be kept perfectly clean space between

the fins.

Depending on the way of getting the air to the cylinders, there are two types of

cooling by air:

or direct air cooling.

or forced air cooling.

Direct air cooling

The air incident on the vehicle when driving, turn frozen engine, so depending
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on the cooling of the speed of the vehicle, not the engine.

Idling, the cooling is minimal, as performed by radiation only and low revolutions

of the engine. Therefore it is only used in small displacement motorcycles with

engine exposed to the air.In cars and trucks would be completely ineffective, the Elimination of heat by

radiation inside the engine compartment would be minimal.

Forced air cooling

Cooling air from the engines, these usually closed by the body, is necessary to

channel the air, channeling it into the cylinders and cylinder head.

It has a turbine that activates and increases the flow, which is moved by a strap

mounted on a pulley on the end of the crankshaft. The fan sucks outdoor air

and directs it the parties to cool.An automatic choke regulates the passage of air depending on the needs of the

engine. Thus, in the cold start, short air inlet and engine will quickly reach its

temperature regime.

Advantages

ordesignand simplified construction.

or low weight of the engine (it has elements such as radiator, sleeves or pump).

Minimal entertainment, or to lack of coolant, bomb or sleeves.

or small size of the engine, having no camera for liquid.or greater thermal performance (less losses of heat by cooling).

or which is the optimal regime of the engine temperature before liquid cooling.Disadvantages

or cooling irregular, since it depends on the air temperature, altitude and speed

of the vehicle.

or they are more noisy, because the air to pass between the fins produces

vibrations.or cooled very quickly (the strangler often use).

or worse filled cylinder (lower power), reached temperatures.

or used Boxer engines or cylinder, by channelling the air better.

Cooling by liquid

It is the generalized system using current cars.

In this system, cylinders and cylinder block constitute an envelope inside which

circulates coolant. The coolant also circulates through the interior of the stock

through a few holes provided for this purpose (liquid Chambers).Cameras are evenly distributed around the cylinder and combustion chamber.
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This liquid, which is heated in contact with the walls, is then directed to the

radiator, where transfers its heat to the ambient air to then return to the cylinder

block.

The heat capacity of the liquid is very high, being sometimes greater than the

air. For this reason, the volume of fluid Chambers, cylinders and the speed of

movement of the liquid, should contribute to not let the water reach boiling point.Elements of liquid cooling systems

Below we describe the components of a system of cooling elements by forced

circulation of fluid:

or House of water.

or radiator.

or elastic joints.or water pump.

or fan or electroventilador.

or thermostat.

or control elements.

Water Chamber

They are a few hollow practiced in the engine block and the cylinder head. By

which circulates the coolant. They surround the parts which are in direct contact

with the flue gas (cylinder, combustion chambers, seating of spark plugs andvalves guides).

They are characterized by the flow of fluid that circulates in the engine. Radiator

Its mission is to cool the hot water from the engine. It is located, usually at the

front of the vehicle in such a way that the air influences on him during their

displacement.

The parts of the radiator are indicated in theJoins the chassis of elastic form by rubber and flexible sleeves to the engine,

avoiding possible damage with the vibrations of the engine and the vehicle.

Alloys based on copper (brass) are generally used to manufacture.While it is true that the greater the front surface of the larger radiator cooling

(more surface area in contact with the air) will also be, nor should be an

excessive surface, if so the engine would take much to reach its optimal

operating temperature or would not reach it. In some isolated cases some

shutters are mounted on the front of the radiator to regulate the radiator


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surface exposed to the impact of the air.

For this reason, the effectiveness of a radiator, depends on the surface

exposed to the impact of the air.

To improve the aerodynamic coefficient of the vehicle and that the radiator

surface is sufficient, are made thick radiators rather than very high.The tubular radiator consists of a series of cylindrical or flat tubes; long and thin;

vertical or horizontal, surrounded by a few fins of high thermal conductivity that

attach you and at the same time serve as cooling surface.Abroad and produced by the fan air passes through the tubes, absorbing the

heat of their surfaces and with them water for them descending.

The water falls vertically or horizontally and the air that penetrates horizontallyfrozen it through the tubes that have a high conductivity.

In honeycomb radiator the refrigerator body is formed by fine and short tubes

with their ends ensanchados in hexagonal shape.

These tubes are soldiers each others ways that between them make a narrow

space for water, while the horizontal tubes are crossed by the air of progress.The surface of cooling is very large. They are little used because of its high

price.

At the top of the radiator is ready a plug that can be sealed (modern system) or

security (old system) valve.

Water pump

In the cooling process, the movement is activated by a bomb which is

sandwiched in the circuit between the bottom of the radiator and block, forcing

the circulation of the coolant (forced cooling).

The most used pump is centrifugal type palettes, i.e. water that reaches the

wheel of palettes, which tour inside a body of light alloy pump, is collection by

them and in its turn the expels forcefully towards the periphery, forcing her to

move cameras from water.Pump is installed front or laterally and receives his movement of the crankshaft

through the strap that in some cases also drives the fan.

To avoid that the water exit from the axis, is it mounted a device type press or

Board of rubbing, which is currently the most widely used.The shaft of the pump is mounted eccentric in the body of the same, with the

aim of saving the step of water around the wheel.


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You should check and review the State and the pump belt tension. If it is

destensada the engine warming could produce skating it. If it were very

stretched it would affect the pump bearings and the own belt.

You don't have to be either very stretched or destensada, allowing flexibility

about 2 centimeters, approximately.0

Elastic joints

The radiator joins body elastically (rubber heel) and the engine via flexible pipes

(sleeves) so that the vibrations do not adversely affect the radiator.

Fan. Electro-ventilador

It is the element responsible for passing enough airflow for cooling water

through the radiator. It also frozen some external bodies such as generator,pump, pump gasoline and carburetor.

In older models the fan is mounted on the same shaft to water pump and while

the engine runs, does it the fan. This causes that the fan works when engine not

needs, i.e., when the vehicle is cold or underway and take advantage of the air

current produced in its route. This implies aconsumptionof energy, since

nowadays cars are, mostly, from front-engine, and can take advantage of the

current produced by the March.

Currently cars are equipped with an electroventilador with a thermoelectriccommand, so that it enters operation by purchasing water from the cooling

circuit a given temperature, avoiding unnecessary losses of power by dragging

in regimes in which the use of the fan is not necessary.

One of the elements of the electroventilador is the fan, which is a small

propeller, two to six blades. The greater the number of these, stronger will be

the air flow provided; also will be the most effective current the more long are

the blades, until you reach a maximum that would begin to lose its

effectiveness.The blades are made from sheets of steel, aluminum alloy or molded plastic.

They must be sufficiently robust so that they can absorb the deformations, as

well as being well balanced so that they do not produce vibrations.

The electroventilador comes into operation when the engine temperature is

higher than the regime, puts it into operation the termocontacto that receives

the temperature of the coolant.

The termocontacto is located, usually in a lower part of the radiator or in the

same stock.

When the vehicle is in motion, air shines directly on the radiator, so the liquid
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cooling is assured. When driving at low speed, or when the vehicle is stopped,

the radiator cooling is lower, and the temperature of the liquid will rise.

The electroventilador can be mounted front or behind the radiator. In either

case, the sense of the air will always be radiator to engine (outside to inside).1

Advantages

or possibility of placing the radiator in the position that suits. In this way it can

put the radiator in the front of the vehicle, with the transverse engine, and to

mount it front or behind the fan.

or the March is quieter.

or cooling, to be independent of the speed of the engine and of the vehicle,

prevents overheating when the engine has to work long time idling.or the engine consume less to a same power, not having to move the fan with

the strap.

Disadvantages

or minimum, although it should be noted the increased complexity of the

system, which increases the possibility of failures (the components of the

electric circuit).

Types of fans

Currently used fans that only spin when the engine temperature rises to acertain degree.

Fan with electromagnetic coupler

It is equipped with a magnetic clutch that is connected when the water

temperature rises to a certain degree.

Fan with hydraulic coupler and thermal regulation by air from the radiator

The Union between fan and the engine is ensured by a hydraulic coupler whose

action is determined according to the amount of fluid that gets it.

This liquid (oil hydraulic fluid or coats), is contained in a cavity prepared in thehub of the fan or in a separate tank, and its introduction into the coupler is

controlled by a valve to a bimetal fixed on the cube of the fan and subjected to

the temperature of the flow of air that has passed through the radiator.

Fan with hydraulic coupler and cooling liquid (viscous fan) Thermal regulation

Its operation is based on the same principle as the previous. The silicone used

as element of friction, but regulation of functioning is regulated by the action of

the coolant on the bimetal which acts on the valve step and not the air that

passes through the radiator.

Thermostat


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The engine needs to be refrigerated, but as mentioned above, not in excess,

that a too low temperature produces a bad vaporization of gasoline that

condenses on the walls of the cylinders, then mixing with oil and reducing its

lubricating qualities, resulting in increased fuel spending and a worse greasing.

So need a device (thermostat) that makes the cooling not to act when the

engine is cold, so quickly achieve optimal performance temperature (this

temperature, measured in the cooling fluid, is 85 to 90 C approximately).

This same device must allow full or partial cooling of the water, depending on

the temperature of the engine.

The Mission of the thermostat is therefore maintain the temperature of the

engine at the optimal performance. This acts on the passage of the water by

regulating the temperature on the 85 C. If there is an excess of cooling (March

night at low temperatures), thermostat is again close, warming up the engine.

To maintain the temperature of the engine, acting on the movement of the fluid,

is used a valve of double effect (thermostat), sandwiched in the circuit of output

of the stock towards the radiator.

Thermostats used are devices capable of producing a mechanical action when

it varies the temperature of the environment where they are located, using

generally two types:

or thermostat of bellows.

or wax thermostat.

Bellows thermostat

It consists of a metallic Depot closed, very fine iron, with bellows or accordion-

shaped walls. This deposit is a liquid or substance very volatile, as for example:

ether, paraffin, etc.

2

This valve when the engine is cold, is closing the passage of the fluid into theradiator and allows it to the pump. To heat up the fluid in the engine is heated

the deposit of the thermostat with the volatile liquid, this is place and increases

in volume. The deposit, by this increase in volume drags on, opening the valve

and allowing the passage of the fluid into the radiator, which closes the step

towards the pump.

If circulating with the vehicle, the engine temperature drops, very low outside,

the liquid of the valve that was volatizado, condenses, decreases its volume

and the reservoir shrinks, the valve closing the passage of the coolant to the


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radiator and opening the step towards the cylinders (through the water pump)

until again reaches the proper temperature.3

Wax thermostatThermostats of wax works to simulate the of the of bellows, replacing the

volatile liquid by wax.4

This system is currently the most used.

Control elements

Driver must, at all times, to check the temperature of cooling water, in order to

detect possible anomalies in the circuit of cooling or engine immediately.The control board is equipped for this purpose; well with a luminous witness,

well with a temperature indicator.

Luminous witness

The luminous witness glows when the normal operating temperature is not

reached. When the operating temperature is reached, the lamp shuts down, but

returns to ignite if the weight is excessive.

This luminous witness is commanded by a termocontacto which is situated in

the butt or on the radiator.The termocontacto is a device that runs the luminous witness to alert the driver.

It consists of a bimetallic plate deformed depending on the temperature. The

deformation of this sheet sets or short circuit the pilot lamp.5

Temperature indicator

According to the accuracy of the device, it will be equipped with a graduation,

indicating the exact temperature of the engine, in areas of different colors,

corresponding to a normal or abnormal operation.

These temperature indicators are electrically sent by a thermistor that sits in the

butt or on the radiator.

The thermistor is a resistance that, depending on the temperature, let a more

less intense stream. This variation of flow makes to deflect the needle on the

temperature indicator.6

Cooling circuits


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Today, in general, is used in vehicles cars, circuit closed or sealed cooling.

There is another type of circuit, the open cooling which we will take into account

as the basis of the above, although it is not normally used.

Open circuit

The plug filling radiator on top has a safety valve. This valve connects with the

atmospheric pressure and its mission is the avoid occurring do not overload the

circuit. When inside the refrigeration circuit produce excessive pressure which

could damage any of its elements, the circuit gets in contact with the

atmosphere through the valve, causing the evacuation of internal to external

steam and returning air to the interior of the tank.

This system has the disadvantage that the lost liquid is unrecoverable, so we

often control the level of the radiator to establish losses.

Elements are indicated in the 7 components of the circuit.7

Closed or sealed circuit

This circuit is to connect the radiator with a small deposit called expansion

vessel. Thus the fluid is lost abroad and may be recoverable.

Safety valve that allows the removal of fluid from the radiator, is located in the

cap of closure or at the entrance to the expansion vessel.8

This valve allows the passage of water vapor pressure towards the expansion

vessel (fig.18) until that matched with the pressure in the radiator. If the

pressure too low in the radiator, the valve allows the passage of fluid from the

glass of expansion into the radiator and restores so pressure and level in the

radiator.9

The passage of fluid between the two elements is achieved by difference of

pressure of the element with more pressure towards the element with less

pressure from the radiator to the glass or vice versa.

The expansion vessel communicates with the outside if the operating pressure

is very higher than the established and makes it through the safety valve that

leads the expansion vessel.

The pressure in the radiator, is generally higher than atmospheric. Due to this

pressure in the radiator, the boiling point of the fluid increases, i.e., boils at

more than 100 C.


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In this system there is no fluid losses. If any we should revise the circuit and

locate the point where the leakage occurs to remedy it.

The 0 represents the set of elements that make up the circuit:

Coolant fluids

Used water treated with certain additives, as a coolant because of its chemical

stability, good driving, for their abundance and economy.

Single water has major drawbacks such as:

or calcareous salts which obstruct the pipes of the circuit (hardness). Corrected

distilling water.

or at temperatures of boiling is strongly oxidizing, attacking the circuit and its

elements.

or below 0c solidifies and increases its volume, and can disable the cooling

circuit.

To avoid these drawbacks mixes water with antifreeze and other additives,

called to the mix coolant. This liquid has the following properties:

or decreases the freezing point of water up to - 30 C, according to their

concentration.

or prevents the corrosion of the metal parts of the circuit, due to the additives

that fall within its composition.

Thus, the coolant will be composed of:

or distilled water.

or antifreeze (ethylene glycol).

or Borax (2 to 3%): inhibitor of corrosion and oxidation.

or antifoaming agent.

or dye.

Maintenance

This maintenance will consist of the following points:

or periodic checking of the level of the coolant in the expansion vessel. The

level of liquid must be included between the minimum and maximum marks

contained in the expansion vessel. It is not ever completely fill the glass, you

should leave a free space for the steam.

or periodic cleaning of the circuit, according to the manufacturer's instructions.

or checking for leaks and replacement of damaged flexible sleeves.

or maintenance of the good general condition and the pump belt tension. It

should carry a spare belt and tools to mount it.

or checking the operation of the thermostat and the entry into operation of the


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electroventilador.

or external cleaning of the radiator.

Documents

System of Cooling