Engine Cooling

Explain the terms conduction,convection and radiation?

Radiation is when heat is transferred directly through space, for example sunlight is a form of radiation because you can feel the heat from the sun but it can not be seen. Convection is the transfer of heating the water from only movement. when steam is produced the heat flows in the evaporated water and this is how the heat follows the currents. Conduction is the term used to explain the heat transfer from one solid to another. for example when you put a spoon in a cup of hot water the metal partials are rubbed together and that heats up the spoon from the water this is a common way conduction works. heat can also travel from one solid to another.

Indirect cooling?

On a boat the engine is cooled by water because most of the time there is a lack of air flowing fast enough to funnel much, the raw water is sucked from the ocean by a raw water pump and pumped through a series of water jackets around the engine. this cools the main components of the engine and in turn makes for better running conditions

Direct cooling?

Air cooling is an example of direct cooling as the body of the car or boat will scoop up air and force it into the engine compartment, this means the engine will have more fresh air to intake into the turbo or engine through the radiator.

What are the the problems you get with indect and direct cooling?

With direct there is normally not enough air flow to cool the engine by its self as boats operate at much lower speeds than cars most of the time. For indirect, most boats are operated in salt water around the world and with saltwater possessing great corrosion property's it means that the internals of the engine will start to rust and corrode over years of salt sitting in the intake pipes and jackets of the engine.

What is the purpose of a thermostat?

Every common engine has a thermostat that sits between the radiator and the main engine block, it is usually around 5cm in diameter and sits flush in its own housing. its job is to block the flow of coolant to the engine until the system has heated up. by letting the engine warm up faster it reduces engine wear and increases the car or boats fuel efficiency.

Pressure cap?

Basically the pressure cap is just a release valve that will let the pressure inside of the radiator out when it reaches that designated PSI, this is usually around 15 on most car engines. This will increase the boiling point of the coolant inside of the radiator by about 25 degrees Celsius. When the coolant in the radiator heats up the particles expand, this means the pressure cap will release the pressure when it expands and in turn make the boiling point much higher.  

What is the purpose of a core plug and why is it used?

Core or freeze plugs as they are sometimes referred to are small caps near the bottom of the engine block. they are fitted in the manufacture stage when the mold for the engine is made up. they are mainly used more in colder climates when liquid in the engine expands and it has no where to go the plugs will pop out to release the pressure instead of cracking the engine block or doing and damage to the engine.

What is the purpose of a heat exchanger?

A heat exchanger in a specializes device that assists in the transfer of heat from one liquid to another or from one liquid to a solid. In some cases, a solid wall may separate the fluids and prevent them from mixing. In other designs, the fluids may be in direct contact with each other. In the most efficient heat exchangers, the surface area of the wall between the fluids is maximized while simultaneously minimizing the fluid flow resistance.

How does the heat exchanger work?

http://www.ehow.com/video_4973845_a-heat-exchanger-work.html

This video explains well how the common heat exchanger works in a motor vehicle

What is the core of the heat exchanger made of?

The core of a heat exchanger is based on the same idea at a radiator core but is made from a special fibrous paper, which have high moisture permeability, anti-rends, anti-mildew features; with ABS framework,
which is not easy to break, long service time, pro-environment; with galvanized sheet
cover plate and plastic handle. 

How does the centrifugal circulating water pump work?

A circular pump circulates a liquid or gas around in a round piece of pipe, because the pipe is a loop the pump does not need to work as hard and only uses power when necessary. the most common type of circular pump is the centrifugal pump that is powered by a small electric motor in a waterproof housing. the motor drives a small impeller which pushes water past it. 

Why is it important to lubicate the impellor when fitting from new?

When a  new impeller is fitted to a engine or pump the water or lubricant will be drained from the system. this mean when you put the new impeller into the socket there will be no lube and in turn if it way started straight away it would burn out the new impeller very quickly. so when it is fitted you should lube up the new part so it can not be damaged in the initial start up.   

When fitting a impeller what should you check before refitting the housing and why?

That the impeller is offset from the center of the housing. this is because when the impeller turns it scoops the water with the blades and the offset of the center means the water will be picked up easier and there will be no water that can escape from the side of the blades. when an impeller is fitted you must also to a thorough test on all the blades at a small hole or crack a grow very fast when the first start up occurs after servicing.

What is the purpose of a oil cooler and how does it work?

What is the process of a intercooler/aftercooler how does it work?

Hot air from the turbo flows through tubes inside the intercooler. The turbo air transfers heat to the tubes, warming the tubes and cooling the turbo air. Outside air (or water) passes over the tubes and between fins that are attached to the tubes. Heat is transferred from the hot tubes and fins to the cool outside air. This heats the outside air while cooling the tubes. This is how the turbo air is cooled down. Heat goes from the turbo air to the tubes to the outside air.

Why do we have Inhibitors & antifreeze?

It keeps the engine's coolant from freezing in the winter. Ice takes up more space than liquid water, so it would break open the radiator & possibly the engine block. It also has some stuff to slow rusting inside the system, but the main purpose is anti-freeze. You don't want to use pure anti-freeze since it can't cool the engine as well after everything warms up.

How do you test Antifreeze?

 Make sure your car engine is cool. Open the hood of your car and find the coolant reserve container. It is usually a clear plastic tank and if you follow the hoses on your radiator it will connect with the reserve container. It will have lines on it to indicate wether your fluid levels are low or high.

Unscrew the cap to the reserve tank and pour the Antifreeze/Coolant in. You can use a funnel if you need to, so you can avoid spilling. (If your reserve tank is empty you should also add some fluids to the radiator itself.) When you have finished pouring in the correct amount, screw the cap back on.

If your car doesn't have a reserve tank for the Antifreeze/Coolant, pour the fluids directly into your radiator. To check the fluids directly in the radiator, look into it. You should be able to see the fluid.

If you need to pour the fluids directly into the radiator itself, make sure the engine is completely cooled before you unscrew the radiator cap. When the cap is removed, pour a little Antifreeze/Coolant directly into the radiator, being careful not to over flow it.

Make sure you never unscrew the radiator cap on a HOT ENGINE, the fluids and steam could spurt out and burn you. Remember how hot it is in there.

What is cavitation corrosion?

Erosion-corrosion is caused by the relative movement between a corrosive fluid and a metal surface. The mechanical aspect of the movement is important and friction and wear phenomena can be involved. This process leads to the formation of grooves, valleys, wavy surfaces, holes and a worn look.

Describle the terms:

Corrosion Fatigue?

Corrosion-fatigue is the result of the combined action of an alternating or cycling stresses and a corrosive environment. The fatigue process is thought to cause rupture of the protective passive film, upon which corrosion is accelerated. If the metal is simultaneously exposed to a corrosive environment, the failure can take place at even lower loads and after shorter time.

Crevice corrosion?

 This sort of corrosion is only present when there are small cracks or creases in tight areas. the salt sits in these areas and because they are in remote areas the salt is not washed out and it will sit there and end up corroding the metal on which it sits.

What is Electrolysis?

Electrolysis is the separating of a compound into its constituent elements by passing an electrical current through it when in a molten or aqueous state. The word electrolysis means the process of breaking molecules to smaller parts by using an electric current. Positive and negative poles of an electric source, such as a battery, can absorb opposite ions of an electrolyte, causing separation of ions and creation of a new substance.

How do you prevent corrosion?

• Use metals below the water that are as close to each other as possible on the galvanic scale. Don't mix metals.
• Fasteners must always be more noble than the fitting on which they're used.
• Put a zinc on it...!  But don't put too much zinc on it! Weld the zinc on if possible, or bolt the zinc directly to the piece.
• Never paint a zinc anode!
• When bringing AC shore power aboard, it should always first pass through a true marine grade isolation transformer.
• Battery chargers must be a marine quality isolation transformer type.
• Use bonding if necessary, if you have a highly complicated electrical system, in order to reduce the electrical shock hazard.
• Do everything possible to avoid stray currents in the water, and to prevent them aboard

What are sacrifical anode made off?

Anodes are made of Zinc and other very weak metals, they are made of this so that the other stronger metal is not eaten away because the corrosion is focused on the weaker metal. boats have many anodes all over the boats hull and are fitted with a single or two screws through the middle.

Where would you place them in the marine industry?

Anodes are fitted in many places all over the hull, the main points are where the electrical current meets the water and this is normally where the corrosion starts. theses are hull fittings like sea cocks and where the shaft exits the hull. Stern legs are also a large point where corrosion can occur and this means they are fitted with numerous anodes.

WEBSITES
http://ethemes.missouri.edu/themes/1369
http://auto.howstuffworks.com/question248.htm
http://auto.howstuffworks.com/cooling-system7.htm
http://www.ehow.com/how-does_4963320_circulator-pump-work.html
http://blogs.howstuffworks.com/2009/04/15/how-does-a-turbocharger-with-intercooler-work/
http://en.wikipedia.org/wiki/Electrolysis
http://www.waterheaterrescue.com/pages/WHRpages/English/Longevity/water-heater-anodes.html
http://www.thegluepeople.co.uk/v1/html/marine_industry.html
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