cooling systems

Explain the terms ( Kinetic energy) Conduction,convection and radiation?

CONDUCTION:

Conduction happens between objects at different temperatures which are in contact with each other. Heat flows from the warmer to the cooler object until they are both at the same temperature.

CONVECTION:

Convection is the most efficient way to transfer heat. Convection occurs when warmer areas of a liquid or gas rise to cooler areas in the liquid or gas.

RADIATION:

Coolant heated from flowing through the engine is fed into the header of the radiator via the inlet and then cools down as it circulates through the tubes to opposite header and cold coolant exits back into the engine via the outlet, and this cycle is repeated. As it circulates through the tubes, the coolant transfers its heat to the tubes which, in turn, transfer the heat to the fins that are present between each row of tubes. The fins then radiate the heat transferred by the tubes to the surrounding air, the process is radiation.

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

Indirect cooling

Marine engines use an enclosed cooling system. On the top of the engine there is a small tank that uses both, fresh water and coolant. This fresh water is circulated through the engine and through a heat exchanger. The fresh water, in this system, absorbs the heat of the engine. Raw water is still drawn up through the seacock but only flows through the heat exchanger jacket. This cooler raw water absorbs the heat from the fresh water through the heat exchanger jacket and is then pumped out the exhaust.

Direct cooling

Direct cooling uses a raw water cooling system. It can be fresh or salt water. The waterdrawn through a seacock fitting into the engine , and pumping it through the engine's water jacket and ports by way of a mechanical water pump. The water flows through the engine and directly out the exhaust. This cooler water absorbs heat from the engine to help keep it cool.

What is the puppose of a thermostat?

Thermostat : Thermostat is a device which regulates the flow of water after reaching to the ideal temparature required for the smooth function of engine.Thermostat opens at specified temp acting as one way valve.

Pressure cap

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 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

Why is engines fitted with a core plug, and what is the purpose of a core plug?

Core plug: Core plug is also known as a welsh plug or cold plug. It is designed to take out the sand which the manufacturer's use to mould the block and also in to take out snow in frost conditions.

What is the purpose of a heat exchanger?How does the heat exchanger work?What is the core of the heat exchanger made of?

Fresh water cooling systems, also known as a closed cooling systems, come in several varieties. The most common type utilizes a Heat Exchanger which functions similarly to the radiator in a car. Coolant (antifreeze) is circulated through one side of the heat exchanger where it is cooled by raw water that passes through the other side of the heat exchanger. The engine coolant is then circulated back into the engine. The raw water is expelled out of the boat through the exhaust.

How does the centrifugal circulating water pump work?

A centrifugal pump is a rotodynamic pump that uses a rotating impeller to create flow by the addition of energy to a fluid

How does a raw water pump work?

Raw water cooling systems draw water from outside the boat (seawater or lake water). Water is pumped from the source to the engine block then the engine circulation forces the raw water through the engine block and the water is expelled through the exhaust. Raw water cooling systems are relatively simple and the standard cooling system on most Marine Engines. The raw water pump in most cases is inside the outdrive. On larger engines and inboard engines the raw water pump is located inside the boat and is driven by a v-belt or directly off of the crankshaft. The danger is using salt water as a coolant in your engine. Salt water can be highly corrosive. Running salt water through your engine block and exhaust manifolds will lead to destructive corrosion that is unseen until your engine or exhaust manifolds fail.
marine engines cooled with raw water, especially ones that use salt water, have a shorter life span than marine engines cooled with a closed cooling system

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

After the new impellor is in place it is important to lubricate it to prevent wear until water is circulating

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

When refitting an impellor, the gasket has to be intact and in place. Then when bolting down the housing, the housing should be bolted down evenly.

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

An oil cooler works similar to an radiator ,it circulates oil instead of coolant.This takes away the heat by the process of radiation the heat from the oil and help prevent overheating.

What is the processT of a intercooler/aftercooler how does it work?Why do we have Inhibitors & antifreeze?

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 and marine industry which covers its primary function of convective heat transfer for internal combustion engines.Inhibitors used to prevent corrosion

How do you test Antifreeze?

What is cavitation corrosion?

Cavitation Corrosion occurs in areas with high flow rates and rapid pressure changes. This causes gas bubbles to collapse. This gives a high force on the metal surface which can remove oxide and give an active aluminium surface.

Efficient design to avoid large pressure changes or hard surface layers are ways to avoid cavitation corrosion.

What is galvanic corrosion?

Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially to another when both metals are in electrical contact and immersed in an electrolyte.

Describle the terms
Stray Current Corrosion
Stray current corrosion occurs when a metal object becomes anodic with respect to another structure. When the object is anodic to another structure, the surface acts as if it is a sacrificial anode, i.e., the surface is dissolved while electrically protecting the other cathodic structure

Stress corrosion
Stress corrosion is the unexpected sudden failure of normally ductile metals subjected to a tensile stress in a corrosive environment, especially at elevated temperature in the case of metals.

Corrosion Fatigue

Corrosion fatigue is fatigue in a corrosive environment. It is the mechanical degradation of a material under the joint action of corrosion and cyclic loading. Nearly all engineering structures experience some form of alternating stress and are exposed to harmful environments during their service life.

Crevice corrosion

Crevice Corrosion refers to the localized attack on a metal surface at, or immediately adjacent to, the gap or crevice between two joining surfaces. The gap or crevice can be formed between two metals or a metal and non-metallic material. Outside the gap or without the gap, both metals are resistant to corrosion.
The damage is normally confined to one metal at localized area within or close to the joining surfaces.

What is Electrolysis?

Electrolysis is the passage of a direct electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes and separation of materials.

How do you prevent corrosion?

Why and what is bonding in the marine industry?

What are sacrifical anode made off?

Sacrificial anode made of lead aluminium and zinc.

Where would you place them in the marine industry?

All metal objects exposed to sea water: pipelines, piers

What is the purpose of a water muffle?

Muffler converts harmful carbon monoxide and hydrocarbons to water vapor and carbon dioxide. Some converters also reduce harmful nitrogen oxides. The converter is mounted between the exhaust manifold and the muffler.

Muffler:The muffler serves to quiet the exhaust down to acceptable levels. The combustion process is a series of explosions that create a lot of noise. Most mufflers use baffles to bounce the exhaust around dissipating the energy and quieting the noise