ENGINE COOLING SYSTEM: COMPONENTS, TYPES AND WORKING PRINCIPLES

A vehicle’s engine-cooling system serves not just to keep the engine cool, but to also keep its temperature warm enough to ensure efficient, clean operation. System components include a radiator to dissipate heat, a fan or fans to ensure adequate airflow for radiator cooling, a thermostat valve that opens when the desired operating temperature is reached and a water pump (or coolant pump) to circulate coolant through the engine, hoses and other components. Most vehicles now employ an expansion tank that allows the coolant to expand, and exit, the cooling circuit when hot, and to return when the car is turned off and the engine cools. The cooling system also incorporates elements of the cabin’s ventilation system, because engine heat is used to warm the car’s interior.

While running, an engine continuously produces heat and converts it into power. This heat is derived by burning fuel in the engine. But as we all know, there is no engine in the world which is 100% efficient.

There is always some amount of heat energy which gets wasted. If we do not transmit this heat energy into the atmosphere, this heat will overheat the engine. This overheating will result in engine seizing. In engine seizing, due to excess heat piston gets melted inside the cylinder. It avoids this trouble of overheating a car is provided with the engine cooling system.

An engine cooling system is a system integrated with the engines. It carries away excess heat from the engine with the help of a flowing fluid. This fluid can be air or water.

COMPONENTS OF COOLING SYSTEM

1. RADIATOR:

Cools off the anti-freeze/coolant mixture by allowing air passing through the tube/fin area to dissipate the heat generated by the engine.

2. WATER PUMP:

Draws the cooled anti-freeze from the radiator and pumps it through the engine block, cylinder head(s), heater core and back to the radiator.

3. FREEZE PLUGS:

Is actually a steel plug designed to seal holes in the engine block and cylinder head(s) created from the casting process. In freezing weather they may push out if there is not enough anti-freeze protection.

4. HEAD GASKET /TIMING COVER GASKET:

Seals the major parts of the engine. Prevents oil, anti-freeze and cylinder pressure from mixing together.

5. HEATER CORE:

Provides heat to the interior of the car by using heat removed from the antifreeze and blown in by the blower motor. May cause steam, odor or actual dripping inside the car when it leaks.

6. THERMOSTAT :

Controls the minimum operating temperature of the engine. The thermostat is closed when the engine is cold in order to speed warm-up and opens when the normal operating temperature is reached to allow the anti-freeze / coolant to pass through the radiator.

7. HOSES (Radiator, Heater, By-pass):

Connect the other main components of the cooling system. Hose manufacturers recommend replacing every 4 years regardless of appearance because there may be deterioration of the inside of the hose which cannot be seen.

8. FAN CLUTCH:

Senses the temperature of the air coming through the radiator and either slips or binds up to pull the required amount of air through the radiator.

9. ELECTRIC COOLING FAN:

Most front-wheel-drive cars use this because of the transversely mounted engine. It is turned on by a system of sensors and relays when the engine reaches about 230 F and stays on until R is cooled to about 200 F.

TYPES OF COOLING

1. LIQUID OR INDIRECT COOLING SYSTEM

In a liquid cooling system, an engine is surrounded with water jackets. With the help of a pump, this water gets circulated in this water jacket.

Water flowing in these jackets takes out heat from the engine. This hot water then flows through a radiator, where it gets cooled from the cold heat blown through a fan.

In this system, the water takes heat from the engine and that water gets cooled by the air and then again gets circulated to the engine.

This is an indirect cooling process, where an actual cooling thing that is air is not directly cooling the system. The air is cooling the water and water is cooling the engine.

Liquid or indirect cooling system is mainly used in big engines, like that of cars and trucks.

Advantages

1. The compact design of engines

2. It provides even cooling to the engine

3. The engine can be installed at any location of the vehicle. It is not necessary to install an engine at the front.

4. It can be used in both small and big engines

Limitations

1. Here water jacket becomes one extra part of the engine.

2. Water circulation consumes power, thus reduces engine efficiency.

3. In case of failure of the cooling system, serious damage could happen to the engine.

4. Cost of the system is considerably high.

5. It requires routine maintenance, and thus puts extra maintenance cost burden.

2. AIR OR DIRECT COOLING SYSTEM

In a direct cooling system, an engine is cooled directly with the help of air flowing through it. It is the same cooling system which is used to cool our bike engines.

As we can see here, the air is in direct contact with the engine hence it is also known as a direct cooling system.

Air cooling system is used for small engines, like that of bikes and grass cutter, etc.

Advantages

1. Design of the engine becomes simpler.

2. Repair is easy in case of damages.

3. Absence of bulky cooling system makes system maintenance easily.

4. No danger of coolant leakage.

5. The engine is not subjected to freezing troubles.

6. Weight of the system is less.

7. It is a self-contained unit, as it does not requires a radiator, header, tanks, etc.

8. Installation of the air-cooled system is easy.

Limitations

1. It is applicable to only small and medium-sized engines.

2. It can only be used at the places where ambient temperatures are lower.

3. Cooling is not uniform.

4. Higher working temperature as compared to water-cooled engines.

5. It produces more aerodynamic noise.

6. Specific fuel consumption is slightly higher.

7. Lower maximum allowable compression ratios.

8. The fan, if used consumes almost 5% power generated by the engines.

Characteristics of an efficient engine cooling system

Following are two main characteristics of an efficient engine cooling system.

1. It should be capable of removing about 30% of the heat generated in the engine while maintaining the optimum working temperature in the engine.

2. It should remove heat at a faster rate when the engine is hot and remove the engine at a slow rate when the engine is cold.