Engine Cooling System

The cooling system inengine (cooling system).

The purpose of the engine cooling system

Of the total heat energy generated by the combustion of the fuel-air mixture in a gasoline engine, approximately 24 to 32% is converted into kinetic energy that is used as working power (wasted per power stroke). While about 29 to 36% is lost with the exhaust gas, 7% by radiation, and 32 to 33% is dissipated by the cooling system. If the heat transferred to the combustion chamber wall is not removed as quickly as possible, the piston or cylinder may be damaged by this heat or the lubricating oil cap may break. If this heat is excessively cooled, so much heat energy will be transferred to the coolant that the effectiveness of the heat is reduced. Therefore, the cooling system must be controlled to maintain the correct temperature according to the operating condition. Therefore, the engine’s cooling system controls the engine’s operating temperature, and the increased loss in the cooling system reduces engine performance.

Water Cooling System Components: –

1-        Reserve tank
2-                          Radiator
3-                 Pressure Cap
4- Lower elbow.                         Lower Hose
5- The upper elbow.                         Upper House
6- Water pump.                         Water Pump
7- Cooling shirts.                        Water Jacket
8-          Thermostat
9- Cooling fan.                         Cooling Fan
 

 
 
Water cooling system working theory :-

liquid cooling system

Refrigerant is used – a liquid containing special chemicals mixed with water. Cooling water (coolant) flows through passages (cooling shirts) in the engine and through the radiator. The cooling water is circulated by the water pump, and the thermostat controls the temperature. The thermostat shuts off when the engine is cold, allowing only cooling water to circulate in the engine block, bypassing the thermostat and radiator. This allows the engine to warm up faster and uniformly so that “hot spots” are eliminated. When the cooling water reaches a high temperature, the thermostat opens and allows the cooling water to pass into the radiator. The hotter the cooling water, the more times the thermostat is opened, allowing more water to pass into the radiator. The thermostat also controls the length of time the cooling water remains in the radiator so that heat is effectively dissipated.
The radiator receives hot cooling water from the engine and lowers its temperature. Air flowing around and through the radiator draws heat from the cooling water. The function of the radiator fan connected to the radiator is to ensure that the water temperature is lowered when driving at low speeds or when the vehicle is stopped.

Cooling water: –

Water absorbs more heat by volume than any other liquid, which is another good reason to use water. But water alone causes problems. Ordinary impurities in tap water (ordinary water) are harmful to engines and interact with metals, causing corrosion and rust, and this is what we often notice when using ordinary water, especially in the radiator. Water also allows electrolysis, an electrochemical process that causes metals to rust. In modern cooling systems, chemicals known as inhibitors are added to the water to reduce or prevent corrosion. There are other additives that are used to prevent the water from boiling in the coolant. Another harmful property of water is that it expands when it freezes. This is one of the problems faced by liquid-cooled engines when temperatures drop below freezing. In cold, stopped engines, water in the cooling system can freeze—and expand—with enough force to cause damage to the engine block and radiator. But there is an additional substance known as antifreeze that lowers the freezing point of water to below the outside temperature. This can prevent the coolant from freezing.

Thermostat: –

The thermostat constantly monitors the temperature of the cooling water and regulates its flow through the radiator. Thermostats are powered by a heat-sensitive, positive-pressure motor. This consists in the use of a specially prepared wax and a dusty metal pellet tightly placed in a heat-conducting copper cup with a piston inside a rubber lid. The heat causes the wax ball to expand, which in turn pushes the piston out and opens the valve. This thermal motor senses temperature changes and moves the valve position to control the flow of cooling water, thus controlling the temperature of the coolant.
The thermostat is usually installed in the front of the engine above the engine block. The thermostat is installed inside a cavity in the engine where it is exposed to hot coolant. The top of the thermostat is covered by the water outlet housing that is used to connect the radiator hose to the radiator.

There is a big mistake that occurs, which is that many car users remove the thermostat permanently from the cooling cycle, and this is a mistake, especially since the thermostat is very important when starting the engine because, as we mentioned, it helps the engine reach the operating temperature and many face a special problem in the winter, which is the engine delay in the Management.

water pump: –

The water pump is usually installed at the front of the cylinder block and is usually driven by the propeller belt. Its function is to adequately direct the water from the lower tank of the radiator to the engine cooling chambers. This water, after absorbing heat from the engine, circulates back to the upper radiator tank.
The water pump is a rotating disc with blades that pushes water out by centrifugal force and then pushes it into the water jacket. The shaft is fixed to the water pump housing and rotates on bearings. There is a sealant that prevents water from leaking
 

 
 
 
 
 
Radiator: –

The function of the radiator is to reduce the temperature of the coolant coming from the engine by dissipating the heat into the surrounding air. The radiator consists of a group of small tubes arranged in “rows”, called the “core” and can be placed in a vertical design, or a horizontal design (known as cross-flow). At each end of the radiator core there is a “tank”, an upper tank (inlet) and a lower tank (outlet). Among the factors affecting radiator efficiency are: the basic design of the radiator (core thickness, number of rows, tank capacity), the area and thickness of the radiator core exposed to the cooling air flow, the amount of cooling air, and the difference between the coolant temperature and the cooling air temperature.
 
 
 

Radiator pressure cap: –

The pressure cap in the radiator is installed above the filling neck and must be tight. It is known that the boiling point of water is 100 degrees Celsius, so the radiator pressure cap increases the air pressure inside the cooling system, which leads to an increase in the degree to which the water boils. Water at a high temperature enters the radiator without boiling, and the difference in temperature between air and water increases, then heat is transferred from water to air more quickly, the quality of cooling improves, and evaporation decreases.
 
 
 

  
Cooling Shirts: –

The cylinder body is equipped with cooling shirts that surround the cylinders and cylinder heads of the engine. Coolant flows through the cooling shirts around each of the combustion chambers, cylinders, valve bases and valve stems. This means that the cooling shirts are located in the cylinder body and cylinder head.

Compensation water tank (bag): –

It is a tank connected to the radiator neck through a rubber overflow tube, and it compensates for the water that the cooling system may lose or when the pressure inside the system drops to maintain the pressure inside the system.
The water level inside the tank must be maintained between the two specified levels:

1- As the increase of water above the upper limit leads to an increase in pressure inside the system and thus the engine temperature rises above the permissible limit.
2- The lack of water from the lower limit leads to a decrease in pressure inside the system, and thus to the rapid boiling of cooling water.

Through the expansion tank (compensation), the water level in the cooling cycle can be observed.

fan :

The mechanical type radiator fan is driven by a belt drive. In most cases, the mechanical fan is installed on the water pump and is driven by the same drum that rotates the water pump. There are many modern cars that are characterized by the use of electric cooling fans, thanks to the small size of the engine and the abundance of air flow requirements. It pushes a strong stream of air through the radiator blades and pipes to cool the coolant, and there are two types of them:

1. It rotates with the ignition switch on and the engine running.
2. Rotated by a thermostat sensitive to the temperature of the engine or coolant.