Continuously running a car or an automobile can heat up the engine, and reach up to its extreme position beyond your thinking. According to the study, in engine cylinders the temperature of the burning gases can reach up to 1773.15K – 2273.15K (1500°C – 2000°C). It is more than the temperature and Melting Point of Platinum (1768°C) and Titanium (1668°C), which can oxidize the lubrication oil inside the engine and deposit carbon on the surface.
The amount of heat delivered to the cylinder walls is too high and if this heat is not removed from the cylinder, it results in seizing the piston, high fuel consumption, pre-ignition and burning of lubricants, etc.
Only 30% of heat is used by the engine to convert into mechanical work, where 30% heat is useless and 40% heat exhausted by the exhaust fans. Not all heat generated by fuel combustion in engine cylinders is converted into useful power in the crankshaft. Thus to remove the excess heat from the engine cylinder a cooling system is used.
A system in the engine which is used to maintain the temperature or excess heat is known as the cooling system of the engine. When the engine is hot, it must remove the heat at a rapid rate. At the beginning of the engine, the engine cooling should be very slow so that the different working parts can reach their operating temperature in a few time.
Kinds of Cooling System
Two types of cooling systems are used in the engine.
- Air Cooling System
- Water Cooling System
Air Cooling System
Air cooling systems are typically used in small engines up to 15–20 kW. In these types of systems, the heat conducted by the outermost parts of the engine is radiate and the air is driven away from the stream, which is obtained from the atmosphere. An air-cooled engine is simpler to create than a water-cooled engine because heat is transferred directly from the cylinder and head to the air.
When the vehicle is normally driven at sufficient speed to provide sufficient wind speed to transfer heat, the whole cooling system is only the fins on the air-cooled engine. The air-cooled engine has a fan or blower, to improve the airflow in the rear of the wings adequately, with the small or slow movement of air.
As you know the air cooling system usually uses in small vehicles such as scooters, motorcycles, small car engines and also provides in some small industrial engines, where the forward speed of the machine gives good velocity to cool the engine.
Air Cooling System Advantages
- It has low manufacturing prices.
- It doesn’t require high maintenance.
- This doesn’t contain liquid coolant, so there will be no problem like leakage and freezing.
- The engine has light in weight because it has no cooling pipe radiator, fan pump, and liquid cooling jacket.
- Installation, assembling, disassembling of the engine is easy and simple.
Air Cooling System Disadvantages
- The cooling of the engine is non-uniformly.
- In comparison to the water cooling system, it is less efficient.
- This generates aerodynamic noises.
- It can only be used for short-sized engines, because of its small capacity for heat wastage.
Water Cooling System
In the water cooling system, water is circulated via the water jacket around each valve seats, valve stems and combustion chamber. The water-cooled engine block and cylinder head have reciprocating cooling channels. All channels at the top of the cylinder head converted to a single outlet.
This removes excessive heat generated in the engine and protects it from overheating and keeps the engine at working temperature for efficient and economical work.
The water continuously moves by a centrifugal water pump which is operated by V-belt from the pulley on the engine crankshaft. It drives hot coolant from the engine to the radiator, a form of the heat exchanger. After passing from the radiator, water is poured into the drain and the water is pumped through the cylinder inlet route.
Parts in Water Cooling System
- Water Pump
- Antifreeze Mixture
- Thermostat Valve
- Water Jackets
Types of Cooling System
- Thermosyphon Cooling System
- Impeller Circulation Cooling System
- Pump Circulation Cooling System
- Pressurized Cooling System
Thermosyphon Cooling System
This system works on the principle that the hot water has lower density and rises up, and cold water is being heavier that goes down.
In these types of systems, the radiator kept at the upper level than the engine for easy flow of water towards the engine. This is how hot water in the water jacket rises and goes over the radiator, from where it passes and cools, and is collected in the bottom tank. In these systems, the rate of supply is too low.
Impeller Circulation Cooling System
This is an updated version of the thermosyphon cooling system. The main motive of the impeller cooling system is to provide the right regulation, capable of the maximum engine cooling pump efficiency. And it is all the same except that it has a small impeller unit powered by the engine to increase the circulation rate of water.
Pump Circulation Cooling System
This system has the same construction as the thermosyphon cooling system except that it uses a centrifugal pump for circulating water in a water jacket and radiator.
It is a modern system of water cooling in which water is circulated effectively by cylinder block to the radiator and back via a centrifugal pump driven by the engine V-belt.
Pressurized Cooling System
This is an updated version of the pump circulation cooling system. In this, you will get the special radiator cap with a spring-loaded pressure valve and a vacuum valve. This cap becomes gas-tight when the engine gets heat, water vapor is formed and is not allowed outside by the cap.
Therefore a boiling point of water is raised in the system. So that the working temperature of the engine also increases, higher temperature gives better thermal efficiency.
As the coolant temperature increases, the setpoint of variable pressure relief valve also increases and the system relief pressure automatically varies with the coolant temperature over a range of pressures whose upper limit is enough greater than the set point of the relief valve in the pressure cap so that the maximum system operating pressure is still finite by the pressure cap.
Water Cooling System Advantages
- The water-cooling system is efficient as compared to the air-cooling system.
- Cylinder, cylinder head, and valve’s uniforming cooling, it is different from the air cooling system.
- Water-cooled engines have lower fuel consumption than air-cooled engines.
- Water-cooled engines do not require a more frontal area.
- If we install a water cooling system, there is no need for an engine on the front end of the moving vehicle.
- The cooling system can be easily stationed anywhere on the vehicle. In some vehicles, it is at the rear, while in air-cooled engines, this is not possible.
- The engine is less noisy than an air-cooled engine, as it has water for soaking noise.
Water Cooling System Disadvantages
- The water cooling system needs pure water to work properly.
- It totally depends on the supply of water.
- The water pump which supplies the water absorbs a lot of energy.
- In the case of cooling system failure, the engine may suffer severe damage.
- Water coolant system requires regular maintenance, its parts require more maintenance.
- The Water cooling system is expensive because it has many parts.
- The cost of the water cooling system is quite high.
- The water cooling engine is heavy because it contains lots of water inside and it also has large numbers of parts.