Types of Cooling System In Engine
In this article, we discuss the types of cooling system In Engine. The following two systems are used for cooling the I.C engines these days:
The Necessity of Cooling System In Engine
All the I.C engine require a cooling system because combustion of fuel takes place inside the engine itself. All the heat produced by the combustion of fuel in the engine cylinders is not converted into useful power at the crankshaft. Only about 30% of the heat is converted into mechanical work. About 40% goes off through the exhaust. The remaining 30% is useless to waste heat.
It is seen that the quantity of heat given to the cylinder walls is considerable and if this heat is not removed from the cylinders, it would result in the seizing of the piston, high fuel consumption, pre-ignition and burning of lubricant etc.
Keeping the above facts in view, it is observed that suitable means must be provided to dissipate that excess heat from the cylinder walls so as to maintain the temperature below certain limits. Therefore the method of removing away the excess heat from the engine cylinder is called a cooling system.
Types of Cooling System In Engine
Following are the two type of cooling system for engine:
- Air cooling system
- Water cooling system
Air cooling system
Air cooled system is generally used in small engines say up to 15-20 kW. The air system is used in the engines of motorcycles, scooters, aeroplanes and other stationary installations. In countries with cold climate, this system is also used in car engines.
In this system, the heat is dissipated directly to the atmospheric air by conduction through the cylinder walls. In order to increase, the rate of cooling, the outer surface area of the cylinder and cylinder head is increased by providing radiating sins and flanges. In bigger units, fans are providing to circulate the air around the cylinder walls and cylinder head.
Advantages of Air Cooled System
Following are the advantages of the air-cooled system:
- The air cooled system has no radiator or pump so the system is light.
- In case of water cooling system there are leakages, but in this case, there are no leakages.
- Coolant and antifreeze solutions are not required.
- This system can be used in cold climates, where if water is used it may freeze.
Disadvantages of Air Cooled System
- Comparatively, it is less efficient.
- It is used in aeroplanes and motorcycle engines where the engines are exposed to air directly.
Water Cooling System
The water cooling system is used in the engines of cars, buses, trucks, etc. In this system, the water is circulated through water jackets around each of the combustion chambers, cylinder, valve seats and valve stems.
The water is kept continuously in motion by a centrifugal water pump which is driven by a V-belt from the pulley on the engine crankshaft. After passing through the engine jackets in the block and cylinder heads.
The water is passing through the radiator. In the radiator, the water is cooled by air drawn through the radiator by a fan. Usually, the fan and water pump are mounted and driven on a common shaft. After passing through the radiator, the water is drained and delivered to the water pump through a cylinder inlet passage. The water again circulated through the engine jackets.
Parts of Water Cooling System
- Thermostat valve.
- Water pump
- Water Jackets.
- Antifreeze mixtures.
Types of Water Cooling System
water cooling system has the following types:
- Thermosyphon cooling system.
- Impeller circulation system.
- Pump circulation system.
- Pressurised cooling system.
1. Thermosyphon Cooling System
In this system, the natural convection of water is used. i.e hot water has a lower density and rises up. The hot water in the water jacket rises up by this way and goes radiator top, from where it passes down and is cooled, and is collected in the bottom tank.
From the bottom tank again it goes to the water jacket of the cylinder block. This natural circulation system is used in very old model cars.
2. Impeller System
This is an improvement over the thermosyphon cooling system. And it is similar in all respects except that it has small impeller unit driven by the engine itself to increase the circulation rate of water.
3. Pump Circulation
This is the modern arrangement of water cooling in which the water is circulated effectively from the cylinder block to the radiator and back by means of a centrifugal pump driven by the engine v-belt.
4. Pressurised System
This is an improvement over the pump circulation system of cooling. In this system, there is a special radiator cap having a spring-loaded pressure valve and vacuum valve.
The cap is gas tight when the engine is heated, water vapour is formed and this is not allowed to go out. Therefore a boiling point of water in the system is raised, so that the working temperature of the engine also rises, Higher temperature gives better thermal efficiency.
The pressure valve opens when the pressure in the system exceeds a certain predetermined valve, say 0.5 kg cm². and allow the steam to escape, thereby avoiding excessive pressure formation. When the engine is cooled the vacuum valve opens and compensate the loss of water or air.
Advantages of Water Cooling System
- Uniform cooling of the cylinder, cylinder head and valves.
- Specific fuel consumption of engine improves by using a water cooling system.
- If we employ a water cooling system, the engine need not be provided at the front end of moving vehicle.
- The engine is less noisy as compared with air-cooled engines, as it has water for damping noise.
Disadvantages of Water Cooling System
- It depends upon the supply of water.
- The water pump which circulates water absorbs considerable power.
- If the water cooling system fails then it will result in severe damage of the engine.
- The water cooling system is costlier as it has a number of parts. Also, it requires more maintenance for its parts.
Difference Between The Air Cooling System and Water Cooling System
In [Cooling system for ic engine] The following point is important for the comparison of air cooling and water cooling system.
Air Cooling System
- The design of this system is simple and less costly.
- Weight of the cooling system (per b.h.p. of the engine) is very less.
- The fuel consumption (per b.h.p. of the engine) is more.
- Its installation and maintenance are very easy and less costly.
- There is no danger of leakage or freezing of the coolant.
- It works smoothly and continuously. Moreover, it does not depend on any coolant.
Water Cooling System
- The design of this system is complicated and more costly.
- Weight of the cooling system (per b.h.p. the engine) in much more.
- The fuel consumption (per b.h.p. the engine) is less.
- Its installation and main tenace in difficult and more costly.
- There is a danger of leakage or freezing of the coolant.
- If the system fails, it may cause serious damage to the engine within a short time.
- What is Thermodynamics and Laws Of Thermodynamics
- Cooling system for ic engine in vehiclemaintenanceandrepairs.com
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