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. If the heat is not released from the cylinder, then, it will 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 engine cylinders. It converts the heat 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 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.
Types of cooling systems in Cars
Two types of cooling systems are used in the engine.
- Air Cooling System
- Water Cooling System
Car Air Cooling System
Air cooling systems are 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. 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 automobile 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 a small automobile such as scooters, motorcycles, small car engines and it 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.
Car Engine Water Cooling System
In the water cooling system, water is circulated via the water jacket around each valve seat, 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
(1) Water Pump:
This is a centrifugal type pump. It is located at the front of the cylinder block and is usually driven by means of a belt. This type of pump consists of the following parts:
- body or casing
- impeller (rotor)
- bearings, or bush
- water pump seal
The bottom of the radiator is connected to the suction side of the pump. The power is transmitted to the pump spindle from a pulley at the end of the crankshaft. Seals of various designs are incorporated in the pump to prevent loss of coolant from the system.
The main purpose of the radiator is to cool down the water received from the engine. The radiator consist of three parts:
- Upper tank
- Lower tank
Hot water from the upper tank, which comes from the engine, flow in the downward direction through the tubes. The heat contained in the hot water is conducted to the copper fins present around the tubes. An overflow pipe, connected to the upper tank, permits excess water or steam to escape. There are three types of radiators:
- Gilled tube radiator- It is the oldest type of radiator, although it is still in use. In this, water flows inside the tubes. Each tube has a large number of annular rings or fins pressed firmly over its outside surface.
- Tubular radiator- The only difference between a gilled tubes radiator and a tubular one is that in this case there are no separate fins for individual tubes. The radiator vertical tubes pass through thin fine copper sheets.
- Honeycomb or cellular radiator- The cellular radiator consists of a large number of individual air that is surrounded by water. In this, the blockage of any passage affects only a small part of the cooling surface. However, in the tubular radiator, if one tube becomes clogged, the entire cooling effect is lost.
The fan is generally placed on the water pump pulley, although in some engines it is attached directly to the crankshaft. A fan helps to solve two purposes in the cooling system of an engine.
- The fan draws atmospheric air through the radiator and thus increases the efficiency of the radiator in cooling hot water.
- Throws fresh air over the outer surface of the engine, which takes away the heat conducted by the engine parts and thus increases the efficiency of the entire cooling system
(4) Antifreeze Mixture:
In order to prevent the water in the cooling system from freezing, some chemical solutions which are known as anti-freeze solutions are mixed with water. In cold areas, if the engine is kept without this solution for some time, the water may freeze and expand leading to damage in the cylinder block, cylinder head, pipes and/or radiators. The boiling point of the anti-freeze solution should be as high as that of water. An ideal mixture should easily dissolve in water, be reasonably cheap and should not deposit any foreign matter in the jacket pipes and radiator.
(5) Thermostat Valve:
It is a kind of check valve which opens and closes with the effect of temperature. It is fitted in the water outlet of the engine. During the warm-up period, the thermostat is closed and the water pump circulates the water throughout the cylinder block and cylinder head. When the normal operating temperature is reached, the thermostat valve opens and allows hot water to flow towards the radiator. Standard thermostats are designed to start opening at 70 to 75°C and they fully open at 82°C. High-temperature thermostats, with permanent anti-freeze solutions. start opening at 80 to 90°C and fully open at 92°C. There are three types of thermostats: (a) bellow type, (b) bimetallic type and (c) pellet type.
- Bellow type valve: Flexible bellows are filled with alcohol or ether. When the bellows are heated, the liquid vaporizes, creating enough pressure to expand the bellows. When the unit is cooled, the gas condenses. The pressure reduces and the bellows collapse to close the valve.
- Bimetallic type valve: This consists of a bimetallic strip. The unequal expansion of two metallic strips causes the valve to open and allows the water to flow in the radiator.
- Pellet type valve: A copper wax pellet expands when heated and contracts when cooled. The pellet is connected to the valve through a piston, such that on the expansion of the pellet, it opens the valve. A coil spring closes the valve when the pellet contracts.
Types of Water Cooling System
- Thermosyphon Cooling System
- Impeller Circulation Cooling System
- Pump Circulation Cooling System
- Pressurized Cooling System
(1) Thermosyphon Water 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.
(2) 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.
(3) Pump Circulation Water 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 come back via a centrifugal pump driven by the engine V-belt.
(4) Pressurized Water 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. The cap becomes gas-tight when the engine gets heat, water vapor is formed on 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 the 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 automobile.
- The cooling system can be easily located anywhere in the car. 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 different parts.
- The cost of the water cooling system is quite high.
- The water cooling engine is heavy because it contains lots of water inside. It also has large numbers of parts.
The cooling system of the car keeps the engine from getting overheated, not to keep it cool. It also increases the thermal efficiency of the engine.