COOLING SYSTEM IN IC ENGINES

Need Of Cooling System:
               The internal combustion engines are generally used in automobile industries and have wide applications. These engines are meant for continuous running and due to that high amount of heat is produced to pressure and frictional forces. Hence to meet with efficiency, optimum engine temperature has to be maintained during its running and according to that point engine cooling system is very important.

Types of Cooling System:
                The cooling system for IC engines is divided into basically three types:
1) Air Cooling System
2) Liquid Cooling System
3) Oil Cooling System

Air Cooling System:
                In air cooling of IC engines, the air passes over the fins attached to the engine cylinder, either by vehicle movement or sometimes there may be a forced pull of air towards engine for maximum cooling. So it again divided the natural air cooling and forced air cooling. In general, natural air cooling is efficient for small engines from 5 Ps to 2o Ps.
                The important part of air cooling system is engine fins. The engine fins are the extended portion of the cylinder block (or sometimes cylinder head) casting that increased area to be exposed to the air and the hence engine gets cool very quick. These fins are designed in such way that the maximum air gets passed over them results in efficient cooling.
E.g. Bajaj Pulsar 150, Hero Extreme, Yamaha FZ

Liquid Cooling System:
                 Study of the liquid cooling system is very important, because along with heavy engines, smaller engines are also equipping this system on them. Probiking industry, most of the portion of four wheeler and heavy industry using the liquid cooling system. The cooling system is used for wide variety of applications from 20 Ps to onwards.

Liquid Cooling System consists of:
1) Water Pump
2) Hoses
3) Thermostat
4) Radiator 
5) Radiator Fan 
6) Radiator Pressure Cap
7) Coolant Tank
8) Coolant
               Now I am going to give you the information about the liquid cooling system in details.
1) Water Pump:
              The water pump is the simple device, that helps the coolant to circulate in the system as long as the engine is running itself. The water pump is generally the centrifugal type of pump and connected to the driven shaft or any shaft according to design. Due to circulation only hot liquid (coolant) goes to the radiator and comes back with being cool. 
2) Hoses:
              Hoses or Hose pipes are used to connect coolant path outside the engine or subsystems/ components of the coolant system. i.e. engine coolant into engine coolant bypass or engine coolant out to radiator coolant in etc. These hose pipes are made up of the special type of rubber and it can withstand for relatively high temperature.
3) Thermostat:
               The thermostat is a device or valve that measure the temperature of the coolant and allow to pass the hot coolant through it to the radiator, only after reaching the predetermined coolant temperature. If the coolant is not hot enough then the path is blocked to the radiator and the coolant gets circulated through the bypass system to water pump till reaching to the required temperature to open the thermostat valve. The thermostat has spring action to retain its position after allowing hot liquid to the radiator.
4) Radiator:
               The radiator is the component of the liquid cooling system, that is used to cool the coolant delivered from the engine. The radiator core is generally made up of the flattened metal tube like aluminium or copper (i.e. having high thermal conductivity) with aluminium zigzag strips connecting successive tubes. These aluminium zigzag strips increase the area to be exposed to the atmosphere and hence induces cooling efficiency by reducing heat to the atmosphere. It is generally placed in front of the vehicle that helps it more to cool quickly as upcoming air flow is directed towards it and carries away heat quickly from the system.
5) Radiator Fan:
                The radiator fan is generally mounted in between the radiator and the engine. It helps to induce air towards the radiator by pulling air flow and helps to get engine cool very quickly.
6) Radiator Pressure Cap:
                The radiator pressure cap is the simple device mounted on the radiator top that helps to maintain the pressure in the cooling system up to the preset value. If system pressure exceeds more than that of predetermined value then it gets open to release the excess pressure in the system. 
 7) Coolant Tank:
               The coolant tank is very important to store the coolant in the system. Its capacity is designed by taking all considerations into account. For refilling the coolant, there is opening in the coolant tank.
8) Coolant:
                The coolant is the most important in the cooling system because when it circulates through the coolant path, takes away the heat from engine components and releases to the atmosphere via the radiator. So that functioning of the engine remains smooth and efficient.
              The coolant used in the liquid cooling system is generally glycol based coolant and used with 50:50 of distilled water. It helps as anti-freeze and apart from that, some anti-rust or additives can be added to the coolant. Always remember that used the coolant specified by the manufacturer only and with distilled water. The normal tap water may contain some impurities and harm the components of the system by corrosive action or deposition.
E.g. Bajaj Pulsar 200NS, KTM Duke 390, Benelli TNT 300

Oil Cooling System:
                Oil cooling system is also same as the liquid cooling system. The only difference is the coolant is replaced by the oil as the coolant, which is used as the lubricant too. To use the oil as the lubricant, special type of oil is used with the specific grade, viscosity and flashing point.

Oil Cooling System consists of:
1) Oil Pump
2) Pressure Relief Valve (PRV)
3) Hoses
4) Oil Cooler
                Here is some extra information about the oil cooling system. The oil cooled engine is not preferred due to change in the viscosity of the oil at higher temperature though it is used as better than that of air cooling system and cost effective than the liquid cooling system.
1) Oil Pump:
               The oil pump is the important part of the oil cooling system. It plays the role of circulating the oil through the entire system. This pump is designed more powerful such as to pump oil for the both purpose i.e. for the lubrication and the cooling also.
2) Pressure Relief Valve:
               The pressure relief valve (PRV) is used to maintain pressure in the system to fulfill the conditions of safety and releases the pressure when raises more than specified limit. So that the excess oil pressure is released to sump. In some cases, the oil pressure sensor (OPS) may be used and at that time system is controlled by the electronic chip.
3) Hoses:
               The hoses are used to carry oil from engine to oil cooler and to bring it return back to the engine after cooling.
4) Oil Cooler:
                The oil cooler is used as the radiator in the liquid cooling system and has the same function too. The oil cooling generally not used for the heavy vehicles and used in light vehicles like two wheelers, hence the size of the oil cooler is less than that of the radiator in liquid cooling.
E.g. Bajaj Avenger 220, Pulsar 220, TVS Apache 200