To make engine survive cooling system is important. The normal
working temperature of engine is 180-210 C and the engine burns fuel hotter
than the melting temperature of engine material. If the engine is working for a
long time the temperature is surely going to much higher than normal
temperature of engine. In order to maintain this temperature, cooling system is
introduced in the engine. The cooling is done in consideration with engine
block/head metal temperature limit, lubrication and knocking (SI engine).
Construction
- Radiator
- Coolant pump
- Coolant reservoir or overflow tank
- Radiator cap
- Thermostat valve
- Engine coolant temperature sensor
Properties of coolant
- Effective heat transfer
- Prevention of cooling system corrosion
- Effective boiling point
- Freeze point depression where or if required
- Chemical stability
Working
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| Coolant Pump |
Coolant pump- It circulates the coolant from the
engine block to radiator. The coolant pump is driven by the crankshaft using
the belt drive.
Thermostat valve- The coolant after circulating in
the engine block absorbs the heat from the cylinders. The coolant continues to
circulate in the engine up to it does not reach to particular temperature that
opens the thermostatic valve. Thus regulates the amount of hot coolant flowing
to radiator. The principle of thermostat valve is increase in pressure due to
increase in temperature. The high pressure pushes the valve to open.
Radiator- It is the heat exchanger that works on
the principle of convection. The hot fluid is allowed to flow through small tubes
of radiator which is air cooled by the air flowing through the front of the car
in to the radiator. The motor driven fan or blower turns on itself when the
engine coolant temperature sensor senses temperature above 95 C in order to
enhance the cooling by forced convection.
Radiator Cap- The radiator cap has two function
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| Radiator Cap |
To maintain the pressure higher than atmospheric
pressure. The boiling temperature increases with increase in pressure. Thus helps
coolant to remain in liquid state and radiator to work efficiently.
To release the pressure when over pressured. The radiator
cap behaves as a pressure cooker weight, release pressure when it reaches to specific
value that compresses the spring of cap and opens the valve.
Caution- DO NOT OPEN WHEN HOT
The coolant is at high pressure and temperature can
burst out and burn you.
Coolant reservoir- the coolant reservoir provides
the coolant to the cooling system when the coolant level is less in the system.
It is also called overflow tank as it stores the coolant that overflows from
the cooling system. The coolant in the coolant reservoir should not filled
above the full mark shown on the tank because the coolant expands and contracts
in the cooling system due to high temperature and pressure. Thus you might
observe the change in level of coolant in the coolant tank.
How Car Heater Works
The car heater works in a same way as radiator
works. It uses the hot coolant before sending it out of thermostat valve. The
hot fluid passes through the heat exchanger tubes and the air blows over it by
the help of car ventilation fan. The temperature of air increases while passing
over these hot tubes and thus send hot air inside the cabin.
