If we want to make a cooling system, we have to distribute fuel
for some necessities like loss in friction, loss in exhaust gases, loss to the
cylinder walls and useful work at the crankshaft. However, cooling beyond
optimum limits is not desirable, because it decreases the overall efficiency
due to the following reasons:
Thermal efficiency is decreased due
to more loss of heat to the cylinder walls.
The vaporization of the fuel is less;
this results in a fall in combustion efficiency.
Low temperatures increase the
viscosity of lubricant and hence more piston friction is encountered, thus
decreasing the mechanical efficiency.
Some other methods of cooling
Air cooling
Water cooling
Liquid cooling
Air cooling
The basic principle involved in this method is to have a current of air flowing continuously over the heated metal surface from where
the heat is to be removed. The heat dissipated depends upon some factors.
Air-cooled engines are lighter because of the absence of the
radiator, the cooling jackets and the coolant. They can be operated in extreme
climates, where the water may freeze. In certain areas where there is a scarcity
of cooling water, the air-cooled engine is an advantage. Air-cooled engines get
warmed up earlier than the water-cooled engines.
Water cooling
In a water cooling system, the cylinders of the engine are surrounded
by water jackets through which the cooling water flows. Heat flows from the
cylinder walls into water which goes to the radiator where it loses its heat to
the air.
Liquid cooling
Sometimes
instead of water, other liquids having higher boiling points are used for engine
cooling. Examples are glycerin and ethylene glycerol. A higher boiling point
increases the capacity of the liquid to carry heat and consequently weight of
the coolant and hence that of the radiator is decreased.
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