Classification and types of Engine Cooling System (automobile engineering)

1. Engine cooling system

• The engine temperature rises when it is running. Particularly, the combustion chamber and crankshaft are exposed to high temperatures caused by burnt gases and by friction of parts moving at high speeds.
• If lubrication becomes insufficient due to heat, or parts deforms due to thermal expansion, the engine will overheat and may seize.
• Though design consideration is given to the materials and shapes of parts so that they are not so badly affected by thermal expansion, the engine still requires a cooling system which can dissipate heat effectively.
• Cooling systems can usually be classified as either air-cooling systems or water-cooling systems.

2. Types of cooling system

1. Air cooling system (natural and forced circulation).

2. Water cooling system (natural and forced circulation).

1. Air cooling system

• In this system, the engine is cooled by air so the system has a simple construction. There are two ways of cooling.

a. Natural air-cooling

• The engine is positioned so that its exterior is exposed to air as much as possible. 
• To increase the area of the engine exposed to air, the cylinder and cylinder head are fitted with fins. For better heat dissipation, special consideration is given to the size, shape and orientation of the fins. 
• This type of cooling system is the most widely used in general motorcycles.

b. Forced-air-cooling system 

• When the engine is positioned in the frame or not well exposed to air, the forced-air-cooling system is used.
• This system uses a fan which is driven by the engine, and air is blown to the cylinder and cylinder head. For efficient cooling, a duct or bar is provided so that air is directed effectively. Also, the cylinder fins are specially shaped.
•  This cooling system is mainly used in scooters.

2. Water-cooling system 

In this system, water is sent to jackets (water passages) in the cylinder and cylinder head. After cooling, the water returns to the radiator, is cooled by air, and then is sent to the jackets again. 

There are two different methods of water circulation.

a. Natural Circulation cooling system

• Natural circulation system (convection) in which heated water moves upwards.

b. Forced circulation cooling system

• One is the system in which water is force-circulated by a water pump, and the other the forced-circulation system uses a thermostat in addition to the water pump.
• The thermostat is used to stop the water from flowing out of the radiator until the engine has warmed up.
• When the engine temperature rises above a specific level, the water in the radiator is allowed to circulate around the engine.
• Most water-cooled engines use this type of water-cooling system..