Thermo-syphon Cooling System – Working , Diagram , Advantages

• Thermo-syphon water cooling system is based on the fact that water becomes light on heating. The thermo-syphon cooling arrangement is shown in figure.
• The top and bottom of the radiator are connected to the top and bottom of the cylinder water jacket respectively with the help of pipes.
• The radiator is cooled by causing air to flow over it. Air flow is achieved by vehicle motion or a fan provided.
• The heated water in cylinder water jacket becomes light and moves out of the upper connection pipe into the radiator and travels down from upper tank to lower tank, rejecting heat as it travels. This cooled water from the lower tank is passed into the cylinder water jacket and hence circulated again for the process.
• An important limitation of this system is that the cooling depends only on temperature and is independent of engine speed. Also the circulation of water starts only after the engine has become hot enough to cause thermo-syphon action.

Diagram Of Thermo Syphon Cooling System :

The advantages of thermo-syphon cooling are :
(a) Cheap as no water pump is required.
(b) Reliable as there are no moving parts.
(c) Circulation of water depends solely on engine temperature. The hotter the engine, the greater is the circulation.

Disadvantages of thermo-syphon cooling are as follows 
(a) In order to achieve efficient circulation, the radiator top tank must be well above the engine. This needs a high bonnet line.
(b) Cooled water enters the engine at the bottom of the cylinder, where the engine normally runs fairly cool and it heats up to maximum as it reaches the top of the cylinders. Therefore, it has a reduced cooling effect on the hottest part of the engine.
(c) Difficult to fit an interior heater successfully without a water pump.
(d) Under conditions of very heavy load or in hot climates the water may not circulate as quickly as required.
Incorporation of a water pump insures positive water circulation and removes all the disadvantages of the thermo-syphon cooling process.

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