PRIN. OF INTERNAL COMBUSTION ENGINES - OD1619 LESSON 2/TASK 3
motor. The fan ensures an airflow through the radiator at times when there is no
vehicle motion. It should be noted that the downward flow of coolant through the
radiator creates what is known as a thermosiphon action. This simply means that as
the coolant is heated in the jackets of the engine, it expands. As it expands, it
becomes less dense and therefore lighter. This causes it to flow out of the top
outlet of the engine and into the top tank of the radiator. As the coolant is
cooled in the radiator, it again becomes more dense and heavier. This causes the
coolant to settle to the bottom tank of the radiator. The heating in the engine
and the cooling in the radiator, therefore, creates a natural circulation that aids
the water pump. The earliest automotive vehicles relied on thermosiphon action and
used no water pump.
FIGURE 64. LIQUIDCOOLED SYSTEM.
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