Engine cooling — primary function of the radiator fan Within a liquid-cooled automotive engine, what is the main purpose of the radiator fan during low vehicle speed or high thermal load operation?

Difficulty: Easy

Correct Answer: it blows air through the radiator when necessary

Explanation:


Introduction / Context:
Radiator fans (engine-driven or electric) maintain airflow across the radiator core when ram-air from vehicle motion is insufficient. This prevents coolant temperatures from exceeding limits in traffic, at idle, or under high load at low speed.


Given Data / Assumptions:

  • Liquid-cooled engine with thermostat, radiator, and fan shroud.
  • Fan control may be viscous clutch or ECU-controlled electric motor.
  • Ambient and load conditions where natural airflow is inadequate.


Concept / Approach:
The radiator rejects heat from the coolant to ambient air. The fan’s purpose is to force or pull air through the radiator fins, sustaining the heat transfer rate independent of vehicle speed.


Step-by-Step Solution:

Coolant absorbs heat from the engine and flows to the radiator.Fan induces airflow through the core, increasing convective heat transfer.Temperature is controlled by thermostat and fan switching to maintain optimal engine temperature.


Verification / Alternative check:
Fan activation at idle coincides with rising coolant temperature; switching off the fan typically causes temperature to climb, confirming its role.


Why Other Options Are Wrong:

  • Driving the water pump by wind: water pumps are belt or gear/electric driven, not by fan wind.
  • Blowing directly on the block: primary heat rejection occurs in the radiator, not by air on the block.
  • Drawing heat out of the engine bay: incidental, not the primary design purpose.
  • Dehumidifying intake air: unrelated to the cooling system fan.


Common Pitfalls:
Missing shrouds which greatly reduce fan effectiveness; incorrect fan rotation; failed relays/sensors preventing timely activation.


Final Answer:

it blows air through the radiator when necessary

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