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Convection - Free and Forced Convection

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Estimated time: 7 minutes
  • Definition: Free (Natural) Convection
  • Definition: Forced Convection
  • Examples
  • Key Points: Free and Forced Convection
Maharashtra State Board: Class 11

Definition: Free (Natural) Convection

When a hot body is in contact with air under ordinary conditions, the air removes heat from the body by a process called free or natural convection.

Maharashtra State Board: Class 11

Definition: Forced Convection

The convection process can be accelerated by employing a fan to create a rapid circulation of fresh air. This is called forced convection.

Maharashtra State Board: Class 11

Examples

Example: Air Around Firewood:

A common everyday example of free convection is air around firewood. When the firewood burns, the surrounding air gets heated, and this heated air naturally rises — carrying heat away from the hot body without any external device to drive the airflow.

Examples of Forced Convection:

Heat Convector: Uses a fan to force air over a heating element, rapidly circulating warm air throughout the room.
Air Conditioner: A fan forces air over cooling coils, accelerating the heat exchange process beyond what natural convection could achieve.
Heat Radiators in IC Engines: A fan forces air through the radiator fins of an internal combustion engine to rapidly dissipate engine heat.
Maharashtra State Board: Class 11

Key Points: Free and Forced Convection

  • When a hot body is in contact with air under ordinary conditions (e.g., air around firewood), the air removes heat by free or natural convection.
  • Land and sea breezes are formed as a result of free convection currents in air.
  • The convection process can be accelerated by a fan creating rapid circulation of fresh air — this is called 'forced convection'.
  • Examples of forced convection: heat convector, air conditioners, and heat radiators in IC engine
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