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Question

Heat is transferred from an insulated pipe to the surrounding still air by ______

The correct answer is
Radiation

Heat Transfer Modes Explained

Heat transfer occurs via three main mechanisms:

  • Conduction: Transfer through direct physical contact.
  • Convection: Transfer via the movement of fluids (liquids or gases).
  • Radiation: Transfer through electromagnetic waves, independent of a medium.

Analyzing Heat Transfer from Pipe to Air

In the case of an insulated pipe transferring heat to surrounding still air:

  • Conduction: Heat conducts from the pipe surface to the adjacent air molecules. However, gases like air are generally poor conductors of heat.
  • Convection: The air is described as 'still', minimizing forced convection. Natural convection occurs due to air density changes but is less effective without air currents.
  • Radiation: The pipe surface, if warmer than the surroundings, emits thermal radiation. This mode is always present and can be significant, especially when convection is limited.

Identifying the Primary Mode

Given the conditions ('still air' limiting convection and insulation potentially reducing conduction efficiency), radiation emerges as the dominant and most effective mode for heat transfer from the insulated pipe to the environment.

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Important Questions from Conduction

  1. In M - L - t - T system, the dimension of thermal diffusivity is -

  2. The transfer of heat through the molecules of matter in any body is called ________.

  3. Unit of thermal diffusivity is

  4. When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by:

  5. Which of the following is a case of steady state heat transfer?

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