Concepts » How Heat is Transferred

How Heat is Transferred

Heat is transferred from one source to another via three methods of transfer: conduction, convection, and radiation.

Conductive:

The transfer of heat flowing through a substance (molecular motion) or to another touching substance. If you touch a pot on the stove, the heat is transferred from the pot to your hand via conductive heat transfer.

Convective:

The transfer of heat in fluids, such as rising heated air, steam, and moisture. If you put your hand above a boiling pot, you will feel heat rising from the pot in the form of steam. This transfer of heat from the pot upwards is via convective heat transfer. Convective heat transfer results in warmer air rising and cooler air settling creating a convection loop termed free convection. A Convection loop can also be generated mechanically with the aid of fan or wind and is then called forced convection.

Radiant:

The transfer of heat via infrared radiation rays that are invisible to the naked eye and unaffected by air currents. If you step outside on a windy sunny day, you will feel the sun's heat rays on your face. This transfer of heat from a heated source across an air space to a colder surface is via radiant heat transfer. All materials radiate radiant heat in ranges from 0% to 100%.

Common examples of radiant heat transfer:

  • Skin warming up when outside on a sunny day via the radiant heat from the sun regardless of the ambient temperature.
  • Roof shingles heated via the radiant heat from the sun.
  • Heat radiating from a light bulb.