Methods of Heat Transfer

What are the three methods of heat transfer?

Define conduction, convection, and radiation.

Answer:

Conduction: This is a flow of heat by direct contact. Heat travels from a warmer object toward a colder object.

Radiation: Radiation is the transfer of energy by electromagnetic radiation. Radiation does not require a medium in which the energy needs to transmit through. Solar radiation warming the Earth’s surface is an example. The radiation transfers from the sun through space and then strikes the Earth. All objects emit radiation. Colder objects emit longer wavelength radiation while warmer objects emit shorter wavelength radiation.

Convection: This is a transfer of heat by mixing a fluid. Convection occurs within liquids and gases. Examples include boiling water and when warm water mixes with cold water. In meteorology, convection is a common heat transfer mechanisms in the troposphere.

Explanation:

Conduction is the transfer of heat due to direct contact between two mediums, or between two parts of the same medium at different temperatures. In conduction, the particles of the hotter medium vibrate faster than the particles of the colder medium, so the particles of the first medium transfer kinetic energy (by means of collisions) to the particles of the second medium, until when the two mediums reach the same temperature.

Convection is the transfer of heat due to movement of masses of molecules in fluid. Convection occurs when a fluid is heated by an external source: the region of the fluid closer to the source gets warmer, so it expands and becomes less dense; as a consequence, it rises while the colder, denser regions of the fluid sink towards the source of heat.

Radiation is the transfer of heat through electromagnetic radiation. Every object emits electromagnetic radiation, so every object transfers heat by radiation. This is the only method of heat transfer that does not require a medium to occur, since electromagnetic radiation can travel in vacuum also.