Convection

Convection is the movement of heat due to the movement of warm matter. Convection is defined as the method of heat transfer through a liquid or solid from places of higher temperature to lower temperature based on the movement of the molecules, because of the different densities.

For example, atmospheric circulation moves warm air to cool places, causing wind. Wind, in turn, can enter and cool a room if the window is open. The movement of the clouds, the ocean currents and many types of heaters are examples of convection.

Forced convection and natural convection

Convection can happen naturally ("natural convection") or because of a moving device ("forced convection").

The fan is a device that produces the movement of the air artificially. The air in this case is moving because of the rotation of the fan. This is is example of "forced convection".

Natural convection happens because a fluid is lighter if is hot and it is heavier if is cold, so if a fluid has a hot part and a cold part, the hot part will naturally move upward and the cold part naturally moves downward. For example, if the water in a pot is hotter near the bottom because of the fire, it moves from the bottom to the surface. At the same time the water near the surface is colder so it moves to the bottom.

Convection currents

Convection currents occur when there are significant differences in temperature between two parts of a fluid. When this happens, hot fluids rise and cold fluids sink. This causes movements or currents in the fluid. Atmospheric circulation, for example, is made by convection currents.

Related pages

• Heat transfer
• Heat conduction
• Thermal radiation