Convection
1. Convection is the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat.
2. Convection is the movement in a gas or liquid in which the warmer parts move up and the cooler parts move down.
Convective flow may be transient (such as when a multiphase mixture of oil and water separates) or steady state (see Convection cell). The convection may be due to gravitational, electromagnetic or fictitious body forces. Heat transfer by natural convection plays a role in the structure of Earth's atmosphere, its oceans, and its mantle. Discrete convective cells in the atmosphere can be identified by clouds, with stronger convection resulting in thunderstorms. Natural convection also plays a role in stellar physics. Convection is often categorised or described by the main effect causing the convective flow.
Thermal image of a newly lit Ghillie kettle. The plume of hot air resulting from the convection current is visible. Convection cannot take place in most solids because neither bulk current flows nor significant diffusion of matter can take place.
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