Skip to main content Skip to Search Box

Definition: convection from Hawley's Condensed Chemical Dictionary

The transfer of heat from one place to another by a moving gas or liquid. Natural convection results from differences in density caused by temperature differences. Warm air is less dense than cool air; the warm air rises relative to the cool air, and the cool air sinks. Forced convection involves motion caused by pumps, blowers, or other mechanical devices.


Summary Article: convection
from The Columbia Encyclopedia

mode of heat transfer in fluids (liquids and gases). Convection depends on the fact that, in general, fluids expand when heated and thus undergo a decrease in density (since a given volume of the fluid contains less matter at a higher temperature than at the original, lower temperature). As a result, the warmer, less dense portion of the fluid will tend to rise through the surrounding cooler fluid, in accordance with Archimedes' principle. If heat continues to be supplied, the cooler fluid that flows in to replace the rising warmer fluid will also become heated and also rise. Thus, a current, called a convection current, becomes established in the fluid, with warmer, less dense fluid continually rising from the point of application of heat and cooler, denser portions of the fluid flowing outward and downward to replace the warmer fluid. In this manner, heat eventually may be transferred to the entire fluid. Convection currents are widely observed in both liquids and gases. Many aspects of weather are connected with convection currents. For example, when a portion of the atmosphere becomes heated by contact with a warm area of land, it rises into the cooler, higher altitudes, with the result that some of the moisture carried with it may be condensed to form clouds and precipitation. Convection currents have been used for heating and ventilation since ancient times. Both hot-air and hot-water heating systems use convection to transfer heat through the entire structure being heated. Convection currents also assist in the ventilation of mines.

The Columbia Encyclopedia, © Columbia University Press 2017

Related Articles


Full text Article convection
Astronomy Encyclopedia

Process of energy transfer in a gas or liquid as a result of the movement of matter from a hotter to a colder region and back again. For...

Full text Article convection
The Encyclopedia of Ecology and Environmental Management, Blackwell Science

Transport of heat or mass by movement of a fluid. If a hot object is placed in a wind tunnel , it will cool at a rate dependent on the wind...

Full text Article convection
The Macmillan Encyclopedia

The transfer of heat within a fluid by means of motion of the fluid. Convection may be natural or forced. In natural convection, the fluid...

See more from Credo