What is the term for the transfer of heat by the movement of fluids?

The transfer of heat by the movement of fluids is called convection.

It occurs in liquids and gases when moving fluid carries thermal energy from one location to another. In natural convection, heating usually makes a fluid expand and become less dense, so it rises while cooler, denser fluid sinks. This circulation can create convection cells, such as the currents in a pot of water heated from below or the rising plume above a fire.

Convection can also be forced. Fans, pumps, and stirrers move the fluid even when buoyancy is not the main cause. Heating and cooling systems use forced convection to transfer energy efficiently, including automobile radiators, air conditioners, and computer cooling systems.

Advection is a related term that emphasizes bulk fluid transport; in heat-transfer contexts, convection generally includes both bulk motion and microscopic conduction within the fluid. Conduction transfers energy through molecular interactions without bulk movement, while radiation carries energy through electromagnetic waves and does not require a fluid.