What does convection refer to in heat transfer?

Convection refers to the process of heat transfer through the circulation of fluids, which can be either gases or liquids. This occurs when warmer, less dense portions of the fluid rise, while cooler, denser portions sink, creating a convection current that facilitates the transfer of heat throughout the fluid. In fire and explosion investigations, understanding convection is crucial because it influences how heat moves in the environment, affecting fire behavior and spread.

The other options describe different modes of heat transfer: conduction, which is the transfer of heat through direct contact between materials; radiation, which involves heat transfer through a vacuum in the form of electromagnetic waves; and conduction through solid materials, where heat is transmitted directly through the material without the movement of the material itself. These modes are distinct from convection, reinforcing why the understanding of convection is specifically tied to the movement and circulation of liquids and gases.