Which heat transfer method is used in forced air heating systems?

In forced air heating systems, convection is the primary heat transfer method utilized. This process involves the movement of air; the heating system uses a furnace or a heat pump to warm air, which is then circulated through ducts and vents using blowers or fans. As the warmed air rises and disperses throughout the space, it transfers thermal energy to the surrounding air and surfaces, effectively increasing the ambient temperature of the environment.

Convection is inherently characterized by the flow of fluids (which includes air) and is crucial in conventional heating systems as it allows for the efficient distribution of heat throughout a space. This mechanism contrasts with conduction, which involves direct heat transfer through materials, and radiation, where heat is transferred through electromagnetic waves. Evaporation involves the change of a liquid to a gas and is not related to heating methods used in forced air systems. Thus, convection is the correct answer as it accurately describes the heat transfer process occurring in these heating systems.