Heat transfer. Illustration showing three forms of heat transfer. Radiant heat is thermal radiation emitted by matter, and can be felt around a fire. Radiant heat from the fire heats surrounding air which expands and rises, transferring heat upwards by convection; this can be felt above the fire. Conduction is the transfer of thermal energy between particles in a material: the cool end of a metal rod becomes hot if the other end is placed in the fire.