free convection

noun1

1. •
   The convection (carriage) of contents of a fluid, such as mass or (especially) heat, by means of currents induced in the fluid by a buoyancy force which is dependent on an acceleration (such as gravity) acting upon density changes in the fluid which are induced by heat.

   • The draft of a chimney due to a fire in a fireplace, and the rising of smoke particles from a fire, are due to free convection.
   • The transfer of heat from a hot object by means of upward hot air currents from the object, is due to free convection.