Convection is the moving of heat from one place to another by heating a substance (fluid) such as air or water and circulating the substance from a heat source to the area to be heated. The same method may be used to cool a space by picking up unwanted heat and discharging it outside of the space. A common example of this is the movement of heat-laden air from a furnace into the rooms of a house where it releases its heat and then returns through the cold air duct to receive another supply of heat from the furnace.
