Convection is one of three forms of heat transfer and stands out because it produces through a fluid ( air, water, ) that it carries the heat between areas with different temperatures. Convection occurs only through fluid materials. To heat up, increase of volume and therefore its density decreases and amount by moving the fluid found at the top and is at a lower temperature. What is called convection, is the transport of heat through the upward and downward flows of fluid.Heat transfer involves the transport of heat in a volume and the mixture of macroscopic elements of hot and cold portions of a gas or a liquid. It also includes the exchange of energy between a fluid and a solid surface or a bomb, a fan or other mechanical device ( mechanical convection, forced or assisted ).Free or natural heat transfer fluid is more hot or cold and in contact with a solid surface, causes a movement due to the differences in density resulting from temperature gradients in the fluid.
