Convection Heat transfer is the process by which energy in one body is communicated to another body with which it is in contact. The transfer of heat always occurs from a body with greater potential and kinetic energy to a body of lower potential and kinetic energy in other words from high to low temperature.
Convection occurs when the matter is heated and the hotter atoms in that matter move faster, spreading out and filling more space. Heat loss by convection occurs when either air or water moves over the patient or the patient moves through air or water.
In boiling water the heat flows into the pot from the burner, heating the bottom of the bath. Then this hot water rises and moves down to cover it, creating a circular motion. In the Radiator, put up warm air and draw in cooler air.