the basics  Convection is the transfer of internal energy into
or out of an object by the physical movement of a surrounding
fluid that transfers the internal energy along with its mass.
Although the heat is initially transferred between the object
and the fluid by conduction, the bulk transfer of energy comes
from the motion of the fluid. Convection can arise spontaneously
(or naturally or freely) through the creation of convection
cells or can be forced by propelling the fluid across the object
or by the object through the fluid.  spontaneous convection
Spontaneous convection is driven by buoyancy for the most part
and surface tension to a lesser extent.   forced convection  The
heat loss due to the forced convection is given by the following
equation called Newton's Law of Cooling …  P =  dQ
 = hA (T − T0)  where …  P = dQ/dt is rate at which heat is
transferred h = convection heat-transfer coefficient (or film
coefficient or film conductance) A = exposed surface area
T = temperature of the immersed objec