Convection Heat Transfer

Convection heat transfer describes the movement of heat between a solid surface and a moving fluid.  The basic equation of convective heat transfer, sometimes known as Newton’s law of cooling, is very straightforward:

                                   q″=h*(T_s-T_f)

where:

q″ is the heat flux, or heat flow per unit area through the solid surface

T_s is the temperature of the solid surface

T_f is the temperature of the fluid far away from the surface

h is the convective heat transfer coefficient

Of course, most of the hard work in doing this kind of heat transfer analysis comes from trying to determine the correct value for the convective heat transfer coefficient, h.  In general, h is a function of the fluid properties, the fluid velocity, and the solid surface geometry including roughness.  In some cases, other factors enter in as well.

Details of calculating h occupy a large part of any introductory heat transfer textbook.  However, it is sometimes helpful to have a rough idea of approximate sizes: