8 Extended Surfaces

Extending the surface of a body in contact with a fluid can enhance heat transfer in convection. Extended surfaces in practice often consist of small–cross section solids that protrude from the main body, such as fins attached to the walls of heat transfer equipment. The main reasons for using fins to enhance the heat transfer rate are (1) to increase the heat transfer surface area, (2) to break up the boundary layer of the flow, and (3) to increase the turbulence as flow passes over or across the fins.