Forced convection

Forced convection is a mechanism, or type of transport, in which fluid motion is generated by an external source (like a pump, fan, suction device, etc.).

This mechanism is found very commonly in everyday life, including central heating and air conditioning and in many other machines.

Forced convection is often encountered by engineers designing or analyzing heat exchangers, pipe flow, and flow over a plate at a different temperature than the stream (the case of a shuttle wing during re-entry, for example).

When the Peclet number is much greater than unity (1), advection dominates diffusion.

Similarly, much smaller ratios indicate a higher rate of diffusion relative to advection.