Definition - What does Superficial Velocity mean?
Superficial Velocity is the volumetric flow rate divided by a cross sectional area. It is the hypothetical flow velocity which considers that only one type of fluid flows through a given cross sectional area or a pipe. Hypothetical means that the Superficial Velocity is not the actual velocity in case of multiphase flow. However, in one phase flow the Superficial Velocity is equal to the mean velocity.
Petropedia explains Superficial Velocity
Real velocity is hard to find as it varies from place to place. Superficial Velocity concept is used mainly because it is unambiguous, does not change and is readily known. We can take an example of a gasifier: if its Superficial Velocity is low, then the pyrolysis process will also be low. On the other hand, if it is high then less unburnt particles will be present.
Superficial Velocity of gas, oil or water is given by-:
V = Q/A, unit is meter per second
Q is the volumetric flow in cubic meter per second
A is the area of cross section in meter sq.