There are two different Bejan numbers (Be) used in the scientific domains of thermodynamics and fluid mechanics. Bejan numbers are named after Adrian Bejan. Thermodynamics In the field of thermodynamics the Bejan number is the ratio of heat transfer irreversibility to total irreversibility due to heat transfer and fluid friction: where is the entropy generation contributed by heat transfer is the entropy generation contributed by fluid friction. Schiubba has also achieved the relation between Bejan number Be and Brinkmann number Br Heat transfer and mass transfer In the context of heat transfer. the Bejan number is the dimensionless pressure drop along a channel of length : where is the dynamic viscosity is the thermal diffusivity The Be number plays in forced convection the same role that the Rayleigh number plays in natural convection. In the context of mass transfer. the Bejan number is the dimensionless pressure drop along a channel of length : where is the dynamic viscosity is the mass diffusivity For the case of Reynolds analogy (Le = Pr = Sc = 1), it is clear that all three definitions of Bejan number are the same. Also, Awad and Lage: obtained a modified form of the Bejan number, originally proposed by Bhattacharjee and Grosshandler for momentum processes, by replacing the dynamic viscosity appearing in the original proposition with the equivalent product of the fluid density and the momentum diffusivity of the fluid. This modified form is not only more akin to the physics it represents but it also has the advantage of being dependent on only one viscosity coefficient. Moreover, this simple modification allows for a much simpler extension of Bejan number to other diffusion processes, such as a heat or a species transfer process, by simply replacing the diffusivity coefficient. Consequently, a general Bejan number representation for any process involving pressure-drop and diffusion becomes possible. It is shown that this general representation yields analogous results for any process satisfying the Reynolds analogy (i.e., when Pr = Sc = 1), in which case the momentum, energy, and species concentration representations of Bejan number turn out to be the same. Therefore, it would be more natural and broad to define Be in general, simply as: where is the fluid density is the corresponding diffusivity of the process in consideration. In addition, Awad: presented Hagen number vs. Bejan number. Although their physical meaning is not the same because the former