New insight into the definitions of the Bejan number

摘要

This paper presents new insight concerning the formulation and definition of one of the two Bejan numbers (Be) derived from the first and second law analysis, namely this one derived from the first law of thermodynamics. The systematic analysis performed reveals the role and physical meaning of the Bejan number (Be) as criterion of similarity or dimensionless variable. It is shown that the unique Bejan number (Be) can be derived from a classic fluid mechanics, whereas the other extensions of Bejan number (Be) for heat transfer or mass transfer are combinations of unique Bejan number (Be) with Prandtl (Pr) or Schmidt (Sc) numbers respectively.