ABSTRACT
A modified form of the Bejan number (Be), originally proposed by Bhattacharjee and Grosshandler for momentum processes, is obtained by replacing the dynamic viscosity (m) appearing in the original proposition with the equivalent product of the fluid density (r) and the momentum diffusivity of the fluid (n). 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 Be to other diffusion processes, such as a heat or a species transfer process, by simply replacing the diffusivity coefficient. Consequently, a general Be 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 Be turn out to be the same.
KEYWORDS
PAPER SUBMITTED: 2013-02-11
PAPER REVISED: 2013-02-11
PAPER ACCEPTED: 2013-02-15
PUBLISHED ONLINE: 2013-04-13
THERMAL SCIENCE YEAR
2013, VOLUME
17, ISSUE
Issue 2, PAGES [631 - 633]
- Bhattacharjee, S., Grosshandler,W. L., The Formation of a Wall Jet Near a High Temperature Wall under Microgravity Environment, Proceedings, ASME 1988 National Heat Transfer Conference, Houston, Tex., USA, 1988, Vol. 1 (A89-53251 23-34), pp. 711-716
- Petrescu, S., Comments on the Optimal Spacing of Parallel Plates Cooled by Forced Convection, International Journal of Heat and Mass Transfer, 37 (1994), 8, pp. 1283
- Awad, M. M., A New Definition of Bejan Number, Thermal Science, 16 (2012), pp. 1251