Entropy generation for a viscous, forced convection through
enhanced rough tubes subjected to constant heat flux was numerically
investigated. The entropy generation and exergy destruction due to the flow
friction and heat transfer was proposed to evaluate the benefits of the utilisation
of different enhanced tubes. The model was based on either measurements or
empirical correlations for both the flow and heat transfer characteristics in plain
and enhanced tubes. Flow of different fluids in rough tubes with
threedimensional internal extended surfaces (3-DIES) were studied. Enhanced
rough tubes, either with continued or regularly spaced tape inserts were
investigated. Based on exergy performance, it was found that the use of hollow
3-DIES tubes in water turbulent flow regime is preferable while segmented
twistedtape inserts is attractive in laminar flow. Also, inline 3-DIES rough
tubes indicate a lower exergy destruction rate when compared with that of
staggered alignments. The correlation for both optimum Reynolds number
(Re*) and minimum percentage exergy destruction (Ψmin%) were obtained for
oil and Ethylene Glycol flows in inline 3-DIES rough tubes as a function of the
exposed heat flux, Prandtl number and the tube ratio (L/D). |
