Abstract:
Effects of wall confinements (β) and of Prandtl numbers (Pr) on the two-dimensional
laminar flow around a heated tapered trapezoidal bluff body are investigated numerically at low
Reynolds numbers (Re) for 0.71≤Pr≤100 and 12.5%≤β≤50%. The critical Reynolds number (i.e.
the switch from a steady to a time-periodic flow) is calculated and it exists between Re = (36 and
37), (60 and 61) and (91 and 92) for β of 12.5%, 25% and 50%, respectively. The Nu (average)
increases with the increasing value of Re and/or Pr and/or β. The variation of Nu (local) on each
surface of the cylinder and the isotherm contours are presented to clarify the role of Prandtl
number and β on transfer of heat from the trapezoidal bluff body. The maximum heat transfer
enhancement with respect to a square bluff body on the basis of equal projected area is found to
be approximately 31% and 45% for β = 12.5% and 25%, and for Pr=0.71 and Re=1. Finally, the
Colburn heat transfer factor correlations are obtained for the preceding range of settings.
Keywords: Trapezoidal bluff body; Blockage ratio; Critical Reynolds number; Prandtl number;
Nusselt number; the Colburn heat transfer factor and Heat transfer enhancement
