Analysis of laminar flow and heat transfer in the entrance region of an internally finned circular duct

Steady laminar forced convection flow and heat transfer in the entrance region of an internally finned circular duct has been analyzed by numerically integrating the governing partial differential equations. The fins are radial continuous and of zero thickness. Two types of thermal boundary conditions are considered: a uniform heat input per unit axial length with peripherally uniform temperature at any cross-section, and uniform temperature both axially and peripherally. Results exhibit the expected high-pressure gradients and heat transfer coefficients in the entrance region, approaching asymptotically the fully developed values at large axial distance. Results are presented for 8, 16, and 24 fin and for fin-height/duct-radius ratios 0.3, 0.6, and 1. The Prandtl number is kept as .707, corresponding to air.