Numerical analyses are conducted for combined free and forced laminar convection in the thermal entrance region of inclined pipes with buoyancy-aided flow. The effects of buoyancy force

pipe inclination angle and axial conduction on the hydrodynamic and heat transfer characteristics are investigated

and numerical res-ults of velocity and temperature profiles

distributions of the Nusselt numbers and wall shear stress are obtained. The velocity and temperature profiles are distorted and become asymmetric

and a reverse flow occurs near the pipe top as the buoyancy effect becomes significant. The wall shear stress varies from minimum at the top pipe wall to maximum at the bottom pipe wall. The axial conduction effect becomes significant at low Pe number. The circumferential average Nusselt number reaches a maximum at an inclination angle between 25° and 45° for Pe=71 but the maximum appears at α=90° for Pe=2.5.