摘要

Mixed convection upward flow in a vertical tube with uniform heat flux has been studied numerically. The three dimensional elliptic conservation equations with variables physical properties and the Launder & Sharma low Reynolds k-ε turbulent model were used to study developing flow for Re=1000 over a wide range of Grashof numbers. The results show that two transitions occur in the fully developed region: at a first critical Grashof number the flow changes from laminar to turbulent and then, at a second higher critical Grashof number the flow changes from turbulent to laminar. The axial evolution of the turbulent kinetic energy, axial velocity profile, skin friction and of the Nusselt number is presented for different Gr.