A numerical investigation of mixed convection in air due to the interaction between a buoyancy flow and the flow induced by a moving plate in a vertical channel is carried out. An unheated plate moves at a constant velocity in the direction of the buoyancy force and the principal walls of the channel are heated at uniform heat flux. The effects of the channel spacing, heat flux and moving plate velocity are investigated and results in terms of the channel walls and moving plate temperatures, air velocity profiles inside the channel, wall stress along the channel wall and the moving plate and Nusselt numbers are given. A composite correlation between Nusselt number and Reynolds and Richardson numbers is proposed in the range from natural convection to forced convection up to Re = 1.32 × 10 4 and 9.86 × 10 −6 ≤ Ri ≤ 1.15 × 10 3 , for the channel aspect ratio in the [20.3–81.2] range.