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 adiabatic plate moves at a constant velocity in the mid-plane of the channel 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 aspect ratio, Rayleigh and Reynolds numbers are investigated and results in terms of the dimensionless channel wall and moving plate temperatures are given. Results show that the larger the channel aspect ratio, L/(b/2), the stronger the effects of the moving plate. Increasing Reynolds number significantly decreases the dimensionless temperature of the channel walls. 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 x 10(4) and 9.86 x 10(-6) <= Ri <= 1.15 x 10(3), for the channel aspect ratio in the [20.3-81.2] range. (C) 2008 Elsevier Ltd. All rights reserved.