The present study focuses on the interaction of the buoyancy-driven flow and pressure-driven turbulent flow inside a rectangular channel. The aspect ratio of the channel is maintained at 6 to compare the results with that of the parallel plate channel studies reported in the literature. The study is carried out using the large eddy simulation for Reynolds number of 6500 and Grashof number of 4.2×10⁸. Water is used as the coolant in the channel. The computational domain is divided into two parts viz. developing section and developed section. The top and bottom plate of the developed section of the channel is heated using constant heat flux. It can be observed from the study that the thermal stratification in the top half of the channel reduces the formation of vortices while the thermal instability near the bottom wall leads to a thicker boundary layer as well as highly chaotic turbulent flow. The bottom plate boundary layer is observed to be almost 50% larger than that at the top plate. The vortex structures observed with present boundary conditions are more aligned to the stream-wise direction as compared to the similar flow conditions but with constant temperature boundary condition.