Heat transfer and flow characteristics of channel-bounded circular cylinder with a slit vent parallel to the flow direction are numerically investigated using openfoam. The interesting feature of this configuration is the formation of the separation bubble behind the cylinder, which significantly alters the near wake characteristics. In this study, the emphasis is given to understand the effect of the slit on forced convection from the cylinder. Simulations were performed by varying the slit width from 0 to 0.25 (in steps of 0.05) for the range of Reynolds number (Re) 60–240. Re is defined based on the diameter of the cylinder (d) and centerline velocity (Uc) at the inlet of the channel. The influence of s/d and Re on the separation bubble, aerodynamic forces, and heat transfer characteristics are studied in detail. Results demonstrate that the slit can manipulate the flow to mitigate adverse effects of vortex shedding and thus can be used as a passive flow control technique. It was observed that the inclusion of the slit in the cylinder delays the onset of vortex shedding, and it also reduces the fluctuations in aerodynamic forces up to 99%. Compared with the solid cylinder, around 38% increase in vortex shedding frequency, a 16% reduction in drag, and a 10% increase in average Nusselt number is observed when the slit width is 0.25d. It was found that the introduction of slit vent in the cylinder not only enhances the heat transfer along with the reduction in expenditure of pressure loss across the cylinder but also suppresses the fluctuations in aerodynamic forces, which causes vortex-induced vibrations and thus improves structural stability and integrity.