A numerical study has been carried out to investigate the mixed convective two dimensional flows in a vertical enclosure with heated baffles on side walls. All walls are assumed to be adiabatic, but baffles are considered as isothermally heated. Thus, cold flow is imposed through an opening at the bottom of the left wall and by taking heat from the baffles the fluid becomes heated and exits through outlet at the top of the right wall of the enclosure. Heated baffles are placed both at the left and right wall of the enclosure. The present study simulates a practical system such as a silencer. The consequent mathematical model is governed by the coupled equations of mass, momentum and energy and these equations are discritized. The discritized equations with specified boundary conditions are sought by Successive under Relaxation (SUR) method. A wide range of pertinent parameters such as Reynolds number 50 ≤ Re ≤ 300, Richardson number 0 ≤ Ri ≤ 10 and Prandtl number 0.01 ≤ Pr ≤ 2.0 are considered in the present study. Various results such as the streamlines, isotherms, heat transfer rates in terms of the average Nusselt number and temperature and also heating efficiency in the enclosure are presented for different parameters. It is observed that Maximum heating efficiency is found at higher value of Reynolds and Richardson number.