Heat exchangers are devices used in industrial processes for the thermal energy transfer. These are available in the market in different types and geometries. In the petrochemical industry, heat exchangers networks are employed in order to obtain the energy necessary for the crude preheating, essential process in petroleum refining for oil separation into various fractions. Due to its thermal performance, low cost and easy maintenance, shell and tube heat exchangers are widely used. One of the configurations of such exchangers, consisting of a fixed tube arrangement supported by baffles, was studied using Computational Fluid Dynamics (CFD), to represent qualitative and quantitatively the physical phenomena of the process. The flow in the shell side and the baffles inclination effect in heat transfer were analyzed by comparing results for three different baffle inclination angles (zero, ten and twenty degrees), using a commercial program of Computational Fluid Dynamics, ANSYS CFX 14.0. The shell side outlet temperature, the optimum baffle inclination angle and the optimal mass flow rate were determined. The simulation model and geometries were validated with data obtained from a study of the Middle East Technical University (2010).