The cooling system is a key factor in power transformer designs. The frequent need for optimized projects further increases the importance of development through of increasingly developed tools. This work aims to evaluate a transformer design, in which the refrigeration is performed through of exhaust fans and heat exchangers installed on the lower side of the transformer. The model is elaborated applying a symmetry, reducing the model to be analyzed. In order to evaluate the best configuration in terms of positioning, flow rate and quantity of understand the main thermal and fluid dynamics characteristics of the flow inside the transformer, the Computational Fluid Dynamics tool is used. The methodology employed is to solve the numerically, through the ANSYS CFX computational package, the flow and energy equations inside the transformer tank.