Heat exchangers are an important part of industrial processes that provide a significant amount of the entire energy system. One of the main problems in the use of heat exchangers is the formation of fouling during their utilization. Fouling production in heat exchangers significantly reduces heat transfer and reduces the efficiency of these devices. Also, increasing the thermal resistance and increasing the pressure drop in the heat exchanger are other problems caused by the formation of fouling. Generally, the formation of fouling is a phenomenon that limits and reduces the efficiency of heat exchangers. Today, with the advancement of technology and due to extensive research on the fouling phenomenon in heat exchangers, researchers have developed several methods to control sediment formation, to slow down and delay it. One of the effective and low cost methods for slowing down fouling growth and increasing the time of operation of heat exchangers is to identify effective factors in fouling formation and optimized operating conditions to reduce fouling yield. Modeling of fouling growth is one of the least costly methods for identifying the factors affecting fouling growth. On the other hand, the existence of different mechanisms for the formation of fouling has caused the modeling of this phenomenon to be difficult. Therefore, in most studies on fouling modeling, a mechanism is considered as the dominant mechanism. In this thesis, the fouling process was investigated in one of the heat exchangers of Isfahan refinery to study more accurately fouling formation. To determine the type and mechanism of formation of fouling, the precipitate formed on the side of the heat exchanger tubes was sampled. The type and mechanism of fouling were determined by experiment. Then, using the CFD method, using the fluent 16.2 software and coding capability (UDF), the sedimentation process was modeled by the mechanism. The formation of fouling with its physical properties on the surface of the heat transfer, the variability of the thickness of the fouling layer along the flow path of the fluid, as well as the fouling removal term, distinguishes the modeling from other modeling. To validate the model, the model was implemented for a laboratory case and the results of the modeling were compared with the experimental results and it was observed that the modeling results are in good agreement with the experimental results. After assuring the accuracy of the model, the effect of different operating conditions on the fouling formation rate was investigated. Finally, by using statistical methods and using Minitab software, while obtaining optimal conditions for fouling formation, the model was implemented for fouling in the heat exchanger of Isfahan refinery.