n the industrial world, heat transfer is one of the phenomena occurring in many important industrial processes. Sometimes we need to add heat and sometimes to remove heat from the systems and the streams. For instance, we use different kinds of heat exchangers. Such as shell-and-tube, plate, helical, spiral and so many other types. Another application of transferring heat is in electrical engineering. In which the goal is to improve the thermal performance of electrical systems like CPUs and Hard Disk Drives. Moreover, Heating, ventilation, and air-conditioning in buildings need an understanding of heat transfer processes to efficiently design HVAC systems. Forced and natural convection, conduction, and radiation are different mechanisms of heat transfer. Phase change including boiling, condensation, and melting may occur in different applications and systems. This happens in the cases that energy is transferred between two or more substances. We want to emphasize that accurate CFD modeling and analysis of the heat transfer mechanisms in such systems leads to cost-effective and optimum designs. By means of heat transfer analysis using ANSYS Fluent, a designer can find out how much heat dissipation we require. what the most efficient cooling method is, and which components are overheated once the system is exposed to a specific heat source.