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ÖgeNumerical investigation of heat transfer by natural convection from perforated rectangular fin heatsi̇nks for various inclination angles(Graduate School, 2022)It is a fact that all devices produce waste heat during their operation. This produced waste heat must be removed from devices in order to ensure the proper operation of devices. Otherwise, devices would be over heated or even burnt. There are many possible ways of dissipating waste heat from devices in today's industry. These systems are generally called as cooling systems. The cooling systems can be divided into two main categories as active cooling systems and passive cooling systems. Both of them are widely used in industry according to application needs. Both have their own pros and cons, which makes it very important to choose the most suitable cooling system for application. Heat transfer mechanism of active cooling systems is based on forced convection. In these systems circulation of cooling fluid is generated via external fan or blower type devices in order to boost the heat transfer rate, which cause them to be energy dependent systems. They are widely used in electronic devices. Their main advantage over the passive cooling system is that they can achieve higher cooling capacities. The main disadvantage of the active cooling system is their need of energy in order to operate accompanied devices (as fan or blower). This energy requirement increases the cost of cooling system, risk of failure and their noise level. In passive cooling systems, heat transfer is provided by natural convection. In these systems, movement of cooling fluid is generated by the density changes within the cooling fluid that caused by temperature gradients. They are easy to manufacture and also cost effective systems. Since they don't include any moving part, their risk of failure and noise levels are less than the active cooling systems. They don't require any extra energy source in order to operate as in case of active systems. However, their cooling capacity is lower than the active cooling systems but with the help of proper design it can be enhanced drastically. Application of increasing the heat transfer area by using the extended surfaces is widely used approach in passive cooling systems in order to increase heat transfer capacity. Pin heatsinks and plate fin heatsinks are most common two examples of passive cooling systems. In the scope of this study, plate fin heatsinks will be examined closely. Plate fin heatsinks are comprehensively studied subject in literature. The effect of fin height, fin spacing, fin thickness and many other parameters on thermal performance of heatsink have been examined in various studies. Since the direction of flow in natural convection is dependent on the direction of gravity, the thermal performance of plate fin heat sinks is greatly affected by the angle of inclination. It is known that by the proper perforation of plate fin heatsink, thermal performance of heatsink can be increased significantly.