Improvement of the air flow in a cooling system including axial fan and heat sink

Cooling is a concept that is encountered almost everywhere in life. From the cooling of an electronic component in a computer to the cooling of the interior volume of a room, there are many applications that are intertwined with this concept. The purpose of each of these applications is the same. This aim is to cool the targeted region, that is to reduce the temperature of the region. But the reason for cooling a region is a matter of difference. For example, while a refrigerator is cooled to keep food fresh, any electronic card in a furnace has a cooling system because it does not work properly when the temperature rises above a certain temperature and the burning is about to occur. The cooling process, which has a large number of application areas, can be applied to the target region in different ways using different components. For example, a refrigeration system is used which is called a vapor compression refrigeration cycle in which a compressor, an evaporator, a condenser and an expansion valve are used to cool the internal volume of a refrigerator. For instance, in a computer chassis, pipes with water flow inside can be described as a cooling system for electronic equipment in the case. Apart from the mentioned cooling systems, there is another cooling system which uses mainly two components, heat sink with heat pipe and fan. The purpose of this cooling system is to reduce the temperature of the surface where the heat sink is in contact. A cooling system consisting of fan and heat sink with heat pipe can be used in different ways in different devices. This system can be used on a device in an open space, rarely, or in a hollow structure with inlet and outlet openings for safer use. The inlet openings are referred to as air suction for the fan and the outlet openings as air discharge. The fan sucks air through the suction openings and outflows from the discharge openings. Mentioned air openings may have different sizes and geometries. The suction and discharge openings with different areas and shapes directly affect the air flow. With this situation in mind, the concept of flow rate and homogeneous flow related to air flow is emphasized. When concepts have been studied and interpreted for a fan - heat sink with heat pipe cooling system, it has been found that the suction and discharge openings have a direct influence on the air flow rate and homogeneity of the flow. It has also been concluded that the high air flow and homogeneous air flow have a positive effect on cooling performance. In the scope of the thesis, a structure with suction and discharge openings, a fan and a heat sink with heat pipe is considered as the cooling system. The effects of the geometric changes in the suction and discharge openings, the shape of the air flow (homogeneity or non - homogeneity) and the flow rate have been studied numerically and experimentally. It is aimed to take a step in improving the cooling performance by improving the flow. As a result of the literature survey made with the aim of this subject and purpose, the academic articles outlined are summarized and the studies about the flow rate and form of the flow of these academic articles are emphasized. In the scope of the thesis, firstly flow measurement test was carried out in the wind tunnel of an experimental prototype, which is considered as the current situation. This prototype has a straight vent with 2 mm diameter holes. A fan and a heat sink with heat pipe are located within a structure called a cooler chamber. This structure has air outlet openings from the side parts near the base. As a result of the experimental work carried out to make numerical studies reliable, the flow rate obtained was recorded as 13.89 L / s. The velocity of flow was obtained by using this value, and then the Reynold number was calculated. The end result is that the flow has a turbulent structure. The first step of numerical studies using ANSYS 17.2 commercial software is a numerical analysis of the current situation. In the process of realizing this analysis, a mesh independency study was carried out and the concept of mesh quality was examined in detail and the effect of errors caused by mesh on numerical analysis results was minimized. In addition, SST k-omega turbulence flow model was used for all numerical analyzes performed. The flow rate obtained as a result of the numerical analysis of the current situation is recorded as 13.20 L / s. Numerical validation was achieved with a relative error of about 4.97%, compared with the flow rate obtained from the experimental study and the flow rate obtained from the numerical analysis. Considering the velocity contours obtained as a result of the numerical analysis of the current situation, it is concluded that a homogeneous flow does not exist. Particularly, it has been observed that the flow of air through the fins of the heat sink with heat pipe does not have a homogeneous structure. Based on the literature researches made in the scope of the thesis and the results of the numerical analysis of the current situation, it has been decided to make 3 different changes on the current situation. These 3 parameters are; the diameter of the vent holes, the number of outlet openings and their settlement and the geometry of the vent. The vent hole diameters are considered at 3 different levels: 2 mm, 3 mm and 3.5 mm. The number of outlet openings and their settlement is defined as the additional outlet area. The first level of this parameter is the absence of additional outlet slots. The other two levels are those involving additional outlet slots that increase the outlet area by 18% and 30%. Therefore, this parameter is examined at 3 different levels. Finally, the vent geometry is dealt with at two different levels, flat and curved. All possible cases arising from combinations of the levels of said parameters have been determined and numerical analyzes of these cases have been carried out. The flow rates obtained for all cases are noted. The effects of the parameters on the target output (flow rate) were examined separately by using DOE (Design of Experiment) tool of MINITAB 17 commercial software. The amount of increase caused by the parametric changes in the flow rate is expressed in 3 different graphs. The maximum flow rate is obtained when the curved vent with a hole diameter of 3.5 mm is used and there is an additional 30% outlet area. As a result of the numerical analysis, the flow rate obtained for this case was recorded as 18.14 L / s. When the velocity contours of this situation are examined, it is seen that the flow is both faster and more homogeneous than the current situation. Considering the numerical analysis results obtained, the case was chosen as the final case with a curved vent with a hole diameter of 3.5 mm and a 30% additional outlet area. The velocity contours of the current situation and the final case are compared with each other, and an increase in the velocity value in the final case according to the current situation is observed. At the same time, it has been seen that the air flow is in a more homogeneous structure. As a result, it has been found that the change in the suction – discharge geometry of a cooler compartment containing a fan and a heat sink with heat pipe as the cooling system with suction and discharge openings is significant for air flow. The geometric changes mentioned in the thesis have been made to improve the homogeneity of the air flow and the air flow rate has been increased. The work done has an effect on improving the cooling performance.