The heat sink is used to increase heat transfer from heated surface to air. The seize and the geometry of the fins affect on the heat transfer coefficient. The heat transfer prediction represents the first step to get the optimal design. The purpose of the present study is to predict the effectiveness of two types of closely spaced fins, the first arrangement is parallel cylindrical fin array and the second type is hollow parallel cylindrical fin array. Also there are two types of heat sink with respect to the fan location, the first type is the cooling fan attached in order to draw the hot air up and away from the heatsink fixed outside on the heat sink to let the axial air flow and the other with enclosure cutout template. The heat sink geometry are designed with Solidworks 14 and exported to ANSYS FLUENT 15.0.7 CFD code. Reynolds number were taken at a range 4000-16000, so k-Ԑ model turbulence model was used in to simulate mean flow characteristics for turbulent flow conditions. Constant heat flux condition was proposed with range between 1000-10000 kW/m 2. The Results of temperature contour lines depicted a variation from the base to the extended surfaces tips especially with the fins from outside to the core of the heat sink. This explain that the heat sink with a cooling fan fixed in the enclosure cutout template more effect than the second type with second fan fixation for the two types of fins. Nusselt numbers indicated that cylindrical fins performed better in heat transfer than the hollow fins.

The heat sink is used to enhance heat rejection from heated surface to air. The seize and the geometry of the heat sink with the shape of the extended surfaces have a great influence on the heat transfer coefficient. The first step to get the optimal design is to predict the heat transfer by conduction in solid walls of heat sink and then by convection between the solid and air flow. The purpose of the present study is to predict the effectiveness of closely spaced parallel rectangular fin array arrangement. The electronic processor was represented by the copper heat sink base with thermal conductivity of 401 W/m.K. The 72 fins with the geometry above mentioned were exposed to heat transfer with conduction and convection along all the boundaries except the bottom from which heat flow toward air flow domain. Mesh generation at a specific cells, number of element and number of nodes were taken under temperature difference validation. The experiments were done under impinging air flow rate with Reynolds number ranged between 4000-16000. The flow was turbulent so the k-Ԑ turbulence model needed to simulate mean flow characteristics. Constant heat fluxes boundary conditions were proposed with range between 10000-70000 kW/m2. The Results of temperature contour lines depicted a heat trend from the hot base through the extended surfaces to the fin tips. The fins were aligned in the core of heat sink showed higher temperature gradient compared with the fins existed in lines surrounded the core. The thermal resistance decreased as the Reynolds number increased and the Nusselt number increased as the Reynolds number increased and also when the heat flux increased. The Reynolds number depicted increasing as the Nusselt number increased and so the heat rejected from the heat sink base increased. There is a good agreement between the experimental and simulating results at error percentage not exceed 2%.

Heat rejection from electronic components by heat sink is still a viable cooling solution. The optimal heat sink design enables higher heat transfer performance. The purpose of the present study is to predict the effectiveness of heat sink elliptical closely spaced fins subjected to impinging air cooling. The air fan is the main source of impinging air, then its position and direction with the heat sink take the main role in present work. Two positions of fan location are studied. The first position where the fan is outside the heat sink and the second case where the fan is existed in a cut out template. So there are one impinging air inlet with four transverse outlets and one axial exit opposite to the air flow inlet. Reynolds number were taken at a range 3400-16000, the flow was turbulent so k-ϵ model turbulence model was used as our choice to simulate mean flow characteristics for turbulent flow conditions. The heat sink base was subjected to constant heat flux condition and proposed with range between 10000-40000 kW/m 2 to keep the base temperature at a temperature around 100 o C. The Results of temperature contour lines depicted a variation from the base to the extended surfaces tips. The comparison between the two cases results showed high temperature difference in the case with the cut out template. Nusselts numbers indicated that the second case performed better in heat transfer than the first case. The experimental and numerical results showed a good agreement with a difference not exceeding 2%.Cite this article as: Mohammed AA, Razuqi SA. Effect of air fan position on heat transfer performance of elliptical pin fin heat sink subjected to impinging air flow.