Experimental study of the heat sink assembly with oblique straight fins

Vertical planar fin array is used in conventional heat sinks for CPU cooling to create extended surfaces for the enhancement of heat transfer. The cross-sectional areas within this parallel fin array always remain unchanged. However, as the number of fins increases to meet the challenging task generated from a high-speed CPU, the area of the flow channel decreases and the flow resistance thus grows considerably in spite of the increase in the heat transfer areas. In this work, to reduce this undesired blockage on the incoming airflow, oblique planar fins were utilized in heat sink assemblies to improve the overall performance of the heat sink assembly. In addition, a high-pressure, axial-flow fan (70 × 70 × 15 mm3) was designed to incorporate with the vertical and oblique fins to form complete heat sink assembly units. The prototypes were fabricated using a CNC machine. Besides, a CPU simulator for an Intel Pentium IV processor was constructed and utilized to execute the thermal-performance measurement for comparison with the reference fan. The amount of power consumption the CPU simulator used was 82 W. Experimental results indicate that, due to the larger surface area and accelerating flow between the fins, the heat sink assembly with oblique planar fins shows better performance than that with typical vertical fins. For the case of high-pressure fan operating at 2000 rpm, the extra cooling effect could result in a reduction of 6 °C on the CPU case temperature by introducing oblique fins. Furthermore, even though the flow-rate of the designed fan operating at 4000 rpm was only 31.4 CFM, which was 5.7 CFM lower than the reference fan, its static pressure and static efficiency were, respectively, 1.3 mm Aq and 3.8% higher than those of the reference fan. At low flow rates, the designed fan yields a better heat-dissipation capability than the reference fan. Obviously, the static pressure of cooling fan is the dominant factor for a high-resistance heat sink assembly.