Design and optimization of pin fin heat sinks for low velocity applications

This study was undertaken to optimize the design of pin fin heat sinks (PFHS) for use in low velocity applications where there is plenty of open space around for the air to bypass the heat sink, if it encounters a high pressure drop across it. The goal of this study was to maximize the thermal performance and keep the design such that it is easily manufacturable and low in cost. A special test fixture using a heat flux meter was designed to test heat sinks for thermal performance. Several aluminum PFHS having a 25×25 mm base size, heights from 5 to 25 mm, pin arrays of 4×4 to 8×8, and pin fin cross sections from 1.5×1.5 mm to 2.5×2.5 mm were fabricated and tested for thermal performance. Some of the commercial aluminum heat sinks with various surface finishes (such as black anodized, gold chromated, clear anodized and untreated) were also evaluated to determine the effect of surface treatment on thermal performance, Studies were also done to compare the thermal performance of similarly sized pin fin and extruded plate fin heat sinks. The heat sink tester and test data for heat sinks used in this optimization study are reviewed in this paper. Results show that it is possible to design an optimum PFHS for any flow situation. However, it is not realistic to have several heat sink designs to cover various applications. In low velocity (about 1 m/s or less) unshrouded flow, the best compromise for an aluminum PFHS with about 25×25 mm base size and heights up to 15 mm is the 6×6 pin fin configuration with fin cross sections of 1.5×1.5 mm