Pressure drop and thermal resistance characteristics of plain-fin heat sink with impingement flow

Despite extensive research on plain-fin heat sinks with impinging flow, there have been few studies that evaluate the impact of flow nonuniformity on their performance, in spite of the fact that flow nonuniformity at the inlet is a key factor affecting heat sink performance. This study developed a novel methodology to quantitatively assess the flow nonuniformity at the heat sink inlet by combining experimentally measured pressure distributions and numerical analysis. Experiments were conducted with varying flow rates and fin heights ranging from 40 L/min to 180 L/min in the range of 5 mm-25 mm, respectively. A flow nonuniformity index was used to quantify the flow nonuniformity at the heat sink inlet, and its values ranged from 0.2 to 1.3 in all experimental cases. The study demonstrated that flow uniformity can be improved by increasing both the fin height and flow rate. The nonuniformity index-based region map was introduced to estimate the heat sink's thermal resistance and pressure drop behaviors under impingement flow. The study found that the flow condition at the heat sink inlet can be considered as a uniform flow condition when the flow nonuniformity index is less than 0.2, which indicates that the fin height is 25 mm and the Reynolds number is greater than 350 in the present experiments. The heat sink's thermal performance under uniform flow condition was superior to that under nonuniform flow condition at a constant flow rate. In conclusion, the flow condition at the heat sink inlet, along with geometric configuration and flow rate, plays a critical role in the plain-fin heat sink performance with impingement flow.