ABSTRACT

Growth in computational capacity combined with a decrease in the size of digital devices has led to increasing demand for more active and efficient cooling of electronics. In this study, an experimental investigation into two different sizes of central orifice Synthetic Jet Actuators (SJAs) is conducted to evaluate their heat transfer as well as noise generation characteristics. Two SJAs (40 mm and 20 mm) are examined, covering a distinct span of frequencies ranging from low to medium (<5500 Hz) in regards to the effect of SJA size over performance. The SJAs’ disk deflection, structural frequency, and jet exit velocity were measured to fully characterize the jet performance. The maximum Nusselt number for the largest SJA was 3 times more than the smallest SJA, where the evaluation of stroke length suggests no effective synthetic jet formation for the smallest SJA. The noise from the SJAs was measured in an anechoic chamber using three microphones, Fast Fourier Transform (FFT) of the sound pressure levels provide contributions to different tones in the resulting noise. 1/3 Octave Constant Percentage Bandwidth (CPB) analysis was performed to identify the frequency bands making the largest contribution to the noise. The largest SJA showed the highest heat transfer at acceptable noise levels during the operation below resonance frequency.

摘要

计算能力的增长以及数字设备尺寸的减小导致对电子产品更主动和高效冷却的需求不断增加。在这项研究中，对两种不同尺寸的中央孔口合成射流执行器 (SJA) 进行了实验研究，以评估它们的传热和噪声产生特性。研究了两个 SJA（40 毫米和 20 毫米），就 SJA 尺寸对性能的影响而言，覆盖了从低到中 (<5500 Hz) 的不同频率范围。测量了 SJA 的圆盘偏转、结构频率和射流出口速度，以充分表征射流性能。最大 SJA 的最大努塞尔数是最小 SJA 的 3 倍，其中对冲程长度的评估表明，对于最小的 SJA，没有有效的合成射流形成。来自 SJA 的噪声是在消声室中使用三个麦克风测量的，声压级的快速傅里叶变换 (FFT) 对产生的噪声中的不同音调做出贡献。执行 1/3 倍频程恒定百分比带宽 (CPB) 分析以确定对噪声贡献最大的频带。在低于共振频率的操作期间，最大的 SJA 在可接受的噪音水平下表现出最高的热传递。执行 1/3 倍频程恒定百分比带宽 (CPB) 分析以确定对噪声贡献最大的频带。在低于共振频率的操作期间，最大的 SJA 在可接受的噪音水平下表现出最高的热传递。执行 1/3 倍频程恒定百分比带宽 (CPB) 分析以确定对噪声贡献最大的频带。在低于共振频率的操作期间，最大的 SJA 在可接受的噪音水平下表现出最高的热传递。