Abstract Homogeneous thin-film agitators used in a channel flow have shown enhanced thermal-hydraulic performances compared to a clean channel benchmark. In this study, an experimental study was carried out to explore the performances of three inverted structurally inhomogeneous stepped agitator designs in the same channel flow in order to further improve the overall thermal-hydraulic performance of a heatsink. The three agitator designs were constructed by connecting two sections of material with different lengths while maintaining the constant total length of 6 mm as in our previous study: a relatively thicker 125-μm material mounted on the channel wall as the trailing edge and a thinner 25-μm material as the free leading edge. The new designs were expected to maximize fluid mixing enhancement but minimize pressure loss due to the unique structure of the inhomogeneous materials. Experiments in this study covered a wide Reynolds number range from 300 to 9000. High-speed footage was used to capture the dynamic motion of the agitators. At the same time, a time-resolved particle image velocimetry (TR-PIV) system was used to characterize the vortex dynamics due to the motion of agitators in various flow conditions. A synthetic thermal-hydraulic performance factor, η, taking into consideration both the Nu number enhancement and friction factor increment, was used to evaluate the overall effects of the added agitator features in the channel flow compared to a clean channel benchmark. Results show that a maximum factor of about 1.5 has been achieved, and it stays above 1 under most of the test conditions in this study, indicating great benefits for enhanced thermal transport.

中文翻译：

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通道流中的倒置结构不均匀阶梯式搅拌器

摘要 与清洁通道基准相比，通道流中使用的均质薄膜搅拌器显示出增强的热工水力性能。在本研究中，为了进一步提高散热器的整体热工水力性能，进行了一项实验研究，以探索三个倒置结构不均匀阶梯式搅拌器设计在同一通道流中的性能。三种搅拌器设计是通过连接两个不同长度的材料部分而构建的，同时保持我们之前研究中 6 毫米的恒定总长度：安装在通道壁上作为后缘的相对较厚的 125 微米材料和较薄的 25 -μm 材料作为自由前缘。由于非均质材料的独特结构，新设计有望最大限度地增强流体混合，但最大限度地减少压力损失。本研究中的实验涵盖了从 300 到 9000 的广泛雷诺数范围。使用高速镜头捕捉搅拌器的动态运动。同时，使用时间分辨粒子图像测速 (TR-PIV) 系统来表征由于搅拌器在各种流动条件下的运动而产生的涡流动力学。综合考虑了 Nu 数增强和摩擦系数增量的综合热工水力性能因子 η 用于评估与清洁通道基准相比在通道流中添加的搅拌器特征的整体效果。结果表明，达到了约 1.5 的最大系数，