Flow boiling in copper microchannel heat sink is widely used for the cooling of high power electronic modules, particularly the IGBT power electronic modules with large sizes. However, it is challenging to significantly enhance the flow boiling performance of copper microchannel heat sink due to the long-lasting issue of vapor backflow and liquid supply that severely deteriorates flow boiling heat transfer. Also, a high channel length to hydraulic diameter ratio (L/Dh) of a large heat sink is not favorable for efficient two-phase transport, resulting in the early occurrence of boiling crisis. In this work, a relatively large copper heat sink (L × W = 10 cm × 5 cm) comprised of Tesla microchannels characterized with excellent flow diodicity was designed and fabricated. The L/Dh ratio of the as-designed heat sink is about 220, which is much larger than the reported studies. In this new heat sink, the periodic Tesla valve structures in each channel is capable of inhibiting the severe vapor backflow to dramatically enhance the two-phase transport and then delay the dryout of heating surface. To demonstrate the advantages of our design, the flow boiling performances in terms of heat transfer coefficient (HTC), critical heat flux (CHF), and two-phase flow stabilities were experimentally studied and a comprehensive comparison against a heat sink consisted of plain-wall microchannels is presented. Experiments were conducted on DI-water with total inlet flow rate varying from 20 ml·min-1 to 50 ml·min-1. The results of this study show that flow boiling performances and two-phase flow stabilities are significantly enhanced owing to the successful suppression of two-phase backflow and efficient two-phase transport. For example, at a flow rate of 50 ml·min-1, the CHF and HTC of this design in the forward direction are about 30.6 W·cm-2 and 49.7 kW·m-2K-1, respectively, accompanied by significant enhancements of 57.4 % and 106.7 %, respectively, in contrast to the heat sink with plain wall microchannels. Additionally, the standard deviations (STD) of wall temperature and pressure drop of the conventional heat sink are 17.1 and 12.6 times higher than that of this new heat sink. Visualization studies were conducted to elucidate the working mechanism of Tesla valves in regulating vapor backflow.

中文翻译：

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在由 Tesla 微通道组成的相对较大的铜散热器中流动沸腾


铜微通道散热器中的流动沸腾广泛用于大功率电子模块的冷却，尤其是大尺寸 IGBT 电力电子模块。然而，由于蒸汽回流和液体供应的长期问题严重恶化了流动沸腾传热，因此要显著提高铜微通道散热器的流动沸腾性能是一项挑战。此外，大型散热器的高通道长度与水力直径比 （L/Dh） 不利于高效的两相传输，导致沸腾危机的早期发生。在这项工作中，设计和制造了一个相对较大的铜散热器 （L × W = 10 cm × 5 cm），该散热器由具有优异流动二极管性的特斯拉微通道组成。设计散热器的 L/Dh 比约为 220，比报道的研究大得多。在这个新的散热器中，每个通道中的周期性特斯拉阀结构能够抑制严重的蒸汽回流，从而显着增强两相传输，然后延迟加热表面的干燥。为了证明我们设计的优势，我们实验研究了传热系数 （HTC）、临界热通量 （CHF） 和两相流稳定性方面的流动沸腾性能，并与由光壁微通道组成的散热器进行了全面比较。在总入口流速为 20 ml·min-1 至 50 ml·min-1 的去离子水中进行实验。本研究结果表明，由于成功抑制两相回流和高效的两相传输，流动沸腾性能和两相流稳定性得到显著提高。 例如，在 50 ml·min-1 的流速下，该设计的 CHF 和 HTC 在正向方向上分别约为 30.6 W·cm-2 和 49.7 kW·m-2K-1，与具有光壁微通道的散热器相比，分别显着提高了 57.4% 和 106.7%。此外，传统散热器的壁温和压降的标准差 （STD） 分别是这种新型散热器的 17.1 倍和 12.6 倍。进行了可视化研究以阐明 Tesla 阀门在调节蒸汽回流方面的作用机制。