Fundamental Investigations for Very High Heat-Flux Innovative Operations of Milli-Meter Scale Flow Boilers

高热流的去除在许多关键应用中至关重要，例如电子冷却或数据中心冷却（电子处理器或组件产生的热量必须迅速消散以保持它们可靠地工作）。消除热量最有效的方法之一是通过相变过程，例如在加热装置背面集成的冷却通道中沸腾。在电子应用中，热量通常是在芯片级产生的，由于尺寸小，由于蒸汽阻塞通道和通道不稳定，会产生显着的功能和沸腾效率问题。提出的研究将集中在如何通过确保加热表面有一层薄的连续蒸发膜来克服效率问题。这些方法的成功开发将确保提高计算机和电子设备的可靠性，并实现更密集的包装和更小的占地面积。在提出的研究中，预计在外部施加的两相（液体和蒸汽）脉动下具有高的热流通量能力。由于脉动产生了薄而波状的沸腾液体膜，并覆盖了整个热交换表面。研究将证实是否可以通过适当调整平均准稳定膜厚剖面（在没有脉动的情况下）以及控制叠加波的幅度（通过控制施加脉动的幅度）来实现沿流动锅炉长度的高热通量值。这是可以预料的，因为靠近波槽的液膜流动动力学是由接触线流动物理控制的，这导致波槽在热交换表面附近“粘住”。因此，在所提出的脉动操作下，在大多数位置，平均液膜厚度将显著减小，对流效应（在换热面和液汽界面之间的液体流动）将同时增加。

CBET-1402702High heat flux removal is of critical importance in a number of key applications such as electronic cooling or data center cooling (where heat generated by electronic processors or components have to be rapidly dissipated to keep them working reliably). One of the most effective ways of removing heat is through a phase change process such as boiling in cooling channels integrated on the back side of the heat-generating device. In electronic applications, the heat is typically generated at the chip-level, and due to the small sizes, significant functionality and boiling efficiency problems arise due to the vapor blocking the channel, and instabilities in the channel. The proposed research will focus on methods that will overcome the efficiency issues by ensuring a thin continuously evaporating film on the heated surface. Successful development of these methods will ensure improved reliability of computer and electronic devices and enable denser packaging and smaller footprint.For the proposed study, high heat-flux capabilities are expected under externally imposed pulsations in the two phases (liquid and vapor). Thin and wavy boiling liquid films arise as a result of the pulsations, and cover the entire heat-exchange surface. Investigations will confirm if one can achieve high heat-flux values along the length of the flow boiler by a suitable adjustment of the mean quasi-steady film thickness profile (in the absence of pulsations) along with amplitude control of superposed waves (by controlling the amplitude of imposed pulsations). This is expected because the liquid film flow dynamics near the wave-troughs are dominated by the contact-line flow physics which causes the wave-troughs to "stick/dwell?" near the heat exchange surface. Therefore, under the proposed pulsatile operations, at most locations, the mean liquid film thickness will be significantly reduced and convection effects (in the liquid flow between the heat-exchange surface and the liquid-vapor interface) will be concurrently increased.