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

CBET-1402702高热流排出在电子冷却或数据中心冷却等关键应用中至关重要(电子处理器或组件产生的热量必须迅速散失，以保持其可靠工作)。最有效的散热方法之一是通过相变过程，例如在集成在制热设备背面的冷却通道中沸腾。在电子应用中，热量通常在芯片级产生，由于尺寸小，由于蒸汽阻塞通道和通道中的不稳定性，会出现显著的功能性和沸腾效率问题。拟议的研究将集中在通过确保加热表面上连续蒸发薄膜来克服效率问题的方法。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，并实现更密集的封装和更小的占地面积。对于拟议的研究，预计在外部施加脉动的两个相(液体和蒸汽)下具有高热流能力。脉动产生的沸腾液膜薄而起伏，覆盖了整个换热表面。研究将证实，是否可以通过适当调整平均准稳态油膜厚度分布(在没有脉动的情况下)和叠加波的幅度控制(通过控制施加的脉动的幅度)来获得沿流动锅炉长度的高热流量值。这是意料之中的，因为波谷附近的液膜流动动力学是由接触线流动物理控制的，这导致波谷“粘/停？”在热交换面附近。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，而对流效应(在换热面和汽液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.