EAGER: Innovative 3-D, multiscale flow-boiling wick

许多热系统依赖于对蒸发表面的被动（毛细管）或主动（泵送）液体供应。在蒸发表面附近，液体供应和蒸汽去除必须竞争（例如，池和流动沸腾），除非它们被保持液体（润湿相）和蒸气的毛细管体分开。在大的局部热通量下的有效热传递继续需要创新和变革的表面增强设计，并且一个场所已经使用毛细管体来控制邻近蒸发表面的相的分布。虽然毛细作用为液体供应到表面提供吸力，但需要考虑各种液体和蒸汽阻塞限制，因此这是具有重要应用的基本热工水力问题。 提出了一种新型的三维、多尺度、分布式蒸发芯散热器，其饱和液体散热能力可达1000 W/cm ~ 2，这将是一项新的纪录。建议在互联网上创建和提供毛细管体的说明性热工水力学，如冠芯（CW）。该项目对CW的理论优化的结果将推进高通量源的热管理，并将用于与工业界的合作，该工业界将在高热流下制造和测试热沉原型，代表高功率激光应用中发现的热通量。在饱和流动沸腾中，局部热阻取决于局部相分布、重力方向和两相流不稳定性。提出了一种独特的芯结构来控制液体输送、蒸汽去除和热传递，使得该阻力与位置（距前缘的距离或局部蒸汽质量）和重力无关，并将其减小到小于0.05 K/（W/cm 2）（即，传热系数大于2 × 105 W/m2-K），并将干燥极限[临界热通量（CHF）]提高到大于1000 W/cm 2。这种多维毛细结构，称为冠状芯（CW）的目的是分离和控制的液体和蒸汽的流动路径的基础上集成的蒸发和蒸汽逃逸结构。CW将液体输送和液体扩散蒸发功能分开，是PI和Advanced Cooling Technologies（ACT）Inc.先前开发的调制芯的演变。用于被动系统（池沸腾和蒸汽室）。CW向覆盖加热表面的薄蒸发芯（烧结颗粒单层，其中后退的弯月面和局部热不平衡允许低热阻）提供液体，通过高渗透性液体引导多个动脉（柱）芯延迟表面干燥（增加CHF），并通过穿孔的屏蔽层顶部创建蒸汽空间和通风。筛顶穿孔开口和间距的选择是为了在其上方的液体边界层流动中产生蒸汽流惯性或延迟蒸汽层的形成。在拟议的实验中，CW将由烧结的微米铜颗粒构成（与单层相比，柱的颗粒更大）和穿孔铜屏蔽层（几层金属丝网），并在水流沸腾下单侧加热（大横截面积通道）进行测试。三个多孔体中的级联毛细管压力（液体压力）通过孔径选择来仔细匹配，以确保不间断的液体流动。柱的高度和节距为毫米量级，蒸汽预成形节距可以大于柱以控制离开的蒸汽动量，并且通道将具有厘米量级的水力直径。

Many thermal systems rely on passive (capillary) or active (pumping) liquid supply to evaporation surfaces. Adjacent to evaporation surface, liquid supply and vapor removal have to compete (e.g., pool and flow boiling) unless they are separated with capillary bodies holding the liquid (wetting phase) and vapor. Efficient heat transfer under large local heat flux continues to demand innovative and transformative surface enhancement designs, and one venue has been use of capillary bodies to control distribution of phases adjacent to the evaporation surface. While the capillarity provides the suction for the liquid supply to the surface, there are various liquid and vapor choking limits to consider, so this is a fundamental thermal-hydraulic problem with important applications. A new three-dimensional, multilength scale, distributed evaporation wick is proposed for heat sink capable to removing 1000 W/cm2 with saturated liquid, and this will be a record. It is proposed to create and make available on Internet, illustrative thermal-hydraulics of the capillary bodies, such as the canopy wick (CW). The results of this project on theoretical optimization of CW will advance the thermal management of high-flux sources and will be used in a collaboration with industry which will fabricate and test a heat-sink prototype at high heat fluxes representative of those found in high-power laser applications. The industry collaboration allows for industrial interactions for the University of Michigan students.In saturated, flow boiling the local thermal resistance depends on the local phase distributions, gravity direction, and two-phase flow instabilities. A unique wick structure is proposed to control the liquid delivery, vapor removal, and heat transfer making this resistance independent of the location (distance from the leading edge, or local vapor quality) and gravity, and reducing it to less than 0.05 K/(W/cm2) (i.e., heat transfer coefficient lager than 2x105 W/m2-K), and increase the dryout limit [critical heat flux (CHF)] to larger than 1000 W/cm2. This multidimensional capillary structure, called the canopy wick (CW) aims at separating and controlling the liquid and vapor flow paths based on the integrated evaporation and vapor-escape structures. The CW divides the liquid delivery and liquid spreading-evaporation functions and is an evolution of the modulated wicks previously developed by PI and Advanced Cooling Technologies (ACT) Inc. for passive systems (pool boiling and vapor chambers). The CW provides liquid to a thin evaporation wick (sintered particle monolayer, where the receding meniscus and local thermal nonequilibrium allow for low thermal resistance) covering the heated surface, delays surface dryout (increasing CHF) through high-permeability liquid-directing multiple artery (posts) wick, and creates vapor space and venting with perforated screenlayer roof. The screen-roof perforation opening and pitch are selected to create vapor flow inertial or delayed formation of vapor blanket in the otherwise liquid boundary-layer flow over it. In the proposed experiment, the CW will be constructed from sintered micrometer copper particles (larger particles for posts compared to monolayer) and perforated copper screenlayer (few layers of wire screen), and tested under water flow boiling with one-side heating (large cross-section area channel). The cascading capillary pressure (liquid pressure) in the three porous bodies is carefully matched by pore-size selection to ensure uninterrupted liquid flow. The post height and pitch are of the order of millimeter, the vapor preformation pitch may be larger than the posts to control the exiting vapor momentum, and the channel will have a hydraulic diameter of the order of centimeter.