Spray cooling high power dissipation Applications (SANGRIA): From fundamentals to Design

许多技术的进步越来越依赖于从小区域耗散大量热量的能力。目前电力电子、超级计算机、激光器、X射线医疗设备、核聚变反应堆覆盖层、航天器和混合动力汽车电子设备的设计以及未来的改进都依赖于创纪录的高传热率。这种设备所需的散热速率的快速增加导致了从更传统的风扇冷却散热器附件到液体冷却技术的转变。然而，在单相中操作的液体冷却技术现在已经达到其极限，被迫在非常低的入口温度和极高的质量流率下运行，导致不可接受的高压降和表面温度梯度。迫切需要创新的方法来克服这些重大缺点：其中一种方法是喷雾冷却。喷雾冷却使用喷嘴将液体冷却剂分解成细滴，这些细滴单独地撞击在加热表面上。“低温”和“高温”喷雾冷却应用分别涉及低于和高于临界热通量（CHF）的表面温度。单相喷雾冷却（仅依赖于液体显热上升）提供比液体冷却更高的操作稳定性和空间均匀的热去除，降低了大的表面热梯度的可能性，这对于易碎的电子元件尤其重要。两相喷雾冷却（依赖于液体显热上升和潜热）上级单相系统，此外，与池/流动沸腾替代系统相比，对从加热表面去除蒸汽的阻力小得多，从而实现上级的液滴表面接触。事实上，在两相应用中，CHF从1.2 MW/m2（水池沸腾）增加到10 MW/m2（水喷雾）。SANGRIA是一个雄心勃勃的3年合作研究计划，旨在研究喷雾冷却的基本机制和传输过程。该项目结合了尖端的实验技术，提供时空分辨的热，界面和流体动力学领域的诊断，多尺度理论，建模和3-D高保真数值模拟，桥接分子和连续尺度。SANGRIA产生的深刻见解将被利用来提供我们的工业合作伙伴实际可实施的工具，以最大限度地发挥影响。工业和学术合作伙伴将在研究计划期间提供额外的技术支持和反馈，以及直接影响工业的途径。工业伙伴包括这一技术的可能用户：TMD有限公司（电子设备、高热通量装置制造商）; Oxford naNosystems（强化传热表面制造商）; ANSYS（软件开发）; Siemens（软件开发）; Spraying Systems Co.（喷嘴制造商）; Syngenta（喷嘴用户）。LaVision为他们的粒子大师系统提供了15%的折扣。来自诺丁汉大学、索邦大学、达姆施塔特工业大学和九州大学的学术合作伙伴是国际公认的单相和两相热系统专家，包括喷雾冷却。在HEXAG和PIN会议期间的参与和介绍将促进反馈和技术转让。

The advancement of numerous technologies has become increasingly reliant on the ability to dissipate large quantities of heat from small areas. Current designs in power electronics, supercomputers, lasers, X-ray medical devices, nuclear fusion reactor blankets, spacecraft, and hybrid vehicle electronics, and future improvements, rely on record high heat transfer rates. This rapid increase in heat dissipation rates required by such devices has led to a transition from more traditional fan-cooled heat-sink attachments to liquid cooling techniques. Liquid cooling techniques operating in single-phase, however, have now reached their limit being forced to run at very low inlet temperatures and exceedingly high mass flow rates, resulting in unacceptably high pressure drops and surface temperature gradients. Innovative approaches are urgently needed to overcome these significant shortcomings: one such approach is spray-cooling. Spray-cooling uses a nozzle to break up the liquid coolant into fine droplets that impinge individually on a heated surface. 'Low'- and 'high-temperature' spray-cooling applications involve surface temperatures below and above the critical heat flux (CHF), respectively. Single-phase spray-cooling (relies on liquid sensible heat rise only) provides greater operational stability and spatially uniform heat removal than liquid cooling, reducing the likelihood of large surface thermal gradients, particularly important for fragile electronic components. Two-phase spray-cooling (relies on liquid sensible heat rise and latent heat), are superior to single-phase systems and furthermore, compared to pool/flow boiling alternative systems, offer far less resistance to vapour removal from a heated surface enabling superior drop-surface contact . In fact, the CHF increases from 1.2 MW/m2 (for water pool boiling) to 10 MW/m2 for water sprays in two-phase applications.SANGRIA is an ambitious 3-year collaborative research programme aimed at investigating the fundamental mechanisms and transfer processes underlying spray-cooling. This project combines cutting-edge experimental techniques that furnish spatiotemporally-resolved diagnostics of the thermal, interfacial, and hydrodynamic fields, with multi-scale theory, modelling and 3-D high-fidelity numerical simulation that bridge the molecular and continuum-scales. The deep insights generated from SANGRIA will be harnessed to provide tools that are practically implementable by our industrial partners in order to maximise impact.Industrial and academic partners will provide additional technical support and feedback during the research programme plus pathways for direct industrial impact. The industrial partners include possible users of this technology: TMD Ltd (manufacturers of electronic equipment, high heat flux devices); Oxford naNosystems (manufacturers of enhanced heat transfer surfaces); ANSYS (Software development); Siemens (Software development); Spraying Systems Co. (Nozzle manufacturers); Syngenta (users of nozzles). LaVision offered a 15% discount on their Particle Master System. The academic partners from the University of Nottingham, Sorbonne University, Technical University of Darmstadt and Kyushu University are internationally recognised experts in single and two-phase thermal systems, including spray cooling. Participation and presentations during the HEXAG and PIN meetings will facilitate feedback and technology transfer.