BOiliNg flows in SmAll and mIcrochannels (BONSAI): From Fundamentals to Design

BONSAI是一个雄心勃勃的3年研究项目，旨在研究沸腾流动的基本传热和传质特性在沸腾通道。它将基于空间/时间分辨诊断的尖端实验与高保真界面分辨数值模拟相结合，最终为高性能紧凑型蒸发器提供经过验证的热设计工具。拟议的项目汇集了伦敦帝国理工学院、伦敦布鲁内尔大学和诺丁汉大学研究人员的多学科专业知识，并得到了3个世界领先的研究机构的支持：艾伦图灵研究所、欧洲核子研究中心（瑞士）和VIR 2AL;以及11个行业合作伙伴：Aavid Boyd Thermacore，Alfa拉瓦尔，CALGAVIN，HEXAG&PIN，HiETA，Hubbard/Daikin，IBM，Oxford nanoSystems，Ricardo，由微电子工业驱动的器件封装的最近趋势已经对从cm 2量级的面积去除MW/m2量级的较高热负荷提出了越来越高的需求。在某些应用（例如制冷）中，需要新的“绿色”制冷剂，但由于易燃性或成本，需要小体积的制冷剂，而在其它应用（例如用于EV和其它应用的电池）中，不均匀或不稳定的散热对性能和寿命非常有害。多微通道蒸发器中的流动沸腾有望以低流体体积满足这种具有挑战性的要求，还允许在远远超出当前技术水平的系统中实现更好的温度均匀性和更小的泵送功率。（热交换）和环境（有效的能量利用）的兴趣，近年来对沸腾传热的理解有所提高，重点是流型转变和特性，压降和传热性能。然而，我们目前的理解还不足以促进这些微型换热器在工业中的更广泛应用，这仍然是未开发的。BONSAI专门针对解决蒸发设备中沸腾的基本现象及其与工业设计的相关性而定制。要解决的挑战包括通道形状和表面特性对流动不稳定性的影响，传热和压降，以及液体-蒸汽界面随时间变化的演变，薄液膜动力学，流场，干蒸汽补丁，热点和局部传热特性之间的关系。将通过理论和新颖的机器学习方法开发基于物理的设计工具，以预测工业相关热工水力参数对系统性能的影响。与我们合作伙伴的合作将确保与工业需求保持一致，并加速向工业转移技术。此外，HiETA将提供金属增材制造散热器，这些散热器将根据压印技术进行评估，作为批量生产微通道热交换器的方式，Oxford nanoSystems将提供纳米结构表面涂层，和IBM将支持参观他们的研究实验室，重点是数值求解器的有效并行化和扩展研究。拟议的研究不仅将使两个-这不仅将有助于提高阶段热解决方案的效率，从而满足各工业部门当前和未来的需求，而且还将提高数据中心的热管理效率，从而减少能源消耗和碳足迹，并回收和再利用目前被丢弃的废热。这将是实现英国2050年排放目标的重要一步。此外，邦赛将与EPSRC 2016-20年交付计划的繁荣成果相结合，并实现与制造未来主题相关的技术进步，为建设一个生产力和弹性国家做出贡献。

BONSAI is an ambitious 3-year research project aimed at investigating the fundamental heat and mass transfer features of boiling flows in miniaturised channels. It combines cutting-edge experiments based on space/time-resolved diagnostics, with high-fidelity interface-resolving numerical simulations, to ultimately provide validated thermal-design tools for high-performance compact evaporators. The proposed project assembles multidisciplinary expertise of investigators at Imperial College London, Brunel University London, and the University of Nottingham, with support from 3 world-leading research institutes: Alan Turing Institute, CERN (Switzerland) and VIR2AL; and 11 industry partners: Aavid Boyd Thermacore, Alfa Laval, CALGAVIN, HEXAG&PIN, HiETA, Hubbard/Daikin, IBM, Oxford nanoSystems, Ricardo, TMD and TTP.The recent trend towards device miniaturisation driven by the microelectronics industry has placed an increasing demand on removing higher thermal loads, of order of MW/m2, from areas of order cm2. In some applications (e.g. refrigeration) new 'green' refrigerants are needed, but in small volumes due to flammability or cost, while in others (e.g. batteries for EV and other applications) non-uniform or unsteady heat dissipation is highly detrimental to performance and lifetime. Flow boiling in multi-microchannel evaporators promises to meet such challenging requirements with low fluid volumes, also allowing better temperature uniformity and smaller pumping power, in systems that go well beyond the current state-of-the-art. Due to significant industrial (heat exchange) and environmental (efficient energy use) interest, the understanding of boiling heat transfer has improved in recent years, with focus on flow pattern transitions and characteristics, pressure drop, and heat transfer performance. However, our current understanding is simply insufficient to facilitate the wider use of these micro-heat-exchangers in industry, which remains unexploited.BONSAI has been tailored specifically to address the fundamental phenomena underlying boiling in miniaturised devices and their relevance to industrial design. The challenges to be addressed include the impact of channel shape and surface characteristics on flow instabilities, heat transfer and pressure drop, and the relationship between the time-dependent evolution of the liquid-vapour interface, thin liquid-film dynamics, flow field, appearance of dry vapour patches, hot spots, and local heat transfer characteristics. The extensive experimental/numerical database generated will be exploited via theoretical and novel machine-learning methods to develop physics-based design tools for predicting the effects of industrially-relevant thermohydraulic parameters on system performance. The collaboration with our partners will ensure alignment with industrial needs and accelerate technology transfer to industry. In addition, HiETA will provide Metal Additive Manufacturing heat sinks that will be assessed against embossing technologies as ways of mass-producing microchannel heat exchangers, Oxford nanoSystems will provide nano-structured surface coatings, and IBM will support visits to their Research Labs focussed on efficient parallelisation of the numerical solver and scale-out studies.The proposed research will not only enable a wider adoption of two-phase thermal solutions and hence the meeting of current and future needs across industrial sectors, but also will lead to more efficient thermal management of data-centres with associated reduction in energy consumption and carbon footprint, and the recovery and reuse of waste heat that is currently being rejected. This will constitute an important step towards meeting the UK's emission targets by 2050. Additionally, BONSAI will integrate with EPSRC Prosperity Outcomes of Delivery Plan 2016-20 and enable technological advances in relation to the Manufacturing the Future theme, contributing to a Productive and Resilient Nation.