Flow Boiling and Condensation of Mixtures in Microscale

该提案是由爱丁堡大学布鲁内尔大学和伦敦玛丽女王大学的国际领先的英国传热研究小组与四个工业合作伙伴（Thermacore, Oxford Nanosystems， Super Radiator coil和Rainford Precision）在微制造和热管理领域合作的联合项目。制造工艺的进步和随后在更高功率密度下运行的更小规模电子设备的使用导致对热管理系统的关键需求，以提供密集的局部冷却。为了防止电子元件的故障，必须仔细控制任何电子设备所有部件的工作温度。这可能导致整个设备的热去除率要求平均至少为2 MW/m2，在局部“热点”的峰值速率高达10-15 MW/m2。直接空气冷却限制在约0.5 MW/m2，而液体冷却系统仅能达到0.7 MW/m2。其他技术尚未实现超过1兆瓦/平方米的热通量。在微通道中沸腾提供了获得如此高的热流密度和均匀表面温度的最佳前景。在封闭系统中，需要一个同样紧凑和有效的冷凝器将热量排出到环境中。在高热流密度下，蒸发器干燥会造成严重的问题，导致表面局部过热，从而可能烧毁依赖这种蒸发冷却的电子元件。使用新型混合物，称为“自润湿流体”，其表面张力特性使其能够改善热表面的润湿，潜在地为增强冷却技术提供了空间。在这个项目中，将研究两种不同的酒精水溶液（其中一种是自湿润的），以确定它们是否能提供超过2 MW/m2的闭环冷却系统所需的必要蒸发和冷凝特性。爱丁堡大学的研究人员将使用先进的成像技术，研究混合物的润湿和蒸发/冷凝的基本原理，以确定蒸发和冷凝的最佳混合物浓度和传热表面涂层。在伦敦布鲁内尔大学，将研究流体在金属单微通道和多微通道蒸发器中的应用。伦敦玛丽女王大学的研究人员将对紧凑交换器中混合物的冷凝进行实验和理论研究。综合结果将用于设计一个完整的微尺度闭环蒸发冷却系统。Thermacore将提供微型热交换器，Oxford Nanosystems将提供结构表面涂层。可持续发展的发动机系统，超级散热器线圈，并将提供建议，并代表额外的方式，采取发展源于这项研究，以市场。雷福德精密公司将为布鲁内尔大学提供微型工具，并支持其在微加工中的应用。

This proposal is for a joint project between internationally-leading, UK heat transfer research groups at the Universities of Edinburgh, Brunel and Queen Mary, London in collaboration with four industrial partners (Thermacore, Oxford Nanosystems, Super Radiator Coils and Rainford Precision) in the areas of micro-fabrication and thermal management. Advances in manufacturing processes and subsequent use of smaller scale electronic devices operating at increased power densities have resulted in a critical demand for thermal management systems to provide intensive localised cooling. To prevent failure of electronic components, the temperature at which all parts of any electronic device operates must be carefully controlled. This can lead to heat removal rate requirements averaging at least 2 MW/m2 across the complete device, with peak rates of up to 10-15 MW/m2 at local 'hot spots'. Direct air cooling is limited to about 0.5 MW/m2 and liquid cooling systems are only capable of 0.7 MW/m2. Other techniques have not yet achieved heat fluxes above 1 MW/m2.Boiling in microchannels offers the best prospect of achieving such high heat fluxes with uniform surface temperature. In a closed system an equally compact and effective condenser is required for heat rejection to the environment. At high heat flux, evaporator dry-out poses a serious problem, leading to localised overheating of the surface and hence potentially to burn out of electronic components reliant on this evaporative cooling. Use of novel mixtures, termed 'self-rewetting fluids', whose surface tension properties lend themselves to improved wetting on hot surfaces, potentially offers scope for enhanced cooling technologies.In this project, two different aqueous alcohol solutions (one of which is self-rewetting) will be studied to ascertain whether they can provide the necessary evaporative and condensation characteristics required for a closed-loop cooling system capable of more than 2 MW/m2.Researchers at the University of Edinburgh will study the fundamentals of wetting and evaporation/condensation of the mixtures to establish the optimum mixture concentrations and heat transfer surface coating for both evaporation and condensation, using advanced imaging techniques. At Brunel University London, applications of the fluids in metallic single and multi microchannel evaporators will be investigated. Researchers at Queen Mary University London will carry out experimental and theoretical work on condensation of the mixtures in compact exchangers. The combined results will feed into the design of a complete microscale closed-loop evaporative cooling system.Thermacore will provide micro-scale heat exchangers and Oxford Nanosystems will provide structured surface coatings. Sustainable Engine Systems, Super Radiator Coils and will provide advice and represent additional ways of taking developments originating from this research to the market. Rainford Precision will provide Brunel University micro tools and support on their use in micromachining.