微通道内超临界二氧化碳流动与换热基础研究

Small reactor is not only the development direction of the new safe nuclear power that US Department of Energy intensively focused on but also the future trend of the fourth generation reactors. However, it also faces the problems of heat transfer limited by the space layout and operation safety requirements. Microchannel heat dissipation, as a new cooling technique, has high energy conversion efficiency, which has been widely used in semiconductor, aviation and so on. If applied in small reactors, this technology can effectively improve its intrinsic safety and power generation efficiency, and will be a great theme of nuclear power area. Supercritical carbon dioxide can reduce the pressure of the reactor and enhance power generation efficiency by raising the temperature. Under the conditions of supercritical carbon dioxide and by means of numerical analysis and experimental research, the project which focused on the flow heat transfer law of the fluid in microchannel will carry out the following research: 1) Launching a detailed investigation on the influence of the factors, such as temperature, velocity, flow resistance, efficiency of heat transfer. Apply numerical simulation to get quantitative law model which is appropriate for the condition of critical. 2) Put forward the structure of an efficient microchannel heat sink which gives some references to the design of the cooling components of the small reactor. The research achievement of this project has important theoretical significance, which will provide a firm theoretical foundation for the key technique of microchannel heat sink and the basis of optimization for small reactor thermal management system.

小型反应堆是未来第四代核电堆的研究热点，是前美国能源部重点支持的新型安全核电发展方向。由于空间布置和运行安全要求，其也面临着散热方面的问题。微通道散热作为一种新型散热技术，具有高能量转换效率，在半导体、航空等领域中已被广泛应用。该技术应用到小型反应堆中可有效提高其固有安全性和发电效率，是小型核电发展的关键性技术。超临界二氧化碳可降低反应堆压力，通过提高温度来增强发电效率，本项目围绕超临界二氧化碳条件下微通道中流体的流动换热规律，数值分析与实验研究相结合，开展以下研究：1）深入探讨温度、速度、流动阻力、换热效率等多种因素的影响，运用数值模拟获得适用于临界条件下的定量规律模型；2）提出高效微通道换热器的结构形式，为小型反应堆冷却部件的设计提供一定的参考。本项目研究成果将为微通道散热的关键技术提供坚实的理论基础，为优化小型反应堆的热系统提供依据，具有重要的理论意义和工程应用价值。

本项目以提高小型反应堆发电效率为目标，考虑反应堆内换热器结构和工况的对称性、连续性，提出了单通道、双通道、三通道和多通道等简化模型用以模拟反应堆内全尺寸换热器，通过建立微尺度下流动换热数学物理模型，将理论研究与可视化试验相结合，深入研究其流动换热规律。针对表面粗糙度、摩擦因子、流动速度、宽高比等对流动换热的影响进行了数值分析。将基础理论成果应用于技术开发，设计了高效的微通道换热器原型，成功研制了相应系统。新系统具有很好的换热性能，压损小、功耗少，为真实工况下反应堆换热器的优化打下基础。此外，还将微尺度散热原理应用于潮流能发电装置的散热。