Heat transfer at supercritical pressures

亚临界压力（10 ~ 16兆帕）水冷核反应堆是20世纪40年代末开始研制的，已经使用了近50年。与此同时，早在20世纪50年代，美国和俄罗斯就开始研究超临界水冷核反应堆的概念。目前，一些国家（加拿大、欧盟、日本、韩国、俄罗斯和美国）在国际上成功地部署了用于燃煤电厂的超临界和超超临界锅炉和涡轮机的基础上，已开始朝这个方向努力。在核反应堆中使用超临界水的主要目标是：1)利用升高的温度和直接循环涡轮机将现代核电站（NPPs）的热效率从33%提高到40 - 45%用于发电，或超过50%用于热电联产；2)使用更紧凑的设计，从而降低资本和运营成本，从而降低资本和电能成本（约1000美元/千瓦）。因此，支持超临界水反应堆活动的拟议工作将包括以下部分：1)为超临界水反应堆主要冷却剂（如轻水）和两种模拟流体（如二氧化碳和R-134a）建立可靠的超临界传热数据库；2)建立超临界水、二氧化碳和R-134a的传热关系式，该关系式可以在广泛的流动条件下适用，并确定传热恶化的条件；3)进行分析，寻找从超临界水到模拟流体的模型参数，反之亦然；4)在加拿大安大略理工大学设计并建造了用于超临界水和模拟流体实验的小型自然循环换热环路。5)在Chalk River实验室参与超临界强迫对流换热实验，并使用俄罗斯测试设施的数据模拟管道和束状几何流动的流体。6)通过创新研究和世界级的出版物和演讲，在发展SCWR概念方面保持世界领先地位；7)为核工程和热工领域急需的高素质人才（HQP）提供教育基础和培训。长期目标是为燃料束建立超临界-水传热数据库，并为计算这些条件下的传热系数和恶化传热极限建立可靠的相关性。此外，这些相关性必须解决热工液压安全问题。

Water-cooled nuclear reactors operating at subcritical pressures (10 - 16 MPa) started to be developed at the end of 1940s and have been used for the last fifty years.  At the same time, i.e., as early as the 1950s, concepts of SuperCritical Water-cooled nuclear Reactors (SCWRs) were studied in the USA and Russia.  Currently, several countries (Canada, European Union, Japan, Korea, Russia, and USA) have started to work in that direction, building on the successful international deployment of supercritical and ultra-supercritical boilers and turbines for coal-fired power plants.  The main objectives of using supercritical water in nuclear reactors are:1) Using the increased temperatures and a direct-cycle turbine to increase the thermal efficiency of modern nuclear power plants (NPPs) from 33% to 40 - 45% for electricity production, or more than 50% with co-generation, and2) Using a more compact design that results in decreased capital and operational costs and hence in decreased capital and electrical energy costs (~$1000 US/kW).Therefore, the proposed work in support of SCWR activities will consist of the following parts:1) Creation of a reliable supercritical heat-transfer database for the primary SCWR coolant such as light water and for two modelling fluids such as carbon dioxide and R-134a;2) Developing heat-transfer correlations for supercritical water, carbon dioxide and R-134a, which can be applicable within a wide range of flow conditions and identify conditions for the deteriorated heat transfer;3) Conducting analysis to find modelling parameters for scaling from supercritical water to modelling fluids and vice versa;4) Designing and building a small-scale natural-circulation heat-transfer loop for experiments in supercritical water and modelling fluids at the University of Ontario Institute of Technology.5) Participating in supercritical forced-convection heat-transfer experiments in water and modelling fluids flowing in tubes and bundle geometries at Chalk River Laboratories and using data from Russian test facilities.6) Keeping a leading role in the world in developing the SCWR concept through innovative research and world-class publications and presentations; and7) Creating an educational basis and training of Highly Qualified Personnel (HQP) in the area of nuclear engineering and thermalhydraulics, whom are desperately needed in industry.    Long-term objective is a creation of the supercritical-water heat-transfer database for fuel bundles and reliable correlations for calculating heat transfer coefficient at these conditions and limits for the deteriorated heat transfer.  Also, these correlations have to address thermalhydraulics safety issues.