超临界CO2阵列射流流动换热特性与强化传热机理研究

Supercritical CO2 Brayton cycle has been recognized as an ideal power cycle feasible for the next-generation power generation technology with higher parameters and efficiency. To achieve the targeted cycle parameters and efficiency, while ensuring the compactness and economical efficiency of the heat exchanger, highly efficient heat transfer of supercritical CO2 is one of the keys. In the proposed project, theoretical, numerical and experimental works will be carried out jointly to study the flow and heat transfer of multiple supercritical CO2 impinging jets. The characteristics and regulating rules of supercritical CO2 impinging jets heat transfer will be discovered, together with the exploration of structures for the heat exchanger fulfilling different demands. As a result, the coherence and perfect match between multiple impinging jets heat transfer and supercritical CO2 Brayton cycle can be realized. Meanwhile, suitable and efficient heat transfer enhancement measures will be proposed and the related mechanisms will be revealed. Based on heat transfer correlations of single jets/ artificial neural network, methods for the prediction of multiple impinging jets heat flux field and the optimization of parameters will also be set up. This project not only spotlights the characteristics of supercritical CO2 Brayton cycle itself and the working fluid, but also focuses on the basic questions of multiple impinging jets flow, heat transfer and heat transfer enhancement. More technological choices on supercritical CO2 heat transfer is expected from the investigation. In the meantime, theoretical basis can be provided for the regulation and enhancement of heat transfer, together with the solution and parameter optimization methods for the design of heat exchanger. The proposed project will be of great importance to the development and application of power generation technologies based on supercritical CO2 Brayton cycle.

超临界CO2布雷顿循环是适用于下一代更高参数和效率的发电技术的理想动力循环，超临界CO2的高效换热则是实现循环设计参数与效率、保证换热器紧凑性与经济性的关键之一。本项目拟采用理论、模拟和实验相结合的方法对超临界CO2阵列射流流动换热过程进行研究，以掌握超临界CO2阵列射流流动换热特性和换热调控规律，探索满足不同换热需求的换热器结构，实现阵列射流换热与超临界CO2布雷顿循环的高效协同匹配；同时，提出合理有效的强化传热手段并揭示其强化传热机理，构建基于单喷嘴射流换热关联式/人工神经网络的阵列射流热流密度场预测方法和参数优化方法。本项目既突出超临界CO2布雷顿循环和工质的特性，又兼顾阵列射流流动换热和强化传热的共性基础问题，可以进一步丰富超临界CO2换热的技术方案选择，为换热的调控和强化提供理论基础，为换热器设计提供思路与参数优化方法，对推动超临界CO2布雷顿循环发电技术的发展与应用有重要意义。

超临界CO2布雷顿循环是适用于下一代更高参数和效率发电技术的理想动力循环，超临界CO2的高效换热则是实现循环设计参数与效率、保证换热器紧凑性与经济性的关键之一。本项目综合采用理论、模拟和实验相结合的方法对超临界CO2阵列射流流动换热过程开展了研究。 首先在不同换热工况和典型换热器结构下对超临界CO2的基本流动传热规律进行了研究，揭示了浮升力、离心力以及工质物性变化对流动传热过程的影响，提出了“分区强化”的强化传热思路并验证了其有效性；其次，将超临界CO2与阵列射流相结合，对平面和曲面上的阵列射流流动传热特性进行了研究，发现等壁面温度条件下射流相比于横掠表面的流动其换热可强化达30%，同时，探究了不同因素对阵列射流传热流动过程的影响机制，设计了一种新型射流式套管换热器；第三，基于磁力泵等设备设计并搭建了可实现最高压力15MPa、最高温度200℃的超临界CO2换热实验系统，对射流式套管换热器的换热效果进行了初步验证，也为后续研究提供了硬件基础；最后，基于神经网络和CFD算例中的大量网格节点数据，提出了一种阵列射流热流密度场的快速预测方法，并进一步结合常见换热器形式提出了一种换热器参数优化方法，可以实现局部热流的快速预测与换热器参数优化。本项目既重点考虑了超临界CO2的特性，又兼顾阵列射流流动换热和通道内强化传热的共性基础问题，可以进一步丰富超临界CO2换热的技术方案选择，为换热的高效调控提供理论基础，为换热器设计提供思路与参数优化方法，对推动超临界CO2布雷顿循环发电技术的发展与应用有重要意义。