双超临界流体间传热特性及复杂通道对其影响研究

With the outstanding transfer effectiveness of supercritical fluid, supercritical carbon dioxide Brayton cycle is considered as a new improved energy conversion system. In this cycle the performance of recuperator has great influence on the whole system effectiveness, where the heat transfer occurs between two supercritical fluids. With the background of advanced nuclear power reactor system using the supercritical carbon dioxide Brayton cycle, the investigation of the coupled heat transfer characteristic of double supercritical fluids with the continuous changed boundary conditions and complex flow path are carried out. The valuable data of coupled heat transfer of double supercritical fluids would be gotten. With the investigation of the radial/axial temperature distribution of supercritical fluid in tube, the relevance between the heat transfer and the aberrant fluid physical properties would be analyzed. And the effect of complex flow path on the heat transfer characteristic also would be investigated. On the basis of above experimental result and corresponding theoretical analysis, a general half experience and half theoretic correlation for the coupled heat transfer between two supercritical fluids would be proposed and the effects law of complex flow path would also be gotten. The result will be helpful to understand the mechanism of coupled heat transfer characteristic of double supercritical fluids and the influence of complex flow path. The present research provides theoretical basis and technical support for the design and performance improvement of advanced power systems including nuclear power reactor which employs supercritical fluids as working fluids.

利用超临界流体优良的输运特性的超临界二氧化碳布雷顿循环是一种新型能量循环系统，系统中发生双超临界流体耦合传热过程的回热器对循环性能影响显著。本项目以超临界二氧化碳布雷顿循环的先进反应堆为背景，开展双超临界流体在不断变化的传热边界条件和复杂流动通道中的耦合传热过程研究，得出宏观下双超临界流体耦合传热下的数据，同时进行超临界流体径向/轴向温度分布研究，获取流道内流体物性畸变与传热特性间的关联，以及复杂流道结构对双超临界流体间耦合换热的影响，结合相应的理论分析得到具有一般性的双超临界流体间耦合传热的半经验-半理论关系式模型和复杂通道对其的影响规律。本研究将促进深入理解双超临界流体间耦合传热的机理，以及复杂通道的影响，为包括新一代先进核反应堆等在内的新型先进动力系统的设计和性能优化提供理论基础和技术支撑。

超临界二氧化碳布雷顿循环系统回热器中发生的双超临界流体耦合传热过程对循环性能影响显著，本项目以此为背景开展双超临界流体在不断变化的传热边界条件和复杂流动通道中的耦合传热过程研究。.通过水平套管内超临界水耦合流动传热特性实验研究，得到了温度、流量、压力、浮升力等参数对传热与阻力特性的影响规律。分析对比了已有的典型传热经验关联式的不足，建立了Dittus-Boelter形式的双超临界水耦合传热预测经验关联式。针对传统经验关联式预测模型的不足，采用概率密度函数与人工神经网络方法对传热预测模型进行修正与改进，取得了较好的效果。.建立了双超临界水耦合传热数值计算模型，得到了主流温度、流体入口温度、双侧流体流量变化等参数对传热的影响规律。建立了不同热边界下的超临界传热计算模型，得到了不同热边界条件下流量、入口温度和热流密度-质量流速比对传热的影响规律，分析了不同热边界条件下边界层对传热影响的作用机制。.设计并制造了非均匀热流密度单管试验件与高温高压多点式温度测量装置。建立了非均匀热流密度超临界传热计算模型，得到了热流密度分布、质量流速、入口温度等参数对流动传热特性的影响规律。.进行了印刷电路板式换热器(PCHE)内超临界二氧化碳耦合流动传热试验，换热器流道形式为连续S型半圆通道与非连续菱形通道，获得了宝贵的实验数据，得到了温度、流量、压力等参数对超临界传热特性的影响规律。建立了PCHE数值计算模型，得到了流量、温度、压力对PCHE内超临界流动传热的影响规律，分析了PCHE横截面形状对流动传热特性的影响，提出了相应的换热器设计准则。.项目促进了深入理解双超临界流体间耦合传热的机理以及复杂通道的影响，为新型先进动力系统设计和性能优化提供理论基础和技术支撑，具有一定的工程意义。