超临界CO2太阳能热发电中热化学储能反应器的传热机理研究

Compared with the conventional sensible heat energy storage and latent heat energy storage, ammonia-based solar thermochemical energy storage (TCES) has the advantages of high energy density and capability of being simply stored with little heat loss. Supercritical CO2 (S-CO2) Brayton cycle is with the potential to achieve a high efficiency with a compact and cheap power cycle. The exothermic reactor is the key to integrate ammonia-based solar TCES with S-CO2 Brayton cycle, which is with a high operating temperature, a dramatic axial temperature gradient and S-CO2 mixed convection. There has not been any research conducted on analyzing the heat transfer process of the exothermic reactor comprehensively. The objective of the proposed research is to investigate the heat transfer process in the exothermic reactor. In this project, a more accurate model will be developed to compute effective thermal conductivity of the catalytic bed in the reactor. Also, a pseudo-homogenous model including the axial conduction will be developed to study the effect of the axial conduction on the reactor performance. Moreover, a correlation containing buoyancy factor will be developed using CFD model simulations, experiments and correction methods. The correlation will be further utilized to develop a more accurate S-CO2 mixed convection simulation model. Last but not least, the effect of the reactor’s geometry and configuration on thermal resistance of the reactor will be investigated. A more refined design guide will be proposed to enhance heat transfer of the exothermic reactor.

与传统显热式和潜热式太阳能储能相比，太阳能氨基热化学储能具有能量密度高、储存简易和长期储存热损少等优点。超临界CO2（S-CO2）布雷顿发电循环具有效率高及成本低等优点。氨基热化学储能系统中的放热反应器是结合太阳能氨基热化学储能与S-CO2布雷顿循环的关键。由于放热反应器具有工作温度高、轴向温度变化剧烈与S-CO2混合对流复杂等特性，还没有相关研究成果能够准确预测分析放热反应器的传热机理。本项目以太阳能氨基热化学储能系统中放热反应器为对象，开展传热机理的研究。修正有效导热系数的计算方法，建立包含轴向热传导的拟均相模型，揭示轴向热传导效应的作用规律。提出包含浮升力因子的S-CO2混合对流传热关联式，修正S-CO2混合对流传热模型。揭示催化剂与S-CO2工质通道等的几何结构参数对于反应器总热阻的影响规律，提出放热反应器结构设计方面强化传热的准则，完善放热反应器强化传热过程的设计理论和方法。

与传统显热式和潜热式太阳能储能相比，太阳能氨基热化学储能具有能量密度高、储存简易和热损少等优点。超临界二氧化碳（S-CO2）布雷顿发电循环具有效率高及成本低等优点。氨基热化学储能系统中的反应器是耦合太阳能氨基热化学储能与S-CO2布雷顿循环的关键。由于反应器具有工作温度高、轴向温度变化剧烈以及S-CO2混合对流传热复杂等特性，并且目前针对反应器的传热机理的研究还存在很多不确定性。本项目以太阳能氨基热化学储能系统中反应器为对象，开展传热机理的研究。修正有效导热系数的计算方法，建立包含轴向热传导的拟均相模型，揭示轴向热传导效应的作用规律。提出考虑浮升力作用的S-CO2混合对流传热关联式，修正S-CO2混合对流传热模型。结合催化剂床拟均相模型和S-CO2混合对流传热模型建立完整反应器模型。基于完整准确的反应器模型，首次提出自热式合成氨反应器，并成功实现将S-CO2加热至700℃。在上述研究的基础之上，利用反应器模型研究反应器总热阻，揭示催化剂与S-CO2工质通道等的几何结构参数对于反应器总热阻的影响规律，提出反应器结构设计方面强化传热的准则，完善反应器强化传热过程的设计理论和方法。