适用于中低温热能利用的有机朗肯-卡林纳联合循环的热力学研究

There is vast amount of medium-low temperature energy in renewable energy field and industrial process. How to convert this energy into power in an efficient and economical way is of great significance for energy saving and environment protection. As far as the existing thermodynamic cycle used for medium-low energy utilization is concerned, its thermodynamic perfection and the system techno-economics are affected due to the performance of heat absorption process and the characteristics of working fluid. Considering the characteristics of different medium-low temperature energy sources, the popular organic Rankine cycle and the Kalina cycle are selected for establishing a combined thermodynamic cycle whose thermodynamic perfection is achieved by some relevant amendments and(or) supplementary measures which focus on the technical feasibility and economic viability. On this basis, the optimization object function is proposed for the optimization study of working fluids and cycle parameters of different combined cycle configurations. Moreover, the thermophysical properties of novel working fluids and(or) mixed working fluids are calculated and estimated. The laws and mechanism in the optimization of combined thermodynamic cycle used for medium-low temperature energy utilization will be revealed. The optimal cycle configuration, working fluids, and cycle parameters will be obtained for different heat sources utilization. The research results can serve as the basis of future application researches.

在可再生能源领域及工业生产过程中存在着大量的中低温热能，对其进行高效和经济的动力利用，具有重要的节能环保和经济意义。现有中低温热能利用系统中所应用的或研究中所提出的热力循环受到循环吸热过程特性和工质性质的影响，使其热力学完善度、系统的技术经济性均受到了一定的限制。本项目拟针对各种中低温热源的不同特点，选择常用的有机朗肯循环及卡林纳循环，以高的热力学完善度为基本着眼点，以技术可行性和经济可行性为限定条件，通过引入相关的修正/补充措施，提出有机朗肯循环-卡林纳联合热力循环设计。在此基础上，建立优化目标函数，对不同循环设计形式下的工质和循环参数进行优化研究，对新工质及混合工质的热物性进行估算研究。期望揭示中低温热能利用联合热力循环优化中的相关机理与规律，针对不同的中低温热源得到优良的“循环形式-循环工质-循环参数”组合。为相关的应用研究提供基础依据。

项目考虑到现有中低温热能利用系统中所应用的热力循环受到工质性质的影响，主要围绕中低温热源的特点，从有机工质的热力学性能、环保性能指标及经济性表现三方面详尽研究了有机朗肯循环(ORC)。首次提出了温熵（T-s）图中干工质及等熵工质饱和蒸气线转折点的概念，首次建立了“近临界区三角形”模型，筛选得到了适用于开式热源与闭式热源的有机工质；基于基团贡献法提出了一种有机工质辐射效率的估算方法，此方法可用于新工质辐射效率的估算；同时估算了各基团对有机工质臭氧消耗潜势ODP的贡献值；使用经济性指标对ORC进行了热经济性分析，得到了循环最优工况点。此外，项目分析研究了卡林纳循环(Kalina Cycle)所用氨水混合工质热物理性质的计算方法，在此基础上对由有机朗肯循环(ORC)和卡林纳循环(Kalina Cycle)所构成的联合热力循环进行了分析优化。项目亦对循环关键部件单螺杆膨胀机的性能、有机工质在套管换热器中的换热特性及涂层对中低温余热回收换热器导热性能的影响进行了实验研究并得到了相关机理与规律。. 项目提出的“近临界区三角形”模型及有机工质辐射效率的估算方法可以为中低品位热能利用筛选循环工质进而提高能源利用率提供新思路和基础依据。