低品位热能驱动的超临界有机朗肯循环工质筛选的研究

发布时间：2018-03-17 02:32

本文选题：有机朗肯循环　切入点：超临界　出处：《华北电力大学》2014年硕士论文　论文类型：学位论文

【摘要】：在低品位能源利用技术中,有机朗肯循环(ORC)发电技术具有热效率高、设备简单、环境友好等特点,得到了各国研究者的普遍重视。由于循环工质物性对循环性能具有重要影响,因此工质筛选成为ORC研究中最重要的方向之一。与亚临界循环相比,超临界循环中工质无等温沸腾段,能够取得与热源更优的温度匹配,有效提高循环热效率。超临界循环工质筛选的研究中,存在三个关键科学问题：系统与热源的耦合、运行参数对系统性能的影响、工质物性的循环影响机理。本文围绕超临界有机朗肯循环工质筛选,首先提出一种系统与热源耦合的热力学计算新方法,即给定热源的进口温度、出口温度及质量流量,在窄点约束下对工质循环性能进行计算分析。新方法采用Fortran语言编程寻优并调用物性软件Refprop9.0进行求解。其次,针对进口温度423.15K,出口温度343.15K的低温烟气热源,选取三种典型工质R218、R134a、R236fa,计算分析临界温度对循环性能的影响。提出了三种运行模式：(1)低临界温度工质的灵活运行模式,即运行压力与温度为一矩形域；(2)中等临界温度工质的分歧运行模式,即两个运行压力与某一运行温度相对应；(3)高临界温度的受限运行模式,即仅有一个运行压力与某一运行温度相对应。提出了能够量化蒸发器内热源流体与有机工质流体温度匹配程度的平均积分温差。高临界温度工质的蒸发器平均积分温差较小,因此(?)效率较高,循环性能好。而低临界温度工质蒸发器内平均积分温差大,循环性能较差。最后,基于临界温度对循环性能的讨论,在给定热源下,选取高临界温度候选工质进行工质筛选。通过比较循环热效率、(?)效率及单位质量净输出功,并综合工质的毒性、可燃性、环保性,发现在热源温度为423.15K的超临界循环中,R134a为优选工质。R1234ze循环性能次之,但具有优良的环保特性,建议应用于环保要求较高的场所。本文核心创新点在于在国际上最早明确了给定热源温度下基于工质临界温度的筛选准则,为超临界ORC循环及工质筛选提供了有价值的设计及运行依据,主要工作发表在Energy上。
[Abstract]:In the low grade energy utilization technology, organic Rankine cycle (ORC) power generation technology has the advantages of high thermal efficiency, simple equipment and environmental friendly features, has received much attention of researchers all over the world. Because the circulation of refrigerants has an important effect on the cycle performance, so the refrigerant selection has become one of the most important direction in the research of ORC compared with subcritical cycle, supercritical circulating working fluid in non isothermal boiling section, and can obtain better heat source temperature, and effectively improve the thermal cycle efficiency. Research on supercritical refrigerant screening, there are three key issues: coupling system and heat source. The effects of operating parameters on the system performance. The influence mechanism of circulation of refrigerants.
This paper focuses on the supercritical organic Rankine cycle refrigerant selection, a new method to calculate the thermodynamics first proposed a system coupled with the heat source, heat source is given inlet temperature, outlet temperature and mass flow in the narrow constraints on refrigerant cycle performance are analyzed. A new method using Fortran language programming and optimization of software call Refprop9.0 is used to solve the problem.
Secondly, the inlet temperature of 423.15K outlet temperature of flue gas temperature, heat source 343.15K, select three typical refrigerants R218, R134a, R236fa, calculation and analysis of effect of critical temperature on the performance of the cycle is proposed. Three operation modes: (1) the flexible operation mode of low critical temperature of refrigerant, the operating pressure and temperature for a rectangular domain; (2) different operation mode of secondary critical temperature of refrigerant, namely two operating pressure with a corresponding operating temperature; (3) limited operation mode of high critical temperature, only one operating pressure and a corresponding operating temperature is proposed. The average temperature in the evaporator to integral quantization the heat source fluid and organic working fluid temperature matching degree. The average integral evaporator temperature smaller high critical temperature of refrigerant, so the efficiency is high, (?) and good cycling performance. The average integral temperature low critical temperature of refrigerant in the evaporator,. The ring performance is poor.
Finally, discuss the critical temperature on the performance of the cycle based on the given heat source, selection of high critical temperature of the working fluid of the candidate refrigerant selection. By comparing the thermal cycle efficiency, efficiency and quality of the unit (?) the net power output, and refrigerant toxicity, flammability, environmental protection, found in the heat source temperature is 423.15K the supercritical cycle, R134a is the preferred refrigerant.R1234ze cycle performance, but has excellent environmental protection characteristic, proposed applied to the environmental requirements of high places.
The core innovation of this paper is that the screening criteria based on working temperature critical temperature at the given heat source temperature were first identified internationally, which provided valuable design and operation basis for the supercritical ORC cycle and the selection of working fluids. The main work was published on Energy.

【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM61

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