分级抽汽回热式有机朗肯循环系统热力性能分析

发布时间：2018-06-13 02:30

本文选题：有机朗肯循环 + 低温余热　；参考：《南昌大学》2016年硕士论文

【摘要】：有机物朗肯循环(Organic Rankine Cycle,ORC)系统是解决资源利用率低下的一个重要方法。采用有机朗肯循环对低温余热进行回收是一项可行且效率较高的技术,不但对技术要求较低,而且较容易实现。ORC对于改善当下能源环境具有非常重大的作用。本文的研究工作有如下几个方面:1.对部分有机工质饱和性质、干湿性、环保性及其他性质进行比较,探究了蒸发温度、冷凝温度、过热度、膨胀机绝热效率等对基本ORC热力性能的影响,得出过热度对系统性能影响不大这一结论,相对于水蒸气朗肯循环有较大优势。2.建立了三种改进型ORC模型——再热式ORC、回热式ORC、抽汽回热式ORC,分别探究了再热压力比、回热度、抽汽压力对热力特性的影响。同时分别与基本ORC对比,发现再热式ORC最大作用在于能提高膨胀机输出功,回热式ORC的热效率明显提高,回热效果是非常明显的,抽汽回热式ORC膨胀机输出功有较大幅度减少,约为39.62%,这是由于一部分工质被用于回热,而循环热效率增加了7.22%。3.建立了二次抽气回热式ORC系统模型,对抽汽压力的选取提出了三种方案,分别对三种方案进行计算分析,得出抽汽压力分别为冷凝器出口温度和蒸发器入口温度等分点方案下对应的饱和压力时热效率最大。并在最佳抽气压力方案下,与一次抽汽回热系统热力性能进行比较,发现热效率较一次抽气回热系统提高4个百分点左右。分析了过热度对二次抽汽回热系统特性的影响,发现过热度对热效率影响较小。4.对二次抽气回热ORC系统进行了热回收效率分析。探究了最佳抽气压力方案下,蒸发温度、低温热源流体入口温度、膨胀机绝热效率对热回收效率的影响。发现存在最佳蒸发温度值使膨胀机输出功和热回收效率为极大值。随热源流体进口温度升高,(火用)效率降低而系统热回收效率升高。当膨胀机绝热效率升高,系统热效率、(火用)效率及热回收效率均升高。
[Abstract]:Organic Rankine cycle ORC (Organic Rankine cycle ORC) system is an important method to solve the problem of low resource utilization. Using organic Rankine cycle to recover low temperature waste heat is a feasible and efficient technology, which not only requires low technical requirements, but also has a very important role in improving the current energy environment. The research work of this paper has the following aspects: 1. The effects of evaporation temperature, condensation temperature, superheat, adiabatic efficiency of expander on the thermal properties of basic ORC were investigated by comparing the saturation, dryness, environmental protection and other properties of some organic working fluids. It is concluded that the superheat has little effect on the system performance and has a great advantage over the water vapor Rankine cycle. Three kinds of improved ORC models, reheat ORC, regenerative ORC and extraction regenerative ORC, were established. The effects of reheat pressure ratio, reheat degree and extraction pressure on thermodynamic characteristics were investigated respectively. At the same time, compared with the basic ORC, it is found that the most important function of the reheat ORC is to increase the output work of the expander, the thermal efficiency of the regenerative ORC is obviously improved, the regenerative effect is very obvious, and the output work of the exhaust steam regenerative ORC expander is greatly reduced. This is about 39.62 because some of the working fluids are used to regenerate and the cycle heat efficiency increases by 7.22.3. In this paper, the model of secondary pumping regenerative ORC system is established, and three schemes are put forward to select the extraction pressure, and the three schemes are calculated and analyzed respectively. The maximum thermal efficiency is obtained when the extraction pressure is the outlet temperature of the condenser and the inlet temperature of the evaporator. Under the optimal pumping pressure scheme, the thermal performance of the primary extraction regenerative system is compared with that of the primary extraction regenerative system, and it is found that the thermal efficiency is about 4 percentage points higher than that of the primary extraction regenerative system. The influence of superheat degree on the characteristics of secondary extraction steam recovery system is analyzed. It is found that superheat degree has little effect on thermal efficiency. The heat recovery efficiency of ORC system is analyzed. The effects of evaporation temperature, inlet temperature of low temperature heat source and adiabatic efficiency of expander on heat recovery efficiency were investigated. It is found that there is an optimum evaporation temperature to maximize the output work and heat recovery efficiency of the expander. With the increase of inlet temperature of the heat source fluid, the exergy efficiency decreases and the heat recovery efficiency increases. When the adiabatic efficiency of the expander increases, the exergy efficiency and heat recovery efficiency of the system increase.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK115

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