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Thermodynamic analysis and comparative investigation of a new combined heating and power system driving by medium-and-high temperature geothermal water
Energy Conversion and Management ( IF 10.4 ) Pub Date : 2021-02-24 , DOI: 10.1016/j.enconman.2021.113914
Chenxing Ren , Jianyong Wang , Haifeng Chen , Xiaoqin Liu , Meng An

Geothermal energy is one of the most promising renewable energy. In order to improve the overall utilization degree of medium-and-high temperature geothermal water by flash cycle, a new combined heating and power system is proposed to provide electricity and domestic hot water at the same time. This new system is integrated by single-stage flash cycle and ammonia-water absorption heat pump cycle, of which the heat pump cycle recovers two streams of waste heat of the flash cycle, including the waste heat of the turbine exhaust steam and the geofluid drained from the flasher. The mathematical models of the new system is established at length in this article, and a numerical simulation is conducted to present the preliminary design condition. The simulation results show that the thermal efficiency and exergy efficiency of the system could reach 81.8% and 46.99% respectively under the condition of 170℃ geothermal water. Then a thermodynamic parameter analysis is carried out to explore the impact of five key thermodynamic parameters on the system performance. The results show that an optimal flash pressure happens to make the system exergy efficiency maximal, and there is a similar case for the generator temperature. Within some certain value ranges, a higher rectification column pressure brings about a sharp drop in the exergy efficiency, whereas a higher ammonia concentration of ammonia-strong solution leads to the exergy efficiency rising. Additionally a higher evaporation pressure just has slightly positive effect on the exergy efficiency. Finally an optimization and comparison study is implemented between the proposed system and four flash cycle based combined systems, and the optimization results indicate that the proposed system has a better performance no matter from the viewpoint of the first law or the second law of thermodynamics.



中文翻译:

中高温地热水驱动新型热电联产系统的热力学分析与比较研究

地热能是最有前途的可再生能源之一。为了通过闪蒸循环提高中高温地热水的综合利用率,提出了一种新的供热兼用的电力系统,可以同时提供电力和生活热水。该新系统通过单级闪蒸循环和氨水吸收热泵循环进行集成,其中热泵循环可回收闪蒸循环的两股废热,其中包括涡轮机废气的余热和排出的流体流从闪光灯。本文详细建立了新系统的数学模型,并进行了数值模拟以给出初步的设计条件。仿真结果表明,该系统的热效率和火用效率可达81。170℃地热水条件下分别为8%和46.99%。然后进行热力学参数分析,以探索五个关键热力学参数对系统性能的影响。结果表明,最佳的闪蒸压力恰好使系统的火用效率最大化,并且发电机温度也存在类似情况。在某些特定值范围内,较高的精馏塔压力会导致有效能值急剧下降,而较高的氨浓度的氨-强溶液会导致有效能值升高。另外,较高的蒸发压力仅对本能效率产生积极影响。最后,对所提出的系统与四个基于闪光周期的组合系统进行了优化和比较研究,

更新日期:2021-02-24
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