Abstract:

As one of the most promising low-grade thermal power generation technologies, the organic Rankine cycle (ORC) has received increasing attention in recent years. Compared to the conventional high-grade fossil energy to power conversion technologies, ORC is much more sensible to the environmental temperature variation due to the low temperature nature of heat sources. This study proposes a novel zeotropic ORC in which the mixture composition can be tuned in response to the environmental temperature using liquid - separation condensation. A thermodynamic optimization model is formulated to optimize the mixture composition according to the environmental temperature. A superstructure of liquid-separation condensation based composition tuning system is constructed. The tuning process of the novel system is modelled and incorporated into the zeotropic ORC. Case study is elaborated to validate the thermo-economic effectiveness of the novel ORC. The results show that the thermo-economic effectiveness of the proposed ORC can be improved by up to 38.90%/15.35% for constant/sliding pressure regulation compare to the conventional ORC in terms of 100℃ heat source. Furthermore, the comparison of five zeotropic mixtures indicates that the performance improvement is significantly sensible to the mixtures.

Key words: organic Rankine cycle, zeotropic mixture, composition adjustment, liquid-separation

摘要：

作为最具潜力的低品位热能发电技术之一，有机朗肯循环（ORC）近年来受到越来越多的关注。与传统的高品位能源发电技术相比，其运行性能对环境温度的变化极其敏感。提出一种新型非共沸混合工质ORC系统，利用分液冷凝器调节混合工质组分，以适应环境温度的变化，进而提高系统性能。根据环境温度的变化构建热力学优化模型获得最优组分；冷凝过程中利用分液冷凝器和组分调控系统改变混合工质组分。通过案例验证了新系统的热经济性能优势，研究结果表明：对于100℃热源，在定压运行工况下，新系统较传统系统的经济性可提高38.90%，而在滑压运行工况下，新系统较传统系统的经济性可提高15.35%，且使用不同非共沸混合工质时，系统性能有显著差异。

关键词: 有机朗肯循环, 非共沸混合工质, 组分调控, 分液冷凝器