基于实际换热的ORC亚/跨临界综合评价

本文以有机朗肯循环(ORC)跨临界与亚临界工质换热特性最新研究成果为基础,采用热力学指标热源回收效率,以及经济学中的净现值(NPV)概念,结合换热面积分析,建立了考虑实际换热情况的热力学及经济性模型,更合理、更全面地对亚临界循环与跨临界循环的热力学性能和经济性进行了统一分析,为工程实际中亚临界和跨临界的选择提供了参考。本文结果表明,当综合考虑换热器面积、NPV等经济性指标时,跨临界循环在单纯的热力学分析中所展现的高于亚临界的优势减少。针对工业余热,系统的优化区间覆盖跨临界与亚临界,为P/P_c=0.82～1.30,T₃=103～147℃,其热源回收效率可达61%,经济效益较高,且对透平入口温度、压力的变化不敏感,能容纳一定的参数波动。对比使用不同换热关联式,使用专门针对有机工质发展的换热关联式计算得到的循环优化区间发生了改变,由此可见,开展对ORC工质的换热特性研究,发展更加准确的换热关联式是完善系统优化的重要途径。

Comprehensive Evaluation of Subcritical/Supercritical ORC Based on Actual Heat Transfer

Based on the latest research results of heat transfer characteristics of organic Rankine cycle(ORC)transcritical and subcritical refrigerants,a thermodynamic and economic model considering actual heat transfer conditions is established by using the thermodynamic index heat recovery efficiency and the concept of net present value in economics.The thermodynamic and economic analysis is more comprehensive and reliable which provides a reference for the selection of subcritical and transcritical cycles in engineering practice.When the heat exchanger area and NPV are taken into account,the superiority of supercritical cycles over subcritical cycles in simple thermodynamic analysis is reduced.For industrial waste heat,the optimization interval of the system crosses the supercritical and sub-critical,P/P_c=0.82～1.30,T₃=103～147℃,and the recovery efficiency of heat source can reach 61%.The economic benefit is high,and the change of temperature and pressure is not sensitive,so the system can accommodate certain fluctuations.