驱热力过程理论模型的热力学分析

为研究双热源联合循环的热力性能极限,构建了两介质热功转换系统理想热力学模型,并提出了驱热力过程的基本概念。通过分析热机循环区间与热泵循环区间过程功量之间的关系,对驱热力过程进行分类,并通过输出功量占比进行定量分析。构建并求解了顺流型和逆流型驱热力过程函数。分析了不同类型驱热力过程在理想条件下的热力特性与性能极限。研究结果表明:顺流型驱热力过程的最大过程功量大于逆流型,且放热介质与吸热介质间的温度交叉现象更为明显。吸热介质等效温升可用于判断驱热力过程类型,其最大值表征了输出功量极限。实际系统的评价研究指出,串联型联合循环的总换热量是基本型ORC的1.97倍,更适用于同时具有热电需求的场合。但其净输出功效率（6.55%）、效率（26.61%）、热力完善度（36.38%）均显著低于基本型有机朗肯循环。双热源联合循环实际系统的热力性能提高方法值得研究。本研究可为不同类型两介质热功转换系统的热力性能极限与评价提供理论指导。

Thermodynamic analysis of a theoretical model of exergy-driven thermodynamic process

To study the thermodynamic performance limit of two-heat-source combined cycle, an ideal thermodynamic model of two thermal medium heat-work conversion system was constructed. The concept of exergy-driven thermodynamic process (EDTP) was proposed and classified by analyzing the process power relationship between the heat engine region and the heat pump region. Quantitative analysis was performed through the proportion of output power. The parallel flow and counter flow EDTP functions were constructed and solved. The thermal characteristics and thermodynamic performance limits of different types of EDTP under ideal conditions were analyzed. Results showed that the maximum process work of the parallel flow EDTP was greater than that of the counter flow EDTP, and the temperature crossover trend between the exothermic medium and the endothermic medium of the parallel flow EDTP was more obvious. The equivalent temperature rise in the endothermic medium could be used to determine the type of EDTP, and its maximum value could characterize the limit of output power. The evaluation of actual system showed that the total heat exchange of the series-type cogeneration system was 1.97 times that of the basic organic Rankine cycle (ORC), which is more suitable for occasions with simultaneous thermoelectric demand. However, the net output power efficiency (6.55%), exergy efficiency (26.61%), and thermodynamic perfectibility (36.38%) were significantly lower compared with the basic ORC. The method to improve the thermal performance of the two-heat-source combined cycle is worthy of study. This research can provide theoretical guidance for the thermodynamic performance limit and evaluation of different types of two thermal medium heat-work conversion systems.