The organic Rankine cycle (ORC) has been proven as one of the most effective technologies for low-grade heat recovery. However, its efficiency is limited due to exergy losses caused by the large temperature difference between the heat source and working fluid in the evaporator. To enhance the ORC system efficiency, in this paper, a novel partial evaporating dual-pressure ORC (PEDORC) system is proposed. A mathematical model is developed to evaluate the system thermal characteristics and investigate the effects of key parameters (e.g. evaporating temperature, quality, superheat temperature, energy distribution) on the system performance. Results show that an optimal evaporating temperature in the evaporators exists to achieve the maximum net power output and exergy efficiency. However, the system thermal efficiency increases as the evaporating temperature increases. Furthermore, the best thermal performance occurs when the thermal energy is properly distributed in the evaporators I and II. The performance of the proposed PEDORC system is further compared with the simple ORC (SORC) and basic dual-pressure ORC (BDORC) systems. The results show that the net power output and exergy efficiency of the proposed PEDORC system are increased by up to 27% and 4.6%, respectively, in comparison to the SORC system. By comparing with the BDORC system, the net power output and exergy efficiency of the proposed system are increased by up to 9.2% and 4%, respectively, and the Levelized Cost of Electricity is reduced by up to 4%. These analyses demonstrate that the proposed PEDORC system is an effective means to recover low-grade thermal energy.

有机朗肯循环（ORC）已被证明是用于低级热回收的最有效技术之一。然而，由于热源与蒸发器中的工作流体之间的较大温差导致的火用损失，其效率受到限制。为了提高ORC系统的效率，本文提出了一种新型的部分蒸发双压ORC（PEDORC）系统。建立了数学模型来评估系统的热特性，并研究关键参数（例如蒸发温度，质量，过热温度，能量分布）对系统性能的影响。结果表明，蒸发器中存在最佳蒸发温度，以实现最大净功率输出和火用效率。然而，随着蒸发温度的升高，系统的热效率也随之提高。此外，当热能适当地分布在蒸发器I和II中时，会产生最佳的热性能。所提出的PEDORC系统的性能进一步与简单的ORC（SORC）和基本的双压力ORC（BDORC）系统进行了比较。结果表明，与SORC系统相比，拟议的PEDORC系统的净功率输出和火用效率分别提高了27％和4.6％。通过与BDORC系统进行比较，该系统的净输出功率和火用效率分别提高了9.2％和4％，而平均电费降低了4％。这些分析表明，提出的PEDORC系统是回收低等级热能的有效手段。