基于混合工质的多级蒸发ORC理论极限性能研究

Organic Rankine cycle (ORC) has been widely used as the primary choice to realize power generation from low temperature waste-heat, and the combination of zeotropic mixture and dual-pressure evaporation has been evidenced their potential to significantly improve the thermal efficiency of ORC. However, it is still unclear how the multiple stages of evaporation affect the performance. In this study, a multi-pressure evaporation ORC based on zeotropic mixture (MZORC) was proposed, a heat transfer limit model was developed based on the entransy analysis, and the processes of ORC (BORC), dual-pressure evaporation MZORC and tri-pressure evaporation MZORC were simulated with Aspen Plus. The results show that MZORC can improve the performance by reducing both the heat loss and entransy dissipation caused by the evaporation. When the heat source is 423.15 K and the ambient temperature is 298.15 K, the net output power of tri-pressure evaporation MZORC can be improved by 38.6% compared with BORC, and those of BORC, dual-pressure evaporation MZORC, and tri-pressure evaporation MZORC can reach 65.0%, 79.0% and 90.1% of the theoretical limit, respectively, i.e., increasing the number of evaporation units will result in performance enhancement, approaching the theoretical limit.