Open Access

ARTICLE

Thermodynamic, Economic, and Environmental Analyses and Multi-Objective Optimization of Dual-Pressure Organic Rankine Cycle System with Dual-Stage Ejector

Guowei Li^1,*, Shujuan Bu², Xinle Yang², Kaijie Liang¹, Zhengri Shao¹, Xiaobei Song¹, Yitian Tang³, Dejing Zong⁴

1 Yingkou Institute of Technology, School of Mechanical and Power Engineering, Yingkou, 115014, China
2 Liaoning Technical University, School of Mechanical Engineering, Fuxin, 123000, China
3 CNPC Second Construction Co., Ltd., Petrochina Lanzhou Petrochemical Company, Lanzhou, 730060, China
4 China Power Construction Group Shandong Power Construction First Engineering Co., Ltd., Jinan, 250000, China

* Corresponding Author: Guowei Li. Email:

Energy Engineering 2024, 121(12), 3843-3874. https://doi.org/10.32604/ee.2024.056195

Received 16 July 2024; Accepted 09 September 2024; Issue published 22 November 2024

Abstract

A novel dual-pressure organic Rankine cycle system (DPORC) with a dual-stage ejector (DE-DPORC) is proposed. The system incorporates a dual-stage ejector that utilizes a small amount of extraction steam from the high-pressure expander to pressurize a large quantity of exhaust gas to perform work for the low-pressure expander. This innovative approach addresses condensing pressure limitations, reduces power consumption during pressurization, minimizes heat loss, and enhances the utilization efficiency of waste heat steam. A thermodynamic model is developed with net output work, thermal efficiency, and exergy efficiency (W_net, η_t, η_ex) as evaluation criteria, an economic model is established with levelized energy cost (LEC) as evaluation index, an environmental model is created with annual equivalent carbon dioxide emission reduction (AER) as evaluation parameter. A comprehensive analysis is conducted on the impact of heat source temperature (T_S,in), evaporation temperature(T₂), entrainment ratio (E_r1, E_r2), and working fluid pressure (P₅, P₆) on system performance. It compares the comprehensive performance of the DE-DPORC system with that of the DPORC system at T_S,in of 433.15 K and T₂ of 378.15 K. Furthermore, multi-objective optimization using the dragonfly algorithm is performed to determine optimal working conditions for the DE-DPORC system through the TOPSIS method. The findings indicate that the DE-DPORC system exhibits a 5.34% increase in W_net and η_ex, a 58.06% increase in η_t, a 5.61% increase in AER, and a reduction of 47.67% and 13.51% in the heat dissipation of the condenser and LEC, compared to the DPORC system, highlighting the advantages of this enhanced system. The optimal operating conditions are T_S,in = 426.74 K, T₂ = 389.37 K, E_r1 = 1.33, E_r2 = 3.17, P₅ = 0.39 MPa, P₆ = 1.32 MPa, which offer valuable technical support for engineering applications; however, they are approaching the peak thermodynamic and environmental performance while falling short of the highest economic performance.

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