A new understanding on thermal efficiency of organic Rankine cycle: Cycle separation based on working fluids properties. (1st February 2018)

• Record Type: Journal Article
• Authors: Wang, Yongzhen; Zhao, Jun; Chen, Guibing; Deng, Shuai; An, Qingsong; Luo, Chao; Alvi, Junaid
• Is Part Of: Energy conversion and management. Volume 157(2018)
• Page Start: 169
• Page End: 175
• Publication Date: 2018-02-01
• Subjects: Organic Rankine cycle -- Cycle separating -- Working fluids selection -- Molecular complexity -- Performance prediction -- Superheat degree; Direct energy conversion -- Periodicals; Energy storage -- Periodicals; Energy transfer -- Periodicals; Énergie -- Conversion directe -- Périodiques; Direct energy conversion; Periodicals; 621.3105
• DOI: 10.1016/j.enconman.2017.11.079
• Languages: English
• ISSNs: 0196-8904

Abstract

Graphical abstract: Highlights: A thermal efficiency method of ORC from separating TS map is newly built. Variation of η SORC with molecular complexity and superheat degree can be revealed. The same reduced temperatures of different pure fluids display equal efficiencies. Abstract: The pivotal of organic Rankine cycle (ORC) promotion and optimization is revealing the thermodynamic relationship between cycle configuration, condition and its working fluid properties. Different from the traditional numerical calculation method (TNCM) of ORC, a new thermodynamic cycle separating method (TCSM) is introduced in this paper. Then, efficiency of ORC is conducted expediently by TCSM where Triangle cycle ( η TC ), Carnot cycle ( η CC ) and Brayton cycle ( η BC ) efficiencies are regarded as variables, that is, η SORC = f ( η TC, η CC, η BC ) . When comparing with TNCM, TCSM not only has the acceptable precision for all the investigated 21 working fluids, but also the influence of critical temperature, molecular complexity of the working fluid and superheat degree as well as the reduced operating conditions of ORC can be revealed qualitatively and quantitatively. Finally, three conclusions are revealed: (1) Relationship between ORC limited efficiency (the reduced evaporating temperature of 0.9) and critical temperature of working fluid is revealed; (2) When superheat degree increases, ORC efficiency of dry fluid decreases and wet fluid increases linearly, while the variation of isotropic working fluid remains constant; (3) If the reduced temperatures of two different working fluids are equal, the corresponding efficiencies are equal too. The proposed thermodynamic cycle separating method provides an approach for working fluids selection and performance prediction of ORC.