Science China Technological Sciences

, Volume 61, Issue 12, pp 1802–1813 | Cite as

Shift-characteristics and bounds of thermal performance of organic Rankine cycle based on trapezoidal model

  • XinGuo LiEmail author
  • JingYi Wang
  • XiaoSong Wu


In consideration of the constraints of actual working fluids on theoretical study of organic Rankine cycle (ORC), a trapezoidal cycle (TPC) with theoretical model to simulate ORC was proposed in previous works. In this study, mathematical models of working fluids including model of simulated saturation curve (MSSC) and model of linear saturation lines (MLSL) are proposed and built. Combining mathematical models of working fluids and TPC, the thermodynamic characteristics and principles of TPC (or ORC) can be studied or predicted theoretically. There exists a shift-curve of net power output with corresponding shift-temperature of heating fluid for working fluids, which indicates the shift of net power output from having optimum condition of maximum power to monotonic increase with evaporation temperature. This shift-characteristic is significant to working fluid selection and evaluation of cycle performance, for it indicates that cycle without optimum condition can yield higher net power output than the cycle with optimum condition. Equations to calculate the shift-temperature in ORC (or TPC) are derived; and equations to calculate the highest optimal evaporation temperature and highest maximum power as the highest optimum condition at this shift-temperature are obtained. Based on TPC and its theoretical model, the lower and upper bounds of thermal performance (maximum power and corresponding thermal efficiency) of TPC (or ORC) can be demonstrated and acquired. TPC can develop to Carnot cycle or trilateral cycle that it is significant to use TPC as a generalized cycle to study the general principles and characteristics of the cycles.


organic Rankine cycle (ORC) trapezoidal cycle (TPC) mathematical models of working fluids shift-temperature of heating fluid for working fluid bounds of thermal performance 


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Copyright information

© Science in China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.School of Mechanical EngineeringTianjin University, Key Laboratory of Efficient Utilization of Low and Medium Grade EnergyTianjinChina

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