Analysis of the Maximum Efficiency and the Maximum Net Power as Objective Functions for Organic Rankine Cycles Optimization

Abstract

Maximum efficiency and maximum net power output are some of the most important goals to reach the optimal conditions of organic Rankine cycles. This work compares two objective functions, the maximum efficiency function, β, and the maximum net power output function, ω. The van der Waals and PC-SAFT equations of state are used to calculate the qualitative and quantitative behavior, respectively. The analysis is performed for a set of eight working fluids, considering hydrocarbons and fourth-generation refrigerants. The results show that the two objective functions and the maximum entropy point are excellent references for describing the optimal organic Rankine cycle conditions. These references enable attaining a zone where the optimal operating conditions of an organic Rankine cycle can be found for any working fluid. This zone corresponds to a temperature range determined by the boiler outlet temperature obtained by the maximum efficiency function, maximum net power output function, and maximum entropy point. This zone is named the optimal temperature range of the boiler in this work.

Performance Analysis of Organic Rankine Cycle with Internal Heat Regeneration: Comparative Study of Binary Mixtures and Pure Constituents in Warm Regions

“…For example, Herath et al assessed the performance of simple ORC using seven working fluids: R-134a, R-245fa, benzene, methanol, ethanol, acetone, and propane (R-290) [23]. Their work indicates that ORC systems utilizing benzene and methanol as working fluids exhibit higher efficiency than other fluids studied for Evaporator temperatures in the range of 100 to 200 • C. González et al studied basic ORCs with eight working fluids, including hydrocarbons and fourth-generation refrigerants [24]. Their work provides a set of tools and recommendations specifically designed to aid in the optimization process of these systems, including the selection of appropriate working fluid for a given operating condition.…”