scholarly journals Inert and Reactive Working Fluids for Closed Power Cycles: Present Knowledge, Applications and Open Researches

2018 ◽  
Author(s):  
Silvia Lasala ◽  
Romain Privat ◽  
Jean-Noël Jaubert
Keyword(s):  
Present Knowledge ◽  
Working Fluids ◽  
Power Cycles

Performance Analysis and Comparison Study of Transcritical Power Cycles Using CO2-Based Mixtures as Working Fluids

2016 ◽  
Author(s):  
Jiaxi Xia ◽  
Jiangfeng Wang ◽  
Pan Zhao ◽  
Dai Yiping
Keyword(s):  
Critical Temperature ◽  
Parametric Optimization ◽  
Design Parameters ◽  
Working Fluid ◽  
Comparison Study ◽  
Software Environment ◽  
Working Fluids ◽  
Power Cycles ◽  
Power Cycle ◽  
Thermodynamic Performance

CO2 in a transcritical CO2 cycle can not easily be condensed due to its low critical temperature (304.15K). In order to increase the critical temperature of working fluid, an effective method is to blend CO2 with other refrigerants to achieve a higher critical temperature. In this study, a transcritical power cycle using CO2-based mixtures which blend CO2 with other refrigerants as working fluids is investigated under heat source. Mathematical models are established to simulate the transcritical power cycle using different CO2-based mixtures under MATLAB® software environment. A parametric analysis is conducted under steady-state conditions for different CO2-based mixtures. In addition, a parametric optimization is carried out to obtain the optimal design parameters, and the comparisons of the transcritical power cycle using different CO2-based mixtures and pure CO2 are conducted. The results show that a raise in critical temperature can be achieved by using CO2-based mixtures, and CO2-based mixtures with R32 and R22 can also obtain better thermodynamic performance than pure CO2 in transcritical power cycle. What’s more, the condenser area needed by CO2-based mixture is smaller than pure CO2.

Cyclic Methylsiloxanes as Working Fluids for Space Power Cycles

1993 ◽  
Vol 115 (3) ◽  
pp. 130-137 ◽  
Author(s):  
G. Angelino ◽  
C. Invernizzi
Keyword(s):  
High Temperature ◽  
Full Potential ◽  
Working Fluids ◽  
Power Cycles ◽  
Thermodynamic Performance ◽  
High Level ◽  
Organic Fluids ◽  
Large Wheel ◽  
Turbine Exhaust ◽  
Fast Rotating

The potential merits of cyclic polymethylsiloxanes, particularly those conventionally denominated D4 and D5, as working fluids for space power cycles are discussed. The attractive technical characteristics of these substances which are fully nontoxic, moderately flammable, and stable at high temperature are presented. Some experimental results on vapor pressure and on thermal stability are reported. A maximum operating temperature of about 400°C appears achievable. A comprehensive thermodynamic analysis comparing siloxanes with other classes of high temperature fluids is performed. The peculiar characters of siloxane cycles are found to be: a good overall efficiency achieved through a massive regeneration, a moderate expansion work, and an abundant volume flow at turbine exhaust. A number of two-stage turbines for two power levels (i.e., 30 and 5 kW) were designed using an appropriate optimization program. The resulting main features of such expanders were a satisfactory efficiency, a low rotating and peripheral speed, and a comparatively large wheel diameter. These characteristics seem of particular interest for low capacity systems where, with other fluids, turbines tend to be impractically small and fast rotating and where a high level of regeneration becomes more acceptable. In considering for the sake of comparison the thermodynamic performance of many classes of organic fluids, it becomes apparent that the full potential of organic power cycles in view of the variety of future needs has not yet been thoroughly investigated.

scholarly journals Performance Comparison of Advanced Transcritical Power Cycles with High-Temperature Working Fluids for the Engine Waste Heat Recovery

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5886
Author(s):  
Xinxing Lin ◽  
Chonghui Chen ◽  
Aofang Yu ◽  
Likun Yin ◽  
Wen Su
Keyword(s):  
High Temperature ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Performance Comparison ◽  
Design System ◽  
Working Fluids ◽  
Power Cycles ◽  
System Parameters ◽  
Pressure Cycle

To efficiently recover the waste heat of mobile engine, two advanced transcritical power cycles, namely split cycle and dual pressure cycle, are employed, based on the recuperative cycle. Performances of the two cycles are analyzed and compared through the development of thermodynamic models. Under given gas conditions, seven high-temperature working fluids, namely propane, butane, isobutane, pentane, isopentane, neopentane, and cyclopentane, are selected for the two cycles. At the design system parameters, the highest work 48.71 kW, is obtained by the split cycle with butane. For most of fluids, the split cycle has a higher work than the dual pressure cycle. Furthermore, with the increase of turbine inlet pressure, net work of the split cycle goes up firstly and then decreases, while the work of dual pressure cycle increases slowly. For the split cycle, there exists a split ratio to get the maximum network. However, for the dual pressure cycle, the larger the evaporation temperature, the higher the net work. On this basis, system parameters are optimized by genetic algorithm to maximize net work. The results indicate that the highest work 49.96 kW of split cycle is obtained by pentane. For the considered fluids, except cyclopentane, split cycle always has a higher work than dual pressure cycle. Due to the higher net work and fewer system components, split cycle is recommended for the engine waste heat recovery.

The Totally Supercritical Steam Cycle

1969 ◽  
Vol 91 (2) ◽  
pp. 113-119 ◽  
Author(s):  
J. H. Potter
Keyword(s):  
Supercritical Pressure ◽  
Heat Rejection ◽  
Working Fluids ◽  
Power Cycles ◽  
Heat Addition ◽  
Power Stations ◽  
Steam Cycle

Recently a number of new power cycles have been proposed in which heat rejection as well as heat addition has been at supercritical pressure. Although a number of working fluids have been suggested, the present study is restricted to steam. The advantages and limitations of the totally supercritical steam cycle are explored in terms of the conditions under which modern power stations operate.

Effect of the Working Fluid on Performance of the ORC and Combined Brayton/ORC Cycle

2017 ◽  
Author(s):  
Alireza Javanshir ◽  
Nenad Sarunac
Keyword(s):  
Thermal Efficiency ◽  
Organic Rankine Cycle ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Cycle Performance ◽  
Working Fluid ◽  
Working Fluids ◽  
Power Cycles ◽  
Topping Cycle ◽  
Selection Of

This study focuses on the power cycles such as organic Rankine cycle (ORC) and combined regenerative Brayton/ORC. The selection of working fluids and power cycles is traditionally conducted by trial and error method and performing a large number of parametric calculations over a range of operating conditions. A methodology for selection of optimal working fluid based on the cycle operating conditions and thermophysical properties of the working fluids was developed in this study. Thermodynamic performance (thermal efficiency and net power output) of a simple subcritical and supercritical ORC was analyzed over a range of operating conditions for a number of working fluids to determine the effect of operating parameters on cycle performance and select the best working fluid. New expressions for thermal efficiency of a simple ORC are proposed. In case of a regenerative Brayton/ORC, the results show that CO2 is the best working fluid for the topping cycle. Depending on the exhaust temperature of the topping cycle, Isobutane, R11 and Ethanol are the preferred working fluids for the bottoming (ORC) cycle, resulting in highest efficiency of the combined cycle. Finally, a performance map is presented as guidance for selection of the best working fluid for specific cycle operating conditions.

scholarly journals System Design and Application of Supercritical and Transcritical CO2 Power Cycles: A Review

2021 ◽  
Vol 9 ◽  
Author(s):  
Enhua Wang ◽  
Ningjian Peng ◽  
Mengru Zhang
Keyword(s):  
Power Systems ◽  
Environmentally Friendly ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Low Grade ◽  
Heat Sources ◽  
Technological Advancement ◽  
Working Fluids ◽  
Power Cycles ◽  
Low Grade Heat

Improving energy efficiency and reducing carbon emissions are crucial for the technological advancement of power systems. Various carbon dioxide (CO2) power cycles have been proposed for various applications. For high-temperature heat sources, the CO2 power system is more efficient than the ultra-supercritical steam Rankine cycle. As a working fluid, CO2 exhibits environmentally friendly properties. CO2 can be used as an alternative to organic working fluids in small- and medium-sized power systems for low-grade heat sources. In this paper, the main configurations and performance characteristics of CO2 power systems are reviewed. Furthermore, recent system improvements of CO2 power cycles, including supercritical Brayton cycles and transcritical Rankine cycles, are presented. Applications of combined systems and their economic performance are discussed. Finally, the challenges and potential future developments of CO2 power cycles are discussed. CO2 power cycles have their advantages in various applications. As working fluids must exhibit environmentally-friendly properties, CO2 power cycles provide an alternative for power generation, especially for low-grade heat sources.

Sign in / Sign up

Export Citation Format

Share Document