scholarly journals Thermal Efficiency Gains Enabled by Using CO2 Mixtures in Supercritical Power Cycles

Energy ◽  
2021 ◽  
pp. 121899
Author(s):  
F. Crespi ◽  
P. Rodríguez de Arriba ◽  
D. Sánchez ◽  
A. Ayub ◽  
G. Di Marcoberardino ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Efficiency Gains ◽  
Power Cycles

Performance Comparison and Parametric Analysis of sCO2 Power Cycles Configurations

2018 ◽  
Author(s):  
Ali S. Alsagri ◽  
Andrew Chiasson ◽  
Ahmad Aljabr
Keyword(s):  
Power Output ◽  
Thermal Efficiency ◽  
Performance Comparison ◽  
Specific Power ◽  
Brayton Cycle ◽  
Computationally Efficient ◽  
Power Cycles ◽  
Optimization Study ◽  
Specific Power Output ◽  
Improve Calculation

A thermodynamic analysis and optimization of four supercritical CO2 Brayton cycles were conducted in this study in order to improve calculation accuracy; the feasibility of the cycles; and compare the cycles’ design points. In particular, the overall thermal efficiency and the power output are the main targets in the optimization study. With respect to improving the accuracy of the analytical model, a computationally efficient technique using constant conductance (UA) to represent heat exchanger performances is executed. Four Brayton cycles involved in this compression analysis, simple recaptured, recompression, pre-compression, and split expansion. The four cycle configurations were thermodynamically modeled and optimized based on a genetic algorithm (GA) using an Engineering Equation Solver (EES) software. Results show that at any operating condition under 600 °C inlet turbine temperature, the recompression sCO2 Brayton cycle achieves the highest thermal efficiency. Also, the findings show that the simple recuperated cycle has the highest specific power output in spite of its simplicity.

Simplified Analyses of Some Vapour Power Cycles

1996 ◽  
Vol 210 (3) ◽  
pp. 191-202 ◽  
Author(s):  
J H Horlock
Keyword(s):  
Thermal Efficiency ◽  
Low Pressure ◽  
Power Cycles ◽  
Turbine Expansion ◽  
The Difference

A range of vapour power cycles is analysed, using the assumption originally made by Schaff that along a turbine expansion line the difference between the (local) enthalpy (h) and the liquid enthalpy at the same pressure ( hL) may remain unchanged (β = h – hL is constant). The thermodynamics of the assumption are critically examined and it is found to be valid only over strictly limited ranges of properties (usually low-pressure levels). However, if such limitations are accepted, the analyses provide understanding of the effects of various key parameters on thermal efficiency, and of measures (such as feed heating, reheat, dual pressure boilers, etc.) that are taken to raise that efficiency.

Effect of Carbon Dioxide Recirculation and Pressure on Efficiency of the TIPS and ENEL Oxy-Coal Power Cycles

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Md. Moheiminul I. Khan ◽  
Mehrin Chowdhury ◽  
A. S. M. Arifur Rahman Chowdhury ◽  
Jad Aboud ◽  
Norman Love
Keyword(s):  
Flow Rate ◽  
Flue Gas ◽  
Thermal Efficiency ◽  
Pressure Range ◽  
Aspen Plus ◽  
Dominant Factor ◽  
Power Cycles ◽  
Thermodynamic Cycles ◽  
Coal Power ◽  
Cycle Efficiency

Abstract This paper presents the results of thermal efficiency of two coal based oxy-combustion thermodynamic cycles that are modeled using aspen plus. The objective of the present study is to perform a parametric analysis, investigating the effect of different recirculation ratios at different pressures on the efficiencies of the cycle named for the company, ENEL, and the thermo energy power system, TIPS, cycles using aspen plus® software. Variables include the flue gas recycle flow rate, the combustor temperature, and the operational pressure. Five recirculation ratios were investigated, ranging from 20% to 75%. It was determined that as the amount of recycled gas into the combustor increased, the thermal efficiency increased for both the TIPS and ENEL cycles. The highest thermal efficiency for TIPS is 37% and for ENEL is 38%, both occurring at a 75% recirculation ratio. After investigation, since combustion temperature and specific heat capacity decreases at higher recirculation ratios, the mass flow rate was the dominant factor that contributes to the increase in thermal efficiency of the cycle. At each recirculation ratio, the effect of pressure is also determined. For ENEL, the increase in cycle efficiency is 10% over the pressure range of 1–12 bar at a recirculation ratio of 20%, while the increase in cycle efficiency is only 1.5% at a higher recirculation ratio of 75%. For TIPS, the cycle efficiency increases by 4% at the recirculation ratio of 20% and increases by 3% at the recirculation ratio of 75% for a pressure range of 50–80 bar.

Thermodynamic Analysis of Supercritical and Subcritical Rankine Cycles

2016 ◽  
Author(s):  
Martín Salazar-Pereyra ◽  
Raúl Lugo-Leyte ◽  
Angélica Elizabeth Bonilla-Blancas ◽  
Helen Denise Lugo-Méndez
Keyword(s):  
Fuel Consumption ◽  
Thermodynamic Analysis ◽  
Thermal Efficiency ◽  
Heat Rate ◽  
Maximum Pressure ◽  
Steam Quality ◽  
Supercritical Conditions ◽  
Power Cycles ◽  
Low Pressure Turbine ◽  
Pressure Steam

In this work the thermodynamic analysis of two power cycles operating at ultracritical and supercritical conditions (300 bar, 600°C), and conventional or subcritical (124 bar, 538°C) is made. The supercritical cycle has ten and eight stages of regenerative feed heating. The conventional cycle has seven and six stages of regenerative feed heating. The aim of this analysis is to show the variation of work out, thermal efficiency, the heat rate, specific steam and fuel consumptions and the operating range of the pressure of overheating. For example, supercritical conditions operation of 300 bar and 600°C and a condensation pressure of 0.1107 bar, the maximum pressure reheating is 100 bar, because with a higher pressure, steam quality at the end of the step of expanding the low pressure turbine will be less than 0.88, requiring a second reheating. Additionally, the supercritical Rankine cycles have better thermal efficiency than subcritical cycles, increases in average 6%, and consequently the heat rate and steam and fuel consumption decrease.

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 CFD Simulation and Performance Analysis of Alternative Designs for High-Temperature Solid Particle Receivers

2011 ◽  
Author(s):  
Siri Sahib S. Khalsa ◽  
Joshua M. Christian ◽  
Gregory J. Kolb ◽  
Marc Ro¨ger ◽  
Lars Amsbeck ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Solid Particle ◽  
Thermal Efficiency ◽  
Cfd Simulation ◽  
Phase Particle ◽  
Cfd Simulations ◽  
Power Cycles ◽  
Incident Solar Radiation ◽  
The North ◽  
And Performance

Direct-absorption solid particle receivers are theoretically capable of yielding temperatures in excess of 1000°C, which enables higher efficiency power cycles and lower thermal storage costs. This paper presents rigorous CFD simulations of alternative solid particle receiver designs with recirculation to help identify optimal configurations that maximize the receiver thermal efficiency. The alternative receiver designs considered are a north-facing cavity receiver and a face-down surround-field cavity receiver. The CFD simulations model incident solar radiation from a heliostat field as a boundary condition on the model domain. The CFD simulations also couple convective flow with the thermal and discrete-phase (particle) solutions, which in turn affects absorption of incident solar radiation and thermal re-radiation within the receiver. The receivers are optimized to yield comparable particle temperatures at the outlets of 750–850°C, heated from an injection temperature of 300°C, and are compared on the basis of thermal efficiency. The CFD simulations yielded thermal efficiencies of the north-facing receiver at 72.3% (losses were 6.5% radiative and 20.9% convective) and the face-down receiver at 78.9% (losses were 11.4% radiative and 9.6% convective) at solar noon on March 22. Ongoing efforts are focused on reducing convective and radiative losses from both receiver configurations.

Gas Dynamic Simulation of Shockless Explosion Combustion for Gas Turbine Power Cycles

2017 ◽  
Author(s):  
T. S. Rähse ◽  
C. O. Paschereit ◽  
P. Stathopoulos ◽  
P. Berndt ◽  
R. Klein
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Inlet Temperature ◽  
Power Cycles ◽  
Total Enthalpy ◽  
Gas Dynamic ◽  
Turbine Inlet ◽  
Homogeneous Combustion

With the ongoing stagnation of the progress towards higher efficiency gas turbines, alternative approaches in combustion receive more attention than ever before. Besides, increasing efficiency and reducing emissions at the same time has become a first priority of the industry in the last few decades. Constant volume combustion is considered a technology capable of achieving a significant increase in thermal efficiency when applied in gas turbines. In this work, models of gas turbine cycles with two different combustion methods, being a shockless explosion combustion and an isobaric homogeneous combustion, will be simulated and compared. A code based on the one dimensional Euler equations is utilized to calculate the exhaust gas outlet parameters of the shockless explosion combustion chamber, while taking into account all the gas dynamic phenomena in it. The efficiency of the turbine is computed by steady state operational maps. The simulations provide numerous detailed results with a focus on the dependency of the SEC cycle’s thermal efficiency to the compressor pressure ratio and the turbine inlet temperature. Evaluating the kinetic energy in the total enthalpy of the turbine inlet flow is also an essential investigation.

Theoretical analysis of Rankine cycle operating with zeotropic mixtures of carbon dioxide and hydrocarbons

2021 ◽  
pp. 1-20
Author(s):  
Vineed Narayanan ◽  
Venkatarathnam Gadhiraju
Keyword(s):  
Carbon Dioxide ◽  
Theoretical Analysis ◽  
Heat Source ◽  
Thermal Efficiency ◽  
Multicomponent Mixture ◽  
Rankine Cycle ◽  
Small Scale ◽  
Multicomponent Mixtures ◽  
Power Cycles ◽  
Solar Powered

Abstract There is an increased interest in carbon dioxide based cycles as it requires smaller turbines than conventional Rankine cycles operating with steam. The focus of this work is the study of the performance of a Rankine cycle operating between 500 and 700 K (226.85 and 426.85 °C). Optimum mixtures of hydrocarbons and carbon dioxide have been worked out for use as working fluids in the above temperature range. This study shows that the use of multicomponent mixtures results in higher efficiency and smaller systems suitable for solar-powered small-scale power cycles. A thermal efficiency of 26.5% and volumetric work of 1945 J/l has been estimated with optimum multicomponent mixture derived in this work with a heat source temperature of 600 K and operating pressures of 100 and 40 bar at expander inlet and exit, respectively.

scholarly journals Design of a Simple Model of S. P. P. to Study the Effect of Increasing the Boiler Pressure on the Efficiency of the Model

2021 ◽  
Vol 2 (1) ◽  
pp. 1-7
Author(s):  
Abdlmanam Elmaryami ◽  
Hafied M. B. Khalid ◽  
Abdulssalam M. Abdulssalam ◽  
Alaa A. Abdulssalam ◽  
Mohamed M. Alssafi ◽  
...  
Keyword(s):  
Simple Model ◽  
Thermal Efficiency ◽  
Power Plants ◽  
Rankine Cycle ◽  
Important Application ◽  
Working Fluid ◽  
Operating Pressure ◽  
Steam Power ◽  
Power Cycles ◽  
Steam Power Plants

The Rankine cycle is one example of vapor power cycles. One important application of it is in steam power plants. In this paper, a simple model of the steam power plant is designed to study the effect of increasing boiler's pressures (3, 4, 5, and 6 bar respectively) on the efficiency and the dryness friction of the Model. Properties of the important points in the cycle were calculated consequently the losses in the pump, the losses in the condenser, expansion of the working fluid through the turbine, and the heat transfer to the working fluid through the boiler were determined. From the results, it was found that with the increasing of the boiler's operating pressure the thermal efficiency of the model cycle increases due to a substantial increase in network. Thus net-effect is marked increases in the thermal efficiency of the cycle on account of these measures.

Quantification of Efficiency Gains for Dilute IC Engines due to Increases of the Ratio of Specific Heats

2014 ◽  
Author(s):  
Jerald A. Caton
Keyword(s):  
Thermal Efficiency ◽  
Heat Losses ◽  
Efficiency Gains ◽  
Automotive Engine ◽  
Specific Heats ◽  
Cycle Simulation ◽  
Lack Of Information ◽  
Ic Engines ◽  
Lean Mixtures ◽  
Gas Recirculation

Recent engine developments have demonstrated significant thermal efficiency gains for IC engines employing lean mixtures and high levels of exhaust gas recirculation (EGR). These efficiency gains have often been attributed to reduced heat losses and increases of the ratio of specific heats. No previous publication, however, has provided the quantitative contributions from these two items. This lack of information, therefore, motivated the current work. An automotive engine was selected for this study, and a thermodynamic engine cycle simulation was used for the evaluation. Engine conditions included a range of loads and speeds. For each engine condition, three cases were considered. These cases varied the equivalence ratio from stoichiometric to 0.7, and varied the EGR from zero to 45%. Depending on the engine conditions, the net indicated thermal efficiency increased between 4.2% and 8.9% (absolute) for the engine with the lean mixture (ϕ = 0.7) and EGR (45%). The lower gas temperatures and lean mixtures resulted in reduced heat losses and increases of the ratio of specific heats. For all conditions examined, the majority of the thermal efficiency gains were due to the increases of the ratio of specific heats. The contributions from the increases of the ratio of specific heats toward the efficiency gains ranged between about 46% and 82% for the conditions examined. The rest of the gains were from the reduced heat losses.

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