Power Performance of a Nonisentropic Brayton Cycle

1991 ◽  
Vol 113 (4) ◽  
pp. 501-504 ◽  
Author(s):  
C. Wu ◽  
R. L. Kiang
Keyword(s):  
Heat Transfer ◽  
Power Output ◽  
Finite Time ◽  
Heat Engine ◽  
Heat Transfer Analysis ◽  
Brayton Cycle ◽  
Power Performance ◽  
Engine Efficiency ◽  
Compression And Expansion ◽  
Cycle Efficiency

Work and power optimization of a Brayton cycle are analyzed with a finite-time heat transfer analysis. This work extends the recent flurry of publications in heat engine efficiency under the maximum power condition by incorporating nonisentropic compression and expansion. As expected, these nonisentropic processes lower the power output as well as the cycle efficiency when compared with an endoreversible Brayton cycle under the same conditions.

scholarly journals Optimal temperatures and maximum power output of a complex system with linear phenomenological heat transfer law

2009 ◽  
Vol 13 (4) ◽  
pp. 33-40 ◽  
Author(s):  
Lingen Chen ◽  
Jun Li ◽  
Fengrui Sun
Keyword(s):  
Complex System ◽  
Heat Transfer ◽  
Power Output ◽  
Finite Time ◽  
Heat Engine ◽  
Thermal Capacity ◽  
Maximum Power ◽  
Finite Time Thermodynamics ◽  
Maximum Power Output ◽  
Different Temperatures

A complex system including several heat reservoirs, finite thermal capacity subsystems with different temperatures and a transformer (heat engine or refrigerator) with linear phenomenological heat transfer law [q ? ?(T -1)] is studied by using finite time thermodynamics. The optimal temperatures of the subsystems and the transformer and the maximum power output (or the minimum power needed) of the system are obtained.

The Regenerative Criteria of an Irreversible Brayton Heat Engine and its General Optimum Performance Characteristics

2005 ◽  
Vol 128 (3) ◽  
pp. 216-222 ◽  
Author(s):  
Yue Zhang ◽  
Congjie Ou ◽  
Bihong Lin ◽  
Jincan Chen
Keyword(s):  
Heat Transfer ◽  
Power Output ◽  
Pressure Ratio ◽  
Heat Engine ◽  
Optimal Performance ◽  
Performance Characteristics ◽  
Heat Transfer Area ◽  
Total Heat Transfer ◽  
Heat Engines ◽  
Compression And Expansion

An irreversible cycle model of the Brayton heat engine is established, in which the irreversibilities resulting from the internal dissipation of the working substance in the adiabatic compression and expansion processes and the finite-rate heat transfer in the regenerative and constant-pressure processes are taken into account. The power output and efficiency of the cycle are expressed as functions of temperatures of the working substance and the heat sources, heat transfer coefficients, pressure ratio, regenerator effectiveness, and total heat transfer area including the heat transfer areas of the regenerator and other heat exchangers. The regenerative criteria are given. The power output is optimized for a given efficiency. The general optimal performance characteristics of the cycle are revealed. The optimal performance of the Brayton heat engines with and without regeneration is compared quantitatively. The advantages of using the regenerator are expounded. Some important parameters of an irreversible regenerative Brayton heat engine, such as the temperatures of the working substance at different states, pressure ratio, maximum value of the pressure ratio, regenerator effectiveness and ratios of the various heat transfer areas to the total heat transfer area of the cycle, are further optimized. The optimal relations between these parameters and the efficiency of the cycle are presented by a set of characteristic curves for some assumed compression and expansion efficiencies. The results obtained may be helpful to the comprehensive understanding of the optimal performance of the Brayton heat engines with and without regeneration and play a theoretical instructive role for the optimal design of a regenerative Brayton heat engine.

Using Staged Compression and Expansion to Enhance the Performance of a Gas Turbine Fuel Cell Hybrid System

2009 ◽  
Author(s):  
John VanOsdol ◽  
Edward L. Parsons
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Hybrid System ◽  
Cell Hybrid ◽  
Pressure Ratio ◽  
Heat Engine ◽  
Brayton Cycle ◽  
System Configuration ◽  
Compression And Expansion ◽  
Fuel Cell Hybrid

It has long been recognized that the heat generated from a solid oxide fuel cell (SOFC) is adequate to drive an external heat engine. The combination of the fuel cell plus the heat engine is called a gas turbine fuel cell hybrid power generation system. In most hybrid systems the heat engine consists of a single compressor and single turbine, arranged in either a Brayton cycle or a recuperated Brayton cycle. One characteristic of hybrid power cycles is that the compression costs are substantial. When this cycle is used in a coal fired hybrid system that is configured with an isolated anode stream to isolate and compress CO2, the work to compress the cathode air can greatly exceed the work to compress the CO2. It has also been shown for this same system that using intercooled compression for the cathode air reduces this compression cost. Since there have been no exhaustive studies performed which quantify these effects it is not clear exactly how much reduction in compression cost is possible. In this work we compare three hybrid systems. The first systems has a single compressor and turbine, run at a low pressure ratio as a recuperated Brayton cycle and at high pressure ratio as a simple Brayton cycle (see Figure 1). We then alter the recuperated Brayton cycle using both staged compression and staged expansion. The second system is thus configured with two compressors and two turbines. For this system an intercooler is placed between the compressors and the fuel cell stack is divided into two stacks each followed by a turbine (see Figure 3). Similarly the third system divides the compression and expansion legs of the cycle again into three compressors with intercoolers, and three fuel cell stacks each followed by its own turbine (see Figure 5). As the system configuration is altered by successive divisions of both the compression and expansion legs of the thermal heat engine cycle, the system configuration is transformed from a simple Brayton cycle to a staged approximation to an Ericsson cycle. We show that this new configuration for the gas turbine fuel cell hybrid system not only reduces the high cost of compression, but it makes more heat available for auxiliary system operations. In coal fired systems these auxiliary operations would include pre heating coal for the gasification system, reheating the syngas after cooling or even heating steam for a bottoming cycle.

Finite Time Thermodynamics: Realizability Domain of Heat to Work Converters

2019 ◽  
Vol 44 (2) ◽  
pp. 181-191 ◽  
Author(s):  
M. A. Zaeva ◽  
A. M. Tsirlin ◽  
O. V. Didina
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Energy Conversion ◽  
Conversion Efficiency ◽  
Finite Time ◽  
Heat Engine ◽  
Energy Conversion Efficiency ◽  
Maximum Power ◽  
Working Fluid ◽  
Finite Time Thermodynamics

Abstract From the point of view of finite time thermodynamics, the performance boundaries of thermal machines are considered, taking into account the irreversibility of the heat exchange processes of the working fluid with hot and cold sources. It is shown how the kinetics of heat exchange affects the shape of the optimal cycle of a heat engine and its performance, with a focus on the energy conversion efficiency in the maximum power mode. This energy conversion efficiency can depend only on the ratio of the heat transfer coefficients to the sources or not depend on them at all. A class of kinetic functions corresponding to “natural” requirements is introduced and it is shown that for any kinetics from this class the optimal cycle consists of two isotherms and two adiabats, not only for the maximum power problem, but also for the problem of maximum energy conversion efficiency at a given power. Examples are given for calculating the parameters of the optimal cycle for the case when the heat transfer coefficient to the cold source is arbitrarily large and for kinetics in the form of a Fourier law.

Brayton Cycle Optimization

1997 ◽  
Author(s):  
Sushanta K. Mitra ◽  
Achintya Mukhopadhaya
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Power Output ◽  
Practical Importance ◽  
Heat Transfer Process ◽  
Working Fluid ◽  
Operating Parameters ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
The Ideal

The Brayton Cycle is the ideal cycle for simple gas turbine applications. The heat transfer process in such a cycle is of practical importance as far as power output is considered. The present work focusses on the power output from an ideally reversible Brayton cycle and criteria for optimum power based on its operating parameters like the specific heat of hot and cold fluids, working fluid and heater inlet temperature is discussed here.

scholarly journals Analyses of the Load Following Capabilities of Brayton Helium Gas Turbine Cycles for Generation IV Nuclear Power Plants

2017 ◽  
Vol 3 (4) ◽  
Author(s):  
A. Gad-Briggs ◽  
P. Pilidis ◽  
T. Nikolaidis
Keyword(s):  
Power Output ◽  
Nuclear Power ◽  
Power Plants ◽  
Pressure Control ◽  
Reactor Power ◽  
Critical Parameters ◽  
Power Performance ◽  
Load Following ◽  
Study Results ◽  
Cycle Efficiency

The control system for generation IV nuclear power plant (NPP) design must ensure load variation when changes to critical parameters affect grid demand, plant efficiency, and component integrity. The objective of this study is to assess the load following capabilities of cycles when inventory pressure control is utilized. Cycles of interest are simple cycle recuperated (SCR), intercooled cycle recuperated (ICR), and intercooled cycle without recuperation (IC). First, part power performance of the IC is compared to results of the SCR and ICR. Subsequently, the load following capabilities are assessed when the cycle inlet temperatures are varied. This was carried out using a tool designed for this study. Results show that the IC takes ∼2.7% longer than the ICR to reduce the power output to 50% when operating in design point (DP) for similar valve flows, which correlates to the volumetric increase for the IC inventory storage tank. However, the ability of the IC to match the ICR's load following capabilities is severely hindered because the IC is most susceptible to temperature variation. Furthermore, the IC takes longer than the SCR and ICR to regulate the reactor power by a factor of 51 but this is severely reduced, when regulating NPP power output. However, the IC is the only cycle that does not compromise reactor integrity and cycle efficiency when regulating the power. The analyses intend to aid the development of cycles specifically gas-cooled fast reactors (GFRs) and very high temperature reactors (VHTRs), where helium is the coolant.

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