scholarly journals Performance Optimization of an Air-Standard Irreversible Dual-Atkinson Cycle Engine Based on the Ecological Coefficient of Performance Criterion

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Guven Gonca ◽  
Bahri Sahin
Keyword(s):  
Performance Optimization ◽  
Pressure Ratio ◽  
Performance Criterion ◽  
Coefficient Of Performance ◽  
Cycle Performance ◽  
Temperature Ratio ◽  
Finite Rate ◽  
Ecological Performance ◽  
Atkinson Cycle ◽  
Internal Irreversibility

This paper presents an ecological performance analysis and optimization for an air-standard irreversible Dual-Atkinson cycle (DAC) based on the ecological coefficient of performance (ECOP) criterion which includes internal irreversibilities, heat leak, and finite-rate of heat transfer. A comprehensive numerical analysis has been realized so as to investigate the global and optimal performances of the cycle. The results obtained based on the ECOP criterion are compared with a different ecological function which is named as the ecologic objective-function and with the maximum power output conditions. The results have been attained introducing the compression ratio, cut-off ratio, pressure ratio, Atkinson cycle ratio, source temperature ratio, and internal irreversibility parameter. The change of cycle performance with respect to these parameters is investigated and graphically presented.

scholarly journals Optimization of absorption systems: case of the refrigerators and heat pumps

2019 ◽  
Vol Volume 30 - 2019 - MADEV... ◽  
Author(s):  
René Tchinda ◽  
Paiguy Armand Ngouateu Wouagfack
Keyword(s):  
Performance Optimization ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Entropy Generation Rate ◽  
Design Parameters ◽  
Working Fluid ◽  
Ecological Design ◽  
Ecological Performance ◽  
Heating Load ◽  
Main Components

The new thermo-ecological performance optimization of absorption is investigated by taking the ecological coefficient of performance ECOP as an objective function. ECOP has been expressed in terms of the temperatures of the working fluid in the main components of the system. The maximum of ECOP and the corresponding optimal temperatures of the working fluid and other optimal performance design parameters such as coefficient of performance, specific cooling load of absorption refrigerators, specific heating load of absorption heat pumps, specific entropy generation rate and the distributions of the heat exchanger areas have been derived analytically. The obtained results may provide a general theoretical tool for the ecological design of absorption refrigerators and heat pumps.

Model of irreversible finite-heat capacity heat reservoir absorption heat transformer cycle and its application

2007 ◽  
Vol 221 (12) ◽  
pp. 1643-1651 ◽  
Author(s):  
L Chen ◽  
X Qin ◽  
F Sun
Keyword(s):  
Performance Characteristic ◽  
Variable Temperature ◽  
Coefficient Of Performance ◽  
Cycle Performance ◽  
Working Fluid ◽  
Cycle Model ◽  
Heating Load ◽  
Internal Irreversibility ◽  
General Relations ◽  
Heat Transformer

An irreversible four-temperature-level absorption heat transformer cycle model with variable-temperature heat reservoirs is established, which considers the heat resistances between the heat reservoirs and the working fluid, the internal irreversibility due to internal dissipation of the working fluid, and the heat leakages between the heat reservoirs and the surrounding. The general relations between the heating load and the coefficient of performance are derived, and the general performance characteristic and the optimal performance characteristic are obtained using numerical examples. Moreover, the cycle model and the derived general relations are confirmed by comparing the prediction results of the model and engineering analysis results for real absorption heat transformer, and the cycle performance characteristic are discussed. The results obtained herein can provide some guidance for the optimal design of absorption heat transformer.

Performance Optimization of a Combined Heat Pump Cycle

2003 ◽  
Vol 10 (04) ◽  
pp. 377-389 ◽  
Author(s):  
Lingen Chen ◽  
Yuehong Bi ◽  
Fengrui Sun ◽  
Chih Wu
Keyword(s):  
Heat Resistance ◽  
Steady Flow ◽  
Heat Pump ◽  
Performance Optimization ◽  
Coefficient Of Performance ◽  
Cycle Model ◽  
Heat Leakage ◽  
Heating Load ◽  
Internal Irreversibility ◽  
Optimal Heating

A steady flow combined heat pump cycle model with heat resistance, heat leakage and internal irreversibility is built in this paper. The optimal performance of the model is studied. The relation between optimal heating load and coefficient of performance (COP), as well as the maximum COP and the corresponding heating load are derived.

scholarly journals Performance Optimization of Closed Cycle Gas Turbines

1984 ◽  
Author(s):  
W. Hilary Lee
Keyword(s):  
Performance Optimization ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Performance Model ◽  
Specific Work ◽  
Closed Cycle ◽  
Temperature Ratio ◽  
Working Media ◽  
Cycle Efficiency ◽  
Cycle Temperature

Criteria for optimal cycle pressure ratio with respect to maximum cycle efficiency and maximum net specific work as functions of cycle temperature ratio were developed based on a non-dimensionalized performance model for closed cycle gas turbines. The effects of total specific pressure drop, the component efficiencies, and cycle working media properties on the optimal pressure ratio are discussed.

Monte Carlo Optimization of Two-Stage Cascade R134A Refrigeration System With Flash Chamber

2008 ◽  
Author(s):  
Yousef M. Abdel-Rahim
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Pressure Ratio ◽  
Volume Ratio ◽  
Heat Rate ◽  
Cycle Performance ◽  
Specific Work ◽  
Refrigeration System ◽  
Two Stage ◽  
Monte Carlo Optimization

Present paper studies the optimal characteristics of the two-stage cascade R134A refrigeration system with flash and mixing chambers over its operating ranges of all cycle controlling parameters. The COP, total heat rate in Qin, total work rate in Win and second law efficiency ηII are used as cycle performance parameters. Compared to the practically-limited other rate-based optimization methods and to other experimentally-optimized specific cases of cycle parameters, the application of Monte Carlo method has proved to be very effective for optimizing the cycle performance in its global sense over all cycle controlling parameters. Correlations relating performance and cycle controlling parameters are presented and discussed. Study shows that COP of the cycle can reach a value of 8 at intermediate pressure P2 of about 200 kPa, and a maximum value of 9.92 at about 370 kPa and 720 kPa, beyond which COP goes as low as 4.2. P2 alone has no significant effect on Qin, Win and ηII unless values of other controlling parameters are specified. Values of Qin, Win and ηII can reach as high as 94 kW, 23 kW and 0.85 and as low as 6.8 kW, 1.1 kW and 0.57 respectively depending on other cycle parameters. Neither pressure ratio nor volume ratio of the HP compressor has any effect on Qin, Win or ηII. However, the ratio of inlet to exit temperatures of the condenser has the greatest effect on both ηII and the volumetric specific work of the HP compressor, which is about double the value of the volumetric specific work of the LP compressor. Study shows an almost linear relationship between the two mass flow rates in the upper and lower loops of the cycle, where its value in the lower LP loop is about 75% that in the upper HP loop. Findings of the present work as well as the elaborate application of Monte Carlo method to real cycles can greatly open the way for reducing the trade-off design methods currently used in developing such systems as well as direct the useful experimentations and assessment of such designed systems.

Experimental Investigation of a Desiccant Wheel Cycle

2012 ◽  
Author(s):  
Ali Al-Alili ◽  
Yunho Hwang ◽  
Reinhard Radermacher
Keyword(s):  
Air Conditioning ◽  
Removal Rate ◽  
Dew Point ◽  
Coefficient Of Performance ◽  
Cycle Performance ◽  
Air Conditioners ◽  
Considerable Portion ◽  
Temperature Heat ◽  
Air Conditioning Systems ◽  
Desiccant Material

In hot and humid regions, removal of moisture from the air represents a considerable portion of the air conditioning load. Conventionally, air conditioning systems have to lower the air temperature below its dew point to accomplish dehumidification. Desiccant air conditioners offer a solution to meet the humidity and temperature requirements of buildings via decoupling latent and sensible loads. In this work, the performance of a new desiccant material is investigated experimentally. This desiccant material can be regenerated using a low temperature heat source, as low as 45°C. It also has a unique S-shape isotherm. The effects of the process air stream’s temperature and humidity, the regeneration temperature, the ventilation mass flow rate, and the desiccant wheel’s rotational speed on the cycle performance are investigated. ARI-humid conditions are used as a baseline and the moisture mass balance is maintained within 5%. The results are presented in terms of the moisture removal rate and latent coefficient of performance (COPlat). The results show a desiccant wheel’s COPlat higher than unity when it is coupled with an enthalpy wheel.

scholarly journals Kalina-Flash Cycle Performance Analysis and Parametric Optimization

2019 ◽  
Author(s):  
Raveendra Nath R ◽  
C. Vijaya Bhaskar Reddy ◽  
K.Hemachandra Reddy
Keyword(s):  
Mass Fraction ◽  
Parametric Optimization ◽  
Pressure Ratio ◽  
Cycle Performance ◽  
Second Law ◽  
Water Mixture ◽  
Objective Functions ◽  
Thermodynamic Investigation ◽  
Kalina Cycle ◽  
Multi Objective Genetic Algorithm

In this paper, a thermodynamic investigation is done on a Kalina-flash cycle. This work is initially validated with the Kalina cycle power plant, Wich is commissioned in Husavic. Low-temperature Kalina-flash is considered for this study. This cycle is working with the ammonia-water mixture. The Kalina-flash cycle was optimized in the view of exergy and thermal efficiency. A multi-objective genetic algorithm is used to accomplish optimization. The optimum values of the objective functions are observed to be 40.20 and 11.70% respectively. At last, The influence of the separator inlet dryness fraction, basic ammonia mass fraction, temperature and flash pressure ratio on the first and second law efficiencies are analysed.

An Experimental Study of Turbine Vane Heat Transfer With Leading Edge and Downstream Film Cooling

1990 ◽  
Vol 112 (3) ◽  
pp. 477-487 ◽  
Author(s):  
N. V. Nirmalan ◽  
L. D. Hylton
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Pressure Ratio ◽  
Leading Edge ◽  
External Heat ◽  
Gas Temperature ◽  
Temperature Ratio ◽  
External Heat Transfer ◽  
Turbine Vane

This paper presents the effects of downstream film cooling, with and without leading edge showerhead film cooling, on turbine vane external heat transfer. Steady-state experimental measurements were made in a three-vane, linear, two-dimensional cascade. The principal independent parameters—Mach number, Reynolds number, turbulence, wall-to-gas temperature ratio, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio—were maintained over ranges consistent with actual engine conditions. The test matrix was structured to provide an assessment of the independent influence of parameters of interest, namely, exit Mach number, exit Reynolds number, coolant-to-gas temperature ratio, and coolant-to-gas pressure ratio. The vane external heat transfer data obtained in this program indicate that considerable cooling benefits can be achieved by utilizing downstream film cooling. The downstream film cooling process was shown to be a complex interaction of two competing mechanisms. The thermal dilution effect, associated with the injection of relatively cold fluid, results in a decrease in the heat transfer to the airfoil. Conversely, the turbulence augmentation, produced by the injection process, results in increased heat transfer to the airfoil. The data presented in this paper illustrate the interaction of these variables and should provide the airfoil designer and computational analyst with the information required to improve heat transfer design capabilities for film-cooled turbine airfoils.

The Port Width and Position Determination for Pressure-Exchange Ejector

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Wenjing Zhao ◽  
Dapeng Hu ◽  
Peiqi Liu ◽  
Yuqiang Dai ◽  
Jiupeng Zou ◽  
...  
Keyword(s):  
High Pressure ◽  
Performance Optimization ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Operating Conditions ◽  
Maximum Deviation ◽  
Dimensionless Time ◽  
Pressure Flow ◽  
Outlet Pressure ◽  
Pressure Exchange

A pressure-exchange ejector transferring energy by compression and expansion waves has the potential for higher efficiency. The width and position of each port are essential in pressure-exchange ejector design. A dimensionless time τ expressing both port widths and the positions of port ends was introduced. A prototype was designed and the experimental system was set up. Many sets of experiment with different geometrical arrangements were conducted. The results suggest that the efficiency greatly changes with the geometrical arrangements. The efficiency is about 60% at proper port widths and positions, while at improper geometrical arrangements, the efficiency is much lower and the maximum deviation may reach about 20%. The proper dimensionless port widths and positions at different operating conditions are obtained. For a fixed overall pressure ratio, the widths of the high pressure flow inlet and middle pressure flow outlet increase as the outlet pressure increases and the low pressure flow inlet width is reduced with a larger outlet pressure. The middle pressure flow outlet (MO) opening end remains constant at different outlet pressures. The positions of the high pressure flow inlet (HI) closed end and the low pressure flow inlet (LI) open end increase with the elevation of outlet pressure, however, the distance between the HI closing end and the LI opening end is constant. The port widths and positions have a significant influence on the performance of the pressure-exchange ejector. The dimensionless data obtained are very valuable for pressure-exchange ejector design and performance optimization.

A Feasibility Study of a High-Speed Combustor for Turbomachine Applications

1970 ◽  
Author(s):  
Irving Fruchtman
Keyword(s):  
Turbulent Mixing ◽  
High Speed ◽  
Pressure Ratio ◽  
Small Mass ◽  
Temperature Profiles ◽  
Flow Conditions ◽  
Finite Rate ◽  
High Pressure Ratio ◽  
Series Of Experiments ◽  
Analysis Design

The theoretical analysis, design, and experimental study of a high-speed combustion chamber are described. Such a burner may be used when the compressor outflow speed is so high that diffusion to the usual burner entrance conditions presents severe loss penalties. The study showed for a small mass flow-high pressure ratio turbomachine, that combined diffusor and combustor losses are minimum for a burner entrance Mach number of about 0.5. To design the burner a finite rate chemistry and turbulent mixing computer program was used; the combustor modeling and flame spread predictions are discussed. A series of experiments are described and burner pressure loss and temperature profiles are shown over a range of burner air-flow conditions.

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