Showing papers on "Thermal efficiency published in 2008"
TL;DR: In this article, the authors collected and analyzed the body of work written mainly in scientific journals about diesel engine emissions when using biodiesel fuels as opposed to conventional diesel fuels, focusing on the most concerning emissions: nitric oxides and particulate matter.
1,768 citations
TL;DR: In this paper, an extensive analysis on direct contact membrane distillation performance was developed to estimate the mass flux and the heat efficiency, considering transport phenomena, membrane structural properties and most sensitive process parameters, with the aim to provide optimization guidelines for materials and methods.
729 citations
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01 Jan 2008
TL;DR: In this paper, the authors present a classification of fuel cells based on their properties: 1.1 The Physical Nature of the Thermodynamic Variables, 2.2 The Electrochemical Reaction, 3.3 Determination of the Change in Enthalpy for Non-reacting Species and Mixtures.
Abstract: Chapter 1. Introduction to Fuel Cells. 1.1 Preliminary Remarks. 1.2 Fuel Cells as Electrochemical Engines. 1.3 The Generic Fuel Cell and Stack. 1.4 Classification of Fuel Cells. 1.5 Potential Fuel Cell Applications and Markets. 1.6 History of Fuel Cell Development. 1.7 Summary. Chapter 2. Basic Electrochemical Principles. 2.1 Electrochemical versus Chemical Reactions. 2.2 The Electrochemical Reaction. 2.3 Scientific Units, Constants, and Basic Laws. 2.4 Faraday?s Laws ? Consumption and Production of Specie. 2.5 Measures of Reactant Utilization Efficiency. 2.6 The Generic Fuel Cell. 2.7 Summary. Chapter 3. Thermodynamics of Fuel Cell Systems. 3.1 The Physical Nature of the Thermodynamic Variables. 3.2 Heat of Formation, Sensible Enthalpy, and Latent Heat. 3.3 Determination of the Change in Enthalpy for Non-reacting Species and Mixtures. 3.4 Determination of the Change in Enthalpy for Reacting Species and Mixtures. 3.5 Psychrometrics- Thermodynamics of Moist Air Mixtures. 3.6 Thermodynamic Efficiency of a Fuel Cell. 3.7 Maximum Expected Open Circuit Voltage-The Nernst Voltage. 3.8 Summary. Chapter 4. Performance Characterization of Fuel Cell Systems. 4.1 Polarization Curve. 4.2 Region I: Activation Polarization. 4.3 Region II: Ohmic Polarization. 4.4 Region III: Concentration Polarization. 4.5 Region IV: Other Polarization Losses. 4.6 Polarization Curve Model . 4.7 Summary. Chapter 5. Transport in Fuel Cell Systems. 5.1 Ion Transport in the Electrolyte. 5.2 Electron Transport. 5.3 Gas-Phase Mass Transport. 5.4 Single-Phase Flow in Channels. 5.5 Multi-Phase Mass Transport in Channels and Porous Media. 5.6 Heat Generation and Transport. 5.7 Summary. Chapter 6. The Polymer Electrolyte Fuel Cell . 6.1 The Hydrogen PEFC. 6.2 Water Balance in a H2 PEFC. 6.3 Flow Field Configurations and Stack Design. 6.4 Direct Alcohol Polymer Electrolyte Fuel Cells. 6.5 PEFC Degradation. 6.6 Multi-dimensional Effects. 6.7 Summary. Chapter 7. Other Fuel Cells. 7.1 Solid Oxide Fuel Cells. 7.2 Molten Carbonate Fuel Cells. 7.3 Phosphoric Acid Fuel Cells. 7.4 Alkaline Fuel Cells. 7.5 Biological and Microbial Fuel Cells. 7.6 Summary. Chapter 8. Hydrogen Storage, Generation, and Delivery. 8.1 Modes of Storage. 8.2 Modes of Generation. 8.3 Hydrogen Delivery . 8.4 Summary. Chapter 9. Experimental Diagnostics and Diagnosis. 9.1 Methods to Delineate Polarization Curve Losses. 9.2 Physical Probes and Visualization. 9.3 Degradation Measurements. 9.4 Summary. Appendix. Tables, Figures, and Charts. Index to Tables, Figures, and Charts. Index to Textbook.
651 citations
TL;DR: In this article, an analysis of regenerative organic Rankine cycles using dry organic fluids, to convert waste energy to power from low-grade heat sources is presented, and the evaluation for both configurations will be performed using a combined first and second law analysis by varying certain system operating parameters at various reference temperatures and pressures.
520 citations
TL;DR: In this paper, a two-step solar-driven thermochemical heat engine based on iron oxide and iron oxide mixed with other metal oxide (ferrites) working materials is proposed.
Abstract: Thermochemical cycles are a type of heat engine that utilize high-temperature heat to produce chemical work. Like their mechanical work producing counterparts, their efficiency depends on the operating temperature and on the irreversibility of their internal processes. With this in mind, we have invented innovative design concepts for two-step solar-driven thermochemical heat engines based on iron oxide and iron oxide mixed with other metal oxide (ferrites) working materials. The design concepts utilize two sets of moving beds of ferrite reactant materials in close proximity and moving in opposite directions to overcome a major impediment to achieving high efficiency-thermal recuperation between solids in efficient countercurrent arrangements. They also provide an inherent separation of the product hydrogen and oxygen and are an excellent match with a high-concentration solar flux. However, they also impose unique requirements on the ferrite reactants and materials of construction as well as an understanding of the chemical and cycle thermodynamics. In this paper, the counter-rotating-ring receiver/reactor/ recuperator solar thermochemical heat engine concept is introduced, and its basic operating principles are described. Preliminary thermal efficiency estimates are presented and discussed. Our results and development approach are also outlined.
248 citations
TL;DR: In this paper, the influence of reduction in the concentration of CO 2 in biogas on performance, emissions and combustion in a constant speed spark ignition (SI) engine was studied experimentally.
241 citations
TL;DR: In this paper, the effect of applying a biodiesel with either 10% blended methanol or 10% fumigation methanolisol was compared with diesel fuel, and the results indicated a reduction of CO 2, NO x, and particulate mass emissions and a reduction in mean particle diameter.
237 citations
TL;DR: In this paper, a heat pipe with de-ionic water, alcohol, and nanofluids (alcohol and nanoparticles) was fabricated from the straight copper tube with the outer diameter and length of 15, 600 mm, respectively.
230 citations
TL;DR: In this paper, the performance of a high-temperature solid oxide fuel cell combined with a conventional recuperative gas turbine (GT-SOFC) plant, as well as the irreversibility within the system were examined.
229 citations
TL;DR: It is concluded that it is possible to use tyre pyrolysis oil in diesel engines as an alternate fuel in the future.
221 citations
TL;DR: In this article, an experimental investigation has been carried out to study the heat transfer and friction characteristics by using a combination of inclined as well as transverse ribs on the absorber plate of a solar air heater.
TL;DR: In this paper, a novel photovoltaic solar assisted heat pump (PV-SAHP) system has been proposed and performance tests with a range of condenser supply water temperature were conducted on an experimental rig.
TL;DR: In this paper, the performance parameters and exhaust emissions of a diesel engine fuelled with diesel fuel and a biodiesel, namely cottonseed oil methyl ester (COME), subjected to preheating at different temperatures in order to lower its viscosity have been investigated.
TL;DR: In this article, the performance of an ammonia-water Rankine cycle with a positive displacement expander was evaluated and compared to four organic Rankine cycles and a Kalina-type cycle and showed that, in order to determine the best cycle configuration and parameters, energy efficiency must be used only in conjunction with the amount of the heat recovered from the source.
TL;DR: In this article, the optimization of a combined cycle power plant describing and comparing four different gas turbine cycles: simple cycle, inter-cooled cycle, reheated cycle and intercooled-and-reheated cycle is presented.
TL;DR: In this paper, the effects of different methanol/gasoline ratios on engine power, thermal efficiency, and emissions, especially the exhaust methanols emission, were investigated using three-cylinder, port fuel injection engine.
Abstract: Three typical methanol−gasoline blends M10, M20, and M85 containing 10%, 20%, and 85% of methanol by volume, respectively, were used to investigate the effects of different methanol/gasoline ratios on engine power, thermal efficiency, and emissions, especially the exhaust methanol emission. A three-cylinder, port fuel injection engine was applied. Experimental results show that the engine power/torque ratio under the wide open throttle condition mainly depends on the amount of heat delivered to the engine. The addition of methanol significantly improves the brake thermal efficiency, while the methanol/gasoline ratio has a slight effect on it. Engine out CO and NOx emissions decrease with the increase of the methanol/gasoline ratio. The use of M85 leads to a reduction of CO and NOx by about 25% and 80%, respectively. A gas chromatograph is calibrated and used to measure the methanol emission. Measurement indicates that the addition of methanol in gasoline results in an increase of the unburnt CH3OH emissio...
TL;DR: In this article, a theoretical model based on effectiveness-NTU method was developed for evaluating the thermal efficiency of the collector, the inlet, outlet water temperatures and heat pipe temperature.
TL;DR: In this article, a second-order Stirling model, which includes thermal losses, was developed and used to optimize the performance and design parameters of the engine, and the results showed that the optimal design parameters are introduced in the model, the engine efficiency increases from 39% to 51%, the engine power is enhanced by approximately 20%, whereas the engine average pressure increases slightly.
TL;DR: In this article, a combined power and refrigeration cycle is proposed, which combines the Rankine cycle and the absorption refrigeration cycles, and a parametric analysis is conducted to evaluate the effects of thermodynamic parameters on the performance of the combined cycle.
TL;DR: In this paper, the authors investigated the combustion and emission characteristics of a port-injection SI turbocharged engine fueled with several H 2 / CNG blend ratios (0-50vol%) under various ignition timings.
TL;DR: In this article, an experimental study of port injected n-heptane homogeneous charge compression ignition (HCCI) in combination with in-cylinder diesel fuel direct injection (DI) was conducted on a single cylinder diesel engine.
TL;DR: In this paper, the authors used hydrogen-enriched air as intake charge in a diesel engine adopting exhaust gas recirculation (EGR) technique with hydrogen flow rate at 20 l/min.
TL;DR: In this article, the overall efficiency of the HTSE system was calculated through electrochemical and thermodynamic analysis, and the quantitative effects of three key parameters, electrical efficiency, electrolysis efficiency, and thermal efficiency, were investigated.
TL;DR: In this article, a single-cylinder diesel engine with a rated output of 4.4 kW at 1500 rpm was converted to operate in the dual fuel mode and hydrogen was used as the inducted fuel and rubber seed oil (RSO), RSOME and diesel were used as main fuels in a dual fuel engine.
TL;DR: In this paper, the authors investigated the second-law efficiency of hydrogen combustion in a diesel engine cylinder with respect to the usual hydrocarbon-based fuels and showed that hydrogen combustion can significantly reduce irreversibilities during hydrogen combustion.
TL;DR: In this paper, the authors presented a technical innovation, study of solar power system based on the Stirling dish (SD) technology and design considerations to be taken in designing of a mean temperature differential Stirling engine for solar application.
TL;DR: In this article, the effects of hydrogen addition on the combustion behaviors and cycle-by-cycle variations in a turbocharged lean-burn natural gas SI engine were investigated and it was found that after hydrogen addition the engine's thermal efficiency could keep at relatively high level over a much wider range of equivalence ratios.
TL;DR: In this article, a case study for the HTU conversion of sugar beet pulp (130 kton/a on a dry basis) is presented, and a process description is given, and the heat economy is discussed.
Abstract: The development of the HTU Process is now well under way. A pilot plant with an intake capacity of some 10 kg/h (dry basis) is in operation. Biomass is converted by treatment in liquid water at temperatures from 300 to 350C and pressures from 100 to 180 bar. The product is 'Biocrude', a heavy organic liquid with a lower heating value of 30-35 MJ/kg. A case study is presented for the HTU conversion of sugar beet pulp (130 kton/a on a dry basis). A process description is given, and the heat economy is discussed. For the generation of process heat some external fuel is required (2% of the heating value of the feedstock). The thermal efficiency is defined as the ratio of heating values of biocrude product and feedstock plus external heat input It has a theoretical maximum of 79%. The process designed here has a thermal efficiency of 75%. The total capital expenditure is 30 M$. At a zero cost of feedstock the price of the biocrude product is $153/ton, or $4.6/GJ. A number of items for further improvement of the thermal efficiency is discussed. It requires a systematic exergy analysis. However, any further gain in heat economy has to be traded off against increased capital expenditure and reduced operability.
TL;DR: In this article, the performance of a two-stroke free-piston linear alternator (FPLA) engine for electrical power generation was investigated using Matlab/Simulink, Chemkin, as well as the finite element method (FEM).
Abstract: Matlab/Simulink, Chemkin, as well as the finite element method (FEM) have been used to investigate the performance of the novel development of a two-stroke free-piston engine for electrical power generation. It is called free-piston linear alternator (FPLA). The motion differences between the FPLA and the internal combustion engine (ICE) are also presented. The effects of various resistance loads and equivalence ratios are studied. The simulation results show that the FPLA has a buildup nature to change the top dead center (TDC) according to loads and other parameters. The high compression ratio can be achieved easily by decreasing the equivalence ratio, which is an effective way to increase the indicated thermal efficiency. Besides, the peak temperature is much lower than the traditional engine under the same condition, which could reduce the temperature-dependent emissions.
TL;DR: In this article, the effect of iso-butanol addition to diesel fuel on engine performance parameters has been experimentally investigated and the results indicate that up to 30% isobutanol in fuel blends are better than that of 40%.
Abstract: The effect of iso‐butanol addition to diesel fuel on engine performance parameters has been experimentally investigated. The used engine was a single cylinder four stroke CI engine Type Lister 1–8. The tests were performed at engine speed that ranges from 375 to 625 with an increment of 42 rpm at different loads and with 10, 20, 30 and 40% v/v iso‐butanol‐diesel fuel blends. The overall engine performance parameters measured included air‐fuel ratio (AFR), exhaust gas temperature, brake power (Bp ), brake specific fuel consumption (bsfc) and brake thermal efficiency (η th ). The experimental results show that AFR, exhaust gas temperature, (Bp ) and (ηbth ) decreased and bsfc increased with iso‐butanol addition compared to net diesel fuel. Also, the obtained results indicate that the engine performance parameters when using up to 30% iso‐butanol in fuel blends are better than that of 40%.