Thermal efficiency

About: Thermal efficiency is a research topic. Over the lifetime, 20911 publications have been published within this topic receiving 302373 citations. The topic is also known as: thermodynamic efficiency & efficiency.

Boilers and burners : design and theory

Abstract: 1 Introduction.- 1-1 Principles of Boiler Operation.- 1-2 Classification of Boilers.- 1-3 Description of Boilers.- References.- 2 General Design Considerations.- 2-1 Boiler Specifications.- 2-2 Design Steps.- References.- 3 Fuel and Combustion Calculations.- 3-1 Features of Fuel.- 3-2 Stoichiometric Calculations.- 3-3 Enthalpy Calculation of Air and Combustion Products.- 3-4 Heat Balance.- 3-5 Generation of SO2and NOx.- Nomenclature.- References.- 4 Coal Preparation Systems for Boilers.- 4-1 Coal Preparation Systems.- 4-2 Pulverizing Properties of Coal.- 4-3 Pulverizing Air System.- 4-4 Size-Reducing Machines.- 4-5 Other Components for Coal Preparation Systems.- 4-6 Design of Coal Preparation System for Pulverized Coal Boilers.- 4-7 Fuel Feeding in Fluidized Bed Boilers.- Nomenclature.- References.- 5 Design of Oil Burners.- 5-1 Design of Oil Supply System.- 5-2 Oil Atomizers.- 5-3 Air Registers.- 5-4 Design Principles of Oil Fired Boilers.- Nomenclature.- References.- 6 Boiler Furnace Design Methods.- 6-1 General Design Principles.- 6-2 Flame Emissivity.- 6-3 Heat Transfer Calculations for the PC Boiler Furnace.- 6-4 Water Wall Arrangement.- 6-5 Fouling and Thermal Efficiency Factors for Water Wall Tubes.- 6-6 Temperature Field CoefficientM.- 6-7 Furnace Emissivity.- 6-8 Distribution of Heat Load in Furnace.- Nomenclature.- References.- 7 Convective Heating Surfaces.- 7-1 Design of Superheater and Reheater.- 7-2 Temperature Control in Superheater and Reheater.- 7-3 Adjustment of Heat Absorption in Superheater and Reheater..- 7-4 Economizer.- 7-5 Air Heater.- 7-6 Arrangement of Back-Pass Heating Surfaces.- 7-7 Heat Transfer Calculations for Convective Heating Surfaces.- 7-8 Design Methods of Convection Heating Surfaces.- Nomenclature.- References.- 8 Swirl Burners.- 8-1 Design of a Swirl Burner.- 8-2 Flow Resistance in Swirl Burners.- 8-3 Examples of Swirl Burners.- 8-4 Arrangement of Multiple Swirl Burners.- 8-5 Design Procedure of Swirl Burners.- Nomenclature.- References.- 9 Design of Novel Burners.- 9-1 Types of PC Burners.- 9-2 PC Burner With Blunt Body.- 9-3 Precombustion Chamber Burner.- 9-4 Boat Burner.- 9-5 Co-Flow Jet Burner With High Differential Velocity.- 9-6 Counter-Flow Jet Burner.- 9-7 Dense and Lean Phase PC Burner.- 9-8 Down-Shot Flame Combustion Technique.- 9-9 Low NOxBurner.- Nomenclature.- References.- 10 Tangentially Fired Burners.- 10-1 General Descriptions.- 10-2 Design of Burners With Peripheral Air.- 10-3 Design of Tilting Burners.- 10-4 Burners for Bituminous Coal.- 10-5 Anthracite and Lean Coal Fired PC Burner.- 10-6 Brown Coal Fired Direct Burner.- 10-7 Multifuel Burner.- 10-8 Design Methods for Tangentially Fired Boilers.- 10-9 Example of Burner Design.- Nomenclature.- References.- 11 Fluidized Bed Boilers.- 11-1 Fluidized Bed Boiler.- 11-2 Major Features of Fluidized Bed Boilers.- 11-3 Basics of Fluidized Beds.- 11-4 Bubbling Fluidized Bed Boilers.- 11-5 Circulating Fluidized Bed Boilers.- 11-6 Distributor Plates.- 11-7 Loop Seals.- 11-8 Gas-Solid Separators.- Nomenclature.- References.- 12 Steam-Water Circulation in Boiler.- 12-1 Natural Circulation System.- 12-2 Calculations for Simple and Complex Tube Circuits.- 12-3 Two-Phase Flow Resistance.- 12-4 Height of Economizer Section in the Riser.- 12-5 Worked-Out Example.- Nomenclature.- References.- 13 Forced Circulation for Supercritical or Subcritical Boilers.- 13-1 General Description.- 13-2 Design Principle of Forced Circulation Boiler.- 13-3 Features of Forced Circulation Boilers.- 13-4 Supercritical Boilers.- 14 Corrosion and Fouling of Heat Transfer Surfaces.- 14-1 High-Temperature Corrosion of External Surfaces.- 14-2 Prevention of High-Temperature Corrosion.- 14-3 Low-Temperature Corrosion on External Surfaces.- 14-4 Corrosion and Scaling of Internal Surfaces.- 14-5 Fouling and Slagging.- 14-6 Calculation of Soot and Ash Deposition.- 14-7 Prediction of Slagging Potential.- 14-8 Design Measure for Reduction of Fouling and Slagging.- Nomenclature.- References.- 15 Erosion Prevention in Boilers.- 15-1 Theory of Erosion of Heating Surfaces.- 15-2 Worked-Out Example.- 15-3 Factors Influencing Tube Erosion.- 15-4 Analyses of Erosion of Tube Banks in Cross-Flow.- 15-5 Permissible Gas Velocity for Safe Operation.- 15-6 Erosion Protection for the Economizer, Reheater, and Superheater.- 15-7 Erosion in Tubular Air Heaters.- 15-8 Erosion in Fluidized Bed Boilers.- Nomenclature.- References.- 16 Pressure Drop in Gas and Air Ducts.- 16-1 Draft Systems.- 16-2 Pressure Drop in Air and Gas Duct Systems.- 16-3 Pressure Drop Across Heating Surfaces.- 16-4 Pressure Drop in Natural Draft Gas Path.- 16-5 Pressure Drop Through Air Ducts.- 16-6 Selection of Fans.- 16-7 Pressure Drop Through Water or Steam Tubes.- Nomenclature.- References.- 17 Mechanical Design of Pressure Parts.- 17-1 Selection of Materials.- 17-2 Important Mechanical Properties of Various Materials.- 17-3 Fundamental Metallurgical Concepts to Improve Steel Properties.- 17-4 Design Methods.- 17-5 Thickness (Scantling) Calculations.- Nomenclature.- References.- 18 Tables of Design Data.- Table 18-1 Specific heat of air, flue gas and ash at atmospheric pressure.- Table 18-2 Some physical properties of iron, metal, and selected steels.- Table 18-3 Linear thermal expansion of steel.- Table 18-4 Specific heat capacity of steel.- Table 18-5 Electrical resistivity of steel.- Table 18-6 Thermal conductivity of steel.- Table 18-7 Density, heat capacity, and heat conductivity for metals.- Table 18-8 Thermal properties of the saturated water and steam (arranged by temperature).- Table 18-9 Thermal properties of the saturated water and steam (arranged by pressure).- Table 18-10 Thermal properties of unsaturated water and superheated steam at different pressures.- Table 18-11 Conversion factors.

Thermal Efficiency of Solar Steam Generation Approaching 100 % through Capillary Water Transport.

Abstract: Solar-driven interfacial water evaporation yield is severely limited by the low efficiency of solar thermal energy. Herein, the injection control technique (ICT) achieves a capillary water state in rGO foam and effectively adjusts the water motion mode therein. Forming an appropriate amount of capillary water in the 3D graphene foam can greatly increase the vapor escape channel, by ensuring that the micrometer-sized pore channels do not become completely blocked by water and by exposing as much evaporation area as possible while preventing solar heat from being used to heat excess water. The rate of solar steam generation can reach up to 2.40 kg m-2 h-1 under solar illumination of 1 kW m-2 , among the best values reported. In addition, solar thermal efficiency approaching 100 % is achieved. This work enhances solar water-evaporation performance and promotes the application of solar-driven evaporation systems made of carbon-based materials.

A review of hydrogen and natural gas addition in diesel HCCI engines

Abstract: Homogeneous charge compression ignition (HCCI) engine uses a relatively new mode of combustion technology. In principle, there is no spark plug or injector to assist the combustion, and the combustion auto-ignites in multiple spots once the mixture has reached its chemical activation energy. The challenges in developing HCCI engines are the difficulties in: controlling the auto-ignition of the mixture and the heat release rate at high load operations, achieving a cold start, meeting emission standards and controlling knock. At low engine speeds, early auto-ignition can occur, possibly leading to knocking, while late auto-ignition at high engine speeds will make HCCI susceptible to misfire. Hydrogen greatly reduces emissions levels but with reduced power. However, when hydrogen is combined with diesel in dual-fuel mode, low NOx, CO and particulate matter (PM) emissions levels can be achieved, and engine efficiency can be increased by 13–16%. Numerical methods are commonly used to predict HCCI engines' performance (i.e. emissions levels, brake thermal efficiency and combustion phasing), which is cost-effective compared to solely relying on experimentation. The multi-zone method promises better simulation results compared to the single-zone model by combining detailed chemical kinetics with simplified 3D modeling so that turbulence and inhomogeneity in the mixture are considered; good agreement between simulations and experiments have been achieved. Specific strategies used in the experimental method (e.g. fuel additives, inlet air heating, inlet air pressurizing, exhaust gas recirculation (EGR) and injection methods), and numerical method (e.g. single-zone and multi-zone models, mixing model, turbulence model and multi-dimensional model), and other issues associated with HCCI engines are discussed in this paper.