International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document analyzes the energy and exergy of an extraction back-pressure steam turbine used in a power plant in India. It evaluates the turbine's energy efficiency, exergy destruction, and exergy efficiency at 70% and 85% of maximum continuous rating. The analysis shows that operating the turbine at 85% rating improves the heat rate by 17.01 kJ/kWh, reducing CO2 emissions by 26.89 kg/h, SO2 emissions by 26.89 kg/h, and ash generation by 41.47 kg/day. Exergy, or the useful work potential of energy, provides a more complete analysis than energy alone by considering both quantity and quality of energy.
This document contains information about the Carnot vapor cycle and the simple Rankine cycle. It defines the key processes in each cycle, compares ideal cycles to actual cycles, and provides examples of calculating efficiency, work, heat transfer, and other parameters for steady-flow Carnot and Rankine cycles using water as the working fluid. The document emphasizes that actual vapor power cycles involve friction, pressure drops, and heat losses not present in idealized cycles.
EXPERIMENTAL INVESTIGATION ON THERMAL PERFORMANCE OF POROUS RADIANT BURNER AN...BIBHUTI BHUSAN SAMANTARAY
This paper presents the heat transfer characteristics of a
self-aspirating porous radiant burner (SAPRB) that operates
on the basis of an effective energy conversion method between
flowing gas enthalpy and thermal radiation. The temperature
field at various flame zones was measured experimentally by
the help of both FLUKE IR camera and K-type thermocouples.
The experimental setup consisted of a two layered domestic
cooking burner, a flexible test stand attached with six K-type
thermocouples at different positions, IR camera, LPG setup
and a hot wire anemometer. The two layered SAPRB consisted
of a combustion zone and a preheating zone. Combustion zone
was formed with high porosity, highly radiating porous
matrix, and the preheating zone consisted of low porosity
matrix. Time dependent temperature history from
thermocouples at various flame zones were acquired by using
a data acquisition system and the temperature profiles were
analyzed in the ZAILA application software environments. In
the other hand the IR graphs were captured by FLUKE IR
camera and the thermographs were analyzed in the
SMARTView software environments. The experimental results
revealed that the homogeneous porous media, in addition to
its convective heat exchange with the gas, might absorb, emit,
and scatter thermal radiation. The rate of heat transfer was
more at the center of the burner where a combined effect of
both convection & radiation might be realized. The maximum
thermal efficiency was found to be 64% which was having a
good agreement with the previous data in the open literature.
This document contains 13 questions regarding thermodynamic cycles and processes. It asks the student to analyze ideal Rankine, reheat Rankine, regenerative Rankine, and cogeneration power cycles on T-s diagrams. Several questions involve determining efficiency, work output, heat input, mass flow rates and other key parameters for various steam power plants operating on these cycles. The student is asked to show cycle processes on diagrams and calculate values like thermal efficiency, turbine output, steam quality and mass flow rates.
Gaseous fuel is produced by gasifying coal or coke in a gas producer reactor. There are several advantages to gaseous fuels including ease of handling, rapid combustion, and less excess air needed for combustion. Gaseous fuel can be produced using air only, a mixture of air and steam, or a mixture of oxygen and steam. Adding steam increases the calorific value and volume of the producer gas by decomposing into hydrogen. The amount of steam added cannot decompose all the carbon to CO or steam to hydrogen due to heat balance limitations in the gasification process.
Simulation Studies Of Premixed N-Pentane/Air Liquid Micro CombustionIJERA Editor
With latest improvements in MEMS, combustion based Micro-Power generation devices are seen as alternatives for conventional batteries because of the high energy densities of Hydrogen and other hydrocarbon fuels. An important feature of micro-power system is to utilize the combustion of fuel or propellant in the micro-burner to produce the gas with high temperature and high pressure to drive turbines or other power units, which convert chemical into energy directly or indirectly other forms of energy, for example heat or power. We have concentrated on the usage of Micro combustion as a substitute for conventional batteries .In our study, a Micro Combustor of 1mm x 10mm is taken for Numerical Study. Combustion characteristics of N Pentane-Air mixture in a planar micro-channel is studied numerically. We have performed the liquid fuel combustion of n-Pentane and air to study the effects of liquid fuel combustion in a micro channel. The effect of axial velocity inlet, on exhaust gas temperature and Hydrogen Peroxide addition on exhaust gas concentration was analyzed respectively. We also investigated numerically the combustion characteristics under different conditions such as by varying the DPM, Number of Fuel Streams, and Spray Angle and so on. For this numerical analysis, an experimental model is considered as reference, and the geometry and the boundary conditions are taken from it for the purpose of simulation. In this study, n-Pentane is introduced as liquid droplets at the centerline and the liquid combustion is simulated numerically.
Effect of Addition of Energetic Nanoparticles on Droplet-Burning Rate of Liqu...Saad Tanvir
The document summarizes an experiment that studied the effect of adding aluminum nanoparticles to ethanol droplets on the burning rate of the droplets. Ethanol droplets with 0-5% concentrations of 80 nm aluminum nanoparticles and sizes of 176-400 microns were generated in a stream and ignited. The burning rate was found to increase with higher nanoparticle concentration, with a 5% addition increasing the rate by 140%. The increased burning rate is attributed to the nanoparticles strongly absorbing radiation from the flame, providing more energy to the droplets to vaporize and increase the burning rate. The radiation absorption effect becomes more important for larger droplets.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document analyzes the energy and exergy of an extraction back-pressure steam turbine used in a power plant in India. It evaluates the turbine's energy efficiency, exergy destruction, and exergy efficiency at 70% and 85% of maximum continuous rating. The analysis shows that operating the turbine at 85% rating improves the heat rate by 17.01 kJ/kWh, reducing CO2 emissions by 26.89 kg/h, SO2 emissions by 26.89 kg/h, and ash generation by 41.47 kg/day. Exergy, or the useful work potential of energy, provides a more complete analysis than energy alone by considering both quantity and quality of energy.
This document contains information about the Carnot vapor cycle and the simple Rankine cycle. It defines the key processes in each cycle, compares ideal cycles to actual cycles, and provides examples of calculating efficiency, work, heat transfer, and other parameters for steady-flow Carnot and Rankine cycles using water as the working fluid. The document emphasizes that actual vapor power cycles involve friction, pressure drops, and heat losses not present in idealized cycles.
EXPERIMENTAL INVESTIGATION ON THERMAL PERFORMANCE OF POROUS RADIANT BURNER AN...BIBHUTI BHUSAN SAMANTARAY
This paper presents the heat transfer characteristics of a
self-aspirating porous radiant burner (SAPRB) that operates
on the basis of an effective energy conversion method between
flowing gas enthalpy and thermal radiation. The temperature
field at various flame zones was measured experimentally by
the help of both FLUKE IR camera and K-type thermocouples.
The experimental setup consisted of a two layered domestic
cooking burner, a flexible test stand attached with six K-type
thermocouples at different positions, IR camera, LPG setup
and a hot wire anemometer. The two layered SAPRB consisted
of a combustion zone and a preheating zone. Combustion zone
was formed with high porosity, highly radiating porous
matrix, and the preheating zone consisted of low porosity
matrix. Time dependent temperature history from
thermocouples at various flame zones were acquired by using
a data acquisition system and the temperature profiles were
analyzed in the ZAILA application software environments. In
the other hand the IR graphs were captured by FLUKE IR
camera and the thermographs were analyzed in the
SMARTView software environments. The experimental results
revealed that the homogeneous porous media, in addition to
its convective heat exchange with the gas, might absorb, emit,
and scatter thermal radiation. The rate of heat transfer was
more at the center of the burner where a combined effect of
both convection & radiation might be realized. The maximum
thermal efficiency was found to be 64% which was having a
good agreement with the previous data in the open literature.
This document contains 13 questions regarding thermodynamic cycles and processes. It asks the student to analyze ideal Rankine, reheat Rankine, regenerative Rankine, and cogeneration power cycles on T-s diagrams. Several questions involve determining efficiency, work output, heat input, mass flow rates and other key parameters for various steam power plants operating on these cycles. The student is asked to show cycle processes on diagrams and calculate values like thermal efficiency, turbine output, steam quality and mass flow rates.
Gaseous fuel is produced by gasifying coal or coke in a gas producer reactor. There are several advantages to gaseous fuels including ease of handling, rapid combustion, and less excess air needed for combustion. Gaseous fuel can be produced using air only, a mixture of air and steam, or a mixture of oxygen and steam. Adding steam increases the calorific value and volume of the producer gas by decomposing into hydrogen. The amount of steam added cannot decompose all the carbon to CO or steam to hydrogen due to heat balance limitations in the gasification process.
Simulation Studies Of Premixed N-Pentane/Air Liquid Micro CombustionIJERA Editor
With latest improvements in MEMS, combustion based Micro-Power generation devices are seen as alternatives for conventional batteries because of the high energy densities of Hydrogen and other hydrocarbon fuels. An important feature of micro-power system is to utilize the combustion of fuel or propellant in the micro-burner to produce the gas with high temperature and high pressure to drive turbines or other power units, which convert chemical into energy directly or indirectly other forms of energy, for example heat or power. We have concentrated on the usage of Micro combustion as a substitute for conventional batteries .In our study, a Micro Combustor of 1mm x 10mm is taken for Numerical Study. Combustion characteristics of N Pentane-Air mixture in a planar micro-channel is studied numerically. We have performed the liquid fuel combustion of n-Pentane and air to study the effects of liquid fuel combustion in a micro channel. The effect of axial velocity inlet, on exhaust gas temperature and Hydrogen Peroxide addition on exhaust gas concentration was analyzed respectively. We also investigated numerically the combustion characteristics under different conditions such as by varying the DPM, Number of Fuel Streams, and Spray Angle and so on. For this numerical analysis, an experimental model is considered as reference, and the geometry and the boundary conditions are taken from it for the purpose of simulation. In this study, n-Pentane is introduced as liquid droplets at the centerline and the liquid combustion is simulated numerically.
Effect of Addition of Energetic Nanoparticles on Droplet-Burning Rate of Liqu...Saad Tanvir
The document summarizes an experiment that studied the effect of adding aluminum nanoparticles to ethanol droplets on the burning rate of the droplets. Ethanol droplets with 0-5% concentrations of 80 nm aluminum nanoparticles and sizes of 176-400 microns were generated in a stream and ignited. The burning rate was found to increase with higher nanoparticle concentration, with a 5% addition increasing the rate by 140%. The increased burning rate is attributed to the nanoparticles strongly absorbing radiation from the flame, providing more energy to the droplets to vaporize and increase the burning rate. The radiation absorption effect becomes more important for larger droplets.
The document discusses using direct numerical simulation to study radiation-driven flame extinction in fires. It motivates the study by explaining how flame extinction impacts combustion systems and fire applications. It outlines the objectives to establish flame extinction criteria, construct flammability maps, and explore the relationship between extinction and soot emission. It describes the numerical approach using a DNS solver and models for chemistry, soot formation, and thermal radiation transport. Classical asymptotic analysis is also discussed for analyzing flame structure with and without radiation and soot. Laminar counter-flow flames will be used to obtain flame structure as a function of stretch from ultra-high to ultra-low values.
This document discusses key thermodynamic concepts related to combustion processes, including:
1) Heat of combustion, flame temperature, enthalpy of combustion systems, and equilibrium constants of combustion reactions are the major thermodynamic functions that influence fuel utilization.
2) Heat of combustion represents the potential heat of a fuel and can be used to calculate calorific value. Enthalpy is the heat content of a system at constant pressure.
3) Flame temperature depends on the fuel-oxidant mixture and ranges from theoretical to actual temperatures. The maximum adiabatic flame temperature occurs at slightly excess stoichiometry.
IJERD (www.ijerd.com) International Journal of Engineering Research and Devel...IJERD Editor
This document summarizes a study on a solar integrated collector storage system using a Fresnel lens for domestic hot water applications. The system uses paraffin wax as a phase change material (PCM) for thermal energy storage. Experimental results showed that the PCM was able to store sufficient thermal energy from the sun concentrated by the Fresnel lens to maintain water temperatures around 50-60°C for hot water needs for over 50 minutes without direct sunlight. Graphs of temperature over time demonstrated stable water outlet temperatures during discharge of the stored thermal energy after charging by concentrated solar radiation. The study confirms the technical feasibility of using a Fresnel lens and paraffin wax PCM for an efficient solar thermal energy storage system for
Energy Audit and Heat Recovery on the Rotary Kiln of the Cement Plant in Ethi...IJAEMSJORNAL
This study deals with the energy audit and heat recovery on the rotary kiln taking a cement factory in Ethiopia as a case study.The system is a dry type rotary kiln equipped with a five stage cyclone type preheater, pre-calciner and grate cooler. The kiln has a capacity of 2,000 tons/day.Mass and energy balance has been performed for energy auditing. The energy lost from the kiln shell is about 4.3 MW. By using secondary shell on the rotary kiln about 3.5MW could be recovered safely.This energy saving reduces fuel consumption (almost 9%) of the kiln system, and increases the overall system efficiency by approximately 2–3%.
The document discusses a life cycle analysis of different pallet types and phytosanitary treatment methods. It finds that methyl bromide fumigation has the largest impact on global warming and ozone depletion, while conventional heat treatment has the largest impacts across other environmental categories. Microwave and radio frequency treatment produce lower life cycle impacts than conventional heat treatment or methyl bromide. Wooden pallets with conventional or alternative treatments have a 10-20% lower carbon footprint over their lifecycle than plastic pallets or wood treated with methyl bromide. Plastic pallets do not clearly have environmental advantages over treated wood. Longer heat treatment schedules increase costs and environmental impacts significantly.
1. The document discusses concepts in thermodynamics including classical vs statistical thermodynamics, conservation of energy, units of mass and force, properties of systems and processes.
2. It provides examples of applying concepts like Newton's laws to calculate weight on different planets, mass and weight of air in a room, and acceleration of objects.
3. Key points covered are properties of open and closed systems, intensive vs extensive properties, conditions of equilibrium, and types of processes like isothermal and isobaric.
This is a lecture is a series on combustion chemical kinetics for engineers. The course topics are selections from thermodynamics and kinetics especially geared to the interests of engineers involved in combusition
The document defines key terms in thermodynamics including system, surroundings, open system, closed system, isolated system, exothermic, endothermic, enthalpy, kinetic energy, potential energy, heat, work, state functions, standard enthalpy of formation, standard enthalpy of combustion, and entropy. It also discusses the first and second laws of thermodynamics, Gibbs free energy, and how to calculate thermodynamic properties using standard enthalpies of formation.
Ph d defense_rajmohan_muthaiah_University_of_oklahoma_07_28_2021Rajmohan Muthaiah
This slide describes the thermal transport in polymers, polymer nanocomposites and semiconductors using molecular dynamics simulations and first principles calculations
This document provides an introduction to thermochemistry and the key concepts of enthalpy, enthalpy change, and standard enthalpy of formation. It defines system and surroundings, and the three types of systems - open, closed, and isolated. The key points are:
- Enthalpy change (ΔH) is the difference in enthalpies between products and reactants and indicates whether a reaction is endothermic or exothermic.
- Standard enthalpy of formation (H°f) is the enthalpy change when 1 mole of a substance is formed from its elements under standard conditions.
- Enthalpy of combustion (H°c) is the enthalpy change when 1 mole
This document discusses thermochemistry and calorimetry. It defines key concepts in thermochemistry including the various forms of energy, exothermic and endothermic processes, and systems and surroundings. It introduces the first law of thermodynamics and defines state functions. It also discusses enthalpy, thermochemical equations, and calculations involving enthalpy changes. The document explains calorimetry concepts like heat capacity, specific heat, and how to perform calculations using bomb and coffee cup calorimetry.
1. The document summarizes research on using zirconium particles as an ignition source in the recirculation zone of ducted rockets. Experiments measured the chemical delay times of different minute particles at high temperatures.
2. Theoretical analysis calculated the temperature history of particles in the recirculation zone and related it to the required chemical delay time for ignition. Results showed zirconium has the shortest delay time, making it the most suitable particle for igniting the fuel-air mixture.
3. In conclusion, zirconium was determined to have the highest ignitability and be the most effective choice as an ignition source to forcibly and continuously ignite the fuel-air mixture in the recirc
The document summarizes a master's thesis defense on high pressure steam reactivation of calcium oxide (CaO) sorbents for carbon dioxide capture using calcium looping process. It discusses:
1) The introduction, experimental methodology, results and discussions, conclusions, and future work sections of the thesis.
2) Current CO2 levels and emissions from electricity production in the US, highlighting the need for carbon capture from coal and natural gas power plants.
3) Existing carbon capture technologies like amine scrubbing and their limitations.
4) The calcium looping process for post-combustion CO2 capture and limitations in maintaining sorbent reactivity over multiple cycles.
5) Reactivation of
This document discusses thermo chemistry and key concepts like enthalpy, calorimetry, and Hess's law. It begins by defining open, closed, and isolated systems and explains endothermic and exothermic reactions using energy profile diagrams. It then discusses enthalpy and defines standard enthalpy. Various types of enthalpies are defined like enthalpy of formation, combustion, atomization, and more. Calorimetry is explained as a method to measure heat changes in reactions using calorimeters. Hess's law is introduced as the principle that the enthalpy change of a reaction is the same whether it occurs in one step or multiple steps.
Droplet burning rate enhancement of ethanol with the addition of graphite nan...Saad Tanvir
This document summarizes research on the burning rate of ethanol droplets with the addition of graphite nanoparticles. Key findings include:
- Adding graphite nanoparticles to ethanol droplets increased their burning rate, with a maximum increase of 62% observed with 3 wt.% 50 nm graphite nanoparticles.
- Computational models were developed to analyze how the optical properties of graphite nanoparticles affect radiation absorption within the ethanol droplets. The models show radiation absorption is localized near the droplet surface, promoting faster vaporization and higher burning rates.
- Experiments using a droplet stream combustion setup measured the burning rates of ethanol droplets with different concentrations of 50 nm and 100 nm graphite nanoparticles. Flame appearance and residue analysis provided further insights into
This document discusses thermochemistry and energy changes that occur during chemical reactions. It defines exothermic and endothermic reactions, and how to construct energy level diagrams to represent them. Specific heats of reaction like combustion, precipitation, displacement, and neutralization are also explained. Experiments to determine various heats of reaction are described. The relationships between the heat of reaction and type of reactants, as well as the number of carbons in alcohols are also summarized.
Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
Hess's law states that the total enthalpy change for a reaction is independent of the pathway taken. It allows calculation of enthalpy changes that cannot be measured directly by combining thermochemical equations. The standard heat of reaction (ΔH°) can be calculated from standard heats of formation (ΔHf°) of reactants and products. Hess's law and heats of formation are useful for determining enthalpy changes that cannot be measured in the laboratory.
This document discusses using social media in the classroom. It introduces common social media tools like Facebook, Twitter, blogs and bookmarks and how they can be used for collaboration, communication and sharing ideas. It provides examples of how teachers can incorporate these tools into their classes, such as having students set up blogs to present portfolios or engage in discussions related to class topics. The document encourages teachers to identify real needs where technology can enhance learning objectives rather than using it for its own sake.
Cervello Incorporation has developed mMail, a push email solution delivered over SMS. It allows users to access emails from any mobile device without an internet connection. Key benefits include improved communication, increased availability and productivity for employees on the go. mMail works with various email servers and mobile networks. It offers a cost-effective alternative to Blackberry with pay-as-you-use pricing starting at Rs. 90 per month.
The document discusses using direct numerical simulation to study radiation-driven flame extinction in fires. It motivates the study by explaining how flame extinction impacts combustion systems and fire applications. It outlines the objectives to establish flame extinction criteria, construct flammability maps, and explore the relationship between extinction and soot emission. It describes the numerical approach using a DNS solver and models for chemistry, soot formation, and thermal radiation transport. Classical asymptotic analysis is also discussed for analyzing flame structure with and without radiation and soot. Laminar counter-flow flames will be used to obtain flame structure as a function of stretch from ultra-high to ultra-low values.
This document discusses key thermodynamic concepts related to combustion processes, including:
1) Heat of combustion, flame temperature, enthalpy of combustion systems, and equilibrium constants of combustion reactions are the major thermodynamic functions that influence fuel utilization.
2) Heat of combustion represents the potential heat of a fuel and can be used to calculate calorific value. Enthalpy is the heat content of a system at constant pressure.
3) Flame temperature depends on the fuel-oxidant mixture and ranges from theoretical to actual temperatures. The maximum adiabatic flame temperature occurs at slightly excess stoichiometry.
IJERD (www.ijerd.com) International Journal of Engineering Research and Devel...IJERD Editor
This document summarizes a study on a solar integrated collector storage system using a Fresnel lens for domestic hot water applications. The system uses paraffin wax as a phase change material (PCM) for thermal energy storage. Experimental results showed that the PCM was able to store sufficient thermal energy from the sun concentrated by the Fresnel lens to maintain water temperatures around 50-60°C for hot water needs for over 50 minutes without direct sunlight. Graphs of temperature over time demonstrated stable water outlet temperatures during discharge of the stored thermal energy after charging by concentrated solar radiation. The study confirms the technical feasibility of using a Fresnel lens and paraffin wax PCM for an efficient solar thermal energy storage system for
Energy Audit and Heat Recovery on the Rotary Kiln of the Cement Plant in Ethi...IJAEMSJORNAL
This study deals with the energy audit and heat recovery on the rotary kiln taking a cement factory in Ethiopia as a case study.The system is a dry type rotary kiln equipped with a five stage cyclone type preheater, pre-calciner and grate cooler. The kiln has a capacity of 2,000 tons/day.Mass and energy balance has been performed for energy auditing. The energy lost from the kiln shell is about 4.3 MW. By using secondary shell on the rotary kiln about 3.5MW could be recovered safely.This energy saving reduces fuel consumption (almost 9%) of the kiln system, and increases the overall system efficiency by approximately 2–3%.
The document discusses a life cycle analysis of different pallet types and phytosanitary treatment methods. It finds that methyl bromide fumigation has the largest impact on global warming and ozone depletion, while conventional heat treatment has the largest impacts across other environmental categories. Microwave and radio frequency treatment produce lower life cycle impacts than conventional heat treatment or methyl bromide. Wooden pallets with conventional or alternative treatments have a 10-20% lower carbon footprint over their lifecycle than plastic pallets or wood treated with methyl bromide. Plastic pallets do not clearly have environmental advantages over treated wood. Longer heat treatment schedules increase costs and environmental impacts significantly.
1. The document discusses concepts in thermodynamics including classical vs statistical thermodynamics, conservation of energy, units of mass and force, properties of systems and processes.
2. It provides examples of applying concepts like Newton's laws to calculate weight on different planets, mass and weight of air in a room, and acceleration of objects.
3. Key points covered are properties of open and closed systems, intensive vs extensive properties, conditions of equilibrium, and types of processes like isothermal and isobaric.
This is a lecture is a series on combustion chemical kinetics for engineers. The course topics are selections from thermodynamics and kinetics especially geared to the interests of engineers involved in combusition
The document defines key terms in thermodynamics including system, surroundings, open system, closed system, isolated system, exothermic, endothermic, enthalpy, kinetic energy, potential energy, heat, work, state functions, standard enthalpy of formation, standard enthalpy of combustion, and entropy. It also discusses the first and second laws of thermodynamics, Gibbs free energy, and how to calculate thermodynamic properties using standard enthalpies of formation.
Ph d defense_rajmohan_muthaiah_University_of_oklahoma_07_28_2021Rajmohan Muthaiah
This slide describes the thermal transport in polymers, polymer nanocomposites and semiconductors using molecular dynamics simulations and first principles calculations
This document provides an introduction to thermochemistry and the key concepts of enthalpy, enthalpy change, and standard enthalpy of formation. It defines system and surroundings, and the three types of systems - open, closed, and isolated. The key points are:
- Enthalpy change (ΔH) is the difference in enthalpies between products and reactants and indicates whether a reaction is endothermic or exothermic.
- Standard enthalpy of formation (H°f) is the enthalpy change when 1 mole of a substance is formed from its elements under standard conditions.
- Enthalpy of combustion (H°c) is the enthalpy change when 1 mole
This document discusses thermochemistry and calorimetry. It defines key concepts in thermochemistry including the various forms of energy, exothermic and endothermic processes, and systems and surroundings. It introduces the first law of thermodynamics and defines state functions. It also discusses enthalpy, thermochemical equations, and calculations involving enthalpy changes. The document explains calorimetry concepts like heat capacity, specific heat, and how to perform calculations using bomb and coffee cup calorimetry.
1. The document summarizes research on using zirconium particles as an ignition source in the recirculation zone of ducted rockets. Experiments measured the chemical delay times of different minute particles at high temperatures.
2. Theoretical analysis calculated the temperature history of particles in the recirculation zone and related it to the required chemical delay time for ignition. Results showed zirconium has the shortest delay time, making it the most suitable particle for igniting the fuel-air mixture.
3. In conclusion, zirconium was determined to have the highest ignitability and be the most effective choice as an ignition source to forcibly and continuously ignite the fuel-air mixture in the recirc
The document summarizes a master's thesis defense on high pressure steam reactivation of calcium oxide (CaO) sorbents for carbon dioxide capture using calcium looping process. It discusses:
1) The introduction, experimental methodology, results and discussions, conclusions, and future work sections of the thesis.
2) Current CO2 levels and emissions from electricity production in the US, highlighting the need for carbon capture from coal and natural gas power plants.
3) Existing carbon capture technologies like amine scrubbing and their limitations.
4) The calcium looping process for post-combustion CO2 capture and limitations in maintaining sorbent reactivity over multiple cycles.
5) Reactivation of
This document discusses thermo chemistry and key concepts like enthalpy, calorimetry, and Hess's law. It begins by defining open, closed, and isolated systems and explains endothermic and exothermic reactions using energy profile diagrams. It then discusses enthalpy and defines standard enthalpy. Various types of enthalpies are defined like enthalpy of formation, combustion, atomization, and more. Calorimetry is explained as a method to measure heat changes in reactions using calorimeters. Hess's law is introduced as the principle that the enthalpy change of a reaction is the same whether it occurs in one step or multiple steps.
Droplet burning rate enhancement of ethanol with the addition of graphite nan...Saad Tanvir
This document summarizes research on the burning rate of ethanol droplets with the addition of graphite nanoparticles. Key findings include:
- Adding graphite nanoparticles to ethanol droplets increased their burning rate, with a maximum increase of 62% observed with 3 wt.% 50 nm graphite nanoparticles.
- Computational models were developed to analyze how the optical properties of graphite nanoparticles affect radiation absorption within the ethanol droplets. The models show radiation absorption is localized near the droplet surface, promoting faster vaporization and higher burning rates.
- Experiments using a droplet stream combustion setup measured the burning rates of ethanol droplets with different concentrations of 50 nm and 100 nm graphite nanoparticles. Flame appearance and residue analysis provided further insights into
This document discusses thermochemistry and energy changes that occur during chemical reactions. It defines exothermic and endothermic reactions, and how to construct energy level diagrams to represent them. Specific heats of reaction like combustion, precipitation, displacement, and neutralization are also explained. Experiments to determine various heats of reaction are described. The relationships between the heat of reaction and type of reactants, as well as the number of carbons in alcohols are also summarized.
Asymmetric Multipole Plasmon-Mediated Catalysis Shifts the Product Selectivit...Pawan Kumar
Cu/TiO2 is a well-known photocatalyst for the photocatalytic transformation of CO2 into methane. The formation of C2+ products such as ethane and ethanol rather than methane is more interesting due to their higher energy density and economic value, but the formation of C–C bonds is currently a major challenge in CO2 photoreduction. In this context, we report the dominant formation of a C2 product, namely, ethane, from the gas-phase photoreduction of CO2 using TiO2 nanotube arrays (TNTAs) decorated with large-sized (80–200 nm) Ag and Cu nanoparticles without the use of a sacrificial agent or hole scavenger. Isotope-labeled mass spectrometry was used to verify the origin and identity of the reaction products. Under 2 h AM1.5G 1-sun illumination, the total rate of hydrocarbon production (methane + ethane) was highest for AgCu-TNTA with a total CxH2x+2 rate of 23.88 μmol g–1 h–1. Under identical conditions, the CxH2x+2 production rates for Ag-TNTA and Cu-TNTA were 6.54 and 1.39 μmol g–1 h–1, respectively. The ethane selectivity was the highest for AgCu-TNTA with 60.7%, while the ethane selectivity was found to be 15.9 and 10% for the Ag-TNTA and Cu-TNTA, respectively. Adjacent adsorption sites in our photocatalyst develop an asymmetric charge distribution due to quadrupole resonances in large metal nanoparticles and multipole resonances in Ag–Cu heterodimers. Such an asymmetric charge distribution decreases adsorbate–adsorbate repulsion and facilitates C–C coupling of reaction intermediates, which otherwise occurs poorly in TNTAs decorated with small metal nanoparticles.
Hess's law states that the total enthalpy change for a reaction is independent of the pathway taken. It allows calculation of enthalpy changes that cannot be measured directly by combining thermochemical equations. The standard heat of reaction (ΔH°) can be calculated from standard heats of formation (ΔHf°) of reactants and products. Hess's law and heats of formation are useful for determining enthalpy changes that cannot be measured in the laboratory.
This document discusses using social media in the classroom. It introduces common social media tools like Facebook, Twitter, blogs and bookmarks and how they can be used for collaboration, communication and sharing ideas. It provides examples of how teachers can incorporate these tools into their classes, such as having students set up blogs to present portfolios or engage in discussions related to class topics. The document encourages teachers to identify real needs where technology can enhance learning objectives rather than using it for its own sake.
Cervello Incorporation has developed mMail, a push email solution delivered over SMS. It allows users to access emails from any mobile device without an internet connection. Key benefits include improved communication, increased availability and productivity for employees on the go. mMail works with various email servers and mobile networks. It offers a cost-effective alternative to Blackberry with pay-as-you-use pricing starting at Rs. 90 per month.
The document outlines the agenda for a day-long event on promoting Business and Community Engagement. It introduces the project staff and partners from various universities and colleges. The aims of the event are to share information about JISC's BCE activities, demonstrate the project's review methodology, report common findings and benefits of BCE reviews. The morning schedule includes welcome remarks, an overview of the BCE agenda, a presentation on the project's methodology, and reports from partner institutions. The afternoon consists of additional partner reports, a discussion of good practices and barriers identified, and a demonstration of an online resource developed through the project.
Max Firtman is a mobile and web developer based in Buenos Aires, Argentina. PhoneGap is an open source framework that allows building cross-platform mobile apps using HTML, CSS, and JavaScript. It works by packaging web apps so they can be deployed and run as native mobile applications. PhoneGap supports many mobile platforms but each still requires separate compilation. Debugging mobile web apps can also be challenging. The speaker provides advice around maintaining a single codebase, embracing platform differences, and focusing on performance and the best experience for each context.
I was having a think about how much I love the Royal British Legion's Poppy Appeal, and part of it is how well it captures people's imagination and makes some people actually urgent to take part. This is just some thoughts about it.
Extending the Conversation: Using Instructional Technology to Improve FeedbackGraham Whisen
Improving feedback is a critical component of developing Assessment for Learning. In this session, you will learn how instructional technology tools can be used to provide more effective feedback to students, how to make feedback more convenient for you and your students, and how to involve students in the feedback process. A variety of resources will be shared that can be applied to all subject areas.
There is widespread disagreement over how to accurately measure online traffic and visitors to websites. Content providers often report much higher internal traffic counts than those recorded by third-party measurement firms like Nielsen and comScore, who use panel-based sampling techniques. However, server-side metrics used by content providers have their own limitations. There is no consensus definition of a "unique visitor" and many alternative measurement firms have emerged but also have limitations. As a result, there is confusion in the industry over how to value digital content and online advertising. Some are advocating for new metrics like time spent to better capture audience engagement.
A beginner's guide to getting the most out of talking to strangers. For journalism students and anyone who's interested in how to talk with people and come away with a story.
This document provides an overview and preface for a textbook on Computer Aided Engineering Design. It discusses the motivation and scope of the textbook, which aims to provide thorough coverage of the mathematical foundations and core topics of CAED. The preface outlines the organization of topics covered in the textbook, including geometric modeling of curves, surfaces, and solids as well as applications such as finite element analysis and optimization. It provides guidance to educators on utilizing the textbook for courses on CAD.
How many words can you eliminate with 1 great picture? Got a product? Got an Event? What's your story? Got YOUR paddle? Let us tell YOUR story... One your customers will remember!
The document provides information about various terms and their connections to countries or places.
1) It defines the term "serendipity" and connects it to the discovery of America and Sri Lanka.
2) It explains that the province of Zeeland in the Netherlands gave its name to New Zealand.
3) It describes the Battle of Trafalgar painting and Nelson's signal flag, connecting it to England.
4) It notes that the Southern Lights were named Aurora Australis from the Latin word for "south", similarly to the name Australia.
Thermal Simulation of Biogas Plants Using Mat LabIJERA Editor
The major prerequisite for the optimum production of methane from a biogas plant is the sustenance of digester temperature within the narrow limits (300C-350C). It is experimentally investigated that, the MIT biogas plant is not maintaining optimum temperature, this decreases the efficiency and increases the detention time for charge. To maintain the plant in optimum temperature, it is necessary to find out the heat losses from the biogas plant and the external energy inputs need to operate the plant. Rate of gas yield, and the detention time (time necessary to anaerobically digest organic wastes) in a biogas reactor, are favorable functions of the temperature in the digester. A thermal simulation for MIT biogas plant has developed using matlab in order to understand the heat transfer from the slurry and the gas holder to the surrounding earth and air respectively. The computation has been performed when the slurry is maintained at 200C and 300C, optimum temperature of anaerobic fermentation. If the slurry is considered to be at 350C, the optimum temperature of anaerobic fermentation, the total heat loss from the plant is higher than the heat loss when the slurry is maintained at 200C. The heat calculations provide an appraisal for the heat which has to be supplied by external means to compensate for the net heat losses which occur if the slurry is to be maintained at 350C. A solar system with auxiliary electric heater is designed for maintaining the slurry at 350C.In conclusion; the results of thermal analysis are used to define a strategy for operating biogas plant at optimum temperatures.
This document describes the design of a municipal solid waste incinerator for use in semi-arid regions of West Africa. The calorific value of solid waste in the study area ranges from 5.024 to 5.867 MJ/kg, which is not high enough to sustain incineration. The designed incinerator uses a parallel flow concept and will mix the solid waste with 50% bagasse, a waste fiber residue from sugarcane with a calorific value of 8.59-13.60 MJ/kg, to achieve the required calorific value. Key design specifications of the incinerator include a total volume of 82.5 m3, bed length of 11m, bed
Comparison of Calorific Values of Various Fuels from Different Fuel Stationsresearchinventy
Current research takes in to account of calorific value of various fuel (Diesel) available in the state of Telangana (India). The purpose of this experiment is to determine the heat of combustion for diesel and to learn basic bomb procedures. This experiment will be accomplished by using an adiabatic bomb calorimeter. The fuel sold by different company show different calorific value; by finding out the change in the calorific we can find out the high quality fuel available in the market. This research had covered the importance of calorific value of different fuel (diesel) with the help of a case study from Lords Institute of Engineering & Technology
This document provides information on an engineering thermodynamics course, including its objectives, outcomes, catalog description, textbooks, and course content. The course objectives are to learn the principles of classical thermodynamics and apply them to analyze systems and thermodynamic cycles. The outcomes are for students to differentiate system types, apply the second law of thermodynamics, analyze cycle performance, and solve combustion problems. The catalog description outlines topics like the laws of thermodynamics, phase changes, power cycles, and fuels/combustion. The course content covers basic concepts, the first/second laws, vapor/gas cycles, ideal gas mixtures, and fuels/combustion over 5 units.
Flare radiation-mitigation-analysis-of-onshore-oil-gas-production-refining-fa...Anchal Soni
The main objective of this paper is to calculate the sterile area around an existing vertical flare of length 112 meters, located in an onshore facility and evaluate whether the current design is acceptable during a General Power Failure (GPF) scenario. The sterile area will be calculated at an elevation of 2m, which represents the typical head height for personnel.
A simplified thermal model for the three way catalytic converter (1)Varun Pandey
This document presents a simplified thermal model for predicting the temperature evolution of a three-way catalytic converter (TWC) during cold start conditions. The model uses a semi-empirical approach based on energy and mass balances within the TWC, which is treated as a control volume. The model consists of submodels to represent oxygen storage, static conversion efficiency maps, and dynamic thermal behavior. Parameters for the heat transfer equations are identified using experimental temperature measurements along the length of the TWC monolith during testing on an engine test bench.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Experimental Investigation on Adsorption Capacity of a Variety of Activated C...IJERA Editor
This document summarizes an experimental study that investigated the adsorption capacity of various activated carbon/refrigerant pairs. Specifically, it tested activated carbon powder and granules paired with R-134a, R-407c, and R-507A refrigerants. A finned-tube heat exchanger was used to minimize heat and mass transfer limitations. The maximum adsorption capacities were measured at different temperatures. The highest capacity of 0.8352 kg/kg was found for activated carbon powder paired with R-134a at 25°C, while the lowest capacity of 0.3207 kg/kg was for the same pair at 50°C. Therefore, activated carbon powder with R-134a was determined to
An experimental study is conducted to determine the thermal output of a closed enclosure containing two cylindrical tubes through which biomass is burned. Temperature and energy measurements are taken at various points in the system. Convection and radiation are found to account for 33% of the total energy contained in the fuel wood, representing the useful thermal energy for applications like drying. Mathematical models are developed to describe the thermal energy flows and efficiency of the heat exchanger system.
An experimental study is conducted to determine the thermal output through convection and radiation inside a closed enclosure containing two cylindrical tubes through which biomass is burned. Temperature measurements are taken at various points to calculate the energy transferred. It is found that 33% of the potential energy from the fuel wood is emitted useful energy inside the enclosure for applications like drying. The objective is to quantify the energy and model it for practical uses such as solar collectors and drying.
Analysis of biomass pyrolysis product yield distribution in thermally thin re...Alexander Decker
This document summarizes a numerical study of biomass pyrolysis product yield distribution at different heating rates in the thermally thin regime. A kinetic model consisting of 5 differential equations was used to simulate pyrolysis of maple wood. Results showed that tar yield increased with heating rate while char yield decreased. Gas yield was influenced by secondary reactions and depended on temperature and residence time. Pyrolysis time decreased and temperature increased with higher heating rates. The model can predict product yields for other biomasses given their kinetic parameters.
Apec workshop 2 presentation 12 lh ci cinco presidentes-pemex-apec workshop 2Global CCS Institute
This document outlines a life cycle assessment of CO2 emissions from a CO2-EOR project in southern Mexico. It describes the goal of understanding environmental impacts from a life cycle perspective and estimating CO2 emissions associated with various steps of the project. The methodology estimates emissions using activity data and emission factors. Results found that CO2 emissions from the offshore platform to refinery via the EOR project were 5.41 tCO2eq per ton of CO2 injected, and the project reduced greenhouse gas emissions and environmental impacts compared to business as usual.
This document summarizes a study on the kinetics of methanol synthesis from carbon dioxide hydrogenation over copper-zinc oxide catalysts. Experiments were conducted in a fixed bed reactor between 200-230°C, 50-80 bar, and gas hourly space velocities of 7,800-23,400 h-1 using feeds with H2:CO2 ratios of 2-6 without CO. Kinetic parameters from a previous study were optimized to model the experimental data using a Langmuir–Hinshelwood–Hougen–Watson mechanism. The influences of catalyst support (alumina vs zirconia) and operating conditions on kinetics were examined. The goal was to determine optimized parameters to reliably scale-up the
This document presents a theoretical analysis of a vapor compression refrigeration system using refrigerants R-22, R407C, and R410A. Equations are developed based on the first and second laws of thermodynamics to model the system and analyze parameters such as coefficient of performance (COP), exergetic efficiency, and exergy destruction ratio (EDR). Results show R410A has the highest relative capacity change with increased subcooling degree and COP increase with higher evaporator temperatures. Exergetic efficiency is maximized and EDR minimized at evaporator temperatures of -30 to -35°C. R410A performance is better than R407C based on the thermodynamic analysis.
Calculation guidelines for Rotary Dryer.pdfEd Ryan Ruales
The document outlines the design procedure for a rotary dryer used to dry fertilizer from 5% to 1.5% moisture content. The key steps are:
1) Performing mass and heat balance calculations to determine moisture evaporated, dry solid mass, and total heat duty of 4.4 MJ/hr.
2) Sizing the dryer using the heat duty to calculate required air flow of 14.8 kg/hr, diameter of 2.3 m, volumetric heat transfer coefficient of 398 kJ/hr-m3-K, and length of 18 m.
3) Checking that the outlet air humidity is below saturation and selecting design parameters like number of flights based on sol
Experimental and Modeling Dynamic Study of the Indirect Solar Water Heater: A...IJAAS Team
The document presents an experimental and theoretical study of an indirect solar water heater system in Rabat, Morocco. A theoretical dynamic multi-node model is proposed and validated experimentally. The system includes a 1.91 m2 flat plate collector and 300 L storage tank that heats water solely with solar energy. Experimental data was collected over sunny and cloudy days and showed good agreement with the model, with average deviations of 2-5% for water temperature and 4-9% for useful energy. The thermal efficiency was also determined experimentally and theoretically, agreeing well with industry standards.
International Journal of Engineering and Science Invention (IJESI)inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
This study compared the effects of three flame retardant compounds - potassium aluminum sulfate, diammonium hydrogen phosphate, and ammonium chloride - on the flame behavior of a grass commonly used for roof thatching in Nigeria. Various concentrations of the compounds were applied to grass samples and a series of tests were conducted to evaluate ignition time, flame propagation rate, afterglow time, and flame duration time. The results showed that all three compounds improved the flame retardant properties of the grass by increasing ignition time and reducing flame propagation and duration. The paper explains the flame retardant mechanisms of each compound and concludes that all three are suitable for treating thatch materials to reduce flammability and fire risk.
This study compared the effectiveness of three flame retardant compounds - potassium aluminum sulfate, di-ammonium hydrogen phosphate, and ammonium chloride - at reducing the flammability of a grass commonly used for roof thatching in Nigeria. Various concentrations of the compounds were applied to the grass and tests measured factors like ignition time, flame propagation rate, afterglow time, and flame duration time. The results showed that all three compounds decreased flammability by evolving gases or residues when heated that interfered with the grass's combustion chemistry. Potassium aluminum sulfate and di-ammonium hydrogen phosphate were generally the most effective at higher concentrations, significantly reducing propagation rates and duration times. The study concluded that all three compounds were suitable for
This document compares the results of a 1-D kinetic model developed in MATLAB and a 0-D thermodynamic model developed in Aspen Plus for predicting syngas composition from biomass steam gasification. The kinetic model combines reaction kinetics and hydrodynamics, while the thermodynamic model uses Gibbs free energy minimization and a quasi-equilibrium approach calibrated with experimental data. A comparison of the model results to experimental data at two steam/biomass ratios showed that the models provide similarly results for main syngas components, though the thermodynamic model shows greater increases in H2 and CO2 and lower decreases in CH4 and CO at higher ratios compared to experiments. The thermodynamic model can be used to analyze overall plant performance but
Similar to 2007 AFRC-JFRC Flare Tip Analysis Using CFD (20)
1. American – Japanese Flame Research Committees International Symposium
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Marriott Waikoloa, Hawaii - Oct. 22 –24, 2007
Evaluation of the Air-Demand, Flame Height, and Radiation from
low-profile flare tips using ISIS-3D
Joseph D. Smith, Ph.D. and Ahti Suo-Ahttila, Ph.D.,
Alion Science and Technology, Owasso, Oklahoma, USA
Scot Smith and Jay Modi, Zeeco, Inc.
Zeeco Inc. Broken Arrow, Oklahoma, USA
ABSTRACT
Low-profile flare fields pose significant design challenges including elongated flames,
adequate air supply to burner tips located on inner rows and high radiation flux from the flame to
the surrounding wind fence. Recent work completed by engineers at Alion Science and
Technology for Zeeco, Inc. has focused on analyzing the performance of a proprietary burner tip
used in large low profile gas flares having upwards of 400 burner tips packed together into a
staged piping configuration surrounded by a specially designed wind fence. This paper presents
results from the CFD analysis of this gas flare and illustrates the capability of the CFD tool to
simulate soot formation, radiant flux, flame shape, and flame height for industrial scale low-
profile flare fields. This work was completed in conjunction with flare testing where ethylene
was fired through the burner tips. Data collected during these flare tests included video, radiant
flux, and sound. Test results were used to calibrate the combustion model and to validate CFD
predictions of flame height and air demand. Based on this, predicted flame height and air
demand were provided for two full flare field cases. In addition, estimates of radiant flux to the
surrounding wind fence were provided.
INTRODUCTION
A series of calculations of flare performance have been made. The purpose of the calculations
was to predict air demand under various conditions. In addition, the thermal radiation profile
around the flare was also determined. The primary computational fluid dynamics (CFD) tool
used in this analysis was ISIS-3D [1, 2, 3]. Previously, ISIS-3D has been used in a variety of
pool fire analyses to predict package thermal performance [4]. More recently, ISIS-3D has been
applied to flare analysis. In this application, new combustion models have been implemented for
handling new fuel mixtures including propane and ethylene. The combustion and radiation
models have been compared to flame size, shape, and radiation measurements measured during
single-burner and multi-burner tests under no-wind and low-wind ambient conditions.
The CFD model included various details depending upon the case that was run. For a single
burner case a computational domain of 6 m x 6 m x 30 m was selected. For a multi-burner case a
domain size of 35 m x 35 m x 25 m was selected. For the full field the computational domain
was extended 10m beyond the wind fence surrounding the entire flare field.
2. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
The main objective of this work was to predict the total air demand and the expected flame
height for two operating cases. In addition, the radiation heat flux profile was predicted for the
three burner test, and for the full flare field cases.
The three burner simulations were compared to experimental measurements of radiation
intensity at ground level located 15 m and 30 m from the burner tip. Results of these
measurements provided a partial validation of the overall computational model.
This paper contains descriptions of the various simulations, modeling assumptions and
methodology, computational results, and comparisons to experimental data.
COMBUSTION MODEL
The combustion model in ISIS-3D is a hybrid model combining Arrhenius kinetics and
turbulent mixing. The kinetics and turbulence models are combined by summing the
characteristic time scales. In addition to these dynamic models, sequences of irreversible
chemical reactions that describe the combustion chemistry are required. To facilitate an efficient
and practical CFD calculation, a minimum number of chemical reactions are used that fulfill the
requirements of total energy yield and species consumption and production. From the basis of
heat transfer, flame size, and air demand the details of the chemical reactions are not critical so
long as the oxygen consumption is correctly balanced for a given fuel type. To this end, both
two-step and three-step chemical reaction models for the different fuel types have been used.
A two-step chemical reaction is used for propane. The first reaction considered propane plus
oxygen which reacts to produce water, carbon dioxide and soot. The soot yield fraction was
assumed to be a constant fraction of fuel consumption and fixed at 2.4% as reported in the SFPE
manual [5]. The second reaction consumes soot produced in the first reaction. The two-step
reaction approach required a pilot burner at the flare tip to maintain a flame. This requirement
was due to the relative size of the computational cells compared to individual jet diameters and
the high flow velocities at the tip. Without a pilot flame, the high jet velocities cause the flame to
detach and blow out.
For ethylene and mixed gases, a three-step reaction is used similar to the one used by Greiner
for JP8 jet fuel fires [6]. In a three-step mechanism, the first reaction burns half the hydrogen
contained in the hydrocarbon, and any free hydrogen. The second reaction burns the remaining
hydrogen in the hydrocarbons and most of the carbon, with some degree of soot production. The
third and final reaction burns the soot produced in the second reaction. This sequence of
reactions is more numerically stable since the first reaction has a low activation energy (~20,000
cal/mole) compared to the second reaction, which has a typical hydrocarbon combustion
activation energy of 30,000 cal/mole. The low activation energy of the first reaction allows
partial combustion at low temperatures, releasing approximately 20% of the hydrocarbon heat of
combustion. The partial heat release keeps the fire burning without using a pilot flame.
Furthermore, this sequence is closer to that actually found in hydrocarbon fires. Again, the
stoichiometric details are not critical so long as the fuel, oxygen, and soot are consumed in the
correct proportions.
Propane Combustion model
For propane flames, a two-step chemical reaction is used that burns propane according to the
following formula:
Page 2 of 19
3. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
C3H8 + 3.6 O2 3 CO2 + 1.6 H2O + 0.024 Soot + 46 MJ/kg propane (1)
Soot + 2.66 O2 3.66 CO2 + 32 MJ/kg Soot (2)
The coefficients in the formula are mass weights, not moles.
The Arrhenius kinetics equation and parameters for these reactions were
Rate (moles/m3/sec) = XC2H8 * XO2 *A Exp(-Ta/T) (3)
Where X is the molar concentration of the species (moles/m3), A is the pre-exponential factor
(3.29E10 - 1st reaction and 8.0E11 - 2nd reaction), Ta is the activation temperature (K) (15,922
and 26,500), and T is the local temperature (K).
The characteristic time from the kinetics equation was combined with the characteristic
turbulence time scale
tturb=C ∆x2 / εdiff (4)
Where ∆x is the characteristic cell size, C is a user input constant (0.2E-4), εdiff is the eddy
diffusivity from the turbulence model, and tturb is the turbulence time scale, i.e. characteristic
time required to mix the contents of a computational cell. The reaction rates are combined by
simple addition of the time scales
Ethylene Combustion Model
For unsaturated hydrocarbon combustion, the requirement of using a pilot flame was
eliminated by implementing a three-step chemical reaction. Using this approach, the ethylene
combustion model consisted of the following three step mechanism:
C2H4 + 0.57 O2 0.93 C2H2 + 0.64 H2O + 9.4 MJ/kg ethylene (5)
C2H2 + 2.58 O2 2.7 CO2 + 0.7 H2O + 0.2 Soot + 34.1 MJ/kg intermediate (6)
Soot + 2.66 O2 3.66 CO2 + 32MJ/kg Soot (7)
As before the coefficients are mass weights, not mole weights.
The Arrhenius kinetics equation and parameters for these reactions were:
First Reaction Rate (moles/m3/sec) = XC2H4 * XO2 *1.0e15 Exp(-10,500/T) (8)
Second Reaction Rate (moles/m3/sec) = XC2H2 * XO2 *1.0e11 Exp(-15,500/T) (9)
3 (-20,500/T)
Third Reaction Rate (kg/m /sec) = YC * YO2 *1.0e11 Exp (10)
Where X is a mole concentration (mole density) and Y is a mass concentration (partial mass
density).
The advantage of the three-step reaction is that the first reaction has a low activation energy,
which allows the partial burning and heat release of ethylene. This will maintain combustion
since the partial heat released will allow the second reaction, which produces most of the heat
and all of the soot, to occur. As in the propane combustion model the ethylene Arrhenius
combustion time scale is combined with the turbulence time scale to yield an overall time scale
for the reaction rate.
Page 3 of 19
4. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Mixed Gas Combustion Model
A three-step chemical reaction formulation was implemented for a mixed gas having an
approximate composition of 32% C2H4, 20% C2H6, and 34% H2 (mole percent). Any remaining
gases are ignored in the combustion model.
The simplified 3-step reactions are
0.572 C2H4 + 0.383 C2H6 + 0.043 H2 +0.982 O2
0.53 C2H2 + 0.34 C2H3 + 1.1 H2O + 14.2 MJ/kg (11)
0.61 C2H2 + 0.39 C2H3 + 2.66 O2
2.66 CO2 + 0.813 H2O + 0.181 Soot + 34.4 MJ/kg (12)
Soot + 2.66 O2 3.66 CO2 + 32 MJ/kg (13)
As before the coefficients are mass weights, not mole weights.
The Arrhenius kinetics equation and parameters for these reactions were
First Reaction Rate (moles/m3/sec) = Xfuel * XO2 *1e15 Exp(-10500/T) (14)
3 (-15500/T)
Second Reaction Rate (moles/m /sec) = Xmix * XO2 *1e12 Exp (15)
3 (-20500/T)
Third Reaction Rate (kg/m /sec) = YC * YO2 *1e11 Exp (16)
Flare Nozzle Model
The flare burners have hundreds small holes of various sizes and aligned and divided on each
of the eight arms according to the specific tip design. An STL file containing details of the shape
and size of the flare arms and supporting structures was imported into ISIS-3D to generate an
approximate CAD model of the burner. However the thickness of the arms is on the order of 1
inch, which is below the resolution of the computational grid. As a result the burner model is
approximate which is not a problem however because the grid structure has minimal effect upon
the fluid dynamics around the outside of the flare burner tip. This minimal flow effect was
established by earlier calculations [4] that indicated the primary inflow of oxygen was from the
sides of the flare tip and not from below the flare tip.
Point sources of mass, species, and momentum were used to model each hole in each burner.
ISIS-3D numerically combines any holes that reside in the same computational cell into a single
source. Every hole was included in the simulations so that the mesh structure could be varied
without requiring a separate burner file for each mesh structure. Modeling every hole in every
burner does cause some additional CPU overhead; however there is less likelihood of an error,
since only a single input file is created for all the runs.
To further reduce the likelihood of CAD error that might lead to computational errors,
additional FORTRAN programs were used to calculate the flow area, 3-D coordinate location,
and direction cosines for each hole in each burner, as well as the mass flow rate and velocity of
the flare gas (i.e., propane, ethylene) as a function of driving pressure and temperature.
MODELING ASSUMPTIONS AND APPROACH
The following assumptions were utilized in modeling low profile flares using ISIS-3D:
Page 4 of 19
5. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
1. The total air demand for any case was determined by monitoring the flow across a
rectangular plane situated at a specified height above the ground, and extending 1-3
meters beyond the edge of the outermost burner. For cases with cross wind, the flow
across several planes was monitored and compared.
2. The nozzles were represented as point sources for momentum, mass, and species. The
momentum sources included the directional orientation and flow velocity from each hole.
3. The flow velocity exiting each hole was assumed to be proportional to the square root of
∆P/(½ ρC) where ∆P is the pressure drop of the tip, C is a loss coefficient of 0.85, and ρ
is the fuel density evaluated at the upstream temperature pressure and molecular weight.
4. For sonic conditions, the previous formula for flow rate which utilized an orifice
coefficient of 0.85 and the upstream density and pressure was not used because it is
invalid when the flow becomes sonic. Sonic flow is achieved whenever the driving
pressure exceeds the pressure where the flow reaches sonic conditions for the specific
gas.
5. Combustion of the flare gas was approximated by the appropriate 2 or 3 step irreversible
chemical reaction mechanism with specified kinetics.
6. Thermal radiation was calculated using standard radiation models. Radiation shadowing
by multiple flares was ignored in the CFD calculation but was accounted for in a separate
post-processing calculation that accounted for shadowing and absorption effects.
7. Ambient wind condition, flare gas inlet temperature and pressure, and radiation effects
were measured for each test and used in the CFD model.
8. Flame length was estimated from the location where the concentration of intermediate
species goes to zero.
ISIS-3D, the CFD tool used for these analyses, is a proprietary computer code for modeling
the dynamic behavior of fires influenced by a wide variety of physical processes and is based on
the conservation of mass, momentum, and energy. ISIS-3D has been successfully utilized for a
wide variety of flow / heat transfer applications [1-4, 5, 6].
The computational domain was extended through the entire flare field. For the full flare field
analysis, the wind fence was simulated as a baffle with the appropriate pressure drop to
accurately model flow through the fence. The methodology followed to develop and apply the
CFD tool to model low profile gas flares included the following steps:
1. Carefully review all flare drawings provided and prepare sketches of the flare tip and the
associated flare field. Dimensions not provided were scaled from drawings provided.
2. Set up the geometric domain and generate the computational mesh using the ISIS-3D
preprocessor.
3. Select appropriate physical and numerical sub-models (e.g., turbulence, pressure solver,
energy, etc.).
4. Perform a single burner simulation to determine the expected flow and temperature
profiles around a single burner and compared results to measured experimental data.
5. Perform a three-burner simulation to evaluate burner-burner spacing and compare
predicted flame shape/height to measured experimental data.
6. Based on model validation using flare test data, perform a full flare field analysis for a
given set of operating and ambient conditions.
Page 5 of 19
6. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Computational Domain
The computational domain used for these analyses (see Figure 1) extended several meters past
the edge of all flare tips. For the radiation prediction, the domain extended to a distance of 35 m
in both horizontal directions. The height of the domain was normally taken as 15 m except for
high pressure cases (20 and 30 psi) where the height was extended to 25 m.
Computational Mesh
Each model utilized different degrees of mesh refinement, with a single burner model having
the most refined mesh. A less resolved mesh was used for multi-tip simulations to reduce the
overall computational demand required to obtain a converged solution in a reasonable amount of
time. As seen, all meshes used were based on rectangular orthogonal cell shapes (as opposed to
unstructured cell shapes).
The computational meshes for the single burner, the triple burner, and the full flare field cases
are depicted below (see Figure 2). The dense dark to black areas is where the computational
mesh is beyond the resolving capability of the graphics. As a result the individual lines congeal
into either a dark mass or Moiré patterns (an interference pattern created when two grids are
overlaid at an angle, or when they have slightly different mesh sizes). The burner is only
depicted in the single burner mesh. In the full field cases the burners could not be fully resolved.
Figure 1 – Triple Burner Computational Domain. The domain size for all analyses was 30 m X
35 m X 25 m. The two green objects shown on the right represent the radiation flux meters
located 15 m and 50 m from the flare tip respective
Page 6 of 19
7. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Single Burner Mesh
Three Burner Mesh
Full Flare Field Mesh
Figure 2– Computational meshes for the single burner case (110,000 cells), the three-burner case
(188,000 cells), and the full flare field case (1.2 million cells). Each mesh shows locally fine
mesh near the burners
Page 7 of 19
8. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Boundary Conditions
The Boundary conditions used were hydrostatic pressure on all boundaries except the ground.
No-flow conditions were selected for the ground surface. The only exception to the hydrostatic
boundary condition are those cases where a cross wind was blowing. When a cross wind was
simulated, the upstream boundaries were set to the wind velocity and all other boundaries were
maintained as hydrostatic pressure conditions.
The thermal and species boundary conditions were set to 300 K (27˚C) and air composition
respectively.
Physical and Numerical Sub-model Selection
To simulate fluid flow, the momentum solver was the ISIS-3D LES turbulence model. The
turbulence plays a role in setting the rate for combustion and mixing of the hot plumes with air.
The energy equation was utilized to capture the temperature changes due to combustion and
mixing. The energy equation also included radiation effects.
The species equations were solved to keep track of the distribution and concentration of fuel,
oxygen, intermediate species, soot, and products of combustion (CO2 and H2O). The combustion
model was used to provide the species equations source and sink terms as a function of species
concentrations, local gas temperature, and turbulent diffusivity.
ISIS-3D includes a series of models to predict flame emissivity as a function of molecular gas
composition, soot volume fraction, flame size, shape and temperature distribution. In turn these
variables depend upon solutions to the mass, momentum, energy and species equations. The
radiation transport model is used not only to predict radiation flux on external (and internal)
surfaces, but it also provides source and sink terms to the energy equation so that flame
temperature distribution can be predicted.
Transient Calculation
In each case, the CFD simulation was started with an initial temperature and flow field and
run over sufficient time to allow the flow to reach steady (or quasi-steady) state conditions.
Steady state was determined by examining flow and thermal variables for relative constancy with
time. Since a transient solver was used, all field variables fluctuate in time due to turbulence and
other non-linearity’s in the equation system. However when examining any field variable, no
gradual slope was observed - just short term fluctuations as expected in turbulent flows.
The convergence criteria chosen for the simulations were that the equation of state was
always satisfied to within 0.1% or less at any location in the computational domain. Typically
the convergence criteria was better than the maximum allowable since the time step constraint
was limited by Courant conditions, which allows the flow field to be solved to a higher degree of
accuracy.
Page 8 of 19
9. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Post Processing CFD Results
After the calculation converged at steady conditions, appropriate contours of velocity
magnitude, temperature, and velocity vectors were prepared. Contours and discussion are
presented for each simulation below.
Figure 3 shows a soot isosurface colored by local temperature for a 3-burner test burning
propane. Also depicted are grid lines showing mesh refinement near the burners. Also shown is
the radiation measuring boxes located 15 m and 30 m from the flare tips. The radiation
measuring boxes were objects that were placed into the model from which radiation fluxes could
be extracted. These radiation intensity predictions could then be compared to actual measured
test data.
Figure 3 – Soot isosurface colored by temperature in a 3 burner simulation. Also depicted is the
mesh and radiation flux monitors
Page 9 of 19
10. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
ANALYSES
Single Flare Simulations
Two single flare simulations were performed with two mesh densities. The two flare
simulations were of propane and ethylene with the small flare tip. The finer mesh density was
used for the detailed simulation for comparison to flare measurements while the coarse mesh was
used to test the model under full field conditions. The detailed simulation utilized a mesh density
of 97,000 cells (45 x 44 x 49) applied to a physical domain of 6 m X 6 m X 25 m.
By comparing results from the coarse mesh simulation to results from the detailed mesh
simulation, the solution was tested for grid dependency and overall accuracy. This provided a
method of calibration when applied to the full field simulation. The full field simulation used the
same coarse mesh for each burner. Hence, by calibrating the coarse mesh to give the same result
as both the detailed mesh simulation and the flare test data, then it can be assumed that the full
field calculation is as accurate as possible.
Three Flare simulations
Several three burner flare simulations were performed (see Figure 5 as an example). These 3-
burner simulations burned a verity of fuels including propane and ethylene, each at a variety of
tip pressures. These simulations were performed on a mesh with 188,000 cells which covered a
computational domain of 35 m X 35 m X 30 m so the radiation comparisons to experimental
results could be made at distances of 15 meters and 30 meters. The radiation comparisons
allowed an evaluation of overall model accuracy.
The radiation intensity depends upon many factors such as combustion chemistry, soot
production and burn-up, and fluid dynamics for flame size, shape, temperature and flow
velocities. Of all predicted field variables, radiation intensity had the greatest sensitivity to errors
and/or inadequacies in the CFD model. Hence comparison to radiation measurements provided
the best method of global model validation.
Experimental results for one of the three burner tests are shown in Figure 4. This test was
conducted burning propane at the same flow rate used in the three-burner flare simulation shown
in Figure 3. The measured flame height for the three burner test was approximately 11.9 meters
high compared to the estimated flame height of 12 meters from the simulation.
Full Field Calculations
Four full field calculations were made representing a peak flow case and a sustained mixed
gas case without a crosswind. These calculations had a mesh density of over 700,000 cells for the
mixed gas case and 1,200,000 for the peak flow case. The physical domain simulated was 10
meters beyond the fence perimeter in all directions with an overall height of 25 m. Results from
these cases were used to evaluate the total air demand for the flare as well as the radiation flux to
two midpoints on the wind fence.
Page 10 of 19
11. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Figure 4 – Experimental measurements of flame shape and flame height for single burner test.
Flame lift off represents non-luminous (no-soot) combustion near the tip.
Total Air Demand Results
Total air demand for the full field simulations was evaluated by summing the mass flow
crossing a rectangular horizontal plane located at 20 m elevation and vertical rectangular planes
surrounding the flare burner (s). This created a box surrounding the flare burner and allowed
determination of total air flow. In the absence of a crosswind, flow out through the top plane was
sufficient to quantify total air demand, since all other faces had inflow. The total air demand for
all of the cases run is presented below (see Table 1).
Page 11 of 19
12. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Figure 5 – Experimental measurements of flame shape, flame height, and radiation flux from
a three-burner test firing ethylene under “no-wind” conditions.
Thermal Radiation Estimate
Thermal radiation was estimated for three-burner ethylene flare and the predictions were
compared with experiment. Radiation measurements were made for these tests at distances of
15m (50 ft) and 30m (100 ft), three driving pressures (2.8, 7.3, and 11.4 PSIG), and two tip sizes.
These radiation measurements allow a comparison of the overall accuracy of the ethylene flare
model.
The computational model includes a physical domain of 70 m in horizontal extent by 30 m
high. The number of computational cells was 62 X 62 horizontal X 49 high (188356 total). The
boundary conditions were hydrostatic pressure on the top surface and as reported constant
average wind speeds on the horizontal boundaries. The ethylene was injected at 3 different
pressures to represent the experimental conditions. Radiation meters were simulated as vertically
aligned surfaces and the incoming radiative flux was monitored on those surfaces.
Page 12 of 19
13. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Table 1 – Predicted Results from Cases Considered. Note all calculations were made for a “no-
wind” condition.
!
"! "
#$
%!
"& '( )
%
#$
%!
"& ""( )
*
#$
%!
& '( )
%
#$
%!
& ""( )
*
#$
+
#$
+
+
, +-
One complication of the radiation measurement that needs to be included is the effect of the
heated ground surrounding the flares and radiation meters. Since the flare is emitting a
significant amount of radiation, the ground surrounding the flare heats up. The heated ground
emits radiation and that contributes to the overall radiation flux sensed by the meter. In addition
to emitting radiation, the ground will also reflect any radiation that is not absorbed. To include
the effects of emitted and reflected radiation from the ground surrounding the flares, a ground
surface with an emissivity and absorptivity of 1.0 was included in the model. This ground
surface was allowed to heat to steady state conditions during the simulation. Using an emissivity
and absorptivity of 1.0 allows a reasonable approximation of both emitted and reflected
radiation. The overall energy balance for a grey ground surface that both emits and reflects
radiation is identical to that which absorbs all the incoming radiant heat and re-radiates it at
steady state. Thus a radiation meter, which is assumed to be a grey or black surface, will see the
same incoming radiation flux in both scenarios. If the ground reflects radiation spectrally, rather
than diffusely then some uncertainty would be introduced into this assumption.
A second effect that was included in the calculations was the atmospheric transmissivity. The
atmospheric transmissivity model of Hamins [7] was included for all radiation that passed
Page 13 of 19
14. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
through clear air. The Hamins model depends upon ambient temperature, source temperature,
and relative humidity. It accounts for radiation absorption by water vapor and carbon dioxide.
Table 2 presents the predictions, measurements, and relative error for 12 different cases.
Table 2 – Radiation Predictions and Test Results Comparison
Total
Burner Predicted Measured
Tip Position Pressure Radiation Radiation Difference
Size (m) (psi) (W/m2) (W/m2) (%)
3 15 2.8 2700 3344 -20.0 %
3 15 7.3 4750 4803 -1.0 %
3 15 11.4 6150 6192 -0.7 %
3 30 2.8 650 671 -3.0 %
3 30 7.3 1350 1184 +14.0 %
3 30 11.4 1650 1532 +8.0 %
4 15 2.8 4325 6371 -32.0 %
4 15 7.3 8050 8192 -2.0 %
4 15 11.4 10000 9536 +5.0 %
4 30 2.8 1150 1513 -23.0 %
4 30 7.3 2580 2464 +5.0 %
4 30 11.4 3250 2747 +18.0 %
Note that there were two burner sizes operating at various tip pressures with radiation data
taken at both 15 meters and 30 meters. The ISIS-3D predictions are quite good for most of the
suite of measurements with the greatest deviations at the lowest pressures. It is not clear what
causes the discrepancy between prediction and measurements but the greatest deviations appear
to be for the low pressure cases. One potential cause that is not understood may be related to
wind effects.
As shown in the table above, when the radiative effects of ground emission and reflection are
accounted for, the predicted radiation fluxes are very reasonable, and in some cases quite
accurate. The greatest deviation was for the 15 m (50 foot) large tip, where the radiative flux
was under predicted by 32%. Otherwise, the predicted fluxes are well within experimental error.
The effect of wind speed upon radiation can be illustrated with the following example. The
large nozzle, at a driving pressure of 2.8 psig, was chosen as an example because it had the
greatest deviation of all the experimental measurements. The wind speed was varied from zero to
4 m/s (9 mph). The wind direction was 45 degrees toward the radiation meters but not varied in
the simulations. Wind causes the flare height to shorten, and may cause flares to merge
depending upon wind direction. The calculated radiative flux is shown in Figure 6.
Page 14 of 19
15. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
Figure 6 – Effect of wind speed upon radiative heat flux from a triple burner, ethylene flare at
a distance of 15 m
The sensitivity of radiative heat flux to wind shown in the figure above illustrates that a
momentary reduction in wind speed during the radiation measurement could bring the prediction
and measurement into much closer agreement. The experimental data reported a wind speed
range, but not the exact speed during the measurement. In the simulations the average of the
reported range was used and held fixed during the calculation.
The radiation measurements provide a validation of the overall model because the radiative
heat loss from the fire is the single most sensitive parameter to modeling variables. Radiation
depends upon flame temperature to the fourth power, flame emissivity, and flame size. All of
these variables depend upon solutions to the governing equations, molecular and soot emissivity
models, radiation heat transport models, combustion chemistry models, and the overall setup of
the CFD model (i.e. Mesh, Wind Boundary Conditions, etc.). If any of the input parameters or
models were inappropriate, predicted results would not match experimental measurements as
well as shown in Table 2. In conclusion, the good comparisons to test data indicate that the
model is validated sufficiently for radiation predictions. This conclusion is based upon the twelve
comparisons representing two different nozzles operated at three different pressures each.
The radiation prediction for the full field is more difficult to estimate because radiation
leaving one row of burners must pass through other rows before it reaches the fence. When
radiation passes through other rows of flares, or portions of rows, some of the radiation is
absorbed and re-radiated in other directions. These effects are not considered in the ISIS-3D
radiation model. In ISIS-3D, when radiation leaves a flame no checks are made to see if that
radiation interacts with intervening objects or other flames. This keeps the code fast running
Page 15 of 19
16. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
since shadowing is ignored. When such effects do occur, as in the full field simulation, the user
must explicitly account for them in the radiation prediction.
To modify the predicted full field radiation flux to account for intervening flame absorption, a
simple numerical model with the following assumptions was made.
1. The flame width and height are equal to the row length and predicted flame height. That
is a row of flares behaves as a continuous wall of flames.
2. The flame emissive power is equal to the total radiative heat loss (derived from the ISIS-
3D calculation) divided by the radiative surface area (length*width*2) of all the rows.
3. The flux from any row is equal to the emissive power, times the view factor, times an
attenuation factor for any intervening rows and the atmosphere.
4. The attenuation factor for any row is equal to 1-e(-τ), where τ is the optical thickness of
the row. The optical thickness of the flames is supplied in the ISIS-3D output.
5. The effect of ground reflection and emission is calculated with the same assumptions and
methodology as the 3 burner tests.
A numerical model including these features and assumptions was developed and the results
appear in the table below (see Table 3). Radiation intensity at the midpoint of the fences parallel
to the burner rows was modeled. Radiation to the midpoint on the fence perpendicular to the
rows was not modeled because the rows only partially obscured each other; those cases are
labeled (NA). Partial obscuration was beyond the scope of this simple absorption model since it
requires significantly more complex view factor calculations.
Table 3 shows predictions for the full field radiation flux to the fences. The radiation
predictions directly from ISIS-3D (i.e., not accounting for flare row absorption) are shown in the
upper part of the table cell – labeled “ISIS-3D Output”. The radiation prediction modification
that accounts for flame absorption due to intervening rows are shown in the lower part of the
same cell, labeled (Modification).
Labeling of the walls around the full flare field is taken from a “plan-view” perspective as
left-wall, right-wall, and bottom-wall.
Table 3– Predicted Results from Modifications Investigated
Left Wall Right Wall Bottom Wall
WALL “ISIS-3D Output” “ISIS-3D Output” “ISIS-3D Output” Flame
(Modification) (Modification) (Modification) Optical
CASE W/m2 W/m2 W/m2 Thickness
Case 2 “78,000” “63,000” “108,000” 0.275
Peak Flow 944 T/hr
No Wind (61,000) (35,000) NA
Case 3 “15,000” “15,000” “35,000” 0.28
Sustained 337 T/hr
No Wind (6,600) (6,600) NA
Flame Height Estimate
Flame height is difficult to quantitatively assess. The reason is that ISIS-3D predicts flame
temperature and species concentrations but does not predict visible light intensity which is what
Page 16 of 19
17. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
an observer will rely on to measure flame height (see Figure 4 and Figure 5). The radiation
models predict radiation thermal flux, but since the plume above the visible flame contains CO2,
H2O, and traces of soot, it still radiates albeit in the infrared. Therefore, an alternate procedure
was adopted to predict visible flame height. The procedure selected was to monitor the
concentration of ethylene and select the location where the ethylene concentration equals the
value corresponding to the measured flame height in the triple burner tests. That ethylene
concentration turns out to be a mass fraction of 0.03. Although small amounts of intermediate
products and soot may still be present, the driver for all the chemical reactions is the raw fuel.
Photographs and measurements of the triple burner ethylene tests reveal that traces of soot do
exist in the plume above the visible flame. Thus, monitoring soot concentration overestimates
flame height since the soot concentration at the visible limit is not known.
Using ethylene concentration as a predictor of flame height, the peak full field flame heights
are shown in Figure 7. The view shown corresponds to a ¼-symmetry no wind conditions
simulation. Concentrations shown are iso-surfaces, which are surfaces of constant ethylene
concentration equal to a 0.03 mass fraction. The height shown in this image is 25 m. Flames
from the leftmost row are approximately 13 m high while flames from the rightmost row are
approximately 2 m high. Since Row 1 is a spare, it is not shown. Although only 4 rows are
shown, some of the smaller rows have been combined to form a single row to improve
computational efficiency.
Figure 7 – An isosurface view of ethylene concentration for a 1/4 symmetry peak flow full
field case with no wind. The flame height is shown to be below the fence height.
As shown in Figure 7, the flame height is estimated to be well below the fence level.
Although this is a ¼ symmetry image, the remainder of the field behaves very similarly. A
quarter symmetry problem was chosen to maximize the computational cell density.
Page 17 of 19
18. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
RESULTS
The results of these simulations indicate that the total air demand for the various cases is
beyond the stoichiometric requirement (stoichiometric requirement varies with fuel type) but is
often in the range 15:1 air to fuel mass ratio for many hydrocarbons. The air to fuel ratios for the
various cases range from a high of 150 to a low of 38 (using larger flare tip operated at high
pressure for the 3 burner test). For the full field analysis, the range was from 40 for the peak
flow field to 60 for the sustained case. Thus the calculations results support the conclusion that
sufficient air will be entrained and present to burn essentially all fuel for both the sustained and
the peak flow cases. One caveat is that these air demand calculations represent the “Total Air
Demand” for the system as a whole and do not address the possibility that local air starvation
may occur somewhere in the flare field.
The radiation predictions indicated that high radiation fluxes incident on the center point of
the wind fence are possible (as high as 100,000 W/m2 for peak flow case). For the Peak Flow
case, the radiation flux incident on the wind fence ranges from 35,000 W/m2 to 108,000 W/m2.
For the Sustained Flow case the incident radiation to the wind fence ranges from 6,600 W/m2 to
35,000 W/m2. Flame heights were estimated by monitoring ethylene concentration and selecting
the location where the concentration equals the value found for the flame height measurements in
the triple burner tests. Iso-surface contours reveal that the flame heights for the peak field with
no wind are well below the fence height.
CONCLUSIONS
The work presented in this paper documents a transient flame analysis for the multi-tip low-
profile flare. Objectives for this work include predicting the total air demand and the expected
flame height for a sustained flow case and a peak flow case burning ethylene. The ISIS-3D CFD
model was used to perform the computer simulations for a single burner test and a three burner
test to verify model predictions. Based on model verification, the full field was simulated. Full
field simulations including all burners in the flare field plus the surrounding fence were
conducted. ISIS-3D predictions indicate that sufficient air is entrained through the fence to
prevent flame from extending beyond the top of the fence and from generating noticeable smoke
for the peak flow case which is considered the limiting case. Radiation fluxes to the wind fence
are predicted to be up to 100,000 W/m2.
REFERECNES
1. Suo-Anttila, A., Wagner, K.C., and Greiner, M., 2004, "Analysis of Enclosure Fires Using
the Isis-3DTM CFD Engineering Analysis Code," Proceedings of ICONE12, 12th International
Conference on Nuclear Engineering, Arlington, Virginia USA, April 25-29.
2. Greiner, M., and Suo-Anttila, A., 2004, "Validation of the ISIS Computer Code for
Simulating Large Pool Fires Under a Varity of Wind Conditions," ASME J. Pressure Vessel
Technology, Vol. 126, pp. 360-368.
3. Greiner, M., and Suo-Anttila, A., 2003, "Fast Running Pool Fire Computer Code for Risk
Assessment Calculations," presented at the ASME International Mechanical Engineering
Congress and Exhibition, November 15-21, 2003, Washington, DC.
Page 18 of 19
19. Evaluation of the Air-Demand, Flame Height, and Radiation from low-profile flare tips using ISIS-3D
Advances in Combustion Technology: Improving the Environment and Energy Efficiency
4. Greiner, M, Are, N., Lopez, C., and Suo-Anttila, A., "Effect of Small Long-Duration Fires on
a Spent Nuclear Fuel Transport Package," Institute of Nuclear Materials Management 45th
Annual Meeting, Orlando, FL, July 18-22, 2004.
5. Society Fire Protection Engineers, 1995, Fire Protection Engineering, 2nd Edition, National
Fire Protection Association Publication.
6. Greiner, M., and Suo-Anttila, A., 2006, "Radiation Heat Transfer and Reaction Chemistry
Models for Risk Assessment Compatible Fire Simulations," Journal of Fire Protection
Engineering, Vol. 16, pp. 79-103.
7. Fuss S.P., A. Hamins. 2002, “An estimate of the correction applied to radiant flame
measurements due to attenuation by atmospheric CO2 and H2O”, Fire Safety Journal, Vol.
37, pp. 181-190.
Page 19 of 19