Heat and mass transfer from aerosol bound species, for application in the solar seeded reactor. Supervisors – Prof. Yinon Rudich, Prof. Jacob Karni
A method for measuring the sherwood number of aerosols was developed, utilizing an Aerosol mass spectrometer, a thermal denuder, and a differential mobility analyzer and a condensation particle counter. The goal is to use the measured sherwood number for predicting the nusselt number through the heat to mass analogy, as described in the text.
Biology paper 3 option evolution 11 dp dic 11Galaxia Mercury
This document contains a biology exam for the standard level with 4 questions related to evolution. It provides the instructions to candidates, outlines the scoring rubric, and presents the questions and spaces for answers. The questions address topics like changes in body size over time for a genus of ostracods, the origin of life and eukaryotes, distinguishing features of primates, and implications of gaps in the fossil record for understanding human evolution.
This document describes the design, construction, testing, and results of prototypes for a technology to reduce mercury emissions from small-scale gold refining facilities. It presents the theoretical basis for an aerosol collection system using coagulation and impaction principles. Designs for multiple prototypes are discussed, including the selection of a baffle plate assembly design. The prototypes were tested at six gold shops in Brazil, and sampling methods were used to determine mercury removal efficiency. The testing demonstrated removal of over 90% of airborne mercury from emission gases.
This document discusses microscopy techniques. It describes light microscopes and electron microscopes, including transmission electron microscopes and scanning electron microscopes. Key components of microscopes like the objective lens, ocular lens, stage, and nosepiece are defined. The document also provides a brief history of microscopy, outlining contributions from scientists like Anton Van Leewenhock, Robert Hooke, Robert Brown, Matthias Schleiden, and Theoder Schwann. Sample preparation techniques are covered as well.
The document discusses 9 points about data, information, information technology (IT) and their management. It addresses collecting and analyzing data and transforming it into useful information. It also discusses using information and IT to improve operations and decision making over three and five year periods. Strategies are proposed for effective information management.
Rheological method in food process enginneringVictor Morales
This document provides the table of contents for the book "Rheological Methods in Food Process Engineering" by James F. Steffe. The book covers topics such as stress and strain, fluid and solid behavior, viscometry methods including tube, rotational, and empirical techniques, and applications to foods like sauces, starches, and dairy products. It includes examples and problems related to measuring and modeling the rheological properties of various food materials.
The document provides information about candidates for the degree of Doctor of Pedagogical Sciences at the Kharkiv National University named after Gorky. It lists 13 candidates, their advisors, dissertation topics, and recommends awarding the degree to one of the candidates. The document was prepared for review by the Academic Council of the Institute of Psychology at Kharkiv National University named after Gorky.
This document contains instructions and questions for a 60-minute Common Entrance Examination at 11+ for science. The examination contains 9 multiple choice and short answer questions testing knowledge of science concepts and experiments related to biology, physics, and the Earth. Students are to write their answers on the question paper and are allowed to use a calculator. The examination is administered by the Independent Schools Examinations Board.
This thesis constructs the Fedosov quantization map on the phase space of a single particle for constant curvature manifolds of codimension one, including the two-sphere and de Sitter/anti-de Sitter space-times. The Fedosov algorithm is used to define a star product on the phase space, yielding a noncommutative algebra of observables. Exact solutions are obtained for the Klein-Gordon equation on these spaces, verifying previous results from other quantization methods. The quantization procedure provides a direct connection between star products, the Fedosov algorithm, and the Hilbert space formulation of quantum theory.
Biology paper 3 option evolution 11 dp dic 11Galaxia Mercury
This document contains a biology exam for the standard level with 4 questions related to evolution. It provides the instructions to candidates, outlines the scoring rubric, and presents the questions and spaces for answers. The questions address topics like changes in body size over time for a genus of ostracods, the origin of life and eukaryotes, distinguishing features of primates, and implications of gaps in the fossil record for understanding human evolution.
This document describes the design, construction, testing, and results of prototypes for a technology to reduce mercury emissions from small-scale gold refining facilities. It presents the theoretical basis for an aerosol collection system using coagulation and impaction principles. Designs for multiple prototypes are discussed, including the selection of a baffle plate assembly design. The prototypes were tested at six gold shops in Brazil, and sampling methods were used to determine mercury removal efficiency. The testing demonstrated removal of over 90% of airborne mercury from emission gases.
This document discusses microscopy techniques. It describes light microscopes and electron microscopes, including transmission electron microscopes and scanning electron microscopes. Key components of microscopes like the objective lens, ocular lens, stage, and nosepiece are defined. The document also provides a brief history of microscopy, outlining contributions from scientists like Anton Van Leewenhock, Robert Hooke, Robert Brown, Matthias Schleiden, and Theoder Schwann. Sample preparation techniques are covered as well.
The document discusses 9 points about data, information, information technology (IT) and their management. It addresses collecting and analyzing data and transforming it into useful information. It also discusses using information and IT to improve operations and decision making over three and five year periods. Strategies are proposed for effective information management.
Rheological method in food process enginneringVictor Morales
This document provides the table of contents for the book "Rheological Methods in Food Process Engineering" by James F. Steffe. The book covers topics such as stress and strain, fluid and solid behavior, viscometry methods including tube, rotational, and empirical techniques, and applications to foods like sauces, starches, and dairy products. It includes examples and problems related to measuring and modeling the rheological properties of various food materials.
The document provides information about candidates for the degree of Doctor of Pedagogical Sciences at the Kharkiv National University named after Gorky. It lists 13 candidates, their advisors, dissertation topics, and recommends awarding the degree to one of the candidates. The document was prepared for review by the Academic Council of the Institute of Psychology at Kharkiv National University named after Gorky.
This document contains instructions and questions for a 60-minute Common Entrance Examination at 11+ for science. The examination contains 9 multiple choice and short answer questions testing knowledge of science concepts and experiments related to biology, physics, and the Earth. Students are to write their answers on the question paper and are allowed to use a calculator. The examination is administered by the Independent Schools Examinations Board.
This thesis constructs the Fedosov quantization map on the phase space of a single particle for constant curvature manifolds of codimension one, including the two-sphere and de Sitter/anti-de Sitter space-times. The Fedosov algorithm is used to define a star product on the phase space, yielding a noncommutative algebra of observables. Exact solutions are obtained for the Klein-Gordon equation on these spaces, verifying previous results from other quantization methods. The quantization procedure provides a direct connection between star products, the Fedosov algorithm, and the Hilbert space formulation of quantum theory.
This document is the Bash Reference Manual for version 4.2 of the GNU Bash shell. It provides documentation on Bash's features, including basic shell syntax and operations, shell commands, parameters, expansions, redirections, and built-in commands. The manual is published by the Free Software Foundation and was last updated in December 2010.
This document is a thesis submitted by Chad Furey to Dalhousie University in partial fulfillment of the requirements for a Master of Science degree. The thesis presents a parametric analysis of the shock response of a system of two submerged co-axial cylindrical shells coupled by an inter-shell fluid. Chapter 1 introduces the research, Chapter 2 presents the mathematical formulation, and Chapter 3 describes the solution methodology for the fluid and structural dynamics. Results and discussion from the analysis are provided in Chapter 4, while Chapter 5 presents a parametric study. The conclusion in Chapter 6 summarizes the current research and proposes areas for future work.
This thesis describes simulations of silicon detector response for the β-delayed proton emission of 69Kr. Monte Carlo simulations using MCNPX, GEANT4 and CASINO were performed to aid in the identification of decay branches, which will help determine a proton-capture Q-value for 68Se and advance understanding of x-ray bursts. The author developed and validated simulations of a 207Bi calibration experiment to predict experimental results for the upcoming 69Kr experiment. Simulation code is included in the appendix.
Detailed account of Metaphysical Operations required for the The New Age, for which we had to depend on outside help.
The Time Line was altered,and the 2012 event which would have seen Earth bereft of humanity was changed completely.
These details form the the main message, the rest is about Spiritual Philosophy and the Nature and Destiny of Man.
Σύγχρονες Διδακτικές Προσεγγίσεις για την Ανάπτυξη Κριτικής – Δημιουργικής Σκ...Vasilis Drimtzias
This document discusses the development of educational programs with a focus on synchronous distance learning. It includes sections on the formation of educational programs, categories of actions, and provides the title and theme of one action/energy titled "Appropriate Morphosis of Educational Programs". The document references creating synchronized didactic proposals for the critical-reflective dimension of education and provides a copyright date of 2007.
Cấu trúc dữ liệu và giải thuật[bookbooming.com]bookbooming1
This document provides a summary of data structure and algorithm concepts including:
- Introduction to data structure topics like trees, lists, stacks, and queues.
- Implementation details for common data structures like linked lists, stacks, queues and their operations.
- Algorithmic concepts like recursion, backtracking, and string searching algorithms.
This report analyzes cattle farming and beef certification systems in Xieng Khouang Province, Laos. It finds that the province's current cattle production system differs significantly from international grass-fed beef certification standards. Specifically, Xieng Khouang cattle are raised with minimal healthcare and slaughtering practices that would not meet food safety standards for export markets. The report recommends strategies for Xieng Khouang farmers to improve cattle breeding and grazing, adopt organic practices, and develop slaughtering and marketing systems needed to achieve grass-fed or organic beef certification. This would allow access to higher-price international markets and provide more income for farmers. The report provides cost estimates for certification fees to assist farmers in evaluating options.
The document provides details of the Georgia Tech Team ARES project Hermes. It summarizes the launch vehicle Skyron which will carry a standard payload to 1 mile above ground level and safely recover it. The launch vehicle utilizes several subsystems including a nosecone GPS, payload section, avionics bay, booster section, fins, apogee targeting system, and recovery system. It also summarizes the autonomous ground support equipment which will secure the payload, erect the launch vehicle, and insert the igniter. The document reviews changes made since the critical design review and provides in-depth details of the launch vehicle, ground support equipment, electrical, and flight systems, as well as mission operations, budget, timeline, and
My presentation from SMX Stockholm, 2012. My 'link building dos and don'ts' focus on some of the lessons I've learn't in the past whilst working for a variety of brands in competitive spaces.
This document describes a case study that investigated using videos to teach rural communities in Nigeria about solar cooking. The researcher worked with two non-profits in Nigeria to create locally-made videos in local languages about building and using solar cookers. Nine solar cookers of different designs were built locally and tested. Workshops using the videos helped transfer knowledge about solar cooking. The videos and solar cookers helped build skills and capacity around solar cooking, which has benefits like reducing women's workloads, poverty, and environmental impacts. The study evaluated whether locally-made videos were effective for teaching people new to solar cooking.
English school-books-2nd-primary-2nd-term-khawagah-2019-5khawagah
1. The document contains a list of scrambled words and sentences from different units of study.
2. Students are asked to unscramble words, punctuate sentences, write missing letters, match words and pictures, and answer comprehension questions.
3. The purpose is to review and assess learning from previous lessons.
This document provides standardization guidelines for lung function testing, including spirometry, maximal expiratory flow-volume loops, reversibility testing, vital capacity maneuvers, and peak flow measurements. Key recommendations include definitions of terms, equipment requirements, test procedures, criteria for acceptable maneuvers, and quality control measures. The goal is to promote standardized testing to allow for accurate interpretation and comparison of results across patients and studies.
Porjet de fin d'études Master Ingénierie Informatique : Réseaux, Sécurité et ...Ramsi Koutounda
This document discusses securing an OpenStack cloud computing environment. It begins with an introduction to cloud computing concepts, including definitions, history, models, services, and advantages/disadvantages. It then presents existing cloud solutions, comparing open source options like OpenStack, OpenNebula, CloudStack, and Eucalyptus, and selecting OpenStack for deployment. The document outlines OpenStack's architecture and key modules for compute, storage, networking, identity management, and more. It concludes by introducing the project to implement a secure OpenStack environment.
Bored game design studio prototype_0915jhouchens99
This document provides the rules for a strategic board game called Formation. Players command armies of different units including infantry, cavalry, archers, and alchemists with the goal of defeating other players by capturing their command post. The rules cover game setup, turn order, unit movements and special abilities, formations, and winning conditions. Players place barricades and units in their starting zone, then take turns moving one unit per turn until one player remains as the winner.
This document provides an overview of the anatomy and physiology of the ear, nose, oral cavity, pharynx, larynx and related structures. It covers the development, structures, functions and common diseases of these areas. Key topics include the anatomy of the outer, middle and inner ear; tests for hearing and causes of hearing loss; diseases of the nose, sinuses and pharynx; salivary glands; larynx; and cancers of the oral cavity and larynx. The document is intended as a reference for medical students to review the important concepts in otorhinolaryngology.
The document provides documentation for installing Fedora 17 on x86, AMD64 and Intel 64 systems. It includes instructions for downloading and preparing installation media, planning hardware requirements, starting the installation process, completing installation using the graphical or text-based interface, and troubleshooting installation issues. The guide also covers advanced installation options such as disk partitioning, encrypted partitions, Kickstart automation and setting up a network installation server.
This document provides an introduction to using RStudio for data analysis. It begins with an overview of RStudio and instructions for installation. It then covers important basics like reading data, exploring and modifying variables, and creating script files. Following sections demonstrate descriptive statistics, testing for normal distribution, hypothesis testing, and linear regression. Examples use the tourism dataset. The goal is to introduce RStudio's capabilities for data analysis in a straightforward way.
The document evaluates five implementations of the SPARQL query language for the Semantic Web. It first provides background on the Semantic Web and SPARQL, including the data model and query language specifications. It then describes the methodology for testing each implementation using a dataset from DBpedia.org and sample queries. Each implementation - OpenRDF Sesame, OpenLink Virtuoso, Jena, Pyrrho DBMS, and AllegroGraph - is installed and evaluated based on documentation, loading data efficiently, and computing query results in a reasonable time. The conclusion finds that while some implementations are advanced, they still have problems processing basic SPARQL queries as specified.
This paper aims to provide a benchmark study of three established bearing diagnostic techniques applied to vibration data from the Case Western Reserve University Bearing Data Center. The techniques include envelope analysis of the raw signal, cepstrum prewhitening, and a benchmark method. The results and diagnostic outcomes of each technique are discussed in detail for different bearing fault types and conditions in the data sets. Recommendations are provided on how to best use the data for testing new diagnostic algorithms and how to generate benchmark data in the future.
This document is an introduction to the book "Data Structures and Algorithms: Annotated Reference with Examples" by Granville Barnett and Luca Del Tongo. It provides an overview of the contents of the book, which aims to present common data structures and algorithms with concise pseudocode and explanations. The book covers topics such as linked lists, binary search trees, heaps, sorting algorithms, and string algorithms. It is intended to serve as a reference for students and developers to learn about these essential computing concepts.
This document is the Bash Reference Manual for version 4.2 of the GNU Bash shell. It provides documentation on Bash's features, including basic shell syntax and operations, shell commands, parameters, expansions, redirections, and built-in commands. The manual is published by the Free Software Foundation and was last updated in December 2010.
This document is a thesis submitted by Chad Furey to Dalhousie University in partial fulfillment of the requirements for a Master of Science degree. The thesis presents a parametric analysis of the shock response of a system of two submerged co-axial cylindrical shells coupled by an inter-shell fluid. Chapter 1 introduces the research, Chapter 2 presents the mathematical formulation, and Chapter 3 describes the solution methodology for the fluid and structural dynamics. Results and discussion from the analysis are provided in Chapter 4, while Chapter 5 presents a parametric study. The conclusion in Chapter 6 summarizes the current research and proposes areas for future work.
This thesis describes simulations of silicon detector response for the β-delayed proton emission of 69Kr. Monte Carlo simulations using MCNPX, GEANT4 and CASINO were performed to aid in the identification of decay branches, which will help determine a proton-capture Q-value for 68Se and advance understanding of x-ray bursts. The author developed and validated simulations of a 207Bi calibration experiment to predict experimental results for the upcoming 69Kr experiment. Simulation code is included in the appendix.
Detailed account of Metaphysical Operations required for the The New Age, for which we had to depend on outside help.
The Time Line was altered,and the 2012 event which would have seen Earth bereft of humanity was changed completely.
These details form the the main message, the rest is about Spiritual Philosophy and the Nature and Destiny of Man.
Σύγχρονες Διδακτικές Προσεγγίσεις για την Ανάπτυξη Κριτικής – Δημιουργικής Σκ...Vasilis Drimtzias
This document discusses the development of educational programs with a focus on synchronous distance learning. It includes sections on the formation of educational programs, categories of actions, and provides the title and theme of one action/energy titled "Appropriate Morphosis of Educational Programs". The document references creating synchronized didactic proposals for the critical-reflective dimension of education and provides a copyright date of 2007.
Cấu trúc dữ liệu và giải thuật[bookbooming.com]bookbooming1
This document provides a summary of data structure and algorithm concepts including:
- Introduction to data structure topics like trees, lists, stacks, and queues.
- Implementation details for common data structures like linked lists, stacks, queues and their operations.
- Algorithmic concepts like recursion, backtracking, and string searching algorithms.
This report analyzes cattle farming and beef certification systems in Xieng Khouang Province, Laos. It finds that the province's current cattle production system differs significantly from international grass-fed beef certification standards. Specifically, Xieng Khouang cattle are raised with minimal healthcare and slaughtering practices that would not meet food safety standards for export markets. The report recommends strategies for Xieng Khouang farmers to improve cattle breeding and grazing, adopt organic practices, and develop slaughtering and marketing systems needed to achieve grass-fed or organic beef certification. This would allow access to higher-price international markets and provide more income for farmers. The report provides cost estimates for certification fees to assist farmers in evaluating options.
The document provides details of the Georgia Tech Team ARES project Hermes. It summarizes the launch vehicle Skyron which will carry a standard payload to 1 mile above ground level and safely recover it. The launch vehicle utilizes several subsystems including a nosecone GPS, payload section, avionics bay, booster section, fins, apogee targeting system, and recovery system. It also summarizes the autonomous ground support equipment which will secure the payload, erect the launch vehicle, and insert the igniter. The document reviews changes made since the critical design review and provides in-depth details of the launch vehicle, ground support equipment, electrical, and flight systems, as well as mission operations, budget, timeline, and
My presentation from SMX Stockholm, 2012. My 'link building dos and don'ts' focus on some of the lessons I've learn't in the past whilst working for a variety of brands in competitive spaces.
This document describes a case study that investigated using videos to teach rural communities in Nigeria about solar cooking. The researcher worked with two non-profits in Nigeria to create locally-made videos in local languages about building and using solar cookers. Nine solar cookers of different designs were built locally and tested. Workshops using the videos helped transfer knowledge about solar cooking. The videos and solar cookers helped build skills and capacity around solar cooking, which has benefits like reducing women's workloads, poverty, and environmental impacts. The study evaluated whether locally-made videos were effective for teaching people new to solar cooking.
English school-books-2nd-primary-2nd-term-khawagah-2019-5khawagah
1. The document contains a list of scrambled words and sentences from different units of study.
2. Students are asked to unscramble words, punctuate sentences, write missing letters, match words and pictures, and answer comprehension questions.
3. The purpose is to review and assess learning from previous lessons.
This document provides standardization guidelines for lung function testing, including spirometry, maximal expiratory flow-volume loops, reversibility testing, vital capacity maneuvers, and peak flow measurements. Key recommendations include definitions of terms, equipment requirements, test procedures, criteria for acceptable maneuvers, and quality control measures. The goal is to promote standardized testing to allow for accurate interpretation and comparison of results across patients and studies.
Porjet de fin d'études Master Ingénierie Informatique : Réseaux, Sécurité et ...Ramsi Koutounda
This document discusses securing an OpenStack cloud computing environment. It begins with an introduction to cloud computing concepts, including definitions, history, models, services, and advantages/disadvantages. It then presents existing cloud solutions, comparing open source options like OpenStack, OpenNebula, CloudStack, and Eucalyptus, and selecting OpenStack for deployment. The document outlines OpenStack's architecture and key modules for compute, storage, networking, identity management, and more. It concludes by introducing the project to implement a secure OpenStack environment.
Bored game design studio prototype_0915jhouchens99
This document provides the rules for a strategic board game called Formation. Players command armies of different units including infantry, cavalry, archers, and alchemists with the goal of defeating other players by capturing their command post. The rules cover game setup, turn order, unit movements and special abilities, formations, and winning conditions. Players place barricades and units in their starting zone, then take turns moving one unit per turn until one player remains as the winner.
This document provides an overview of the anatomy and physiology of the ear, nose, oral cavity, pharynx, larynx and related structures. It covers the development, structures, functions and common diseases of these areas. Key topics include the anatomy of the outer, middle and inner ear; tests for hearing and causes of hearing loss; diseases of the nose, sinuses and pharynx; salivary glands; larynx; and cancers of the oral cavity and larynx. The document is intended as a reference for medical students to review the important concepts in otorhinolaryngology.
The document provides documentation for installing Fedora 17 on x86, AMD64 and Intel 64 systems. It includes instructions for downloading and preparing installation media, planning hardware requirements, starting the installation process, completing installation using the graphical or text-based interface, and troubleshooting installation issues. The guide also covers advanced installation options such as disk partitioning, encrypted partitions, Kickstart automation and setting up a network installation server.
This document provides an introduction to using RStudio for data analysis. It begins with an overview of RStudio and instructions for installation. It then covers important basics like reading data, exploring and modifying variables, and creating script files. Following sections demonstrate descriptive statistics, testing for normal distribution, hypothesis testing, and linear regression. Examples use the tourism dataset. The goal is to introduce RStudio's capabilities for data analysis in a straightforward way.
The document evaluates five implementations of the SPARQL query language for the Semantic Web. It first provides background on the Semantic Web and SPARQL, including the data model and query language specifications. It then describes the methodology for testing each implementation using a dataset from DBpedia.org and sample queries. Each implementation - OpenRDF Sesame, OpenLink Virtuoso, Jena, Pyrrho DBMS, and AllegroGraph - is installed and evaluated based on documentation, loading data efficiently, and computing query results in a reasonable time. The conclusion finds that while some implementations are advanced, they still have problems processing basic SPARQL queries as specified.
This paper aims to provide a benchmark study of three established bearing diagnostic techniques applied to vibration data from the Case Western Reserve University Bearing Data Center. The techniques include envelope analysis of the raw signal, cepstrum prewhitening, and a benchmark method. The results and diagnostic outcomes of each technique are discussed in detail for different bearing fault types and conditions in the data sets. Recommendations are provided on how to best use the data for testing new diagnostic algorithms and how to generate benchmark data in the future.
This document is an introduction to the book "Data Structures and Algorithms: Annotated Reference with Examples" by Granville Barnett and Luca Del Tongo. It provides an overview of the contents of the book, which aims to present common data structures and algorithms with concise pseudocode and explanations. The book covers topics such as linked lists, binary search trees, heaps, sorting algorithms, and string algorithms. It is intended to serve as a reference for students and developers to learn about these essential computing concepts.
This document is the introduction chapter of a book on data structures and algorithms. It outlines what the book covers, including pseudocode examples of common data structures and algorithms. It assumes the reader has basic knowledge of Big O notation, imperative programming, and object-oriented concepts. It provides tips for working through the examples and outlines the book's structure. The book is intended to serve as both a reference and teaching tool for data structures and algorithms.
This document is the introduction chapter of a book on data structures and algorithms. It outlines what the book covers, including pseudocode examples of common data structures and algorithms. It assumes the reader has basic knowledge of Big O notation, imperative programming, and object-oriented concepts. It provides tips for working through the examples and outlines the book's structure. The book is intended to serve as both a reference and teaching tool for core data structures and algorithms.
Effectiveness of Brainstorming and Cognitive restructuring counselling techniques in managing psychosocial distress associated with infertility challenges. The book presented areas in which counselling techniques can be applied to assist women with infertility challenges cope with anxiety, depression .
This thesis examines wind speeds over the British Isles using a high-resolution atmospheric model to produce a new wind speed dataset covering the region from 2000 to 2010 at 3km resolution. The author validates the model results against observations from various sources, including meteorological stations, buoys, offshore platforms, and satellites. The ability of the dataset to predict power outputs from current wind farms is demonstrated, and patterns of future wind production are compared to electricity demand patterns to assess the ability of wind generation to meet demand.
This report analyzes the mechanical systems for a hotel swimming pool space. It includes calculations for winter and summer design loads due to factors like infiltration, heat loss, and latent gains from the pool. System designs are provided for ventilation, air conditioning, domestic water, heating, and drawings. The swimming pool was selected as the specialist zone due to the abnormal design conditions and high latent loads.
This document provides an unofficial reference manual for LaTeX version 2e from March 2018. It was originally translated from help manuals for earlier LaTeX versions. The document contains detailed information about LaTeX commands, environments, document structure, fonts, layout, sectioning, cross-references and more. Permission is granted to distribute copies of the manual provided the copyright information is preserved.
This document provides the Wetlands Delineation Manual published in 1987 by the U.S. Army Corps of Engineers. The manual establishes technical guidelines and methods for identifying and delineating wetlands subject to regulatory jurisdiction under the Clean Water Act. It requires evidence of hydrophytic vegetation, hydric soils, and wetland hydrology to designate an area as a wetland. The manual also describes characteristics and indicators used to identify these three wetland parameters and provides detailed methods for routine, comprehensive, and atypical wetland determinations.
This thesis investigates CO2 sorption on various geological media up to 10 MPa at 40°C using experimental methods. The experiments observe an anomaly in total sorption isotherm data at the critical point of CO2. A new theory is proposed to explain this anomaly and a method is developed to correct for the anomalous behavior. Sorption equations are also extended to account for coal swelling and the filling of pore space in materials like sandstone to more accurately model supercritical CO2 storage capacity. The relationship between porosity and maximum CO2 storage capacity is examined for coal and sandstone samples.
The document is a project proposal for an Automated Volume Detection and Fluid Dispensing System submitted by Team 2 to Professor August Allo at The University of Texas at San Antonio. The objectives of the system are to 1) establish a convenience for the beverage service industry by correctly identifying the volume of any cylindrical drinking container placed within the system and 2) become the first fully automated volume detection and advanced beverage dispensing unit. The design process will involve data acquisition using cameras, data analysis/line detection using MATLAB, volume calculation by integrating container edges, and a constant fluid flow rate determined through testing.
Interior Landscape Plants for Indoor Air Pollution AbatementElisaMendelsohn
This document summarizes research on using interior landscape plants to help reduce indoor air pollution. The researchers tested plants' ability to remove benzene, trichloroethylene, and formaldehyde from sealed experimental chambers. They found that several common houseplants, including golden pothos and Chinese evergreen, were effective at removing these chemicals from the air in the chambers within 24 hours. The researchers also designed an indoor air purification system that combines plants with an activated carbon filter to help purify air by moving contaminated air through the carbon where pollutants are absorbed before the air passes over plant roots and soil where further breakdown and removal of pollutants occurs.
This document provides instructions for installing and configuring OpenStack. It describes the OpenStack architecture and services, how to set up the necessary infrastructure components like networking, databases and message queues, and how to deploy the core OpenStack services. It also provides steps for launching a test instance and interacting with basic OpenStack features like networks, block storage and orchestration.
This document discusses the health and economic impacts of air pollution. It finds that air pollution poses significant threats to both human health and economic prosperity worldwide. Exposure to ambient (outdoor) air pollution and household air pollution from cooking with solid fuels causes millions of premature deaths annually. The economic costs of air pollution are also substantial, resulting in the loss of trillions of dollars worldwide each year in reduced economic output and welfare. While some regions have made progress in reducing indoor air pollution, ambient air pollution exposure continues to increase in many areas as economies develop. Stronger action is needed to address both indoor and outdoor air pollution to improve health outcomes and drive sustainable economic growth.
The seventh edition of Kenneth Rosen's Discrete Mathematics and Its Applications textbook is a substantial revision based on extensive feedback from instructors, students, and reviewers. It reflects both improvements based on this feedback as well as insights from the author's experience in industry and academia. Some key benefits of this edition include substantial revisions and improvements based on feedback.
Solutions to apostol analysis problems vol 2Carlos Fuentes
This document contains solutions to exercises from Calculus Volume 1 by T.M. Apostol assigned to doctoral students from 2002-2003. It is authored by Andrea Battinelli from the University of Siena and covers solutions to exercises in chapters 1 through 13 on topics including vectors, lines, and vector-valued functions in n-dimensional space. The document provides detailed step-by-step solutions for over 100 exercises from the original textbook.
This document provides information about analytical chemistry concepts and terminology. It begins with an introduction to units of measurement and expressions of concentration commonly used in analytical chemistry. It then discusses the basic equipment and techniques used to measure mass and volume, prepare standard solutions, and record experimental work in a laboratory notebook. The document emphasizes the importance of careful measurements and calculations in analytical chemistry. It aims to establish a foundation of terminology, concepts, and procedures that are fundamental to quantitative chemical analysis.
Piggott turbine design_code_dakar_presentationHanan E. Levy
The document describes a Blade Element Momentum (BEM) model and battery charging generator model developed in Matlab to estimate electricity production and blade/tower loads for Hugh Piggott wind turbine designs. The model consists of a BEM code that uses turbine geometry and airfoil data to predict shaft power and blade loads, and a generator model that balances blade power with generator output. Test results show the model accurately estimates performance for one turbine design but less accurately for another, identifying areas for improvement. The open-source code and a future web interface are intended to help turbine designers evaluate and optimize their designs.
Wind power siting_and_environmental_issues_newmanHanan E. Levy
This document summarizes a study conducted by Pandion Systems, Inc. and contributors for NYSERDA on the relative risks to wildlife from different electricity generation sources. It finds that risks vary by life cycle stage and across sources. Coal generally poses the highest risks, while wind and nuclear pose lower risks. However, a holistic, cradle-to-grave approach is needed, as all sources affect wildlife. Further analysis is still required to quantify impacts. The framework aims to facilitate rational discussion of comparative wildlife impacts across different electricity generation types and life cycles.
The 1st annual EWB-Israel Conference will be held on Friday, June 8th, 2012 from 9:00-15:00 at the Peres Center for Peace located at 132 Kedem St., Tel Aviv- Jaffa. The conference will include a keynote lecture, project presentations from chapters, hands-on technical workshops, and more. Attendance is free but an RSVP is required by emailing hannahbardin@gmail.com.
This document discusses using an Aerodyne Aerosol Mass Spectrometer (AMS) to measure particulate matter during the Lag Ba'omer holiday in Israel. It provides information on the AMS and how it can be used to measure aerosol composition, size distributions, and organic and inorganic components in real-time. Measurements were taken with the AMS, SMPS, other particle sizers, and compared to EPA PM10 data to characterize particles during Lag Ba'omer celebrations.
Small wind power for rural locations - part 2Hanan E. Levy
This document outlines a two-hour presentation on wind energy harvesting basics and its application for off-grid systems. The presentation will include an example project outlining the steps to design a wind energy system including estimating the wind resource, needs, turbine sizing, choosing AC/DC, battery bank sizing, inverter sizing, economics, comparing products, and reviewing case studies from organizations in countries like Peru, Zimbabwe, Israel and Palestine.
Small wind power for rural locations - part 1Hanan E. Levy
The document outlines a lecture on wind energy harvesting basics, resource assessment, and application for off-grid systems. The lecturer, Hanan Einav-Levy, has experience installing small wind turbines. The 4-hour lecture aims to provide a basic comprehensive understanding of wind energy systems and references for future use. The outline details the topics to be covered, including the global wind resource, wind turbine technology, estimating wind resources, and case studies of off-grid wind projects.
הקמת טורבינת רוח קהילתית - הקואופרטיב לאנרגיות מתחדשותHanan E. Levy
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Digital Marketing Trends in 2024 | Guide for Staying Ahead
Hanan Einav-Levy Msc Thesis
1. Thesis for the degree *+"1' (,%1) *#& 1/"-.
Master of Science ($./#' 8#)"#
Submitted to the Scientific Council of the '! 1$./#, ,9."#' 1!&"#
Weizmann Institute of Science ./#' 7#9$" 7"6#
Rehovot, Israel '+*!$ ,1"-"4*
By 1+#
Hanan Einav-Levy $"' -2$. 724
!"#$!" %&' ($'")"*+# ,)# *-.# (/0# 1/$/#' 1$$")$2 ,3$! 4"1$5
(4, *-.# (/0# '+ ,6'!, (!' ,)# *-.#' (4 *-.# 7$- ,$&"'2+-
Development of Method for Measuring Mass Transfer Coefficients of Particles
and Use of the Mass-Heat Transfer Analogy to Obtain Heat Transfer
Coefficients
Advisors: :($42#
Jacob Karni 8$/"* 7"2$
Yinon Rudich $2*0 -0.$
January 2010 ."!1 3-! -
1
2. Abstract ..........................................................................................................................................6
Acknowledgements.........................................................................................................................7
1 Introduction...............................................................................................................................7
1.1 Solar thermal energy...........................................................................................................7
1.2 Convective heat transfer .....................................................................................................8
1.3 The heat to mass transfer analogy.......................................................................................9
1.3.1 Heat and Mass Transfer in the Continuum Regime ......................................................9
1.3.2 The dynamic transfer conditions ................................................................................10
1.3.3 The transition regime.................................................................................................13
2 Research Objectives ................................................................................................................13
3 Experimental Apparatus and Test Results................................................................................14
3.1 Experimental system ........................................................................................................14
3.1.1 Aerosol generation.....................................................................................................16
3.1.2 Coating with High Vapor Pressure Material (Benzo(a)pyrene)...................................16
3.1.3 Controlled evaporation...............................................................................................17
3.1.3.1 Increase of coating material (BaP) ambient vapor pressure..................................18
3.1.3.2 Initial design .......................................................................................................19
3.1.3.3 Final Design........................................................................................................21
3.1.4 Measurement .............................................................................................................22
3.1.5 Experimental Procedure.............................................................................................25
3.1.5.1 Data collection....................................................................................................25
3.1.5.2 Measurement of the side-center temperature correlation matrix...........................26
3.1.5.3 Data analysis procedure ......................................................................................29
3.2 Results .............................................................................................................................31
3.2.1 Mobility and vacuum aerodynamic distributions........................................................31
3.2.2 SMPS measured and AMS mass based final diameter and shape factor......................33
3.2.3 Effects of Residence time ..........................................................................................36
4 Discussion...............................................................................................................................38
4.1 Derivation of the Sherwood number .................................................................................38
4.2 Possible sources of measurement bias...............................................................................40
4.2.1 Coating thickness effect on the Sherwood number .....................................................40
4.2.2 The influence of coating thickness on the calibration ratio RM ...................................42
4.2.3 Possible uneven flow splitting effect on bias..............................................................45
4.3 Error analysis ...................................................................................................................45
4.4 Repeatability ....................................................................................................................47
4.5 Measurement of the Sherwood numbers for suspended nano-particles ..............................47
4.6 The use of the heat to mass analogy for suspended nano-particles.....................................48
4.7 Measurement of fractal soot particles................................................................................49
4.8 Correlation of heat and mass transfer vs. particle size and shape.......................................49
5 Conclusion ..............................................................................................................................50
Appendix A Calculating the Sherwood number from a non isothermal aerosol mass transfer
experiment ....................................................................................................................................51
Appendix B Theoretical estimation of the diffusion coefficient of nitrogen-PAH mixture .............52
Appendix C Measuring the desorption energy of PAHs from suspended aerosols..........................53
Bibliography .................................................................................................................................54
2
3. List of figures
Figure 1: Relevant models for describing transfer dynamics over different ranges of the Knudsen
number (Fang 2003) ..............................................................................................................11
Figure 2: Sherwood and Nusselt number prediction for the transition regime ................................12
Figure 3: Experimental system diagram ........................................................................................15
Figure 4: Coating process schematics............................................................................................16
Figure 5: Maximum BaP coating vapor density build up in the Thermal Denuder. ........................20
Figure 6: Final Thermal Denuder (TD) design...............................................................................22
Figure 7: Minimal denuded layer thickness vs. number concentration ...........................................24
Figure 8: HR-AMS mass fragments for BaP coating on PSL.........................................................24
Figure 9: Typical raw data for measurement of BaP evaporation from PSL spheres ......................25
Figure 10: TC probe configuration ................................................................................................26
Figure 11: temperature scan for fast and normal flow rates............................................................28
Figure 12: Calibrating the side thermocouples (T0-T8) versus a central probe (T9) .......................28
Figure 13: Particle size distribution for different extents of evaporation corresponding ................33
Figure 14: Comparison of vacuum aerodynamic distribution for m/z=104 and 252 .......................32
Figure 15: Change in coating thickness due to evaporation............................................................35
Figure 16: Shape factor versus coating thickness...........................................................................35
Figure 17: Effect of residence time. 200 nm PSL sphere, 15 nm thick BaP coating........................36
Figure 18: Effect of residence time. 300 nm PSL sphere 20-25 thick BaP coating .........................37
Figure 19: Effect of residence time. 400 nm PSL sphere 22-30 nm BaP coating............................37
Figure 20: Sherwood number vs. particle diameter........................................................................38
Figure 21: The effect of Coating thickness on the evaporation rate for two limiting cases. ............41
Figure 22: Partial coating scenario schematics...............................................................................42
Figure 23: Calibration ratio of AMS fragment peak mass signal vs. SMPS & CPC mass...............43
Figure 24: Median mobility diameter variations for different PSL sphere diameters......................46
List of tables
Table 1 Benzo[a]pyrene (BaP) properties......................................................................................17
Table 2: Typical side-center temperature correlation matrix ..........................................................27
3
4. Nomenclature
ai, j Temperature L [m] Typical length
correlation matrix
D [m],[nm] Particle diameter Lmin [nm] Minimum AMS detectable
coating thickness
Dva [nm] Particle vacuum Loven [m] Thermal Denuder (TD) oven
aerodynamic diameter length
Dm [nm] Particle mobility !
m '' [Kg s·m ] Mass transfer rate
2
diameter
Dm!core [nm] Particle core mobility m0 [ µ g] Residue mass of coating,
diameter obtained by Sherwood theory fit
Dm!TD [nm] Particle mobility mg [Kg] Gas molecule mass
diameter, for aerosols
passing through the TD
Dm!bypass [nm] Particle mobility mm/z [µg / m 3 ] Mass loading of a single m/z
diameter, for aerosols
bypassing the TD
Df [m 2 s] Binary diffusion mv [Kg] Particle coating molecule mass
coefficient
DAMS [nm] Equivalent diameter Mw [g / mole] Molecular weight
calculated according to
AMS and SMPS
measurement
DSh [nm] Sherwood diameter M coat [g / mole] Coating molecular weight
H [KJ / Kg] Latent heat of M AMS [ µ g] Single aerosol coating main
evaporation bypass
M AMS
fragment [m/z] mass, measured
by AMS, for aerosols (general –
TD
M AMS no superscript), or aerosols
bypassing the TD (bypass
superscript), or going through the
TD.
h !W m 2 K # Heat transfer M SMPS [ µ g] Single aerosol coating mass,
" $
coefficient measured by SMPS, for aerosols
M bypass
hm [m s] Mass transfer SMPS
(general, no superscript), or
TD
coefficient M SMPS aerosols bypassing the TD, or
going through the TD.
I [kg / m] Evaporation driving hL Nusselt number
Nu =
force k
ˆ
I [ µ g] Normalized n Analogy fit parameter
evaporation driving
force
k [W / mK ] Thermal conductivity No [#/ m 3 ] Molecule number concentration
kB [m Kg s K ] Boltzman constant
2 2
N [# m 3 ] Particle number concentration
[# cm 3 ]
kv [W / mK ] N 2 gas thermal N bypass [#/ cm 3 ] Particle number concentration,
conductivity for aerosols bypassing the TD
! Knudsen number
Kn =
L
4
5. p [Pa] Pressure V frac Volume fraction of aerosol
ps [Pa] Saturation vapor x o , yo , z o Normalized Cartesian
pressure directions
pd [Pa] Saturation vapor ! [m 2 s] Thermal diffusivity
pressure with Kelvin
effect
! Prandtel number !c Energy accommodation
Pr = coefficient
"
q '' !W m 2 # Heat transfer rate ! Relaxation parameter for ai, j
" $
correlation matrix calculation
Q 3
[m / s] Volumetric flow rate ! o Average gas adiabatic constant
R [J / K·mol] The gas constant ! coat [dyne / cm] Coating material surface
tension
UL Reynolds number !D[m] Coating thickness
ReL =
!
Roven [m] Thermal Denuder !mAMS"SMPS [ µ g] Single aerosol evaporated
(TD) oven radius coating mass, measured by
AMS and SMPS
RM M SMPS Calibration ratio, for !mSMPS [ µ g] Single aerosol evaporated
= aerosols bypassing or coating mass, measured by
M AMS
passing in the TD SMPS
bypass
RM M bypass Calibration ratio, for ! [m] Mean free path
= SMPS aerosols bypassing the
M bypass
AMS
TD oven
S Jayne shape factor ! [m 2 s] Kinematic diffusivity
! Schmidt number !coat [Kg m 3 ] Coating bulk density
Sc =
Df [g cc]
hm L Sherwood number !coat "vapor [Kg m 3 ] Coating vapor density, near the
Sh = particle surface, and in the free
Df !coat "ambient
stream respectively
T [K ] Temperature !p [Kg m 3 ] Particle density
To Normalized !g [Kg m 3 ] Gas density
temperature
Tp [K ] Particle temperature !0 [Kg m 3 ] Normalization unit density for
Jayne shape factor calculation
Tg [K ] Gas temperature ! [!], [K] Lennard Jones potential
!, parameters
kb
Ti (t) [K ] Center of oven ! "m#EV , [ µ g] Repeatability error for !m and
temperature ! I "EV I respectively
T j (t) [K ] Side of oven ! (Kn) Fuchs correction for mass
temperature transfer in transition regime
U [m s] Gas velocity ! Dynamic shape factor
u o , vo , wo Normalized velocity !o Normalized mass fraction
in x o , y o , z o directions
5
6. Abstract
The use of solar energy for the production of solar fuels is currently studied throughout the
world. The first step in the process of solar thermal fuel production is to concentrate the solar flux
onto a gas stream. The gas stream used is typically transparent in the solar wavelengths. Therefore,
an absorbing medium is employed to absorb the solar flux, and transfer the heat to the gas flow.
Recently, Kogan, Kogan & Barak (2005) proposed to use nano-sized black soot particles and the
idea was tested in the solar facilities of the Weizmann Institute of Science.
The aim of this research is to develop a method for measuring mass transfer from nano-
sized particles, such as soot particles, and then obtain heat transfer coefficients through the analogy
between mass and heat transfer. The purpose of the mass transfer experiments in this research is to
examine the influence of the different experimental parameters on the mass transfer rate, and
compare the results to a known theory, thus assessing the efficacy of the measurement method for
obtaining mass and heat transfer coefficients.
A high resolution Aerodyne aerosol mass spectrometer (AMS) in conjunction with a
scanning mobility particle analyzer (SMPS) is used for measuring mass transfer rates of
Benzo(a)pyrene (BaP) from polystyrene latex (PSL) spherical particles of different sizes. The
experimental apparatus consists of a thermal denuder (TD) with a very uniform and stable
temperature profile (±0.2°C over 50 cm). The aerosols were coated by a thin layer of BaP, and then
passed through the TD at different speeds and different temperatures. The remaining mass of the
BaP was measured by the AMS and was compared to the original mass. A scan of different
residence times yields the so-called Sherwood number, which is a dimensionless mass transfer
coefficient, describing the ratio of convective to conductive transfer.
Experiments were carried out in the transition zone, between the continuum and the kinetic
regime where the Sherwood number is expected to decrease monotonically as the particles diameter
decreases in this regime.
Measurements where performed for 200,300 and 400 nm diameter core PSL spheres, coated
by 15-25 nm thick BaP. The results underestimate the theory by 5-25%, with measurement error of
±5-10%, and show the expected trend of increasing Sherwood number with particle diameter. This
implies that the proposed method can measure sublimation of thin coatings on high enough number
concentrations of aerosols, and the results are similar to pure conduction transport theory,
indicating that the process is slow enough and the mass transfer is mainly by conduction.
6
8. Acknowledgements
I would like to acknowledge Jacob Karni and Yinon Rudich for their priceless advice and
support, walking me through the last year and a half of research and education. Yinon sent me to
learn first hand on the operation of the AMS, the main and most complicated measurement
apparatus, without which I would not have been able to conduct this research in the short time
frame I had. He followed my progress closely, making sure I know what I am after at each point.
After my first set of experiments I was perplexed by a clear difference between my results and
the theory. Jacob went with me through my experimental system step by step, trying to figure out
the error, and through his suggestions I found the mistake, and learned to take a pause, and try to
look at the problem from a different point of view. For that lesson I am deeply thankful.
I would also like to thank the Weizmann institute of science for supporting me with a generous
stipend allowing me to dedicate the last 2 years to my Ms.c. studies and research.
1 Introduction
1.1 Solar thermal energy
The use of solar energy for the production of electricity and fuels is investigated in industry
and academy with the purpose of gradual replacement of non-renewable and polluting energy
sources. Solar energy can be utilized in various ways, among them the thermo-solar method, where
the sun’s radiation flux is concentrated and used to heat a fluid, which is either used to drive a
thermodynamic cycle, which in turn drives a generator and produces electricity (Kribus et al.
1998), or to facilitate a high temperature chemical reaction to produce fuel (Kogan, Kogan, and
Barak 2005; Epstein, Ehrensberger, and Yogev 2004). A highly efficient way to facilitate high
temperature chemical reactions using particle-laden flow exposed to high concentration of solar
flux was proposed and tested (Klein et al. 2007).
In this method, a volume of gas, seeded with black soot particles is entrained in a cylinder
and exposed to a high concentration of solar flux. The soot particles absorb the flux, heat up, and
transfer the heat to the gas by conduction primarily.
The experiment conducted by Klein et al. (2007) resulted in an exhaust gas stream with
about 200 K higher temperature then the projected values of their model. The most probable reason
for this is an under estimation of the conductive heat transfer from the soot particles, since the
theory used was based on spherical particles having equivalent surface area to that of the real soot
distribution. Thus a system for measuring the real heat transfer coefficient of soot particles, or any
particle ensemble, as a function of measurable particle morphology parameters such as the mobility
and aerodynamic diameters is desired.
7
9. 1.2 Convective heat transfer
The process of particle to gas heat transfer is best described by the heat transfer equation
q '' = h·(T p ! Tg ) (1)
h !W m 2 K # is a heat transfer coefficient, q '' !W m 2 # is the heat flux per particle surface area,
" $ " $
T p [K ] and Tg [K ] are the particle surface temperature and free stream gas temperature respectively.
The heat transfer coefficient relates the heat flux to the temperature difference, and is a function of
the particle morphology; fluid properties and heat transfer mechanism. The heat transfer coefficient
can be expressed in a dimensionless form, known as the Nusselt number, relating convective to
hL
conductive heat transfer across the surface boundary - Nu = where L[m] is a typical length and
k
k[W / mK ] is the thermal conductivity of the fluid. There are various theoretical and empirical
correlations between the Nusselt number and other non-dimensional parameters of the process such
as the Reynolds, Grashof and Prandtl numbers (Bird, Warren, and LightFoot 2002) describing the
heat transfer of various configurations.
Klein et al. (2007) assumed that the relative velocity between each soot particle and the gas
stream is zero, and used the pure conduction result for spheres – Nusselt = 2 (Bird, Warren, and
LightFoot 2002) ,corrected for the Knudsen number. Since in many cases the particles dimension is
relatively close to the mean free path between the gas molecules ![m] , the heat transfer occurs in
the transition regime, between continuous transfer dynamics and the kinetic regime, 0.1 < Kn < 10 ,
!
as defined by the Knudsen number Kn = . In this region the heat transfer coefficient, and
L
associated Nusselt number, are lower then the continuum solution. Several solutions for the effect
of the transition regime on the Nusselt number exist, all built upon the Fuchs boundary layer
approach (Filippov and Rosner 2000).
To simulate the heat transfer from the soot particles to the gas, Klein et al. (2007) utilized
the volume distribution of the soot particle batch used in their tests, as obtained from SEM images,
and assumed the Nusselt number relating to each volume segments diameter. The resulting
simulations underestimated the experiment by 200 K (~14%).
The main reason for this mismatch is assumed to be the heat transfer coefficient used. The
particles are not spheres, and consequently the equivalent volume approach was not accurate
enough, or may have missed a fundamental difference between the heat transfer from soot
agglomerate particles and an equivalent surface area of spheres. Even simpler, this could be the
result of the in ability to measure the exact surface area of a soot particle distribution by analyzing
2D SEM pictures.
8
10. 1.3 The heat to mass transfer analogy
1.3.1 Heat and Mass Transfer in the Continuum Regime
In the continuum regime there is a mathematical-physical equivalence between the energy
equation for convective heat transfer, and the species mass transfer equation.
The normalized energy equation is (Hong and Song 2007)
!T o o !T
o
o !T
o
1 " ! 2T o ! 2T o ! 2T o %
uo
+v +w = 2 + 2 + (2)
!z o ReL Pr $ !x o
2 '
!x o !y o # !y o !z o &
UL !
Where the Reynolds number is ReL = , the Prandtl number is Pr = , ! [m 2 s] is the
! "
kinematic viscosity, ! [m 2 s] is the thermal diffusivity, U[m s] is a typical velocity, u o , v o , w o are
normalized velocities in the normalized directions x o , y o , z o respectively, and T o is the normalized
temperature.
The normalized mass transfer equation is
!" o o !"
o
o !"
o
1 # ! 2" o ! 2" o ! 2" o &
u o
+v +w = 2 + 2 + (3)
ReL Sc % !x o
2 (
!x o !y o !z o $ !y o !z o '
Where ! o is the normalized mass fraction of the transported species in the gas stream,
!
Sc = is the Schmidt number and D f [m 2 s] is the diffusion coefficient of the species involved in
Df
the gas stream. The analogues mass transfer equation to the integral form of the heat transfer
equation, (equation (1)), is
m '' = hm ·( ! p " !g )
! (4)
!
Where m ''[Kg s·m 2 ] is the mass transfer per unit time and particle surface area; hm [m s] is the
mass transfer coefficient; ! p [Kg / m 3 ] and !g [Kg / m 3 ] are the vapor densities of the species being
transferred from the particle surface and away from the particles respectively. The mass transfer
hm L
coefficient is related to the non-dimensional Sherwood number Sh = in the same manner that
Df
the heat transfer coefficient is related to the Nusselt number.
If the Prandtl and Schmidt numbers are the same (which is not common in most fluids),
then the Sherwood and Nusselt numbers also equal, for the same flow configuration and boundary
conditions. This allows a mass transfer experiment resulting in the Sherwood number to give the
Nusselt number by analogy (Hong and Song 2007). Because the Prandtl and Schmidt numbers are
not the same in practice, the following approximate relationship is used
9
11. n
! Pr $
Nu = Sh # & (5)
" Sc %
Where n is a fit parameter obtained empirically or by calculation according to the geometry and
temperature difference sign (heating or cooling) and is typically between 0.3-0.4 (Incropera and
Dewitt 1996; Bird, Warren, and LightFoot 2002).
Many expressions for the Nusselt number have been obtained from Sherwood number
experiments. For instance, in case of forced convection on a solid sphere
Sh = 2 + 0.6 Re1 2 Sc1 3 (6)
And by analogy
Nu = 2 + 0.6 Re1 2 Pr1 3 (7)
The analogy is valid if the following conditions are met:
1. Constant physical properties
2. Small net mass transfer rates
3. No chemical reactions
4. No viscous dissipation heating
5. No absorption or emission of radiant energy
6. No pressure diffusion, thermal diffusion, or forced diffusion
7. Similar boundary conditions
In the case of pure diffusion, or pure conduction, the Sherwood and Nusselt numbers are not
dependent on the working medium properties (Schmidt or Prandtl numbers) or on flow conditions
(Reynolds number). Therefore, the analogy is expected to be even simpler (further discussion on
the analogy for suspended aerosols in the transition regime is presented in section 4.6).
1.3.2 The dynamic transfer conditions
The objective of the current research is to develop a method for measuring the mass transfer
coefficient for nano-size soot and other aerosols, at atmospheric pressure. The measured mass
transfer coefficient can be used in conjunction with the heat to mass transfer analogy to give the
heat transfer coefficient, which is necessary for further development of the solar thermal seeded
particle reactor configuration (see section 2.1 on Solar thermal energy).
In the current research, all of the conditions stated in the previous section (top of p. 10)
were taken into consideration (see Chapter 4 – Experimental Apparatus and Test Results). The
main difference between the heat-mass transfer analogy as previously used and the current one is
the dynamic transfer conditions. Soot-particles diameter is typically around 200nm ! 10 µ m , which
corresponds to Knudsen numbers of 0.1-10. This is in the transition regime between the continuum
10
12. and free molecular regimes (Figure 1). The analogy is known and holds for the continuum regime,
but has not been tested for the transition or free molecular regime.
The heat and mass transfer equations for the free molecular regime are given by Lees
(1965) for instance, for the case of no net flow perpendicular to a surface
4 2kB p $T
q fm = !
! # g [w m 2 ] (8)
3 m g" Tg $x
4 1 $ %p
m fm = !
! # g [Kg m 2 s] (9)
3 2" pg %x
Where ![m] is the mean free path of the gas-particle system, defined as
$ # + D' !" 2 2
2
! =1 "No & where [m ] is the effective gas molecule cross-section and D[m] is the
% 2 ) ( 4
particle diameter, N o [#/ m 3 ] is the particle number density, mg [Kg] is the gas molecule mass
(apparently, it is not specified in the article) and kB [m 2 Kg s 2 K ] the Boltzman constant.
Figure 1: Relevant models for describing transfer dynamics over different ranges of the Knudsen number (Fang
2003)
For spherical particles the expressions are similar, Filippov and Rosner (2000) give
pg ! c kB % # o + 1(
q fm =
! ' # o $ 1 * (Tg $ T p ) [W m ]
2
(10)
Tg 2 " mg & )
Where ! c is the energy accommodation coefficient (Burke and Hollenbach 1983), and ! o is the
average gas adiabatic constant (Filippov and Rosner 2000). Griffin and Loyalka (1994) give the
mass transfer to a spherical particle in the free molecular regime:
11
13. 8k B
m fm = Tg
! ( "g # " p ) [Kg m 2 s] (11)
! mv
Where mv [Kg] is the molecular mass of the gas phase molecule.
The driving force is similar in both heat and mass transfer expressions (Eq. (10) and (11),
respectively), the temperature difference being analogues to the partial pressure (or concentration)
difference, but there is no direct correspondence of transport properties coefficients. Instead, these
coefficients are related to the pressure, temperature and density of the gas, in different or even
opposite ways. The change of the transport properties in the continuum regime with pressure and
temperature is also not exactly similar, and this is taken into consideration through the n parameter
(Eq. (5)) relating the Schmidt and Prandtel numbers. In the transition regime however, the
deviation from the continuum model is similar for both heat and mass transfer, as can be seen in
Figure 2, reproducing results for the Nusselt number given by Klein et al. (2007), with Davies
results for the Sherwood number shown as well (Eq. (12)). The trend is the same for both non-
dimensional numbers, the deviation arising from the models themselves, as can be seen for the
large variation for the 4 Nusselt models shown. The Fuchs solution for instance, is the same for
both heat and mass transfer in the transition regime (Filippov and Rosner 2000). Analysis of the
heat and mass transfer analogy in the transition regime is provided in section 4.6.
Figure 2: Sherwood and Nusselt number prediction for the transition regime compared. Nusselt plot reproduced
from Klein et al. 2007. Only new addition is the Sherwood number theory by Davies given according to Eq. (12).
The Fuchs model (black dashed curve) applies to both mass (Sh) and heat (Nu) transfer as indicated in the
figure.
12
14. 1.3.3 The transition regime
The experiments presented in Chapter 3.2 were conducted in the transition regime;
0.2 < Kn < 0.7 where the dynamics are best described as a combination of a continuum and free
molecular dynamics, such as the Fuchs 2-layer approach (Filippov and Rosner 2000): The theory is
based on a boundary layer approach. Since there is no general analytical solution of the Boltzmann
equation describing gas behavior in the intermediate regime of moderate Knudsen numbers, an
interpolation formula is used which is based on the separation of the space outside the particle
surface into two parts: Close enough to the surface of the particle (the boundary layer), the
conditions are assumed to be collision-less – no collisions between gas molecules, only gas-aerosol
interactions are assumed. The boundary layer thickness is typically set to be the same as the gas
mean free path. Outside of the boundary layer, the conditions are described by the continuum
dynamics. A consistent solution is found for both regimes by ascribing the same heat (or mass)
transfer rate at the boundary.
Different interpolation formulas exist for mass transfer in the transition regime, as discussed
above. Our results are compared to the derivation of Davies (1978) from ((Hinds 1999) p. 288):
2" + D
ShKn = 2·! (Kn) = 2· (12)
D + 5.33(" 2 D) + 3.42 "
Where ! (Kn) is referred to as the Knudsen correction. Multiplying the Knudsen correction by 2,
gives the pure diffusion result for Re = 0 (as also predicted by equation (6)). The mean free path is
kT
calculated according to ! = [m] where p[ pa] is the pressure. In the limiting cases of
"d p 2
2
N2
4 1
molecular and continuum regimes, the Sherwood number values are therefore · & 2,
5.33 Kn
respectively.
Although this derivation is for the case of a light molecule evaporating through a bath gas made out
of heavier molecules, which is not our case, using more apparently appropriate derivation, such as
Sitarski and Nowakowski (1979) (see Davis 1983) gives very similar results, and so we settled for
this simpler derivation.
2 Research Objectives
The research objectives are:
• Development of an experimental method to measure the evaporative mass transfer from
nano aerosol particles in the transition regime
• Use the analogy between heat and mass transfer to relate the mass transfer coefficient to
the heat transfer coefficient (Eq. (5)).
13
15. An important additional objective is the validation of the proposed method – using spherical
particles suspended in nitrogen – by experimentally obtaining the theoretically predicted rate of
mass transfer, corresponding to each particles size, in the transition regime.
3 Experimental Apparatus and Test Results
3.1 Experimental system
A system was designed and built to measure the mass transfer rate from aerosol particles. It is
composed of the following components (Figure 3: Experimental system diagram):
1. Aerosol Generation:
Create a suspension of monodisperse aerosol – polystyrene latex (PSL) spheres – in
nitrogen at atmospheric pressure.
2. Coating of Aerosol with a thin layer of a high vapor pressure material – Benzo(a)pyrene
(BaP)
3. Evaporation step: Allows the aerosols to flow through one of two paths:
a. A thermal denuder (TD) with precisely controlled temperature and flow rate.
b. Bypass at room temperature
4. Measurement of aerosol mass and composition: the aerosol flow is split into a measuring
system consisting of a scanning mobility particle sizer (SMPS), Aerodyne high-resolution
aerosol mass spectrometer (AMS), and a condensation particle counter (CPC).
The flow is continuously split into these three measurement devices, and measurements are
acquired (>10 Hz), averaged and saved on intervals of 1 second (CPC), 0.5 minute (AMS)
and 1 minute (SMPS). All instruments are controlled through a PC computer. These
instruments are discussed in more detail in section 3.1.5.1
14
16. Figure 3: Experimental system diagram
PSL: polystyrene latex, DMA: differential mobility analyzer
HR-AMS: high resolution aerosol mass spectrometer, CPC: condensation particle counter
SMPS: scanning mobility particle sizer (combination of CPC and DMA)
15
17. 3.1.1 Aerosol generation
A standard atomizer (TSI 3076) was used to atomize a solution of nanopure water and
polystyrene latex (PSL) spheres. A magnetic stirrer was used to ensure homogenous suspension.
85
The suspended aerosols subsequently flow through a silica gel diffusion dryer, followed by a Kr
radioactive source that creates a symmetrical Boltzman charge distribution. In all of the
experiments the particles’ number concentration increased gradually from about 500[#/cc] to about
800[#/cc] (example for 300 nm PSL spheres), due to increased solution concentration caused by
evaporation of water from the solution. The dried and charged aerosols then passed through the
electrostatic classifier (differential mobility analyzer, DMA), set at the PSL spheres nominal
diameter, to remove all other particles, except the PSL-sphere aerosols with the designated
diameter.
3.1.2 Coating with High Vapor Pressure Material (Benzo(a)pyrene)
Figure 4: Coating process schematics
The nearly mono-disperse PSL aerosol (Duke scientific corp., normally D±1-3%) is injected
into an oven containing a batch of the organic material (Figure 4), in which a type T thermocouple
is attached and used to control an electrical heating tape surrounding the glass oven. The glass
vessel has a central input tube, which impinges the aerosols towards the bottom, and an annular
exit. The suspended aerosols typically stay in the oven for 1-7.5 seconds. Another outlet allows for
the insertion of a thermocouple.
The coating materials used is the polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene
(BaP). A PAH was chosen for three reasons:
1. Stable materials, which do not react with PSL or any other material in the system.
16
18. 2. High molecular mass. The HR-AMS fragmentation pattern of BaP has its major peak well
above the 104 m/z (ion mass over charge) peak associated with PSL (see Figure 8)
allowing for simple mass calibration of the main fragment peak and the real coating mass.
3. Vapor pressures are low enough to have very small evaporation rate at room temperature,
but high enough to enable measurements at not too high oven temperatures (oven
temperatures were 80-160 C o )
The coating material chosen for this research is Benzo[a]pyrene (BaP) (see Table 1). There are
tabulated physical-chemical data for this material at the relevant temperature and pressure ranges of
this research, except for the binary diffusion coefficients in nitrogen or air. Values of these
coefficients do not exist for any PAH of relevance to this study, and it was calculated according to
the Chapman-Enskog relationship (see appendix B) according to the LJ parameters (see Table 1).
The residence time in the coating oven was controlled by an additional N 2 flow.
Table 1.A Benzo[a]pyrene (BaP) physical properties
Molecular weight Bulk density Surface tension Melting point
Formula !coat [g / cc] ! coat [dyne / cm]
M coat [g / mol] [ o C]
C20H12 252.3093 1.286 64.7 179
Source: (chemspider.com)
Table 1.B Benzo[a]pyrene (BaP) Lennard-Jones parameters
!
" (!) [K ]
kb
7.66 918.15
!
Source: Using PAH derived fit = 37.15·Mw 0.58 and ! = 1.234·Mw 0.33 from (Wang and
kb
Frenklach 1994)
Table 1.C Benzo[a]pyrene (BaP) vapor pressure parameters
Expression A B
A
B!
P = 101325·10 [Pa]T 6181±32 9.601±0.083
Source: (John James Murray, Roswell Francis Pottie, and Pupp 1974)
3.1.3 Controlled evaporation
Either controlled coating or controlled evaporation of the particles, driven by a vapor pressure
gradient, could have achieved the goals of this investigation. The choice of controlled evaporation
is a natural one, since creating a known vapor pressure difference is much simpler when far away
from the particle the desired partial vapor pressure is zero, rather than a finite number. Activated
17
19. charcoal (Aldrich, granules, 4-14 mesh) is used to absorb BaP vapor and create a zero vapor
pressure environment immediately after the oven section.
3.1.3.1 Increase of coating material (BaP) ambient vapor pressure
Concern related to this experimental design was that the denuded BaP coating might,
a. Change the coating vapor pressure in the vessel’s ambience (which starts as zero)
b. Condense back on the particles as they cool down between the oven and the denuder
The following approach was taken to deal with these issues:
a. The initial vapor pressure of the coating material in the surrounding ambience is zero. The
vapor pressure of the BaP coating in the ambience, after denuding an L[m] layer from a
D + L diameter sphere is calculated according to:
Kg #
!coat "ambient = !coat ·V frac [ 3
];V frac = N ((D + $D)3 " D 3 ) ! 1 (13)
m 6
Where N[# m 3 ] is the particle number concentration, !coat [Kg m 3 ] is the coating material
bulk density, !D[m] is the evaporated coating thickness, and V frac is the volume fraction of
aerosol coating in a unit volume and is smaller then 1, so that the resulting
!coat "ambient ! !coat . Thus, !coat "ambient is the resulting coating material vapor concentration in
the end of the tube after all the coating ( !D[m] ) evaporated. Eq. (13) holds whenever L is
smaller that the initial coating layer.
The surface vapor density is calculated according to the vapor pressure correlation listed in
Table 1 ( ps [Pa] ), and corrected according to Kelvin Law (to give pd [Pa] )
A 4 " coat M coat
B!
#coat R·T p ·D
ps = 101325·10 [Pa], pd = ps ·e
Tp
[Pa] (14)
Where A & B are taken from Table 1, M coat is the molecular mass, R is the gas constant,
T p [K ] is the coating (particle surface) temperature and ! coat [N / m] is the coating surface
tension.
Finally, according to the ideal gas law –
M coat ·pd # Kg &
!coat "vapor = (15)
R·T p % m 3 (
$ '
Where !coat-vapor is the vapor density of the evaporated coating, and pd is the vapor pressure
of the evaporating layer corrected for the Kelvin effect.
Figure 5 shows the relation between Equations(13) and (15). The black lines are !coat "ambient
for two limiting cases, of 20 nm coating completely denuded, with BaP as the coating
material, and the color indicates log( !coat "vapor ) and is shown for different temperatures, and
18
20. particle diameters. The particle diameter influences the vapor pressure through the Kelvin
effect, which, as can be seen, is not large for these diameters.
A temperature of at least 75 o C is needed for the two limiting cases to get a one order of
magnitude difference between the surface vapor pressure and the ambient vapor pressure of
BaP at the end of the Thermal Denuder (TD) oven, which ensures that the difference
between vapor densities will be larger then one order of magnitude in the interior of the
oven. Under these conditions the assumption !coat "ambient # 0 is valid.
b. According to Huffman et al. (2008), who designed and built a fast stepping thermo-denuder
for the measurement of ambient aerosols in conjunction with the Aerosol Mass
Spectrometer (AMS) measurements, and dealt with a similar issue, the condensation of the
coating material vapor on the particle is not a problem. In their configuration the denuder
follows the oven section without any overlap, and the denuder section starts only when the
temperature drops below 10% above the room temperature. During our experiments no back
condensation was detected in cases where only part of the BaP coating evaporated.
3.1.3.2 Initial design
The initial design of the Thermal Denuder (TD) oven, and the activated charcoal tube length
were done according to Huffman et al. (2008), Jonsson, Hallquist, and Saathoff (2007) and Orsini
et al. (1999). The general dimensions of activated charcoal section, and oven diameter, length and
resident times where referenced from Orsini et al. (1999) and Jonsson et al. (2007), and the
possibility of separating the oven (evaporation) and the activated charcoal (absorption of
evaporated coating) was verified by all three papers. The following describes the initial design
verification. A description of the final TD is given in section 3.1.3.
For verifying the flow rates and oven length, the evaporation rate for the initial design diameter
(4.3 mm) was calculated for the aerosols of interest and various oven lengths and flow rates. Klein
et al. (2007) found that in their solar reactor, the most effective soot agglomerates for radiation
absorption and conductive heat transfer to the gas were in the size range of 200 < D < 2000[nm] .
The aerodyne HR-AMS used in the present study (described briefly described briefly in section
3.1.4; for a full description see DeCarlo et al. (2006)) can measure only particles in the size range
of 50 < D < 750[nm] . Therefore the particles tested in the present study were in the size range of
200 < D < 500[nm] .
19
21. Figure 5: Maximum BaP coating vapor density build up in the Thermal Denuder. The Y axis is the diameter of
the denuded particle, showing the negligible effect of the Kelvin effect on the vapor density for particles of 200-
500 nm diameter. The X axis is the temperature of the oven, and the color is negative orders of magnitude
( log( ! )[log(Kg / m
3
)] ) of saturation vapor density of the coating material (BaP). The black line shows the
developed vapor density for the complete evaporation of the coating for two limiting cases as discussed in the
text, and the dashed rectangle shows the experimental conditions, of nominal TD temperature and particle
diameter.
The evaporation rate was calculated by solving the continuum-based differential diffusion
equation (16), including the Fuchs correction for the transition regime (Hinds 1999). The Kn
number equals 0.2-0.7 for particles in the range of 200-500 nm, in nitrogen flow at 1 bar pressure,
at temperatures of 100-200 o C .
dD 4D f T p ·M coat
=- ·p ·"(Kn) for Kn # 1
dt !coat R·Td ·D d
2$ + D (16)
"=
$2
D +5.33 +3.42$
D
kT D
Where ! = [m] is the mean free path, Kn = is the Knudsen number, ! is the Fuchs
2 p" !d 22 !
N
slip correction and D f is the binary diffusion coefficient, estimated by the Chapman Enskog theory
(See Appendix B). T p is the particle surface temperature, assumed to be equal to the average
surrounding temperature at a given flow-wise oven cross section, and Td is the aerosol surface
temperature after the latent heat release due to the evaporation process, according to
DAB MHpd
Td = T! + (17)
RkvTd
20
22. Where H is the latent heat of evaporation and kv is the nitrogen thermal conductivity. It was
assumed that the rate of evaporation during the experiments is slow enough for Td ! T p . This
assumption was validated by calculating Eq. (16) for the temperature ranges used in the
experiments (100-200 o C ). The resulting difference between Td and T p was less then 10 !4 [K ]
indicating this assumption is valid.
The initial design of the TD system was based on the following assumptions:
1. 100% Nitrogen flow
2. Constant temperature profile in the Thermal Denuder
3. Average flow rate used to calculate resident time
4. The times of temperature increase and decrease near the oven inlet and outlet, respectively,
is negligible in comparison to the residence time in the oven.
5. The partial pressure of the coating material far away from the particle surface is zero (this
assumption has been used throughout the prior analysis (see p. (18)), and validated above
(See discussion following Eq. (16)).
An oven tube inner diameter of 4.3 mm was chosen, based on prior designs (Orsini et al. 1999).
A flow rate range of 100-400 cm3 min-1 was used, according to the flow rate requirements of the
other instruments attached (AMS, DMA) and the particle concentration number needed. The
solution of equation (17) for PSL spheres of 200 nm coated with 10 nm of Coronene (the initial
choice for the coating material), at a temperature range of 100-180 o C showed that a residence time
between 1-5 seconds is appropriate, and translates to an oven length of 60 cm according to
Loven
t = !R 2
oven where Roven is the oven inner diameter and Q[m 3 s] is the volumetric flow rate.
Q
3.1.3.3 Final Design
3 different TDs were built. The two earlier designs used heating coils in one and two separately
controlled sections, respectively. The 3rd and final design used a silicon oil heat bath circulating
around the aerosol tube, which yielded the most uniform temperature distribution along the oven.
21
23. Figure 6: Final Thermal Denuder (TD) design. The T’s are thermocouple locations. Flow direction is from left to
right, as indicated by the black arrows. Activated charcoal was used downstream of the oven section, for
absorbing the evaporated coating and preventing re-adsorption to the particles.
Gas flow (Q) is measured before the oven with a differential pressure transducer. 9 type-T
thermocouples (TC) are attached to the outer side of the flow tube (T0 - T8), in the circulating oil
bath volume, and measure the temperature along the 60 cm oven length. Another TC is located
between the oven and the activated charcoal (T9 in Figure 6). A circulation of flow was maintained
in the TD, running through a HEPA (high efficiency particulate air) filter, when the aerosol-laden
flow was diverted to the bypass. This was used to insure that no residue-coating vapor remained in
the TD.
3.1.4 Measurement
The coated aerosols were measured with a combination of instruments. The main flow was
split iso-kineticly (maintaining the same direction and magnitude of flow velocity across the split
cross-section) to 3 streams, flowing into the Aerodyne high-resolution aerosol mass spectrometer
(AMS), condensation particle counter (CPC) and the scanning mobility particle sizer (SMPS).
The coating’s mass and the aerosols’ aerodynamic diameter were measured with a high
resolution AMS, thoroughly described by DeCarlo et al. (2006). Briefly, The AMS samples 85
[cm3 min-1] of gas through a critical orifice, followed by an aerodynamic lens, which focuses the
aerosols into a tight beam. The aerosols expand out of the outlet into a vacuum of 10 !4 [Pa] where
the beams encounter a chopper – a rotating disk with two opposite thin slits – positioned by a servo
in one of three options – open, closed or chopped. In the open mode the aerosol beam does not
impact the chopper, in the closed mode the aerosol beam is completely blocked by the chopper, and
in the chopped mode the aerosols are focused onto the slit in the rotating chopper, and pass through
a close/open cycle at the rate of ~120 Hz. After passing through the chopper the aerosol beam
impacts a cup-shaped tungsten oven at 600-900°C, named the vaporizer, which flash-vaporizes the
22
24. aerosols. The resulting vapor is ionized by electron impact at 70 eV. The resulting ions are
extracted into a time of flight (TOF) high-resolution time of flight mass spectrometer (TofWerk).
The AMS is operating in one of two modes – the average mass mode, in which the open and
closed positions of the chopper are used. The open mode measures the average mass spectrum of
the aerosol and gas stream, while the closed position measurement reflects the gas background
only. The subtraction of the “closed” mass spectrum from the “open” one gives the average aerosol
mass spectrum mm/z [ µ g m 3 ] . In the second mode, the chopper stays in the chopped position. The
chopper is used as the starting signal for a particle time of flight measurement through the 39.5 cm
section following the chopper, and the mass measurement signal is the final measurement thus
giving a measurement of the vacuum aerodynamic time of flight related to each mass spectrum,
which allows to calculate the vacuum aerodynamic diameter dva [nm] .
The AMS detection limit in V-mode (the path of the ions. see DeCarlo et al. (2006)) is
estimated as s < 0.04[ µ g m 3 ] . Combined with the bulk density of BaP this gives the estimated
minimal denuded coating thickness detected by the AMS:
1
# 6s 3 &
Lmin = % + D 3 ( ) D[nm] (18)
$ N !coat " '
Where s is the detection limit, D is the core PSL diameter, !coat is the BaP bulk density (BaP was
the chosen material for all experiments shown here. For the initial design, coronene was used as
well, and so it appears in previous calculations), N[#/ m 3 ] is the aerosol number density, and
Lmin is the minimum detectable BaP layer thickness.
Figure 7 shows a plot of Eq. (18), for relevant core diameters and number concentrations.
As can be seen, the AMS can detect nanometer size coatings, which are small enough to have a
negligible affect the morphology of non-spherical aerosols with a characteristic length bigger then
~30 nm.
23
25. Figure 7: Minimal denuded layer thickness vs. number concentration, for AMS sensitivity of 0.04 µ g / m and
3
BaP as the coating material.
Figure 8: HR-AMS mass fragments for BaP coating on PSL
300 m/z (mass over charge) intensity was used to calculate the mass of the coronene
coating, and 252 m/z was used for the BaP coating (Figure 8). These were based on SMPS, CPC
and differential mobility analyzer (DMA) combination as will be described in the experimental
section 3.1.5.1 below.
In addition, the vacuum aerodynamic diameter measurement (from the AMS) was used to
assess the sphericity of the coating (see section 3.2.1).
The CPC measures particle number concentration N = [# cm 3 ] , combined with the AMS
measurement of the mass loading of the coating material main fragment m/z m252 [ µ g / m 3 ] gives
bypass
the coating mass for each aerosol (Eq. (20)).
24
26. The SMPS measures the mobility diameter distribution of the aerosols, by combining a CPC and a
DMA. The DMA’s voltage is scanned between low and high voltages, set according to the desired
size range, and the CPC counts the number concentration for each voltage. The result can be
inverted to give a mobility diameter distribution (for more detailed description see Rader and
McMurry (1986)).
3.1.5 Experimental Procedure
This section gives a step-by-step description of a typical experiment:
3.1.5.1 Data collection
Different sizes of PSL spheres (200-400 nm diameter) were coated and denuded, in
different oven temperature fields (75<T<130 o C ) and flow rates (80<Q<1400 cm !3 ·min !1 ). Each
experiment consisted of 3 stages – bypass (un-denuded particles), oven (denuded particles) and
bypass again. A typical experiment’s raw data is presented in Figure 9.
Figure 9: Typical raw data for measurement of BaP evaporation from PSL spheres. In this measurement 300
o !1
nm diameter PSL spheres where coated by 25 nm thick BaP, in a 80 C oven and a flow rate of 120 cc·min
Dm [nm] is the peak of a Gaussian fit around the mode of the monodisperse aerosol mobility
diameter distribution measured by the SMPS (the mode diameter is the diameter corresponding to
the highest particle number concentration). Dm!bypass [nm] is the average of Dm [nm] in the bypass
section, and Dm!TD [nm] is the average in the TD section.
25
27. Dm!core [nm] was obtained by measuring the size distributions of the core particles of each PSL
sphere diameter used in the tests.
In addition to these measurements, a correlation was established between the sidewall
temperature measurements of the oven and the temperature at the center of the oven cross section at
each point along the oven’s tube.
3.1.5.2 Measurement of the side-center temperature correlation matrix
The oven temperature distribution, Twall (x j ,t) , which is also referred to as T j (t) , is
continuously measured by thermocouples connected to the outer side of the oven’s tube, evenly
spaced along its axis (Figure 6). This measurement is calibrated against a separated experiment,
where a stiff, thin (1.6 mm diameter) type T thermocouple probe is moved along the oven axis,
measuring the temperatures Tcenter (xi ,t) – also referred to as Ti (t) – at the center-line of the oven
cross section, while the side-wall temperature is also measured. As shown in Figure 9, a small
triangular Teflon holder, with holes at each side, holds the thermocouple probe, allowing the flow
to pass while maintaining the TC tip at the middle of the cross section.
Figure 10: TC probe configuration
The correlation between the center temperature and the wall temperature at close locations
is obtained and averaged over time. A calibration matrix ai, j is then calculated such that
ai, j ·T j = Ti . Since x j points are fewer then xi points, the sparse wall temperature measurements,
which are the only temperature measurements taken during the aerosol denuding experiment, are
each related to a large oven length interval by the last expression.
The 3 closest j points are used with each i point to calculate ai, j according to the following
relations:
# 1&
Ti0 % 1 " (
1 Ti0 $ !'
ai0 , j0 = , ai0 , j0 "1 = ai0 , j0 +1 = where 1 ) ! ) 2 (19)
! T j0 T j0 "1 " T j0 +1
26
28. Ti 0
For the end points ai 0, j 0 = . All other ai 0, j in the row are set to 0. This equation is the result of
Tj0
satisfying ai, j ·T j = Ti with the closest 3 points.
A typical calibration matrix is shown in Table 2, for the temperature profile shown at the
lower part of Figure 11, obtained for 50 mm steps of the probe along the oven center-line (shown in
Figure 12). The steadiness of the oven temperature can be appreciated from this measurement
(Figure 12). The I parameter (see Equation 23) is the vapor density of BaP, multiplied by its
diffusion coefficient of BaP in nitrogen.
Ti
Table 2: Side-center temperature correlation matrix ai, j =
Tj
j0 j1 j2 j3 j4 j5 j6 j7 j8
i0 0.2690 0 0 0 0 0 0 0 0
i1 0.4700 0 0 0 0 0 0 0 0
i2 0.2320 0.4530 0.2320 0 0 0 0 0 0
i3 0.2520 0.4940 0.2520 0 0 0 0 0 0
i4 0 0.2490 0.4980 0.2491 0 0 0 0 0
i5 0 0 0.2490 0.4980 0.2492 0 0 0 0
i6 0 0 0.2490 0.4980 0.2493 0 0 0 0
i7 0 0 0 0.2492 0.4989 0.2492 0 0 0
i8 0 0 0 0 0.2493 0.4982 0.2493 0 0
i9 0 0 0 0 0.2492 0.4980 0.2492 0 0
i10 0 0 0 0 0 0.2492 0.4983 0.2492 0
i11 0 0 0 0 0 0 0.2539 0.4984 0.2539
i12 0 0 0 0 0 0 0.2542 0.4986 0.2542
i13 0 0 0 0 0 0 0 0 1.0351
i14 0 0 0 0 0 0 0 0 0.9770
i15 0 0 0 0 0 0 0 0 0.8000
i16 0 0 0 0 0 0 0 0 0.5925
i17 0 0 0 0 0 0 0 0 0.5430
27
29. !3 !1
Figure 11: Top: temperature scan for fast flow rate of 1400[cm ·min ] and nominal oven temperature of
115°C. The “center of cross section evaporation driving force” is the evaporation driving force (equation (24))
calculated according to the center of cross section temperature profile along the oven (in red)
!3 !1
Bottom: Typical oven temperature profile for I (see Eq. (24)) at flow rate of 400[cm ·min ] and nominal oven
temperature of 85°C
Figure 12: Calibrating the side thermocouples (T0-T8) versus a central probe (T9)
The top of Figure 11 shows the temperature profile during fast flow (Q=1400 cm !3 ·min !1 ) through
the oven. The temperature increase is slower than for 400 cm3 min-1, as expected, and the
evaporation driving force increase is even slower then the temperature increase. Most of the
experiments where conducted in flow rates lower than 700 cm3 min-1, where the flow pattern is
almost as flat as that shown in the lower part of Figure 11. The flow pattern was measured for
several flow rates, and then used to calculate the correlation matrix for these flow rates. The
temperature profile was linearly interpolated for all other flow rates in between.
28
30. 3.1.5.3 Data analysis procedure
1. Defining a “mass calibration ratio” RM : The AMS does not have a 100% collection
efficiency due to bouncing of particles from the hot place without evaporation.
Additionally, only the main fragment was used to calculate the mass of the coating material.
To provide a real mass determination by AMS, a “mass calibration ratio” is defined. The
mobility diameter of coated particles is calculated by fitting the SMPS distribution to a
Gaussian curve around the coarser mode as measured by the SMPS (See Figure 13 in
section 3.2.1). Using this diameter and the known coating mass density, the calibration ratio
RM is calculated between the AMS’s BaP main fragment peak mass (see Figure 8) and the
mass calculated using the SMPS diameter (Eq. (21)):
bypass
m252 1
M AMS =
bypass
bypass
[ µ g] (20)
N 100 3
! 3
M SMPS =
bypass
(Dm"bypass " Dm"core )·#coat ·10 "18 [ µ g]
3
(21)
6
bypass
M SMPS
RM =
bypass
bypass
(22)
M AMS
This value changed with the coating thickness (For the same core particle diameter).
Changing the coating thickness changed the calibration ratio, possibly due to different
bouncing probabilities in the AMS vaporizer (Matthew, Middlebrook, and Onasch 2008).
This is further discussed in section 4.2.2. Also, a slight drift was noticed in this ratio during
experiments, perhaps due to contamination of the vaporizer. Bypassing the oven before and
after TD experiments allows calculation of RM for the segments immediately before, and
immediately after the oven. It was then possible to interpolate RM linearly and obtain a more
accurate RM for each evaporation measurement in the oven.
2. Calculating the mass loss: The mass loss in the oven is calculated for each data point, as
!mAMS"SMPS = M SMPS " RM M AMS
bypass TD
(23)
TD
Where M AMS is calculated according to Eq.(20). The effect of a thin layer on the mobility
diameter of non-spherical particles is not necessarily linear. Therefore, using the SMPS to
calculate the mass will provide correct results for spherical particles only. The SMPS is
used primarily for calibration of the coating mass, and for checking the sphericity of the
coating before and after the evaporation stage, by comparing it to the aerodynamic diameter
as measured with the AMS (see Results section, page 31). A different approach must be
29
31. used to calculate RM in measurements of non-spherical particles. This is further discussed
in section 4.7.
Finally, Eq. (22) and (23) can be written in a more compact form, assuming that
bypass # M AMS &
TD
RM = Rbypass : !mAMS"SMPS = M SMPS ·% 1 " bypass (
$ M AMS '
M
3. Flow velocity correction: The flow velocity measurement is corrected for nitrogen density
decrease due to temperature increase in the oven and constant pressure (conservation of
!ref
mass), according to U i = U ref · where !ref is calculated at room temperature.
!(Ti )
4. Evaporation driving force: The integrated evaporation driving force I[Kg m] defined
below is calculated and integrated for each data point -
tf
I = " !sat D f dt[Kg / m] (24)
0
Where Df is the diffusion coefficient (for further details see Appendix B), and t f is the time
from at least 1% increase in ambient vapor pressure of the coating material until the vapor
pressure returns to at least 1% above the ambient vapor pressure (see Figure 11). 1% was
chosen as a low enough value so the error will be negligible. The use of this integral term in
calculating the Sherwood number is based on a simple derivation shown in Appendix B.
5. Deriving the Sherwood number: !m is measured for the same particle at different
evaporation driving forces, by either increasing oven resident time, or the temperature. A fit
line is calculated on a !m vs. I plot, and the Sherwood number is calculated as the best fit
of
1 "m # m0
Sh = (25)
!D I
Where m0 is the residue mass, obtained by the linear orthogonal distance least square fit.
This method is based on the relationship between the mass transfer coefficient and the Sherwood
number, as derived in Appendix A. m0 accounts a measurement bias Eq. (23) or (26)
Mass loss can alternatively be calculated for spherical particles with the SMPS
measurement alone, according to
" 3
!mSMPS = (Dm#bypass # Dm#TD )·$coat ·10 #18 [ µ g]
3
(26)
6
And the Sherwood number is calculated in the same manner (Eq. (25)).
In all experiments where an SMPS was used along side the AMS and CPC (as illustrated in
Figure 3), !mAMS"SMPS and the resulting Sherwood numbers are shown as well as !mSMPS and the
30
32. resulting Sherwood numbers (see Figure 17, Figure 18 and Figure 19). In initial experiments the
second DMA was used to size-select coated aerosols to a specific size. No SMPS scans were done
for the evaporated particles.
!mSMPS cannot be used for non-spherical particles and is only used here as an independent
comparison for the mass loss. For non spherical particles !mAMS"SMPS will also have to be calculated
in a different manner, this is discussed in section 4.7.
3.2 Results
The main objective of the study is to evaluate the influence of different temperatures and
residence times in the thermal denuder (TD) on the evaporation rate of a coating material for
different PSL particle sizes.
We defined a normalized-driving-force-integral in which both the temperature profile and
ˆ
the residence time are taken into account: I = I·! D[Kg] (Eq. (25), Further discussion in appendix
A). Since the entire oven temperature profile is taken into account through the integration (Eq. (24)
), different temperatures and different residence times can both be shown on a normalized driving
force scale ((see Figure 17, Figure 18 and Figure 19)). An adequate unit for designating the coating
mass of a single aerosol and normalized driving force is 10 9 µ g , since the mass of typical single
aerosol coating is 10-15 to 10-14 gr.
The pressure of the nitrogen in which the particles are suspended is 1 Bar (the system is
open to the atmosphere) in all the measurements presented here.
3.2.1 Mobility and vacuum aerodynamic distributions
A typical mobility and vacuum aerodynamic distributions, measured by the SMPS and
AMS respectively are shown in Figure 13. The right column is based on the 104 m/z peak, which is
the main fragment peak for the PSL particles. The same distribution can be seen in the BaP main
peak, m/z 252 (see Figure 8), but the error is larger, especially for the evaporated particles, due to
the lower amount of material. This is shown for one example measurement in Figure 14.
31
33. Figure 13: Particle size distribution for different extents of evaporation.
Typical SMPS mobility diameter distribution (left column) and AMS-PToF aerodynamic vacuum diameter
distribution (right column) measurement for evaporation of BaP coated PSL particles. As indicated by the gradual
decrease of D m and Dva of the particles flown through the TD, the extent of evaporation increased from 1 to 6, with
a1 and b1 showing the same evaporated particle ensemble, a1 is the mobility diameter distribution, and b1 is the
vacuum aerodynamic distribution. A Gaussian fit is used to calculate a higher resolution mode (diameter
corresponding to maximum particle counts) diameter. Core particles are 300 nm diameter PSL spheres, coated by
o
40-50 nm BaP, Oven average temperature = 85-130 C Flow rate = 400-1400 cc/min. The shape factor (Figure 16)
was calculated according to these measurements.
32
34. Figure 14: comparison of vacuum aerodynamic diameter distribution for 104 m/z (PSL peak) and 252 m/z (BaP
o
peak) for 300 nm PSL spheres coated with 50 nm thick BaP. Oven average temperature = 115 C Flow rate = 700
cc/min.
The distribution is nearly monodisperse. A normal Gaussian fit around 4-8 point
surrounding the SMPS mode and 8-16 points surrounding the m/z 104 PToF mode was used to
calculate the more refined mode diameter for all shape factor calculations.
3.2.2 SMPS measured and AMS mass based final diameter and shape factor
Figure 15 shows the initial aerosol diameter (peak of Gaussian fit around the mode
diameter, shown in Figure 13) as measured by SMPS, for a typical experiment. The Figure shows
33
35. the SMPS measured diameter after evaporation in the TD, and the AMS based diameter, calculated
according to a mass balance
1
# 6 &3
DAMS = % Dcore + RM M AMS (27)
$ !"coat (
'
There is a close agreement between the two.
The difference in sphericity can be calculated by comparing the aerodynamic vacuum
mode diameter and mobility mode diameter. This yields the “Jayne shape factor” (DeCarlo et al.
Dva !0
2004) S = where !0 [Kg / m 3 ] , which is a normalization factor – in the same units as the
Dm ! p
particles density which is calculated according to the combined mass of the PSL core, and BaP
coating, divided by the volume of the coated sphere. The relation between the Jayne shape factor
and the dynamic shape factor can be explained by looking at two limiting cases – the continuum
1 1
limit S ! and the kinetic limit S ! 3 2 , assuming the particle has no internal voids (DeCarlo et
" 2
"
al. 2004). The different shape factors are displayed in Figure 16, for a thick initial coating (50 nm)
of BaP, and thin initial coating of BaP (5 nm), on 300 nm diameter PSL spheres, For a spherical
particle the Jayne shape factor = 1, and for semi-spherical it is ! 1. The dynamic shape factor
approached 1 from above as the particle becomes more spherical. In all the experiments the Jayne
shape factor was above 0.8, and converged towards 1 with the evaporation. This behavior is
expected, since the evaporation tends to make particles more spherical: The vapor density
difference, which is the driving force for evaporation, diminishes at a point inside a “valley” on the
surface of a coated particle, and so the “hills” tend to evaporate faster then the “valleys” leading to
a more spherical particle as the evaporation time increases. The initial coating is therefore mildly
non spherical, and becomes more spherical as the particle outer surface evaporates (annealing).
Further discussion of coating and partial coating effect on evaporation rate is given below in
section 5.2.1.
The Jayne shape factor measured with thick coatings (Figure 14(a)) after most of the
coating evaporated (coating thickness = 10 nm) is higher than one, which is unphysical (DeCarlo et
al. 2004). This is in the range of error of the mobility and vacuum aerodynamic diameter, and
therefore associated with measurement error.
34
36. Figure 15: Change in coating thickness due to evaporation. PSL spheres of 300 nm diameter, coated by 40-50 nm
o
BaP, Oven average temperature = 85-130 C Flow rate = 400-1400 cc/min.
Figure 16: Shape factor versus coating thickness for (a) 50 nm BaP coating (from distributions shown in Figure
o
13) and (b) 5 nm BaP coating, both on 300 nm PSL sphere. Oven average temperature = 85-130 C Flow rate =
400-1400 cc/min.
35
37. 3.2.3 Effects of Residence time
Figure 17 - Figure 19 show the effect of residence time on the evaporation. In this
configuration the oven nominal temperature is held constant, while changing the residence time in
the oven by changing the gas flow velocity. Two trends are observed in Figure 18 (a) and Figure 19
(b): A linear trend, following Eq. (25), and a decaying trend, caused by the lower vapor density of
an incomplete coating, remaining over the particles when the evaporation period is too long. The
flow rates during the experiments were normally set to avoid this decaying trend, and make sure
only part of the coating is evaporated.
S bypass S TD N Rbypass
M
Minimum 0.796 0.815 260 1.76
Average 0.806 0.877 725 1.98
Maximum 0.816 0.936 1600 2.24
Figure 17: Effect of residence time. 200 nm PSL sphere, 15 nm thick BaP coating. TD flow rate sweep 350-780
cc/min at 85 o (upper red fit line), TD flow rate sweep 200-450 cc/min at 80 o (lower red fit line). Associated table
displays minimum, maximum and average values for the Jayne shape factor (see page 33) of the coated particles
S bypass , evaporated particles S TD , number concentration N[#/ cc] and calibration ratio Rbypass
M
36
38. (a) (c)
bypass
S bypass
S TD
N R M S bypass S TD N Rbypass
M
Minimum 0.805 0.88 260 1.6 - - 200 2.2
Average 0.81 0.92 310 2.1 - - 430 2.8
Maximum 0.815 0.94 360 2.7 - - 660 3.6
Figure 18: Effect of residence time. 300 nm PSL sphere (a) 25-30 nm BaP coating, TD flow rate sweep 80-260
cc/min at 85 o (b) 20 nm BaP coating, size selected by second DMA, TD flow sweep 380-1240 cc/min at 85 o
(a) (b) (c)
bypass bypass
S bypass S TD N R M S bypass S TD N R M S bypass S TD N Rbypass
M
Minimum 0.85 0.91 200 2.5 0.77 0.8 75 3.44 0.84 0.87 190 2.1
Average 0.87 0.94 380 2.85 0.81 0.84 500 4.3 0.85 0.89 320 2.4
Maximum 0.88 0.97 570 3.1 0.85 0.88 1550 7.07 0.86 0.91 440 2.7
Figure 19: Effect of residence time. 400 nm PSL sphere (a) 22-30 nm BaP coating, TD flow rate sweep 300-1100
cc/min at 95 o (b) 25-30 nm BaP coating, TD flow rate sweep 380-500 cc/min at 90 o (upper 3 points), TD flow rate
sweep 115-500 cc/min at 85 o (rest of points) (c) 22-30 nm BaP coating, TD flow rate sweep 290-470 cc/min at 85 o .
Associated table displays minimum, maximum and average values for the Jayne shape factor (see page 33) of the
coated particles S bypass , evaporated particles S TD , number concentration N[#/ cc] and calibration ratio Rbypass
M
37
39. 4 Discussion
4.1 Derivation of the Sherwood number
Figure 20: Sherwood number vs. particle diameter for experiments shown in figures 17-19
The Sherwood number (Sh) was derived for different nominal PSL sphere diameters
according to Equation (25), and is compared to the theoretical diffusive mass transfer case in the
transition regime, using Eq (12) (Davies (1978) from Hinds (1999) p. 288)
2" + D
ShKn = 2·! (Kn) = 2·
D + 5.33(" 2 D) + 3.42 "
Theoretically, for a spherical particle, in the continuum regime, where no convective mass
transfer occurs, Sh should equal 2. This is corrected for the transition regime using Eq (12), which
leads to lower Sh. Figure 20 presents the derived Sherwood number for different PSL diameters and
driving force. The dotted line represents the calculated ShKn numbers for these conditions. It can be
seen that most of the measurements fall close to this line, within the measurement errors. The free
kT
mean path ! was calculated according to ! = [m] where p = 101325[Pa] and T is the
"d p 2
2
N2
average of the flat part of the oven, as seen in the bottom of Figure 11. The mass loss calculation,
based on AMS and SMPS, or only on SMPS, are shown in section 3.1.5.3 .
38