Experimental characterization of effervescent atomization

The atomization is a process widely used in aerospace, combustion, or thermal spray coating, and is controllable by adopting different fluids as well as by retrofitting nozzle geometry. Desired characteristics of atomized fluid radically depend on the application of the spraying process which could be achieved by the appropriate selection of the nozzle, as well as changing the operating conditions. The objective of this study is experimental investigation of the atomization process by an effervescent nozzle for a variety of fluids where there is a lack of experimental knowledge. Four different liquids were taken: distilled water, pure glycerol, water-glycerol aqueous solution and suspensions. The suspension is prepared by an optimized proportion for each case in order to mitigate the sedimentation and clogging of suspended beads. We determined the properties of the atomized fluids in accordance to the commonly used quantities in practical applications. Beside the rheology analyses of the fluids, three types of characterization experiments such as shadowgraphs, PIV and PDPA were conducted. Firstly, shadowgraphs were captured and the overall structures of spraying regions were observed. Accordingly, PIV and PDPA data were provided, consisting of a velocity profile in different operating conditions as well as distributions of a droplets’ diameter. The main characteristics of atomized fluids are velocity profiles, droplet size distributions, spray cone angle, and breakup lengths. These characteristics with dimensionless variables, namely Gas to Liquid Ratios (GLRs), are calculated and compared. It was found that varied values of dynamic viscosities and surface tension values have effects on the atomization affecting breakup lengths and droplet size distributions. Various recommendations were provided regarding the experimental results and future works

Validation and Psychometric Properties of the Anger Management Skills Test

Background: More awareness of anger in different social situations can help us to manage it efficiently. Unfortunately, the questionnaire measuring these differences hasn't been validated in Iran. The primary purpose of this study was to investigate the psychometric properties of the Persian version of the Springer anger control skills test. Method: The statistical population of this study was 200 college students consisted of 180 undergraduate, 15 M.Sc, and 5 Ph.D. students at Shiraz University. A random sampling method was used in this research. Springer anger control skills test was completed to assess the validity and reliability, Cronbach's alpha and internal validity, and exploratory factor analysis was used.  Results: Results indicated the reliability of 0.62 and a significant value (0.001).  KMO value was 0.45. Also, a significant difference was found between males and females in anger‏ management and allocated to sociality and non-family relationships (0.001). Simultaneously, there was no significant difference between females and males in other variables and subscales of anger control. Conclusion: Findings illustrate that this scale is reliable and valid and can be used in a clinical context. The difference between male and female in controlling anger in social situations can be related to Cultural influences and having more education; also, this sample only represents the population who had a higher level of education in comparison to others. Besides, they have received more educational training and necessary skills to cope with impulses and social encounters more appropriately

Techno-economic assessment of membrane assisted fluidized bed reactors for pure H2 production with CO2 capture

This paper addresses the techno-economic assessment of two membrane-based technologies for H2 production from natural gas, fully integrated with CO2 capture. In the first configuration, a fluidized bed membrane reactor (FBMR) is integrated in the H2 plant: the natural gas reacts with steam in the catalytic bed and H2 is simultaneously separated using Pd-based membranes, and the heat of reaction is provided to the system by feeding air as reactive sweep gas in part of the membranes and by burning part of the permeated H2 (in order to avoid CO2 emissions for heat supply). In the second system, named membrane assisted chemical looping reforming (MA-CLR), natural gas is converted in the fuel rector by reaction with steam and an oxygen carrier (chemical looping reforming), and the produced H2 permeates through the membranes. The oxygen carrier is re-oxidized in a separate air reactor with air, which also provides the heat required for the endothermic reactions in the fuel reactor. The plants are optimized by varying the operating conditions of the reactors such as temperature, pressures (both at feed and permeate side), steam-to-carbon ratio and the heat recovery configuration. The plant design is carried out using Aspen Simulation, while the novel reactor concepts have been designed and their performance have been studied with a dedicated phenomenological model in Matlab. Both configurations have been designed and compared with reference technologies for H2 production based on conventional fired tubular reforming (FTR) with and without CO2 capture. The results of the analysis show that both new concepts can achieve higher H2 yields than conventional plants (12-20% higher). The high electricity consumptions of membrane-based plants are associated with the required low pressure at the retentate side. However, the low energy cost for the CO2 separation and compression makes the overall reforming efficiency from 4% to 20% higher than conventional FTR with CO2 scrubbing. FBMR and MA-CLR show better performance than FTR with CO2 capture technology in terms of costs mainly because of lower associated CAPEX. The cost of H2 production reduces from 0.28 €/NmH23 to 0.22 €/NmH23 (FBMR) and 0.19 €/NmH23 (MA-CLR)

Die Adhäsion zwischen feinen Pulverteilchen und Nanokontakten : eine Untersuchung mit dem Rasterkraftmikroskop

Um die Handhabung von feinen Pulvern in industriellen Anwendungen zu optimieren, ist ein Verständnis der Wechselwirkungen zwischen einzelnen Pulverteilchen eine fundamentale Voraussetzung. Die Kräfte zwischen kolloidalen Teilchen bestimmen das Verhalten einer Reihe von Materialien wie Farben, Papier, Erdreich und eine Vielzahl industrieller Prozesse. Mit der Erfindung des Rasterkraftmikroskops (Atomic force microscope, AFM) wurde die direkte Messung der Wechselwirkung zwischen mikrometer-großen Teilchen möglich. Der adhäsive Kontakt zwischen einem Teilchen und einer Oberfläche ist ein wesentlicher Parameter für die Analyse von Haftkraftmessungen mit dem AFM. Ziel dieser Studie war es, die Oberflächenkräfte zwischen feinen Pulverteilchen besser zu verstehen. Ich habe die Haftkraft zwischen AFM-Spitzen oder Pulverteilchen, die an AFM-Federbalken befestigt waren, und verschiedenen Festkörperoberflächen gemessen. Es wurden sowohl glatte und homogene Oberflächen wie Siliziumwafer, Glimmer, kristallinem Graphit (HOPG) als auch rauere und heterogene Oberflächen wie Eisenteilchen oder regelmäßige Anordnungen von TiO2 Nanoteilchen auf einem Siliziumwafer verwendet. Im ersten Teil habe ich mich mit der wohlbekannten Tatsache auseinander gesetzt, dass bei Haftkraftmessungen mit dem AFM nicht ein fester Wert, sondern recht breite Verteilungen der Haftkraft beobachtet werden. Meine experimentellen Resultate zeigen, dass sich die Schwankungen der Haftkraft zusammensetzen aus schnellen, zufälligen Fluktuation, die von einem Kraftmessung zur nächsten auftreten, und langsameren Schwankungen, die über einige zehn bis hundert aufeinaderfolgenden Messungen hinweg erfolgen. Diese langsamen Fluktuationen können nicht auf Schwankungen externer Einflussgrößen wie Kontaktposition, Temperatur, Luftfeuchte etc. zurückgeführt werden, da diese konstant gehalten wurden. Selbst wenn zwei Festkörper unter genau den gleichen Bedingungen (gleiche Stelle, Andruckkraft, Richtung usw.) in Kontakt gebracht werden, ist das Resultat für aufeinander folgende Messungen oft unterschiedlich. Die Messung selbst induziert strukturelle Veränderungen im Kontaktbereich, die zu einem geänderten Wert der Haftkraft in der nächsten Messung führen. Im zweiten Teil dieser Arbeit untersuchte ich den Einfluss der Luftfeuchte auf die Haftkraft von Nanokontakten. Die Luftfeuchte wurde möglichst schnell variiert, um Verschleiß der AFM-Spitzen während einer Messreihe zu minimieren. Für hydrophobe Oberflächen wurde keine signifikante Änderung der Haftkraft mit zunehmender Luftfeuchte beobachtet. Für hydrophile Oberflächen ergab die Auftragung von Haftkraft gegen Luftfeuchte entweder ein Maximum oder einen kontinuierlichen Anstieg mit zunehmender Luftfeuchte. Dies kann mit einem einfachen Kontinuumsmodell der Kapillarkraft erklärt werden, das Rauhigkeit der Oberflächen berücksichtigt und verschiedene AFM-Spitzengeometrien oder Teilchenformen durch Überlagerung zweier Kugeln modelliert. Experimentelle Ergebnisse und Modellrechnungen zeigen, dass die genaue Kontaktgeometrie einen entscheidenden Einfluss auf die Abhängigkeit der Haftkraft von der Luftfeuchte hat. Änderungen der Spitzengeometrie auf der sub10 nm Längenskala können zu einer vollständigen Veränderung des Zusammenhangs zwischen Haftkraft und Luftfeuchte führen. Unser Modell erklärt somit auch die großen Diskrepanzen zwischen verschiedenen früheren AFM-Studien zur Abhängigkeit der Haftkraft von der Luftfeuchte.To optimize the handling of fine powders in industrial applications, understanding the interaction forces between single powder particles is fundamental. The forces between colloidal particles dominate the behavior of a great variety of materials, including paints, paper, soil, and many industrial processes. With the invention of the atomic force microscope (AFM), the direct measurement of the interaction between single micron-sized particles became possible. The adhesional contact between a particle and a substrate is a parameter for analyzing pull-off force data generated by AFM. The aim of this study was to understand surface interactions between fine particles. I measured the adhesion forces between AFM tips or particles attached to AFM cantilevers and different solid samples. Smooth and homogeneous surfaces such as silicon wafer, mica, or highly oriented pyrolytic graphite (HOPG), and more rough and heterogeneous surfaces such as iron particles or patterns of TiO2 nanoparticles on silicon wafer were used. First, I addressed to the well-known issue that AFM adhesion experiment results show wide distributions of adhesion forces rather than a single value. My experimental results show that variations in adhesion forces comprise fast (i.e., from one force curves to the next) random fluctuations and slower fluctuations, which occur over tens or hundreds of consecutive measurements. Slow fluctuations are not likely to be the result of variations in external factors such as lateral position, temperature, humidity, and so forth because those were kept constant. Even if two solid bodies are brought into contact under precisely the same conditions (same place, load, direction, etc.) the result of such a measurement will often not be the same as for the previous contact. The measurement itself will induce structural changes in the contact region which can change the value for the next adhesion force measurement. In the second part I studied the influence of humidity on the adhesion of nanocontacts. Humidity was adjusted relatively fast to minimize tip wear during one experiment. For hydrophobic surfaces, no signification change of adhesion force with humidity was observed. Adhesion force-versus-humidity curves recorded with hydrophilic surfaces either showed a maximum or continuously increased. I demonstrate that the results can be interpreted with simple continuum theory of the meniscus force. The meniscus force is calculated based on a model that includes surface roughness and takes into account different AFM tip (or particle) shapes by a two-sphere-model. Experimental and theoretical results show that the precise contact geometry has a critical influence on the humidity dependence of the adhesion force. Changes of tip geometry on the sub-10-nm length scale can completely change adhesion force-versus-humidity curves. Our model can also explain the differences between earlier AFM studies, where different dependencies of the adhesion force on humidity were observed

On-line monitoring of emulsion polymerisation by conductimetry and calorimetry

La concentration de tensioactifs dans les réactions de la polymérisation en émulsion agit directement sur le nombre et la stabilité de particules dans le latex. La mesure en ligne de cette concentration est alors primordiale pour comprendre le mécanisme de formation de ces particules ainsi que la cinétique de la réaction. Cette mesure est alors indispensable pour la supervision et la commande de ces procédés de polymérisation. L'objectif principal de cette étude est de démontrer la possibilité d'utiliser la méthode de conductimétrie pour estimer la concentration de tensioactifs dans le latex. L'influence de différents paramètres pouvant modifier le signal de conductimétrie durant les réactions de polymérisation en émulsion a été étudiée. Nous avons donc établi une relation liant la variation de concentration de tensioactifs à la surface totale de particules dans le latex. La conductimétrie peut également être combiner à la calorimétrie et aux observateurs d'états (les capteurs logiciels) pour estimer le nombre moyen et le diamètre de particules dans le latex. Pour réaliser cet objectif, nous avons utilisé des observateurs à grand gain qui sont bien adapté pour ce type de procédésLYON1-BU.Sciences (692662101) / SudocSudocFranceF