Vapor absorption systems offer advantages over vapor compression systems for air-conditioning systems in some applications. They use heat as their primary energy input and hence provide opportunities to use solar energy or waste heat to drive these systems. The absorber is the most crucial component of the vapor absorption system and has the largest impact on its performance. Absorber design requires a keen understanding of the underlying heat and mass transfer processes in the absorber. The horizontal tube geometry is by far the most popular absorber geometry, due to the high absorption efficiencies achievable without incurring commensurate pressure drops. Several models have been proposed in the literature to model the heat and mass transfer during absorption over horizontal tube banks. However all of them make very simplistic assumptions about the flow profiles in the absorber. High speed flow visualization studies in the literature have shown that the flow occurs in the form of droplets and the formation and the detachment of these droplets and their impact on the tube has significant effects on the heat and mass transfer. Most absorption models in the literature neglect these flow modes and assume the solution to flow as a uniform film. The present study attempts to numerically model the heat and mass transfer in the absorber taking the realistic drop-wise and wavy film flow patterns into consideration. The impact of the fall of these droplets on the tube causes the lithium bromide solution present on the film on the tube to mix and present newer regions of the solution for vapor absorption. The impact of the droplets also causes waves that propagate axially over the liquid film on the tube. The mixing effect and the waves caused due to droplet impact play a very important role in the heat and mass transfer. Results obtained from this study will aid in better understanding of the vapor absorption process, and in the design of more efficient absorbers.

The objective of the research was to develop fundamental understanding of the process of deposition of complex mixtures by the inkjet method. The rheological properties and DOD drop formation dynamics of carbon black pigmented inkjet inks were investigated. It was found that the suspension microstructure responses to bulk motions, leading to shear rate and time dependent shear viscosity. However, DOD drop formation dynamics of highly pigmented inkjet ink and pure Newtonian fluid is similar even though shear rate up to 105 s-1 exists during inkjet jetting process. A proposed explanation for these observations is that the shearing time during DOD drop ejection is insufficient for changing and stabilizing the microstructure of the suspension. The effects of signal amplitude and jetting frequency on DOD drop formation dynamics of pure Newtonian fluids were investigated. A transition of DOD drop formation dynamics when the inkjet nozzle is switched from idle to jetting was identified. A qualitative investigation of DOD drop impaction and post-impaction behavior on inkjet paper and textiles was carried out. Dynamics of DOD drop accumulation and spreading on the substrates and final ink distribution show drastic differences between these two substrates.

Mémoire (M.Sc.)--Université du Québec à Chicoutimi, 1978. / Document électronique également accessible en format PDF. CaQCU

De nombreux procédés de la recherche et de l'industrie utilisent l'extraction liquide-liquide, technique qui permet la séparation sélective de produits au sein d'un mélange. À cet effet, deux liquides non miscibles sont mis en contact : une phase aqueuse et une phase organique, l'une contenant généralement une molécule extractante capable de transférer les éléments désirés à l'autre. Le transfert se produit à la surface de contact entre les deux phases. Après le transfert, les deux phases sont séparées par décantation. Dans la pratique, ces opérations sont effectuées dans des appareils industriels. Pour optimiser et comprendre le fonctionnement de ces dispositifs, il est important de déterminer les caractéristiques fondamentales de l'émulsion. Il s'agit notamment des paramètres liés à la vitesse des écoulements ainsi que ceux liés au mélange des fluides comme l'aire interfaciale, le taux de rétention, ou la distribution en taille de la population de gouttes. Plusieurs techniques d'imagerie peuvent être utilisées pour les mesurer. L'une d'elles, l'holographie numérique, est bien connue pour permettre la reconstruction complète en 3D d'un écoulement à partir d'une seule acquisition. Ce travail de thèse traite d'une application de l'holographie numérique en ligne directement sur des gouttes en mouvement dans une phase liquide continue. La taille des gouttes a imposé l'exploration d'un régime de diffraction peu étudié à ce jour. Dans ce domaine, le modèle du disque opaque classiquement employé n'est pas valide et un meilleur accord est obtenu avec un modèle mixte lui associant une lentille mince. La focalisation des hologrammes est réalisée via une méthode dédiée et automatique qui a été établie à partir d'une étude complète de la littérature. Dans un deuxième temps, afin de mesurer des rétentions plus élevées, elle est complétée par une approche inverse permettant de corriger les mauvais positionnements et de restituer les gouttes non détectées. Ce traitement a été appliqué à des résultats expérimentaux, sur un dispositif de référence produisant des gouttes calibrées, et comparé à des mesures indépendantes. Ces essais ont validé la pertinence de l'holographie pour la caractérisation des émulsions. / Several processes used in research and industry are based on liquid-liquid extraction, a method designed for selective separation of products in a mixture. In liquid-liquid extraction, two immiscible liquids are contacted: an aqueous phase and an organic phase, one of which generally contains an extractant molecule capable of transferring the desired elements to the other phase. The transfer occurs at the contact surface between the two phases. After transfer, both phases are separated by settling. In practice, these operations are performed in industrial apparatus. In order to optimize the operation of these devices, it's important to determine the fundamental characteristics of the emulsion. These include parameters related to the fluid flow velocity as well as parameters related to fluid mixing such as the interfacial area, hold-up, and size distribution of the droplets population. Numerous imaging techniques can be used to measure these parameters. One of them, digital holography, is well-known for allowing complete reconstruction of information about a 3D flow in a single shot. This PhD work deals with a direct application of digital in line holography to droplets rising in a continuous liquid phase. The droplet size imposes a regime of intermediate-field diffraction hardly explored to date. Acquired diffraction patterns show that the usual dark disk model is not valid and that good agreement is obtained with a mixed model coupling thin lens with opaque disk. Hologram focusing is nevertheless performed with a dedicated automated method. A literature review has been conducted to identify the sharpest autofocus function for our application. In a second step, in order to measure high retention rates, an inverse problem approach is applied on all the outliers and missing droplets. This hologram restitution treatment has been applied to experimental results with a comparison to independent measurements. The main results obtained with calibrated droplets are presented detailing the test device and instrumentation. They have validated the relevance of holography for the characterization of emulsions.

Made available in DSpace on 2015-03-26T13:39:43Z (GMT). No. of bitstreams: 1 texto completo.pdf: 440959 bytes, checksum: d22f486cf5e4f4bfebe84fc49fb6dd16 (MD5) Previous issue date: 2006-09-18 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work had the objective to evaluate different spray nozzle by different operational conditions in order to have subsidies for the correct selection of spray nozzle for pesticide application. The work consisted of two experiments. On the first, it was evaluated the deposition of drops on the soybean canopy by spray nozzle XR11002 (XR), TXA8002 (TX), TT11002 (TT) and TJ60-8002 (TJ) exposed to pressure of 827, 552 and 276 kPa. It was quantified the volume median diameter (DMV) of the drop population, density of drops (drops cm-2) and covering percentage. The drops were collected in three positions on the soybean canopy: superior third, medium and inferior of the plant by factorial scheme 4x3x3 (four spray nozzle, three pressure and three positions on the soybean canopy) in a totally occasional sketch with four repetitions. On the second experiment, the technical characteristics of spray nozzle LA-1JC and SR-1 were evaluated by different operational conditions. It was evaluated the pattern check of spray nozzle in test workbench following the pattern ISO 5682/2 on heights of 30, 40 and 50 cm, determining spray nozzle outflow, drops spectrum, left, right and total angle spray. All characteristics analyzed were submitted to pressure of 100, 200 and 300 KPa. In the experiment about the deposition of drops on the soybean canopy, it was realized that the drop population showed higher DMV on the superior third of the plant. However, the nozzle TJ provided drops with homogeneous DMV in the evaluated positions. Independent of spray nozzle utilized, the pressure of 276 KPa allowed deposition of drops with same size on the three positions. For the other pressures, it was obtained higher pressure on the superior third of the plant. The TJ nozzle provided similar covering of the aim on the three third and superior covering on the other nozzle of the medium third and inferior of the plant. The nozzles promoted higher density of drops on the superior third of the plant, decreasing in proportion to reduce the height, except TJ nozzle which showed homogeneous density in the three positions. Analyzing technical characteristics of SR-1 and LA-1JC nozzles, it was observed continuous pattern check to the LAI-JC nozzles in all pressure and SR-1 when utilized pressure of 100kPa that was indicated for stripe. SR nozzle showed discontinued pattern in the pressure of 200 and 300 kPa, which is indicated for application in total area. There was better uniformity in the distribution (lower rate of variation), with lower set at intervals on the nozzles and higher bar height. For both nozzles DMV decreased in proportion to the increase of the pressure. Independent of the work pressure utilized, LA-1JC and SR-1 nozzles provided extremely dense drops. CH is adequate to the patterns of jet plane nozzle (lower than 5) showing great homogeneity in the drops spectrum in every work pressure. LA-1JC nozzle showed higher outflow than SR1, on the pressure of 200 and 300 kPa, having no difference observed when 100 kPa pressure was utilized. The left and right angle of pulverization were symmetrical that there weren t differences between nozzle and pressure. There was increasing on the angle in proportion to the pressure improvement on the nozzle. It is indicated TJ nozzle for pesticides application in adequate climate conditions. / Objetivou-se, neste trabalho, avaliar diferentes pontas de pulverização em diferentes condições operacionais, visando fornecer subsídios para a seleção correta de pontas de pulverização para aplicação de agrotóxicos. O trabalho constou de dois experimentos. No primeiro foi avaliado a deposição de gotas no dossel da soja pelas pontas de pulverização XR11002 (XR), TXA-8002 (TX), TT11002 (TT) e TJ60-8002 (TJ), submetidas a pressões de 827, 552 e 276 kPa. Quantificou-se o diâmetro da mediana volumétrica (DMV) da população de gotas, densidade de gotas (gotas cm-2) e porcentagem de cobertura. A coleta das gotas foi realizada em três posições no dossel da soja: terço superior, médio e inferior da planta em esquema fatorial 4x3x3 (quatro pontas de pulverização, três pressões e três posições no dossel da planta) em um DBC com quatro repetições. No segundo experimento avaliou-se as características técnicas das pontas de pulverização LA-1JC e SR-1 sob diferentes condições operacionais. Avaliou-se o perfil de distribuição das pontas em bancada de ensaios padronizada seguindo a norma ISO 5682/2 em alturas de 30, 40 e 50 cm, determinou-se a vazão das pontas, o espectro de gotas, o ângulo de pulverização esquerdo, direito e total. Todas as características avaliadas foram submetidas as pressões de 100, 200 e 300 kPa. Observou-se no experimento de deposição de calda no dossel da soja, que a população de gotas apresentou maior DMV no terço superior da planta, entretanto a ponta TJ proporcionou gotas com DMV homogêneo nas posições avaliadas. Independente da ponta de pulverização utilizada, a pressão de 276 kPa permitiu deposição de gotas com tamanho uniforme nas três posições. Para as demais pressões, maior DMV foi obtido no terço superior da planta. A ponta TJ, proporcionou cobertura do alvo semelhante nos três terços e cobertura superior as demais pontas no terço médio e inferior da planta. As pontas promoveram maior densidade de gotas no terço superior da planta, decrescendo à medida que se reduz a altura, exceto para ponta TJ, que apresentou densidade de gotas homogênea nas três posições. Avaliando as características técnicas das pontas SR-1e LA-1JC, observou-se perfil de distribuição contínuo para as pontas LA1-JC em todas as pressões e da SR-1 quando utilizado a pressão de 100 kPa, sendo indicado para aplicação em faixa. A ponta SR-1 nas pressões de 200 e 300 kPa apresentou perfil descontínuo, sendo indicado para aplicação em área total. Houve melhor uniformidade de distribuição (menor coeficiente de variação), com menor espaçamento entre pontas e maior altura de barra. Para ambas as pontas, à medida que se aumentou a pressão diminuiu-se o DMV. Independente da pressão de trabalho utilizada, as pontas LA-1JC e SR-1 proporcionaram gotas extremamente grossas. O CH está adequado aos padrões para pontas de jato plano (menor que 5), apresentando boa homogeneidade no espectro de gotas em todas as pressões de trabalho. A ponta LA-1JC apresentou maior vazão em relação a ponta SR-1, nas pressões de 200 e 300 kPa, não sendo verificada diferença quando utilizada a pressão de 100 kPa. O ângulo de pulverização esquerdo e direito foram simétricos não havendo diferenças entre pontas e pressão. Houve aumento no ângulo a medida que se aumentou a pressão para ambas as pontas.

Crankcase ventilation contributes significantly to diesel engine particulate emissions. Future regulations will not only limit the mass of particulate matter, but also the number of particles. Controlling the source of crankcase emissions is critical to meeting the perennial legislation. Deficiency in the understanding of crankcase emissions generation and the contribution of lubricating oil has been addressed in detail by the experimental study presented in this thesis. A plethora of high speed laser optical diagnostics techniques have been employed to deduce the main mechanisms of crankcase oil aerosol generation. Novel images have captured oil atomisation and passive oil distribution around the crankcase of an optically accessed, motored, four cylinder, off highway, heavy duty, diesel engine. Rayleigh type ligament breakup of oil films present on the surface of dynamic components, most notably the crankshaft, camshaft and valve rockers generated oil drops below 10 micrometers. Data illustrated not only crankcase oil aerosol generation at source, but it has provided valuable information on methods to control oil aerosol generation and improve oil circuit efficiency. The feasibility of utilising computational fluid dynamics to predict crankcase oil aerosol generation has been successfully assessed using the experimental data. Particle sampling has characterised the crankcase emissions from both a fired and motored diesel engine crankcase. The evolution of submicron crankcase particles down to 5 nm has been recorded from both engines, including the isolated contribution of engine oil, at a wide range of engine test points. Results have provided constructive insight into the generation and control of this complex emission. The main mechanism of crankcase oil aerosol generation was found to be crankshaft oil atomisation. This atomisation process has been analysed in detail, involving high speed imaging of primary and satellite drop generation and high speed digital particle image velocity of the crankshaft air flow. A promising mechanism of regulating and controlling crankcase oil aerosol emissions at source has been studied experimentally.

Le transport par voie maritime s’est développé très rapidement durant la dernière décennie. Il constitue la solution idéale pour déplacer à faibles coûts d’importantes quantités de marchandises sur de longues distances. L’accroissement de ces échanges entraine inévitablement une augmentation de la fréquentation des routes maritimes, de la densité du trafic et donc du risque d’accident et de naufrage.Les quantités impliquées lors d’un accident étant importantes, un rejet sous-marin de produit chimique issu d’une épave peut provoquer de graves conséquences environnementales et humaines. Or, les mécanismes physico-chimiques apparaissant lors du transfert du produit à la surface sont encore mal compris. Ces mécanismes dépendent de nombreux paramètres dont les propriétés physico-chimiques intrinsèques au produit et celles propres à l’environnement de l’accident.Ce travail de recherche, réalisé en collaboration entre l’Ecole des Mines d’Alès et le Cedre, s’inscrit dans l’amélioration de la compréhension du comportement d’un rejet de produit chimique liquide, flottant et soluble issu d’une épave. Cette étude expérimentale a été réalisée selon 3 points :- La phénoménologie du rejet à la brèche dont l’objectif est de quantifier le débit et les modes de rejet,- Le comportement hydrodynamique du produit libéré et son évolution lors de la remontée dans la colonne d’eau,- Le transfert de matière du produit lors de sa solubilisation dans la colonne d’eau.Pour chaque point, les résultats obtenus sont comparés à ceux prédits par les corrélations disponibles dans la littérature afin de proposer une modélisation globale des conséquences adaptée à la gestion des pollutions marines. / Maritime transport quickly increases during the last decade. It is the cheapest way to transport large quantities of goods over long distances. The growth of this trade necessarily leads to an increase in the traffic density and therefore the risk of accident and sinking increases as well.The large amount of chemicals involved in an accident may threaten the environment and human health in case of shipwreck with underwater chemical release. Unfortunately the physicochemical mechanisms occurring during the transfer of a chemical to the sea surface are still poorly understood. Those mechanisms depend on various parameters such as the physicochemical properties of the chemicals and the specific properties of the accident surroundings. This research was conducted in collaboration with the Ecole des Mines d'Alès and Cedre in a global approach to understand the behaviour of liquid, floating and soluble chemicals released after a shipwreck. This experimental study has been carried out according to 3 main points:- The phenomenology of a release at the breach. The objectives are to quantify the flow rate and the release pattern,- The hydrodynamic behaviour of the released chemicals and their fate in the water column,- The mass transfer of the chemical during its solubilization in the water column.For each point, the results are compared to those predicted by correlations in the literature in order to propose a global model of consequences that is adapted to the marine pollution management.

La recherche développée durant cette thèse constitue la première étape de développement d’une nouvelle méthodologie de détection sans marquage à l’échelle d’une goutte : un nouveau mécanisme de transduction est développé, basé sur l’actuation par électromouillage bi-fréquence d’un réseau d’ondes capillaires à la surface d’une goutte. La résonance capillaire de la goutte est étudiée par détection interférométrique de son apex en mouvement.La faisabilité de cette méthodologie est prouvée en caractérisant la cinétique d’évaporation de la goutte par glissement spectral des ondes capillaires.La deuxième partie de la thèse porte sur la modélisation du transport de biomolécules tensioactives dans une goutte : le transport diffusif, les processus d’ad/désorption aux surfaces, la condition cinématique d’un rayon variable(évaporation) ainsi qu’une quantité molaire finie de biomolécules sont pris en compte. Un nouveau nombre adimensionnel est proposé pour rendre compte de la taille finie d’une goutte. Puis le transport chimique associé au courant de dérive induit par les ondes capillaires (excitées par électromouillage oscillatoire)est pris en compte à l’aide de simulations numériques. Finalement,l’électromouillage haute et basse fréquence est appliqué au cas d’une goutte enrichie par des molécules d’albumine de sérum bovin. En utilisant conjointement l’interférométrie optique et l’imagerie, et en considérant la loi de Lippmann-Young, le vieillissement biochimique de la surface solide mouillée par la goutte est détecté. / This PhD research is thought of as a first step towards label freedigital biosensing. A novel transduction mechanism is developed, based on thegeneration of capillary waves along a drop surface induced by dual-frequencyelectrowetting. Acapillary resonance is measured by interferometry at the movingdrop apex. Aproof of concept of this electro-optical methodology for furtherintegration in a digital microsystem is given with characterization of drop evaporationkinetics. A second part focuses on modeling and numerical calculationsof the transport of surface active biomolecules in the drop. The model includesdiffusion, ad-/desorption phenomena together with a kinematic condition of avariable drop radius (evaporation) as well as a finite molecular amount of surfaceactive biomolecules. A dimensionless number is suggested to take into accountfinite size effects. Drop steady streaming due to oscillating electrowetting isfinally taken into account. Low- and high-frequency electrowetting is appliedto a drop laden with bovine serum albumin. By jointly using interferometry andimaging, enhancement of surface ageing is made evident under electrowetting.

The chamber walls in inertial fusion reactors must be protected from the photons and ions resulting from the target explosions. One way this can be accomplished is through a sacrificial liquid wall composed of either liquid jets or thin liquid films. The x-rays produced by the exploding targets deposit their energy in a thin liquid layer on the wall surface or in the surface of liquid jets arrayed to protect the wall. The partially vaporized liquid film/jet forms a protective cloud that expands toward the incoming ionic debris which arrives shortly (a few s) thereafter. The charged particles deposit their energy in the vapor shield and the unvaporized liquid, thereby leading to further evaporation. Re-condensation of the vapor cloud and radiative cooling of the expanding plasma allow the energy deposited in the liquid to be recovered prior to the next target explosion (100ms). Chamber clearing prior to the next explosion represents a major challenge for all liquid protection systems, inasmuch as any remaining liquid droplets may interfere with beam propagation and/or target injection. Therefore, the primary objective of this research is to experimentally examine the interaction between liquid droplets and low- temperature, low-pressure plasmas under conditions similar to those expected following inertial fusion target explosions and the subsequent expansion. The data obtained in this research will be useful in validating mechanistic chamber-clearing models to assure successful beam propagation and target injection for the subsequent explosion.

An experimental study on impaction of a single drop on solid surfaces was conducted to show the effects of particles on the impact process. The parameters were: volume fraction of particles (0 to 0.3), particle size (0.47 to 250 micron), and ratio of particle size to drop size (0.00017 to 0.074). The effect of particle volume fraction on the spreading process depended on impact speed and substrate. At low impact speed, particles had little effect on the spreading except for surfaces where the equilibrium contact angle was low. For high impact speed, the influence of particles on spreading can be described by the effective viscosity. The effect of particle size on the spreading process also depended on impact speed and substrate. At low impact speed, the drop did not have enough kinetic energy to overcome the energy barrier associated with the large particles. For particle-laden liquids, retraction was affected by particle parameters. When pure liquid drops retracted from the maximum spreading ratio, the retraction appeared to be symmetric around the point of impaction while retraction of the particle-laden drop was sometimes asymmetric. Rebounding on the Teflon film depended on impact speed, particle volume fraction, and particle size. The impact speed must reach a critical value for rebounding to occur. Bouncing results suggested that the probability of bouncing decreased as viscosity increased, impact speed increased, and surface tension decreased. The non-wetting behavior and bouncing probably involved an air layer between the surface and the drop. When a low-velocity liquid drop impacts on a surface, ejection of a secondary drop from the top of the impacting drop was sometimes observed. When Renardy et al.'s (2003) criterion for the range of velocities for existence of a capillary wave was applied to for a 3.2-mm water drop; the range was between 0.2 to 1.5 m/s. However, drop ejection was observed at lower impact speed. When apparent viscosity of the particle-laden liquid obtained from Krieger's equation (1972) was used in the pure liquid models for predicting the maximum spreading ratio, good agreement between model predictions and experimental results was obtained when Park et al's model (2003) was used.