CNPq / Escoamentos bifásicos gás-líquido ocorrem em diversas atividades industriais, como, por exemplo, na exploração e produção de petróleo onde gás e óleo escoam simultaneamente em uma tubulação. Em muitas situações, as condições de eficiência e segurança dos equipamentos e processos onde ocorrem são influenciadas por este tipo de escoamento. Desta forma, extrair características e parâmetros destes padrões a partir de observações e medições experimentais é de grande importância, permitindo o estudo dos fenômenos e, podendo ser utilizada na otimização dos processos envolvidos. Em especial, neste trabalho focou-se no escoamento bifásico em regime intermitente o qual é comumente encontrado na indústria e ainda necessita de investigação. Foi utilizada a técnica conhecida como sensor de malha de eletrodos (wire-mesh) de configuração 8 x 8 eletrodos a qual produz imagens da distribuição das fases na seção transversal de uma tubulação. Com base nos dados brutos do sensor foram desenvolvidas diferentes técnicas de visualização e processamento dos dados a fim extrair características e parâmetros do escoamento intermitente. As técnicas desenvolvidas basearam-se em métodos de processamento de imagens como segmentação e filtragem. Foram realizados testes experimentais com escoamento em uma linha de testes horizontal com 9,2 m de comprimento de 26 mm de diâmetro interno, onde escoamento com diversas condições operacionais foram gerados e analisados. As técnicas desenvolvidas foram validadas através de comparações com filmagem em alta velocidade e com modelos mecanísticos empíricos disponíveis na literatura, apresentando boa concordância com valores de referência. A principal contribuição do trabalho é a disponibilização de um software para visualização e processamento de dados do sensor wire-mesh, o qual pode ser utilizado para estudos posteriores de escoamentos bifásicos. Trabalho desevolvido com bolsa de estudo concedida pelo Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). / Gas-liquid two-phase flows occur in different industrial activities, such as in oil production and exploration where gas and oil flow simultaneously in pipe. Two-phase flow determines in many situations the conditions of efficiency and safety of equipment and processes where they occur. Thus, extracting the flow characteristics and parameters from observations and experimental measurements is of great importance, allowing the study of phenomena and therefore leading to the optimization of the process involved. In particular, this work focused on the two-phase flow under intermittent flow regime which is commonly found in the industry and still needs investigation. A flow measurement technique known as wire-mesh sensor was applied with 8 x 8 electrodes configuration which produces images of the distribution of phases in the pipe cross section. Based on raw data from the sensor different visualization and data processing techniques were developed in order to extract features and parameters of intermittent flow. The techniques developed were based on methods of image processing such as segmentation and filtering. Experiments were performed in a horizontal experimental test facility with 9.2 m length of 26 mm inner diameter, whereby several operating conditions were generated and analyzed. The techniques developed have been validated through comparisons with high-speed camera and empirical mechanistic models available in the literature showing good agreement with reference values. The main contribution of this work is the development of a software for visualization and processing of wire-mesh sensor data, which may be employed for further two-phase flow studies.

IBP, FINEP, ANP / A caracterização de escoamentos bifásicos em golfadas é de grande valia para o monitoramento e controle de processos industriais em que ele ocorre. Neste cenário, o presente trabalho tem como objetivo utilizar técnicas de ultrassom, wire-mesh e filmagem de alta velocidade, para obter parâmetros que permitam a caracterização do fenômeno. Os dados experimentais foram obtidos em uma planta de testes, onde foi gerado um escoamento bifásico horizontal água-ar, no padrão em golfadas, em uma linha de 9 m de comprimento e 26 mm de diâmetro. Os dados adquiridos por ultrassom e wire-mesh foram tratados para obter informações de fração de vazio e de velocidade da bolha. Para auxiliar a análise, foram utilizadas outras técnicas como filmagens de alta velocidade e modelos mecânicos conhecidos na literatura. / Characterization of two-phase flows is important for monitoring and control of many industrial processes. In this regard, the proposed paper uses ultrasonic techniques, wire-mesh sensor and high-speed videometry to extract parameters of interest in horizontal gas-liquid two-phase slug flows. The experimental data were obtained from a test rig, where two- phase flow was generated in a horizontal line of 9 meters in length and 26mm in diameter. The ultrasound and wire-mesh data were processed to obtain parameters for characterizing the two-phase slug flow, such as void fraction and the elongated bubble velocity. To assist the analysis, other techniques such as high speed image acquisitions and theoretical models well know in the literature were used.

CNPq / Escoamentos bifásicos gás-líquido ocorrem em diversas atividades industriais, como, por exemplo, na exploração e produção de petróleo onde gás e óleo escoam simultaneamente em uma tubulação. Em muitas situações, as condições de eficiência e segurança dos equipamentos e processos onde ocorrem são influenciadas por este tipo de escoamento. Desta forma, extrair características e parâmetros destes padrões a partir de observações e medições experimentais é de grande importância, permitindo o estudo dos fenômenos e, podendo ser utilizada na otimização dos processos envolvidos. Em especial, neste trabalho focou-se no escoamento bifásico em regime intermitente o qual é comumente encontrado na indústria e ainda necessita de investigação. Foi utilizada a técnica conhecida como sensor de malha de eletrodos (wire-mesh) de configuração 8 x 8 eletrodos a qual produz imagens da distribuição das fases na seção transversal de uma tubulação. Com base nos dados brutos do sensor foram desenvolvidas diferentes técnicas de visualização e processamento dos dados a fim extrair características e parâmetros do escoamento intermitente. As técnicas desenvolvidas basearam-se em métodos de processamento de imagens como segmentação e filtragem. Foram realizados testes experimentais com escoamento em uma linha de testes horizontal com 9,2 m de comprimento de 26 mm de diâmetro interno, onde escoamento com diversas condições operacionais foram gerados e analisados. As técnicas desenvolvidas foram validadas através de comparações com filmagem em alta velocidade e com modelos mecanísticos empíricos disponíveis na literatura, apresentando boa concordância com valores de referência. A principal contribuição do trabalho é a disponibilização de um software para visualização e processamento de dados do sensor wire-mesh, o qual pode ser utilizado para estudos posteriores de escoamentos bifásicos. Trabalho desevolvido com bolsa de estudo concedida pelo Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). / Gas-liquid two-phase flows occur in different industrial activities, such as in oil production and exploration where gas and oil flow simultaneously in pipe. Two-phase flow determines in many situations the conditions of efficiency and safety of equipment and processes where they occur. Thus, extracting the flow characteristics and parameters from observations and experimental measurements is of great importance, allowing the study of phenomena and therefore leading to the optimization of the process involved. In particular, this work focused on the two-phase flow under intermittent flow regime which is commonly found in the industry and still needs investigation. A flow measurement technique known as wire-mesh sensor was applied with 8 x 8 electrodes configuration which produces images of the distribution of phases in the pipe cross section. Based on raw data from the sensor different visualization and data processing techniques were developed in order to extract features and parameters of intermittent flow. The techniques developed were based on methods of image processing such as segmentation and filtering. Experiments were performed in a horizontal experimental test facility with 9.2 m length of 26 mm inner diameter, whereby several operating conditions were generated and analyzed. The techniques developed have been validated through comparisons with high-speed camera and empirical mechanistic models available in the literature showing good agreement with reference values. The main contribution of this work is the development of a software for visualization and processing of wire-mesh sensor data, which may be employed for further two-phase flow studies.

As a safe long-term management of nuclear wastes, deep geological repositories (DGRs) have been proposed or currently being constructed in several countries. The host rocks in DGRs are saturated with water after the geological disposal facilities (GDFs) are closed and sealed. Significant gas can be generated due to several processes, e.g., the metal corrosion, water radiolysis or microbial reaction of organic materials, etc. The generated gas is anticipated to span throughout the long-term disposal of waste, which may jeopardize the stability of host rocks. Correspondingly, the performance of GDF will be affected since the host rocks provide a final impediment to the radionuclide transport. As gas migration in saturated host rocks is a highly coupled hydro-mechanical (HM) process, either gas-induced micro-fracturing or macro-fracturing may contribute to the development of preferential gas pathways, which needs to be concerned to ensure the feasibility and safety of geological disposal. Current numerical studies on the gas migration behavior devoted to explaining the experimental phenomena in the gas injection tests conducted on the rock materials, in which some behaviors still cannot be well represented, i.e., gas induced fracturing, volulme dilation, anisotropic radial deformation. Therefore, to better represent the actual physical process of preferential gas flow, two modelling frameworks, i.e., macroscopic HM framework and two-scale HM framework, are proposed in the PhD study. For the macroscopic HM framework, a double porosity model is firstly developed based on the dual continuum method, in which the volumetric strains of the porous continuum (PC) and fractured continuum (FC) are work-conjugated to the respective effective stress level. The treatment in two types of porosity allows us to capture that the opening/closure of the fractures is caused by the interaction between the dilation of the PC and the dilation of the FPM, which is beneficial to describe the gas induced fracturing in an implicit way. Then, an enriched embedded fracture model (EFM) is proposed to address the mechanical behavior of fractures. A hyperbolic relation of fracture deformability is incorporated into the rock matrix, as a result the fractured rock shows a nonlinear elastic behavior, which can capture the stiffness degradation due to fracture opening. The equivalent continuum method is provided to derive the effective compliance tensor, which includes the transverse isotropic matrix and two fracture sets. Using the enriched EFM with a three-dimensional (3D) geometry is able to capture the anisotropic radial deformation during gas migration. Although the macroscopic HM framework is able to capture the major HM behaviors related to preferential gas flow, the development of gas dilatant pathways is still represented in an implicit way. Therefore, a two-scale HM framework is developed to explicitly simulate the development of preferential gas pathways. Initiating from the periodically distributed microstructures with microcracks, the asymptotic homogenization method is used to derive the macroscopic governing equations coupled with the normalized damage variable. The time-dependent damage evolution law is obtained from the microscopic mechanical energy analysis for evolving microcracks. Both time effect and size effect are incorporated in the damage model that will affect the overall HM behavior of rocks. The developed two-scale HM framework with single gas flow can qualitatively capture important behaviors, such as the discrete pathways, localized gas flow, unstabilized fracture branching. More specifically, the simulated results demonstrates that the inter-connection of fractures from gas inlet to outlet is a prerequisite for gas breakthrough, accompanied by large amounts of gas flowing out of the sample and a rapid drop in gas injection pressure. Incorporating water flow in the two-scale framework allows the model to quantitatively reproduce the experimental phenomena observed in the laboratory air injection tests, such as gas pressure evolution and mechanical deformation. More importantly, the model exlpaines that the significant differences in controlling gas breakthrough and mechanical deformation are resulting from the arbitrary nature of microstructural heterogeneities. To account for the gas-water interaction in the two-scale HM framework, a fully coupled two-phase flow and elaso-damage model is developed to simulate the laboratory and in-situ gas injection experiments. The model can quantitatively capture the experimental behaviors, e.g., gas pressure evolution and non-desaturation phenomenon. Furthermore, model results show that the highly localized fracture pathways are the major places where gas and water interacts each other, and as a result the rock is still kept fully saturated. As a whole, the obtained numerical results are synthesized and analyzed, the pros and cons of the developed models are discussed. To better improve the model performance, some recommendations are proposed for the future studies.

In this work, we have explored 2D semiconducting transition metal dichalcogenides (TMDs), black phosphorus (BP), and graphene for various applications using liquid and mechanical exfoliation routes. The topical areas of interest that motivate our work include considering factors such as device integration, stability, doping, and the effect of gasses to modulate the electronic transport characteristics of the underlying 2D materials. In the first area, we have integrated solution-processed transparent conducting oxides (TCOs), specifically indium-doped tin oxide (ITO) with BP, which is a commonly used TCO for solar cell devices. Here we have found surface treatment of glass substrates with a plasma before spin-coating the solution-processed ITO, to be effective in improving coverage and uniformity of the ITO film by promoting wettability and film adhesion. The maximum transmittance obtained was measured to be ~75% in the visible region, while electrical measurements made on BP/ITO heterostructures showed improved transport characteristics compared to the bare ITO film. Within the integration realm, inkjet-printing of BP and MoS2 p-n hetero-junctions on standard ITO glass substrates in a vertical architecture was also demonstrated. To address the issue of stability which some 2D materials such as BP face, we experimented with ionic liquids (ILs) to passivation the hydrophilic surface of BP to minimize its oxidative degradation. The enhanced stability of BP was inferred through Raman spectroscopy and scanning probe microscopy techniques, where no observable changes in the A1g and A2g Raman vibrational modes were observed for the BP films passivated with ILs over time under ambient conditions. On the other hand, a blue-shift in these Raman modes was evident for unpassivated samples. Atomic force microscopy measurements on the unpassivated samples clearly revealed the difference in surface characteristics through localized regions of degradation that intensified with time which was absent in IL passivated BP samples. The electronic device measurements for IL coated BP devices showed a more stabilized Ids−Vds characteristic in the 5.4 K to 335 K temperature range. Prototypical demonstrations of stabilized ILs/BP devices at ambient printed on flexible polyimide substrates were also successfully made. At the same time, doping is one of the essential steps required for the modulation of carrier density and electronic transport in electronic and optoelectronic devices, which is the third topical area we have addressed in this work with semiconducting TMDs. Of the conventional approaches used to dope 3D semiconductors, ion-implantation is commonly adopted but given the ultra-thin nature of 2D materials, this approach is not feasible as it causes severe damage to the delicate crystalline lattice of ultra-thin 2D membranes. Instead, we have used plasma-based doping routes with UV-ozone treatement and solution processing using 1,2 dichloroethane, to characterize the temperature-dependent two-terminal and three-terminal electronic and optoelectronic transport of mechanically exfoliated 2D MoS2 and WSe2. A significant difference was seen in the optoelectronic properties between the two dopants, owing to differences in their respective doping mechanisms and the intrinsic structural attributes of the exfoliated flakes. A significant reduction in barrier height was evident after doping using both techniques in MoS2, while an increase in barrier height after soaking in 1,2 dichloroethane was seen in WSe2. Lastly, in the fourth topical area for sensing devices, we have studied the effect of gas-flow in inkjet-printed and spin-coated graphene and MoS2 to modulate the electronic transport for the 2D materials since their increased surface area is an ideal platform to observe interactions with external stimuli, in this case, in-coming gas species. Here, the chamber pressure and change in current with flow of gas was measured in the steady-state, as well as time-dependent dynamic transport toward nitrogen and carbon dioxide. We observed significant differences in the electrical response of mono-elemental graphene and binary MoS2, owing to differences in microstructure and joule heating response to the ambient gas. In conclusion, the findings obtained from our work will provide an important framework to help guide strategies in further improving integration schemes, stability, doping and sensing behavior driven by the unique structural attributes inherent to 2D materials for high-performance devices in the future.

Carbon dioxide (CO2) is a common working fluid for refrigeration systems. The triple point of CO2 (about −56 °C and 0.51 MPa) is often regarded as the lower operating limit for the con-ventional CO2 vapor compression systems, because below this temperature and pressure, solid CO2 could occur and block the system components. However, if the technical issue could be solved and a stable operation of a vapor compression cycle for heat absorption be-low the triple point pressure (or sublimation cycle) could be realized, there would be a great potential for CO2 to replace the common refrigerants with a very high environmental impact such as R-23 for refrigeration applications below −50 °C. The focus of this work is on the dis-cussion of the feasibly of the sublimation cycle regarding the energy efficiency and the block-ing issues. Seven different two-stage and three-stage CO2 sublimation systems are theoretically evalu-ated and compared to a two-stage R-23 system, which serves as a baseline. A calculation model for the systems is developed. The optimum intermediate pressures for each system as well as the high pressure for the systems in transcritical operations are calculated within the given temperature and pressure constraints. Multiple influence factors, such as the ambient temperature, compressor efficiency, are considered in determining the operating limit and evaluating the performance for each system. In order to find out the cause of the blockages in the sublimation system due to the solid CO2, the solid-gas flow is visualized through experiments. Different throttling devices are investi-gated under various inlet conditions. As the sublimator, a heated sight glass assembly is used. It is found that besides the inlet temperature and pressure condition, the tube wall in the down-stream section of the throttling devices has a great influence on the blockages. A larger heat flux also helps to reduce the blockage in the sublimator. Based on the knowledge gained from the theoretical investigation of the cycle variant and preliminary experiments, a cascade sublimation system is designed, constructed and tested. Despite the fact that the system still requires optimization in terms of energy efficiency and operation stability, it is capable of long continuous operation, and thus the basic feasibility of the sublimation cycle is verified. Finally, the further issues and improvement potentials for the heat transfer and sublimator are discussed.:Acknowledgment Abstract Contents Index of figures Index of tables List of abbreviations and symbols 1 Introduction 1.1 Background and Motivation 1.2 Objective and procedure 2 Fundamentals and state of the art 2.1 The R-744 sublimation cycle 2.2 Expansion into solid-gaseous region and critical flow 2.3 Sublimator and solid-gas two-phase flow 2.4 Summary 3 Thermodynamic analysis of sublimation systems 3.1 Definition of the cycle variants 3.1.1 The baseline system 3.1.2 R-744 cascade systems 3.1.3 R-744 booster systems 3.2 Boundary conditions 3.3 Description of the models 3.3.1 Compressor 3.3.2 Heat exchangers 3.3.3 Other components 3.3.4 Fluid properties 3.4 Process calculation and optimization 3.5 Results and discussion 3.5.1 General boundary conditions 3.5.2 Variable temperatures 3.5.3 Variable compressor efficiency 3.5.4 Variable pressure loss and superheating in the sublimator 3.6 Evaluation of the system variants 4 Experimental visualization of the solid-gas flow 4.1 Throttling below the triple point 4.1.1 Experimental setup - test rig I 4.1.2 Results and discussion 4.2 CO2-Sublimation in a horizontal channel 4.2.1 Experimental setup - test rig II 4.2.2 Results and discussion 4.3 Summary 5 Experimental investigation on the performance of a cascade sublimation system 5.1 Experimental setup – test rig III 5.1.1 The refrigerant cycles 5.1.2 The sublimating unit 5.2 Methodology 5.2.1 The measuring procedure 5.2.2 Data evaluation and uncertainty analysis 5.3 Results and discussion 5.3.1 Transient behavior 5.3.2 System performance 5.3.3 Compressor performance 5.3.4 Long period measurements 5.4 Summary 6 Existing issues and optimization potentials 6.1 Blockage-free operation at low wall temperatures 6.1.1 Supplementary experiment 6.1.2 Outlook 6.2 Heat transfer 6.2.1 Supplementary experiment 6.2.2 Outlook 7 Summary Literature Appendix A. Differential evolution A.1 Basics of differential evolution A.2 Convergence of the results for different system variants Appendix B. Mass flow rate from the capillary tubes B.1 Measurement of the mass flow rate B.2. Comparison of the results with the numerical model and correlations Appendix C. Supplement to the measurements of the test rig III C.1 Exemplary measurement of the R-23 operation C.2. Measurement of the air velocity for the sublimator Appendix D. Supplement to the measurements at low wall temperatures D.1. Calculation of the heat transfer coefficients for the airside D.2. Determination of the local sublimation heat transfer coefficients Publications during the PhD study

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Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Distillation column design and operation require understanding of both the hydrodynamic and thermodynamic behaviour and limitations. One of the hydrodynamic aspects that negatively influence separation efficiency in the distillation column is entrainment of the liquid with the rising vapour or gas. Inaccurate entrainment predictions will lead to poor separation efficiencies in the column and consequently over design of the column diameter and/or height has to be incorporated. This has a significant impact on the capital cost due to the size and scale of industrial columns. Therefore, small improvements in entrainment prediction will lead to large savings in capital investment. Previous research published in the open literature focused primarily on the influence of gas and liquid flow rates and, tray geometry on entrainment for the air/water system. Consequently the non-air/water database is small and consists of data obtained from various tray and column geometries. As a result the accuracy of current entrainment prediction models is questionable for systems other than air/water. Therefore, the first objective of this work was to investigate whether current prediction models perform well for systems other than air/water. To prove this air/water, air/ethylene glycol and air/silicon oil data were measured and compared with current prediction correlations. It was found that current prediction models perform poorly for the air/ethylene glycol and air/silicone oil systems. At the same time a new observation was made with regard to froth development and behaviour inside the column. The observation shows that liquid flow rate has a nonmonotonic influence on entrainment, caused by the short (475mm) tray flow path. The second objective was to examine the influence of gas physical properties on entrainment. New entrainment data were measured by individually contacting air, CO2 and SF6 with water and ethylene glycol, while n-butanol was contacted with CO2 and SF6. The data was compared with current prediction models which performed poorly for SF6 results. This shows the inability of these models to predict entrainment for gas systems with high densities. Modified Reynolds and Froude numbers were developed to show the influence of gas physical properties on entrainment. Low modified Reynolds numbers and large modified Froude numbers resulted in high entrainment. The third objective was to determine the influence of liquid physical properties on entrainment. New entrainment data were measured using CO2 with Isopar G, n-butanol, water, silicone oil and ethylene glycol. Current prediction models compared poorly to the data and did not include the influence of liquid viscosity on entrainment. It was found that viscosity had an intricate non-monotonic influence on entrainment. The fourth and final objective was to correlate the influence of gas and liquid properties on entrainment as determined by the previous two objectives. To make the dataset more complete, entrainment was measured for four tray spacings using CO2/Isopar, CO2/nbutanol, air/ethylene glycol, CO2/ethylene glycol, air/silicone oil and CO2/silicone oil (over 1700 data points). Two new correlations are presented to predict the fraction of liquid entraining with the rising gas (L’/G with R2 = 85%) and the fraction of liquid entering the tray that entrains (L’/L with R2 = 92%). The performance of the L’/G correlation (R2 = 85%) is vastly superior to two other prominent correlations (R2 = 61% and 23%). This correlation can be implemented to predict entrainment successfully for different tray geometries by combining the predicted influence of tray geometry, by Kister and Haas (1988), with results from the newly developed correlation. All four objectives are presented as manuscripts for journal publication and serve as alone standing documents. / AFRIKAANSE OPSOMMING: Distillasie kolom ontwerp en bedryf vereis begrip van beide die hidrodinamiese en termodinamiese gedrag en beperkings. Een van die hidrodinamiese aspekte wat skeiding doeltreffendheid negatief beïnvloed in die distillasie kolom is meesleuring van die vloeistof met die stygende dampe of gas. Onakkurate meesleuring voorspellings sal lei tot swak skeiding doeltreffendheid in die kolom en gevolglik word die ontwerp van die kolom deursnee en / of hoogte beinvloed. Dit het 'n beduidende impak op die kapitale koste as gevolg van die grootte en skaal van industriële kolomme. Klein verbeterings in meesleuring voorspelling sal dus lei tot groot besparings in kapitaal belegging. Vorige navorsing gepubliseer in die oop literatuur het hoofsaaklik gefokus op die invloed van gas- en vloeistof vloeitempos en plaat geometrie op meesleuring vir die lug/water sisteem. Gevolglik is die nie-lug/water databasis klein en bestaan van die data wat verkry is uit verskeie plaat en kolom-geometrieë. As gevolg is die akkuraatheid van die huidige meesleuring voorspelling modelle vir stelsels anders as lug/water te betwyfel. Daarom is die eerste doel van hierdie werk om ondersoek in te stel of die huidige voorspelling modelle goed presteer vir stelsels anders as lug/water. Om dit te bewys was lug/water, lug/etileenglikol en lug/silikon olie data gemeet en vergelyk met die huidige voorspelling korrelasies. Daar is bevind dat die huidige voorspellings modelle swak presteer vir die lug/etileenglikol en lug/silikon olie. Op dieselfde tyd was 'n nuwe waarneming gemaak met betrekking tot dispersie ontwikkeling en gedrag binne die kolom. Die waarneming toon dat vloeistof vloeitempo 'n nie-monotoniese invloed op meesleuring het, veroorsaak deur die kort (475mm) plaat vloei pad lengte. Die tweede doelwit was om die invloed van gas fisiese eienskappe op meesleuring te ondersoek. Nuwe meesleuring data was gemeet deur individuele kontak van lug, CO2 en SF6 met water en etileenglikol, terwyl n-butanol slegs met CO2 en SF6 inkontak gebring was. Die eksperimentele resultate word vergelyk met die huidige voorspellings modelle wat swak presteer invergelyking met SF6 resultate. Dit toon die onvermoë van hierdie modelle om meesleuring vir gas stelsels met hoë digthede te voorspel. Gemodifiseerde Reynolds en Froude getalle was ontwikkel om die invloed van gas fisiese eienskappe op meesleuring aan te toon. Lae gemodifiseerde Reynolds getalle en groot gemodifiseerde Froude getalle lei na hoë meesleuring. Die derde doelwit was om die invloed van vloeistof fisiese eienskappe op meesleuring te bepaal. Nuwe meesleuring data is gemeet deur gebruik te maak van CO2 met Isopar G, nbutanol, water, silikon olie en etileenglikol. Huidige voorspellings modelle vergelyk swak met die data en sluit nie die invloed van vloeistof viskositeit op meesleuring in nie. Daar is gevind dat viskositeit 'n ingewikkelde nie-monotoniese invloed op meesleuring het. Die vierde en finale doelwit was om die invloed van die gas en vloeistof eienskappe op meesleuring soos bepaal deur die vorige twee doelwitte te korreleer. Om die datastel meer volledig te maak, is meesleuring vir vier plaat spasiërings met CO2/Isopar, CO2/n-butanol, lug/etileenglikol, CO2/ethylene glycol, lug/silikon olie en CO2/silikon olie (meer as 1700 data punte gemeet). Twee nuwe korrelasies word aangebied om die fraksie vloeistof wat meegesleur word met die stygende gas (L’/G met R2 = 85%) en die fraksie vloeistof wat die plaat binnetree wat meegesleur word (L’/L met R2 = 92%) te voorspel. Die prestasie van die L’/G korrelasie (R2 = 85%) is aansienlik beter as twee ander prominente korrelasies (R2 = 61% en 23%). Hierdie korrelasie kan suksesvol geïmplementeer word om meesleuring vir verskillende plaat geometrieë te voorspel deur die voorspelde invloed van plaat geometrie deur Kister en Haas (1988), met die resultate van die nuut ontwikkelde korrelasie te kombineer. Al vier doelwitte word as manuskripte vir joernaal publikasie aangebied en dien as alleenstaande dokumente.

<p>During operation of heavy ion accelerators a significant pressure rise has been observed when the intensity of the high energy beam was increased. The cause for this pressure rise is ion induced desorption, which is the result when beam ions collide with residual gas molecules in the accelerator, whereby they undergo charge exchange. Since the change in charge state will affect the bending radius of the particles after they have passed a bending magnet, they will not follow the required trajectory but instead collide with the vacuum chamber wall and gas are released. For the Future GSI project FAIR (Facility for Antiproton and Ion Research) there is a need to upgrade the SIS18 synchrotron in order to meet the requirements of the increased intensity. The aim of this work was to measure the desorption yields, η, (released molecules per incident ion) from materials commonly used in accelerators: 316LN stainless steel, Cu, Etched Cu, gold coated Cu, Ta and TiZrV coated stainless steel with argon and uranium beams at the energies 5-100 MeV/u. The measurements were performed at GSI and at The Svedberg Laboratory where a new dedicated teststand was built. It was found that the desorption yield scales with the electronic energy loss to the second power, decreasing for increasing impact energy above the Bragg Maximum. A feasibility study on the possibility to use laser refractometry to improve the accuracy of a specific throughput system was performed. The result was an improvement by up to 3 orders of magnitude, depending on pressure range.</p>