Recent studies have shown that, in a sufficiently deep gas-solid fluidized bed of Geldart A particles, gas streaming may occur allowing gas to bypass a large portion of the particle bed. Since this is a newly observed phenomenon in fluidized beds, there is uncertainty and lack of information about the various aspects of the streaming flow. The objective of the current project is to investigate the streaming phenomenon with a combination of experimentation and modeling. In the experimental part, pressure fluctuations as a measure of the fluidized bed hydrodynamics were used to study the influence of different parameters on the behavior of a deep fluidized bed. Pressure fluctuations have been measured at 8 axial locations from 4 to 150 cm above the gas distributor for bed depths and gas velocities ranging from 0.4 to 1.6 m and 0.04 to 0.20 m/s (equal to 10 to 50 times minimum fluidization velocity), respectively. Two particle size distributions with Sauter mean diameters of 48 µm and 84 µm and two distributor plates with differing percentage open area were also tested for each bed depth and gas velocity. Analysis of pressure fluctuations in the time and frequency domains, in combination with visual observations revealed that streaming flow emerges gradually at bed depths greater than 1 m. Increased gas velocity and fines content act to delay the onset of streaming, but can not completely eliminate it over the range of velocities examined. The two different distributor designs had no measurable effect on the streaming flow. The results of this study are provided in the first section of the present report.<p> In order to further investigate the nature of streaming flow, several cases of forced streams and jetting flows were designed and conducted, in addition to the natural streaming flow in deep beds. Results indicated that the natural streaming most closely resembles the imposed stream which not only the imposed stream, but additional gas added through the distributor. The case of jet flows with no additional gas resembles the severe streaming that might happen in very deep beds with the existence of completely non-fluidized regions. Application of supporting jets in addition to the main gas flow could enhance the fluidization quality to some extent, however, not enough to provide a normal fluidization. Wavelet analysis of the pressure fluctuations showed that in deep fluidized beds, bubbling activity with the typical dominant frequency coexist with the streaming flow, with a minor contribution. Wavelet findings suggested that the streaming flow can be considered to form by increasing the relative importance of one available stream of bubble activity with increasing bed depth. The results of this study are provided in the second section of this report. Further study of the streaming flow was undertaken with computational fluid dynamic (CFD) simulation of the deep fluidized bed. CFD simulation of fine Geldart A particles has met with challenges in the open literature and various modifications have been proposed to be able to model fluidized beds of these particles. In the present work, the commercial CFD codes FLUENT and MFIX were initially tested for the modeling of deep fluidized bed of Geldart A particles. However, simulation results did not show any sign of streaming flow in the fluidized bed. Subsequently, the commercial CFD code BARRACUDATM that has been claimed by the developers to be appropriate for this purpose, was tested. Due to the lack of data on the performance of this code, a simple case of modeling a freely bubbling fluidized bed of Geldart A particles was attempted first. For this purpose, four different simulation cases, which included three different numerical grid sizes and two drag models with a realistic particle size distribution were designed and tested. The simulated bed expansion, bubble size distribution, rise velocity and solid fraction were compared with commonly accepted correlations and experimental data from the literature. The results showed a promising predictive capability of the code without the need for modifying the drag model or other constitutive relations of the model. The third section of the report presents the simulation results of this study.<p> The BARRACUDA code was then used for simulating the deep fluidized bed of Geldart A particles. However, similar to the previous CFD codes tested, instead of streaming flow, bubbling fluidization was predicted. Therefore, a phenomenological model was developed to better understand the streaming flow. According to the model results, the stream represents a zone of much lower pressure drop compared to other parts of the bed, which can be a possible reason for the formation and stability of the streaming flow inside the fluidized bed. The model results showed that increasing the bed depth enhances the streaming flow, while increasing the gas velocity improves the uniformity of the bed and decreases the streaming severity. Streaming flow was found to be less severe for larger particle sizes. All of these trends are in conformity with the experimental results. These findings provide the content of the fourth and final section of this report.

Recent studies have shown that, in a sufficiently deep gas-solid fluidized bed of Geldart A particles, gas streaming may occur allowing gas to bypass a large portion of the particle bed. Since this is a newly observed phenomenon in fluidized beds, there is uncertainty and lack of information about the various aspects of the streaming flow. The objective of the current project is to investigate the streaming phenomenon with a combination of experimentation and modeling. In the experimental part, pressure fluctuations as a measure of the fluidized bed hydrodynamics were used to study the influence of different parameters on the behavior of a deep fluidized bed. Pressure fluctuations have been measured at 8 axial locations from 4 to 150 cm above the gas distributor for bed depths and gas velocities ranging from 0.4 to 1.6 m and 0.04 to 0.20 m/s (equal to 10 to 50 times minimum fluidization velocity), respectively. Two particle size distributions with Sauter mean diameters of 48 µm and 84 µm and two distributor plates with differing percentage open area were also tested for each bed depth and gas velocity. Analysis of pressure fluctuations in the time and frequency domains, in combination with visual observations revealed that streaming flow emerges gradually at bed depths greater than 1 m. Increased gas velocity and fines content act to delay the onset of streaming, but can not completely eliminate it over the range of velocities examined. The two different distributor designs had no measurable effect on the streaming flow. The results of this study are provided in the first section of the present report.<p> In order to further investigate the nature of streaming flow, several cases of forced streams and jetting flows were designed and conducted, in addition to the natural streaming flow in deep beds. Results indicated that the natural streaming most closely resembles the imposed stream which not only the imposed stream, but additional gas added through the distributor. The case of jet flows with no additional gas resembles the severe streaming that might happen in very deep beds with the existence of completely non-fluidized regions. Application of supporting jets in addition to the main gas flow could enhance the fluidization quality to some extent, however, not enough to provide a normal fluidization. Wavelet analysis of the pressure fluctuations showed that in deep fluidized beds, bubbling activity with the typical dominant frequency coexist with the streaming flow, with a minor contribution. Wavelet findings suggested that the streaming flow can be considered to form by increasing the relative importance of one available stream of bubble activity with increasing bed depth. The results of this study are provided in the second section of this report. Further study of the streaming flow was undertaken with computational fluid dynamic (CFD) simulation of the deep fluidized bed. CFD simulation of fine Geldart A particles has met with challenges in the open literature and various modifications have been proposed to be able to model fluidized beds of these particles. In the present work, the commercial CFD codes FLUENT and MFIX were initially tested for the modeling of deep fluidized bed of Geldart A particles. However, simulation results did not show any sign of streaming flow in the fluidized bed. Subsequently, the commercial CFD code BARRACUDATM that has been claimed by the developers to be appropriate for this purpose, was tested. Due to the lack of data on the performance of this code, a simple case of modeling a freely bubbling fluidized bed of Geldart A particles was attempted first. For this purpose, four different simulation cases, which included three different numerical grid sizes and two drag models with a realistic particle size distribution were designed and tested. The simulated bed expansion, bubble size distribution, rise velocity and solid fraction were compared with commonly accepted correlations and experimental data from the literature. The results showed a promising predictive capability of the code without the need for modifying the drag model or other constitutive relations of the model. The third section of the report presents the simulation results of this study.<p> The BARRACUDA code was then used for simulating the deep fluidized bed of Geldart A particles. However, similar to the previous CFD codes tested, instead of streaming flow, bubbling fluidization was predicted. Therefore, a phenomenological model was developed to better understand the streaming flow. According to the model results, the stream represents a zone of much lower pressure drop compared to other parts of the bed, which can be a possible reason for the formation and stability of the streaming flow inside the fluidized bed. The model results showed that increasing the bed depth enhances the streaming flow, while increasing the gas velocity improves the uniformity of the bed and decreases the streaming severity. Streaming flow was found to be less severe for larger particle sizes. All of these trends are in conformity with the experimental results. These findings provide the content of the fourth and final section of this report.

No description available.

This work examines the fundamental behaviour of granular materials in packed/moving beds under simplified blast furnace conditions. Such study has a significant impact on the development of new technology such as pulverized coal injection and the performance of blast furnace operation. Experiments have shown that a number of interesting phenomena appear in blast furnace operation. These phenomena involve rich granular dynamics which currently attract strong interest from a wide scientific and engineering. However, previous work on this area, limited by the research techniques, is predominantly at large scales focusing on phenomenological descriptions, but rarely touching on the basic fundamentals governing these phenomena. A novel discrete element simulation at an individual particle level can overcome these problems. For this purpose, this work conducts a systematic study of these important phenomena, including crater formation, coke collapse, creep motion and particle percolation, by use of the discrete element method (DEM). The experiments and simulations conducted in the impact of a particle stream onto a particle bed using a 20 slot model suggest that the DEM can reproduce the experimental results well under comparative conditions. The crater size is shown to be affected by the discharging rate, discharging height and materials properties, and is related to the ratio of the input energy from the falling stream to the inertial energy from the original packing. Fundamental understanding of coke collapse based on three different configurations: batch charging, self loading and load impact have been investigated. It was found that coke collapse is a kind of continuous avalanche due to top layer particles spreading. Apparent frozen layer under rapidly flowing layer is not stationary and slowly creep motion can be detected at an arbitrary depth. The mean velocity of creep motion decays exponentially with depth. Percolation happens due to both gravity and strain. The percolation velocity under gravity is much greater than that under shear. Size ratio effect is most significant. For size ratio smaller than threshold gravity induced percolation dominate otherwise shear due to the descending of the packed bed. Additionally, this work demonstrates the value of DEM as a tool for complementing experimental observations.

No description available.

No description available.

No description available.

Packed bed reactors are widely used in the chemicals industry and have been studied carefully in the last century. Several reaction engineering models have been developed in order to predict the behavior of such reactors under specified conditions, in order to assist in the sizing during an industrial process conception. These reactors can be categorized using different parameters, and the bed-to- particle diameter ratio - N - is one of them. It has been shown that this parameter influences greatly the transfer phenomena that occur in the bed, and that for ratios under 10, particular attention is needed when considering the wall effects. An impor- tant point that has to be evaluated is the accuracy of the actual chemical reaction engineering models when simulating such beds as it is valid to question the hypoth- esis of a pseudo-continuum model when considering a low bed-to-particle diameter ratio bed. Through high precision Computational Fluid Dynamics calculations, several beds of particles are modeled and studied in term of mass dispersion and reaction rate distribution. Two reaction engineering models - a simple pseudo-continuum model with effectiveness factor, and a model we refer to as "Single pellet" model - and several correlations regarding Peclet numbers are then evaluated under the same conditions in order to determine their accuracy and reliability for that particular kind of bed. Two beds of N = 5.96 and N = 7.99 are studied for dispersion phenomena, and the bed of N = 5.96 is studied for reaction rate distribution. It is shown that the pseudo- continuum model of dispersion stands valid for the higher N, but that none of the correlations we used were able to correctly predict the behavior of the N = 5.96 bed at any of the Reynolds number we considered, only giving close behaviors. We were confronted with some difficulties regarding the reaction simulation under Fluent, but some comparisons were successfully made regarding species and reaction rate distribution in the bed.

The Upper Cretaceous Cerro Toro Formation, southern Chile, is characterised by thinbedded turbidites that envelope a series of coarse-grained, confined slope complex systems, interpreted as part of the Lago Sofia Member. This deep-water slope system overlies basin floor sheets of the Punta Barrosa Formation, and is overlain by the sand-filled slope channels of the Tres Pasos Formation. Particularly distinctive beds, known as TEDs (transitional event deposits), are up to 40 m thick, laterally extensive, have prominent fluted bases, and have a vertical fabric starting with (1) a thin, inversely-graded, clast-supported base; then (2) a normally-graded and clastsupported interval; (3) an increasingly sand and clay matrix-supported conglomerate, with (4) a progressive upwards increase in matrix and normally grading, both in the floating gravel clast and matrix grain sizes, towards the top; and (5) a co-genetic sandstone on top. In the Cerro Toro formation, these TEDs tend to occur as multiple beds in the initial phases of deposition of each channel complex system. The TEDs are highly aggradational, slightly more amalgamated in the channel-axis, and more layered towards the margins. The fabric of these spectacular event beds is described in some detail from measured sections, combined with petrographic analysis and high-resolution field mapping. The 4 km x 200 m channel systems are contained within topographically irregular bathymetric lows that formed sediment pathways, interpreted to be either the result of slope deformation, or contained by poorly preserved, tectonically disrupted or slumped external levee. Syn-sedimentary tectonism is interpreted to be responsible for sharp changes in the system's architecture from channels to ponds, marked by a sharp change in lithofacies from dominantly conglomerates to dominantly sandstones. A refined architectural analysis is proposed, focusing on the recurrent pattern of at least 5 cycles of conglomerate-filled channel systems – ponded sheet sandstones.

<p>Förekomst av trycksår utgör ett omfattande problem inom hälso- och sjukvården fortfarande trots</p><p>kunskap om förebyggande faktorer som presenteras i litteraturen. Detta medför att det</p><p>förebyggande omvårdnadsarbetet avseende trycksår även i fortsättning kan vara en mycket</p><p>angelägen fråga för sjuksköterskan. Syftet i föreliggande studie är därför att belysa</p><p>omvårdnadsåtgärder som kan utföras i vårdbädden för att förebygga trycksår hos äldre.</p><p>Litteraturstudie valdes som metod. Sökorden; pressure ulcer, prevention, bed and mattresses,</p><p>scoles, skin-care, decubitus ulcer, aged och nursing används. För att elektronisk söka relevanta,</p><p>vetenskapliga artiklar i databaserna CINAHL och MEDLINE. Resultatet bygger på åtta</p><p>vetenskapliga artiklar som kvalitetsgranskades. Vid dataanalysen användes en modifierad form av</p><p>komponenten nr 4 i Viginia Hendersons omvårdnadsteori som teoretisk utgångspunkt. Resultatet</p><p>redovisas utifrån två huvudrubriker med två respektive tre underrubriker. Den första</p><p>huvudrubriken är: Hur kan patienter med risk för utveckling trycksår identifieras? Med</p><p>underrubrikerna: Sjuksköterskans kunskaper och bedömningsinstrument. Resultatet visar att</p><p>sjuksköterskan utför riskbedömningar för att identifiera patienter i riskzon men att dessa inte är</p><p>tillräckligt omfattande och att visa faktorer såsom födo-och vätskeintag saknas i bedömning.</p><p>Studien visar också att det finns många olika riskbedömningsinstrument (skalor) med olika</p><p>variabler för att identifiera patienter som ligger i riskzonen för att utveckla trycksår. Den andra</p><p>huvudrubriken är: Att hjälpa patienten inta lämplig kroppsställning när han / hon ligger samt att</p><p>växla ställning, omfattar underrubrikerna: intervall, position och hjälpmedel. Resultatet visar att</p><p>vändning på en tryckreducerande madrass leder till minskning av trycksår grad II-IV. Litteraturen</p><p>visar även att patientens position i vårdbädden inte bör överstiga 30 grader av huvudändan för att</p><p>undvika för höga tryck mot korsbenet generellt ger lägre tryck på patientens hud. Hjälpmedel som</p><p>rekommenderas för tryckavlastning på häl och korsben är exempelvis gelkuddar.</p>