Photocatalysis is a green technology that has been widely used in wastewater treatment. In this work, mass transfer processes in corrugated photocatalytic reactors were characterized both experimentally and through computer simulations. For the experimental work, various drum rotational speeds, reactor liquid volumes and number of corrugations were studied to elucidate their effects on mass transfer phenomena. The mass transfer rate was found to increase with increasing rotational speed. Liquid volumes in the reactor significantly affect the mass transfer rate when 20% of the surface area of the drum was immersed. A higher mass transfer rate was found using the drum with 28 corrugations, which had the lowest mass transfer coefficient when compared to the drums with 13 and 16 corrugations. In the computer simulations, velocity and concentration fields within the corrugated reactors were modelled to explore the characteristics of mass transfer processes. The mass transfer coefficients predicted by the simulations were lower than those measured experimentally due to mass transfer limitations occurring between the corrugation volume and bulk solution in the simulations. Based on mass transfer characteristics, it was determined that the drum with 28 corrugations was the most efficient photocatalytic reactor, and had the lowest mass transfer coefficient among those studied.

Though heating, insulation, wall claddings and cavity-wall construction are considered as measures for remediating moisture and condensation in buildings, ventilation of wall cavities has however become a mantra among architects and other building professionals. Holes of any size and shape are made and located on building facades based on the accepted wisdom that a little air movement will keep the wall cavities dry. Whilst ventilation has been found to be successful in the control of moisture and condensation in rooms and larger enclosures, there is however insufficient understanding of how it works in thin spaces with high aspect ratios, such as the wall cavities studied in this thesis.In order to put in place good control and management practices in the remediation of moisture and condensation in vertical wall cavities by natural ventilation, it is vital to understand the dynamics of airflow in these cavities. In this thesis therefore, different size and shape of slots were employed to numerically investigate the effects of size, spacing and number of the slots on the characteristics of the velocity fields (patterns of airflow and distributions of velocity) in different cavity models. The Reynolds-Averaged-Navier-Stokes (RANS) methodology was employed to simulate the cavity flows under different modelling conditions using FLUENT. The BS 5925 model, an empirical relation for predicting ventilation rates in rooms and other larger enclosures, was employed and modified to predict ventilation rates in these cavities. Experimentally, the mapping of the airstreams in these cavities was obtained under similar reference (inlet) wind speeds employed for the numerical investigations.The results of this study show that there exists a potential at higher wind speeds for natural ventilation in the remediation of moisture and condensation in the cavities of vertical walls. The steady state approach employed in the RANS-based computation of cavity flows in this thesis averages out the peak values of air velocities and therefore gives no information about regions of maxima or minima velocity values even at higher wind speeds. This makes the predicted air change rates insensitive to the inlet air velocities from the ventilation slots and therefore makes the results more applicable for long term control and management of moisture in these cavities. In order to therefore put in place short, medium and long term plans for remediation of moisture in these wall cavities, a time-dependent computation is required. This will also allow the efficiency of the cavity ventilation to be properly assessed. Using the modified BS 5925 model, reasonable predictions were obtained for the air change rates of the wall cavities with the different size of ventilation slots employed. Close agreements are also obtained at lower and higher wind speeds between the predicted ventilation rates from the modified BS 5925 model and the experimental results employed as benchmark for validating the results.

Understanding why fish move the way in which they do has applications far outside of biology. Biological propulsion has undergone millions of years of refinement, far outpacing the capabilities of anything created by man. Research in the areas of unsteady/biological propulsion has been increasing in the last several decades with advances in technology. Researchers are currently conducting experiments using pitching and heaving airfoils, mechanized fish, and numerical fish. However, the surrogate propulsors that are being used in experiments are driven analytically, whereas in this study, a method has been developed to exactly follow the motion of swimming fish. The research described in this thesis couples the image analysis of swimming fish with computational fluid dynamics to accurately simulate a virtual fish. Videos of two separate fish swimming modes were analyzed. The two swimming modes are termed `free-stream swimming' and the `Kármán gait'. Free-stream swimming is how fish swim in a section of water that is free of disturbances, while Kármán gait swimming is how fish swim in the presence of a vortex street. Each swimming mode was paired with two simulation configurations, one that is free of obstructions, and one that contains a vortex street generating D-section cylinder. Data about the efficiency of swimming, power output, and thrust production were calculated during the simulations. The results showed that the most efficient mode of swimming was the Kármán gait in the presence of a Kármán vortex street. Evidence corroborating this has been found in the literature. The second most efficient means of swimming was found to be free-stream swimming in the absence of obstructions. The other two configurations, which are not observed in experiments, performed very poorly in regard to swimming efficiency.

Heat exchangers and steam headers are at the heart of any boiler and are susceptible to a range of failures including tube leaks, ligament cracking, creep and fatigue. These common forms of header failure mechanisms can be exacerbated by local thermal stresses due to temperature and flow maldistribution at full and partial boiler load operations. The purpose of this project is to develop process models of the outlet stubbox header of a final superheater (FSH) heat exchanger in a 620MW coal-fired drum type boiler. The process models were used to assess the impact of steam flow and temperature distribution on the thermal stresses in the header material. The process models were developed using Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA). Thermocouples were installed at key locations on the stubbox headers to monitor metal temperatures and the measured metal temperatures served as boundary values and for validation of the CFD results. The thermocouple data was analysed for three different steady state boiler loads, namely full load, 80% load and 60% load. It showed that the temperature distribution across these headers was not uniform, with a maximum temperature difference across the outlet stubbox of 40℃ at full load and 43℃ at partial loads. Other relevant power plant data, such as steam pressure, was provided from the power plant's Distributed Control System (DCS) and was used as boundary conditions for the CFD models. The exact mass flow distribution across the inlet stubs of the outlet stubbox header was unknown and was estimated using a CFD model of the inlet stubbox header and steam mass flow values from power plant's DCS system. A CFD model was created for each of the three boiler loads at steady state conditions. The CFD results provided the metal temperature profile, internal steam temperature distribution and pressure distribution across the header. The CFD solid temperatures were validated using the thermocouple readings and found to be in agreement. The CFD results were exported to the FEA models, where specific displacement constraints for thermal expansion were utilised. The FEA models were used to assess the extent of thermal stresses due to thermal expansion only, as well as stresses due to thermal expansion combined with internal pressure. High local stresses were found at the borehole crotch corners of the rear outlet branch and inlet stubs. However, these are below 0.2% proof strength at elevated temperatures. The high local stresses thus did not result in local plastic deformation but contribute to exacerbate steady state failure mechanisms such as creep.

Solid Oxide Fuel Cells (SOFCs) are a promising technology in the power-generation sector because of their ability to use either hydrocarbons or pure hydrogen. However, introducing hydrocarbons to SOFCs has the negative effect of poisoning the anode of the SOFC with carbon molecules. These carbon deposits in the anode place mechanical stress on the anode and crack the anode interrupting the nickel-based electron percolation network. Gradual interruption of this network increases anode electrical resistance and can eventually lead to complete SOFC functional failure. However, one technology that may reduce premature anode failure due to carbon deposition is the use of a getter anode. A getter anode intercepts the carbon prior to deposition on the functional anode. In this work, A CFD model was modified to incorporate a getter anode, and the functional anode in the study saw a roughly 60% drop in carbon deposition with the addition of a 0.1mm getter anode, compared to the baseline. Also a trend was found that total carbon deposited on the functional anode decreased as the porosity of the getter anode decreased. However, lengthening the getter anode and decreasing its porosity can potentially starve the functional anode of hydrogen fuel, so a tradeoff exists removing carbon and maintaining fuel cell performance.

Reheating furnace is a furnace that using fuel combustion energy to heat steel products before hot rolling. Materials need to reach the temperature around 1400K uniformly after heating in reheating furnaces. Steel oxidizes during the reheating process. Oxidize scale layer on the surface will changed the heat transfer properties of surface and increase the inner stress of material, reducing the quality of the steel. In this study, a model of scale formation under reheating furnace working condition is developed. The model can be coupled into computational fluid dynamics (CFD). The commercial software, ANSYS FLUENT®, was utilized to give a prediction of furnace atmosphere and calculate the formed scale. A calculator is also developed to predict the scale formation of a single point during the reheating process using measurable flow field data. Furthermore, a series of parametric studies has been investigated to study the influence of operating conditions.

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Diplomová práce zkoumá možnost využití větrného proudění jako hnacího elementu architektonického návrhu za účelem integrace větru jako jeden ze zdrojů získávání energie. Větrné turbíny byly již využity v několika architektonických projektech, spíše však jako doplněk k výškovým budovám, jejichž výška je zřejmým předpokladem pro snažší získávání větrné energie díky dosahu k rychlejším proudům vzduchu. Tento projekt prověřuje skrze architektonický návrh možnost získávání energie z větru i v menších výškách, kde není energetický potenciál tak zřejmý, kvůli výrazně menším rychlostem větru. Výchozím bodem pro rozšíření využití větrné energie je Venturiho efekt, jehož výskyt je možné pozorovat v urbánním prostředí především jako negativní jev působící nepohodlí obyvatelům města, kvůli zvýšeným rychlostem větru. Naproti tomu, když je venturiho efekt předpokládán, může být využit pro zrychlení proudění vzduchu a následného sběru energie. Za účelem podpoření Venturiho efektu pro sběr energie zkoumá projekt, jaký má tvarové uspořádání vliv na proudění vzduchu. Za pomoci simulací proudění tekutin(CFD) a na základě hodinových dat povětrnostních podmínek vybrané lokality, odvozuje možné množství získané energie, různými tvarovými uspořádáními. Energetické zisky jsou srovnávány s předpokládanou energetickou náročností stavby a následně je skrze architektonickou studii prověřována využitelnost stavby jako vítr urychlujícího tvaru stejně tak, jako objektu umožňujícího běžné obývání.

No description available.

This diploma thesis deals with the flow modelling in the ejector using the FLUENT software. It develops a diploma thesis created in the past, where a mathematical flow model in the ejector was created and experimentally tested. The aim of this work is to analyze the ejector calculations and to model a flow in an ejector of the same shape as in the experiment and under the same conditions, too. Another objective was to assess the influence of the throat length and to examine if the pressure in the ejector mixing chamber remains constant. Finally, the disagreement between the experimental figures and the ones gained from the mathematical model of the ejector are discussed.