Dissertationen zum Thema „Cylindrical Tank“

In all branches of industry, especially in power-engineering, thin wall steel structures are extensively used. Land vertical cylindrical tanks are examples of such structures. The manufacture and assembling of these structures are usually accompanied by deviations from an ideal cylindrical form. Therefore, the exact evaluation of real local imperfections and common deviations from the analytical model of the tank is very important for such potentially dangerous structures. The main objective of the presented investigations is to identify stress/strain state of the wall tank with local imperfections from the ideal cylindrical surface, taking into account the membrane theory of the shells by using the natural experiment and finite element’s method.
Visose pramonės šakose, ypatingai energetikoje, plačiai taikomos plonasienės metalinės konstrukcijos. Tokių konstrukcijų pavyzdžiu yra antžeminiai vertikalūs ci-lindriniai rezervuarai. Kadangi šių statinių konstrukcijų gamybos ir montavimo darbus sudėtinga atlikti be lokalių ar bendrų nukrypimų nuo idealios cilindrinės formos, tikslus jų įvertinimas labai svarbus tokiems potencialiai pavojingiems statiniams. Šio darbo tyrimų pagrindinis tikslas yra: talpyklos sienelės su įduba įtemptojo deformuotojo būvio identifikavimas baigtinių elementų metodu ir eksperimentiniu metodu.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2018.
A membrane distillation crystallization (MDC) experimental setup was designed, constructed and commissioned with rectangular mixing crystallizer tanks. The advantages and disadvantages of a rectangular mixing tank are compared to the traditional cylindrical mixing tank with baffling by means of a computational fluid dynamic (CFD) analysis in Ansys Fluent. The effect of tank configuration and geometry on the hydrodynamic and mixing characteristics for efficient momentum, solid suspension, heat and mass transfer were investigated. The hydrodynamic conditions in a crystallizer-mixing tank determine the quality of fluid mixing essential for optimal crystallization. Forty-five degree pitched blade turbines (PBT) were used to provide the agitation in the stainless steel rectangular jacketed tanks. Clear polycarbonate replicas of the rectangular tanks were manufactured to visually observe the mixing process in the tanks. Silica particles were used to represent the calcium carbonate crystals in the experiment. The data gathered from these experiments showed that the tanks should be operated between 600 to 750 rpm in the CFD simulations to simulate partial to complete suspension. In the numerical simulations a rectangular tank was compared to a cylindrical tank with baffling of the same volume. The partial differential equations solved in the numerical simulation were the conservation of mass (continuity), conservation of momentum and additional turbulence equations. In order to solve the turbulent fluid flow characteristics, the industry standard two-equation model, namely the K-epsilon model was used. This model was refined by the addition of the Wen-Yu drag model, the Simonin turbulent dissipation and the Simonin et al. turbulence interaction models. The RANS based RNG (k-ε), derived from the instantaneous Navier-Stokes equation was selected as the preferred model to analyse the hydrodynamic flow fields in the tanks. The 3D sliding mesh method was used to compute a time accurate solution. The Eulerian-granular multiphase model was used to predict the degree of solids suspension in the tanks. The efficiency of mixing within the tank was measured by the tank’s ability to keep the crystals in suspension and preventing any particle from settling at the bottom for more than 1-2 second(s). The mixing tanks were initially loaded with 5% v/v, which equates to a loaded height of approximately 10 mm. The simulations were done with the use of the volume fraction function to visually observe the cloud height and gauge the homogeneity and distribution of the particulates within the fluid flow fields. The results from the experimental setup were compared to the CFD simulations to qualify the use of CFD simulations for the comparison of the geometrically different tanks. Lastly, the findings from the CFD simulations were used to compare the tanks and determine if the rectangular tank built for the MDC experiment perform satisfactorily to replace a standard cylindrical tank with baffling for this application.

Cylindrical shells are widely used in civil engineering. Examples include cooling towers, pipelines, nuclear containment vessels, steel silos and tanks for storage of bulk solids and liquids, and pressure vessels. The loading condition for these shells is quite varied depending on the function of the shell. Axial compression, global bending, external or internal pressure and wind loading are some of the most common loading forms for realistic structures. The failure of these cylindrical shell structures is often controlled by elastic or elastic-plastic buckling failure. Yield failure may occur in thick cylinders in some situations. A cylindrical shell under different loading conditions may display quite different buckling behaviour. The objective of this thesis is to investigate the characteristics of different buckling behaviours of cylindrical shell structures under axial compression, global bending, uniform external pressure and wind pressure. Some challenging practical problems in the design of these shell structures are explored. This thesis is expected to have some far-reaching impacts in defining how to design cylindrical shell structures to give them adequate strength to resist extreme events. Many aspects will be based on the latest Eurocode (EN 1993-1-6, 2007) and Recommendations (ECCS EDR5, 2008). The results show both some strength and some weaknesses in the Eurocode in design of shell structures. New methods are proposed for some practical problems. Some new conclusions and suggestions are derived and are expected to provide some useful knowledge for the improvement of the Eurocode in cylindrical shell design in general.

Los dispositivos de almacenamiento de energía térmica son ampliamente usados en diversos sistemas térmicos caracterizados por un desfase temporal entre la producción de energia y su consumo, como es el caso de los sistemas de energía solar térmica. El diseño optimizado de estos equipos puede representar un considerable aumento en el rendimiento térmico de la instalación de la cual forman parte. En la línea de optimización de sistemas y equipos térmicos, en los últimos años la Mecánica de Fluidos Computacional (CFD) se ha consolidado como una herramienta básica, proporcionando a investigadores e ingenieros un método para ensayar virtualmente sus diseños, disminuyendo los costes en términos de tiempo, recursos y personal. Es en esta línea se encuentran las principales aportaciones de esta tesis, la cual tiene como principal objetivo la simulación numérica de procesos de convección laminar en régimen transitorio y dominios cilíndricos para su aplicación al estudio de los fenómenos de transferencia de calor y dinámica de fluidos que tienen lugar en los tanques de almacenamiento de energía.

Se presenta la metodología seguida para la resolución de las ecuaciones gobernantes de la transferencia de calor y dinámica de fluidos en coordenadas cilíndricas, mostrando las principales particularidades de su discretización para este tipo de geometrías y se detalla el tratamiento realizado para resolver estas singularidades dentro del código numérico. Posteriormente, se expone la metodología para la solución de flujos transitorios e incompresibles y se realiza un riguroso proceso de verificación del código y las soluciones numéricas obtenidas.

Esta metodología se aplica al estudio del comportamiento de los tanques de almacenamiento de energía estratificados. Un aspecto básico del funcionamiento de estos equipos es la calidad de la energía almacenada. Esta calidad viene determinada por el grado de estratificación térmica, en la cual influyen diferentes factores como la mezcla que ocurre debido a las corrientes de fluido que entran durante los procesos de carga y descarga térmica y también debido al intercambio de calor con el ambiente. En este sentido, en este trabajo se analiza la estratificación térmica para diferentes condiciones de trabajo y configuraciones por medio de las simulaciones numéricas multidimensionales. Para medir el grado de estratificación se han tenido en cuenta diferentes parámetros y como resultado del estudio, se propone un parámetro adimensional basado en un análisis exergético. Esta exergía adimensional ha permitido comparar el funcionamiento de los tanques en las diferentes situaciones analizadas y se ha mostrado útil para cuantificar la calidad de la energía almacenada.

Por otra parte, se estudia el comportamiento térmico de los tanques de almacenamiento durante su modo de operación estático y considerando las pérdidas de energía al ambiente. Este estudio tiene como objetivo fundamental caracterizar el proceso de enfriamiento del fluido en tanques que forman parte de sistemas solares térmicos para el rango de bajas y medianas temperaturas. Se presenta la metodología seguida para el análisis, desde la identificación de los números adimensionales que definen el problema, la formulación de un modelo zonal para la predicción del comportamiento térmico, el estudio paramétrico llevado a cabo y el posterior post-proceso de los resultados con el objetivo de proporcionar los parámetros necesarios para alimentar el modelo zonal. El modelo propuesto, junto con las correlaciones obtenidas, predicen correctamente el comportamiento del fluido, constituyendo una alternativa interesante para reproducir el proceso de enfriamiento del fluido en los tanques durante largos periodos de tiempo.
Thermal storage devices are widely used in many thermal systems and applications that are characterised by the delay between energy production and consumption, such as thermal solar systems. The improvement in their design and optimisation is a key aspect in the thermal optimisation of the system, where a good preformance of the storage tank can represent a considerable increase in the overall efficiency of the installation. In the subject of optimisation of thermal equipment, Computational Fluid Dynamics have been consolidated as an indispensable tool providing researchers and engineers with a method to test virtually their prototypes with low effort in time, personnel and resources. This thesis is focused in the numerical simulation of unsteady laminar convection in cylindrical domains and its application to the study of the heat transfer and fluid flow that take place in stratified storage tanks.

The first part of this document is devoted to present the methodology followed for the numerical resolution of the governing equation of heat and fluid flow in cylindrical coordinates. The main particularities of the discretisation of the equations in these geometries, as well as the solution procedure for incompressible and transient flow problems are also presented. Special emphasis is given to the verification of the code, the appropriateness of the discretisation adopted and the verification of the numerical solution obtained.

The second part of this thesis is focused on the study of the heat transfer and fluid flow phenomena that take place in stratified storage tanks, including the performance measures and modeling efforts of these devices. The quality of the energy stored is determined by the degree of the thermal stratification of the storage tank, which is affected by several factors such as the mixing due to the inlet streams during load and unload, the heat losses to the environment, among others. In this sense, thermal stratification analysis is carried out by means of the virtual prototyping of the tanks for different working conditions and configurations. In order to measure the performance of the tanks, different parameters are considered. The analysis led to the proposition of a new exergy-based parameter as a tool for assessing and comparing storage tanks. The usefulness of this parameter for quantifying the quality of the energy stored is also shown.

Furthermore, the thermal behaviour of storage tanks during the static mode of operation considering the heat losses to the environment is also analysed. The study is addressed to characterise the cool down of the fluid inside storage tanks for solar thermal systems in the low-to-medium temperature range. The methodology followed, from the identification of the significant non-dimensional parameters that define the problem, the formulation of a zonal prediction model, a parametric numerical study by means of detailed multidimensional CFD computations and the post-processing of the results in order to feed the global model are exposed in detail. Zonal model presented, together with the correlations given are in good agreement with the numerical results and constitute an alternative for the prediction of the long-term performance of the storage tanks during the cooling process.

碩士
國立虎尾科技大學
機械與機電工程研究所
101
Photosynthetic bacteria are the most efficient producers of hydrogen, which can be cultured as carbon dioxide. In order to understand the effects of photosynthetic bacteria in different media (air, water, and a gas-liquid mixture) for hydrogen production, three kinds of light-emitting diode lights, red, white, and blue, respectively, are used to simulate light intensity in the space of cylindrical tank where photosynthetic bacteria are cultured inside. And different flow rates of air are injected to explore the LED light intensity distribution in the tank space. In this study, for the three media, the illumination and light photon flux in the aqueous medium are the highest, followed by in the gas-liquid mixture, then in the air medium. If light sources of red, white, and blue are altered sequentially, the illumination values from large to small are in the sequence of white, blue, red, respectively; in additionally, light photon fluxes from large to small are in the sequence of red, white, blue, respectively. Considering the illumination problem, red light fades situation is more different from the rest of the light fades will increase with the downward trend in the law, and does not change with the increase in wattage. In this thesis, illumination experimental results show that the values in gas-liquid mixing medium are slightly lower than in the aqueous medium, but the difference is not significant. Therefore, it is conclued that, for subsequent experiment for hydrogen production, using the gas-liquid mixed media is proper because the bubble will not cause great light fades to light and will increase the mixing effects in the cultivation container, hence, it will be beneficial for the growth of algae and to improve the efficiency of hydrogen production purposes.

碩士
中華大學
機械工程學系碩士班
97
A study of the hydrogen storage using metal hydride is presented. We use the energy equation to analyze the associated heat transfer problem based on assuming that thermal equilibrium has been reached between the metal hydride and hydrogen gas. The mass balance between the hydrogen gas and metal hydride is described in terms of the continuity equation. The Forchheimer-Brinkman equation is used to describe the gas flow within the porous medium . The mathematical model developed was solved using a finite volume method, FLUENT6.3 (Fluent, Inc. USA). The effect of bulk diffusion is considered for mass transfer in the solid phase. Temporal and spatial variations of temperature and concentration in hydride bed are plotted. Emphasis is given to monitor the motion of hydrogen within the bed and to the influence of the L/D ratio and porosity. It is observed that a concentration variation in the bed is the driving force for hydrogen flow in hydride beds. The gas movement is observed to be from saturated cooler peripheral region towards the unsaturated hotter core region of the bed.

Natural convection with high cooling effects is of increasing interest in cold region geotechnical engineering. To study natural air convection in a highly-permeable porous medium, convective and conductive heat transfer experiments were carried out using an insulated cylindrical tank filled with styrofoam chips. Convection and conduction were caused by controlling the temperatures at the top and bottom of the tank, and a series of cross-sectional conductive and convective isotherms were generated from collected temperature data. Additional convective patterns were obtained from tests by centrally localized heating below or cooling above. Flow velocities were measured at the center of the tank. Results showed that convective heat transfer rate was higher than thermal conduction. Convective isothermal patterns varied with various boundary conditions and could be influenced by small temperature perturbation. Given appropriate environmental conditions, efficient convective cooling effects can be used to enhance ground freezing or to protect permafrost from degradation.
Geotechnical Engineering

碩士
逢甲大學
土木及水利工程研究所
83
The fluid system under investigation is the one consisting of main circular flow in the circumferential direction, the primary and the secondary vortex flows in the Meridian plane. When Reynolds number exceeds a particular critical value, the vortex breakdowns, phenomena are found near the core of the cylinder, so that the solutions of the tank flow depend on the range of Reynolds number . This study is based on Liao's [1]. numerical method of a semi-implicit-projection, but extendsthe discussion to the three-dimensional model to study flow field in a cylindrical tank. We solve the three-dimensional unsteady Navier-Storkes equations for the numerical solution of the vortex flow-the velocity, then, By the application of the projection method , we obtain the pressure in form of Poisson's equation while the continuity equation is satisfied automatically. From this poission equation, the value of pressure is determined and carried out by FFT and tridiagonal matrix solver. The velocity can be obtained from the momentum equation by using explicit Adams-Bashforth scheme in the circumferential direction in order to release the restriction of θ-direction numerical stability condition so as Δt can maintain Ｏ(Δr，Δz). The most important characteristics of numerical method is that it takes first order accuracy of iteration for solution of pressure and velocity fields. Numerical simulation of the three-dimensional vortex flows by this projection method becomes more feasible than other schemes. In this analysis, we conclude that, in the range of lower and medium Reynolds numbers ,a three-dimensional flow patterns can be achieved in time evolution ,but after a long time period, steady- state flow solution can be reached, and the flow is reduced to axisymmetric case. We also observe that, for higher Reynolds number, the flow structures will be in nonaxisymmetric state.

碩士
國立交通大學
土木工程系
91
This paper illustrates an alternative linear solution for the problem of initial sloshing in a periodically oscillating cylindrical tank. For this problem, a potential with uniform velocity satisfying the lateral boundary condition is presumed to find the complete linear steady solution in the previous works. An undetermined periodic velocity potential associated with a presumed non-uniform velocity potential is solved under reasonable assumption that only the fluid particles at the walls move consistently with the same velocity and other particles in the tank move like standing waves in evanescent mode. The other linear solution for initial sloshing is also derived in this paper using the previous uniform velocity potential like Graham and Rodriguez’s (1952). More than 100 terms required in an infinite series are examined to compute all physical quantities under a tolerance of less than 0.005. Two solutions have the same phases, but have disparity by 13% at the peaks for water elevation. Two solutions for dynamic pressure performs like those for water elevation and have less difference by about 12% at the peaks. For both horizontal and vertical components of particle velocity, two solutions have only slight discrepancy by 6%.

碩士
國立臺灣科技大學
營建工程系
87
This thesis is mainly to perform the dynamic analysis considering the fluid-structure interaction of cylindrical tank to both horizontal and vertical earthquakes. The tank is treated as homogeneous and flexible and the fluid inside is assumed inviscid and incompressible while the effect of surface waves is ignored. The tank is idealized as a finite element system in evaluating the hydrodynamic pressure acting on the tank during horizontal and vertical excitations. The equation of motion and the responses of the tank can then be obtained. Results of the analysis demonstrate that the difference between the fundamental modes of a tank to horizontal and vertical earthquakes is significant, and the water inside lowers the vibration frequencies of the tank. The response of a tank due to vertical earthquakes is significant and must be considered in the analysis and design of a fluid storage tank.

碩士
國立臺北科技大學
自動化科技研究所
92
The objective of this research is to find the dynamic structural characteristics of cylindrical tanks that we have to consider the errors in manufacture process. Because there are many kinds of errors in manufacture process, the current research focuses on two common conditions：(1) the manufacture tolerances of diametrical imperfection, and (2)horizontal inclination. The main issue process is to find the feature factors that can be used in an artificial diagnosis system. The current reports start with the theory derivation, which is based on the true circular cross section. It has been found that the interaction of sloshing and structure seldom occurs in true circular cross section tanks. If the cross section becomes elliptic, the possibility of interaction becomes higher. The main reason stems from that the fundamental frequency of imperfect tanks tends to move to the lower side. As the consequence, it may just coincide with the sloshing frequency generated by the fluid. It happens when tanks have a large tolerance and filled with large percentage of liquid. On the other hand, when we increase the horizontal inclination., the peak value of two natural frequencies of empty tanks will correspond with convective wave frequency. As a result of the phenomenon, the structure will be destroyed.