Yes / This paper proposes the application of a genetic algorithm based methodology for the scheduling of storage tanks. The proposed approach is an integration of GA and heuristic rule-based techniques, which decomposes the complex mixed integer optimisation problem into integer and real number subproblems. The GA string considers the integer problem, and the heuristic approach solves the real number problems within the GA framework. The algorithm is demonstrated for a test problem related to a water treatment facility at a port, and has been found to give a significantly better schedule than those generated using a heuristic-based approach.

Several tanks have failed due to intolerable differential settlements, causing major problems in most cases. The objective of this study is to optimize the bottom plate of the tank so that the differential settlements are reduced to a minimum. Circular plates on an elastic half-space are investigated and the improvements in differential settlements are reported. The plates are loaded by a uniform pressure, and the effects of edge loads, edge moments, and elastic restraints at the edge are considered. A plate with two annular segments having fixed radii is investigated for optimal thicknesses. The plate is also optimized by varying both the radii and the thicknesses. Another plate with three segments is studied, varying the radii and the thicknesses. In all these cases, the plates are examined for a wide range of relative stiffnesses. For a specific relative stiffness, a plate with ten segments of fixed radii is studied. Also, the contact stress distribution is investigated for the case of the three-segment plate. During the study, the results are compared to a uniform plate. As an outcome, the differential settlement is significantly improved compared to the widely used uniform plate. / Master of Science

Master of Science / Department of Mechanical Engineering / Donald Fenton / The need to store and access electronic information is growing on a daily basis as more and more people conduct business and personal affairs through email and the internet. To meet these demands, high energy density data centers have sprung up across the United States and around world. To ensure that vital data centers run constantly, proper cooling must be maintained to prevent overheating and possible server damage from occurring. Emergency cooling systems for such systems typically utilize traditional batteries, backup generator, or a combination thereof. The electrical backup provides enough power to support cooling for essential components within the data centers. While this method has shown to be reliable and effective, there are several other methods that provide reliable emergency cooling at a fraction of the cost. This paper address the lack of information regarding the initial, operation, and maintenance costs of using Thermal Energy Storage (TES) tanks for emergency cooling. From research and various field examples, five emergency cooling system layouts were designed for various peak cooling loads. Looking at the different cooling loads, components, and system operations an economic evaluation of the system over a 20 year period was conducted. The economic analysis included the initial and maintenance costs of each system. In an effort to better understand power consumption of such systems and to help designer’s better estimate the long term costs of TES tanks systems, five layouts were simulated through a program called TRNSYS developed for thermal systems. To compare against current systems in place, a benefit to cost ratio was done to analyze TES versus a comparable UPS. The five simulated systems were one parallel pressurized tank, one parallel and one series atmospheric tank, one parallel low temperature chilled water, and one series ice storage tank. From the analysis, the ice storage and pressurized systems were the most cost effective for 1 MW peak cooling loads. For 5 MW peak cooling loads the ice storage and chilled water systems were the most cost effective. For 15 MW peak loads the chilled water atmospheric TES tanks were the most cost effective. From the simulations we concluded that the pressurized and atmospheric systems consumed the least amount of power over a 24 hour period during a discharge and recharge cycle of the TES tank. From the TRNSYS simulations, the ice storage system consumed 22 – 25% more energy than a comparable chilled water system, while the low temperature storage system consumed 6 – 8% more energy than the chilled water system. From the benefit-cost-ratio analysis, it was observed that all systems were more cost effective than a traditional battery UPS system of comparable size. For the smaller systems at 1 MW the benefit-cost-ratio ranged between 0.25 to 0.55, while for larger systems (15 MW) the ratio was between 1.0 to 3.5 making TES tanks a feasible option for providing emergency cooling for large and small systems.

Die Nutzung regenerativer Energiequellen stellt in vielen Systemen und Versorgungsnetzen wesentlich höhere Anforderungen an die Konstruktion, Auslegung und Betriebsführung von Wärmespeichern als konventionelle Energieträger. Aber auch das Potenzial eines Brennwertkessels kann mit einem optimierten Wasserwärmespeicher besser ausgeschöpft werden. Entscheidend für die Effizienzsteigerung von Wärmespeichern mit ausgeprägter thermischer Schichtung ist die Ausbildung und Aufrechterhaltung einer schmalen Mischzone zwischen dem wärmeren und kälteren Bereich des Speichers. Eine schmale Mischzone und eine niedrige Temperatur im unteren „entladenen“ Speicherbereich wirken sich positiv auf den Wirkungsgrad von Sonnenkollektoren und Brennwertkesseln aus. Beim Einsatz von Wärmepumpen verbessert sich deren Leistungszahl. Der Beitrag zeigt die Auswirkungen der Betriebsweise und der konstruktiven Details des Wärmespeichers, insbesondere der Be- und Entladevorrichtungen, auf, welche durch experimentelle und numerische Untersuchungen ermittelt wurden. / The spreading integration of renewable sources of energy into conventional heat supply systems places high demands on the designing, dimensioning and operation of hot water storage tanks. A pronounced thermal stratification is of positive influence for the efficiency of solar collectors, condensing boilers and the COP of heat pumps connected to the storage tank. The extent of the thermal mixing layer determines the volumetric efficiency of the tank and thus the economics of investment and operation. In this paper, a method is presented by which the losses of hot water storage tanks are correlated to the tank design and operating conditions.

A suite of models were integrated to predict the potential of a large liquid hydrocarbon storage tank fire escalating and involving neighbouring tanks, as a result of thermal loading. A steady state pool fire radiant heat model was combined with a further model, in order to predict the distribution of thermal loading over the surface of an adjacent tank, and another model was incorporated to predict the thermal response of the contents of the adjacent tank. In order to predict if, or when, an adjacent tank will ignite, the radiant heat from the fire received by the adjacent tank must be quantified. There are a range of mathematical models available in the literature to calculate the radiant heat flux to a specified target and each of these models is based on assumptions about the fire. The performance of three of these models, which vary in complication, was analysed (the single point source model, the solid flame model and the fire dynamics simulator computational fluid dynamics model) and, in order to determine the performance of each model, the predictions made by each of the models were compared with actual experimental measurements of radiant heat flux. Experiments were undertaken involving different liquid fuels and under a range of weather conditions and, upon comparing the predictions of the models with the experimental measurements, the solid flame model was found to be the one most appropriate for safety assessment work. Thus, the solid flame model was incorporated into the thermal loading model, in order to predict the distribution of radiant heat flux falling onto an adjacent tank wall and roof. A model was developed to predict the thermal response of the contents of an adjacent tank, in order to predict variations in the liquid and vapour temperature, any increase in the vapour space pressure and the evolution of the vapours within the given time and the distribution of thermal loading over the surface of the tank as predicted by previous models; of particular importance was the identification of the possibility of forming a flammable vapour/air mixture outside the adjacent tank. To assess the performance of the response model, experiments were undertaken at both laboratory and field scale. The laboratory experiments were conducted in the Chemical Engineering Laboratory at Loughborough University and required the design and construction of an experimental facility representing a small-scale storage tank exposed to an adjacent fire. The field scale experiments were undertaken at Centro Jovellanos, Asturias, Spain. An experimental vessel was designed and fabricated specifically to conduct the laboratory tests and to measure the response of a tank containing hydrocarbon liquids to an external heat load. The vessel was instrumented with a network of thermocouples and pressure transmitter and gauge, in order to monitor the internal pressure and distribution in temperature throughout the liquid and its variation with time. The model predicting the thermal response of an adjacent tank was shown to produce predictions that correlated with the experimental results, particularly in terms of the vapour space pressure and liquid surface temperature. The vapour space pressure is important in predicting the time when the vacuum/pressure valve opens, while the liquid surface temperature is important as it governs the rate of evaporation. Combining the three models (the Pool Fire model, the Thermal Loading model and the Response model) forms the basis of the storage tanks spacing international codes and presents a number of innovative features, in terms of assessing the response to an adjacent tank fire: such features include predicting the distribution of thermal load on tanks adjacent to the tank on fire and thermal load on the ground. These models can predict the time required for the opening of the pressure vacuum relief valve on adjacent tanks and the release of the flammable vapour/air mixture into the atmosphere. A wide range of design and fire protection alternatives, such as the water cooling system and the minimum separation distance between storage tanks, can be assessed using these models. The subsequent results will help to identify any recommended improvements in the design of facilities and management systems (inspection and maintenance), in addition to the fire fighting response to such fires.

This is an investigation of the buckling characteristics of short, thin-walled cylinders. This study was required as large storage tanks, which were converted from Boating roof to fixed roofed tanks, were found to buckle when severe atmospheric temperature drops and thus pressure differentials occurred. These severe ambient temperature changes are characteristic of the Highveld in South Africa where the tanks in question are situated. Since this modification is an uncommon procedure, codes of practice for storage vessels do not cover this type of cylinder. For the same reason, research performed in this field is limited. Buckling due to axial loading, lateral external pressure, hydrostatic pressure and a combination of axial loading and hydrostatic pressure are explored in this study. To compare with and verify theory, existing research for each case is examined, and the Finite Element Analysis package MSC Nastran used to determine trends. In some cases, to the best of the author's knowledge, no research exists and numerical analysis is performed to establish the relationships present in those cases. The study is extended to include the design of imperfect cylinders, as defined in the tank code AD Merkblatter where it is stated as being dependant on the major and minor diameters of the imperfect section . The study is also extended to the case of variable wall thickness cylinders, where the thickness variation is symmetrical about the axis of the cylinder. / Thesis (M.Sc.)-University of Natal, Durban, 2001.

Thesis (Ph. D.)--University of Arizona, 1994. / Includes bibliographical references (leaves 233-242).

Orientador: Elias Basile Tambourgi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-19T18:15:28Z (GMT). No. of bitstreams: 1 Pereira_FlavioNelson_M.pdf: 3206674 bytes, checksum: 13d3a08e501d1a7a3efe94db596a1123 (MD5) Previous issue date: 2011 / Resumo: A bomba centrífuga é uma máquina dinâmica que só pode trabalhar nos pontos de sua curva. Consequentemente, a soma das resistências da tubulação e seus componentes durante a operação deve se situar exatamente na sua curva ou curva da bomba. A literatura para a seleção e especificação deste equipamento alimentando apenas um ponto como um tanque ou vaso é vasta, porém, são raros os trabalhos no que concerne a alimentação simultânea de dois ou mais tanques em cotas diferentes, que mostrem o comportamento da pressão ao longo do processo e a curva desse sistema. Esta alimentação simultânea é dita ramificada. O presente trabalho teve por objetivo projetar e montar uma unidade experimental em escala piloto para determinar a curva do sistema e a potência consumida de uma bomba centrífuga quando esta alimenta dois tanques em cotas diferentes utilizando a água como fluido referência, com viscosidade de 1,0 cP e também uma solução de açúcar a 1,2 cP. A unidade consistiu de um tanque de alimentação de 162,5 L construído em acrílico, uma bomba centrífuga com diâmetro do rotor de 200 mm acoplado a um motor em balanço de 2 CV de potência nominal, um inversor de freqüência para controlar a rotação do motor, tubulações de PVC transparentes de 1 in. de diâmetro nominal na descarga da bomba, um rotâmetro com escala de 0 - 12 m3/h, manômetro com escala 0 - 4 kgf/cm2, e dois tanques em acrílico de 72 L cada na descarga instalados em cotas diferentes. A unidade experimental que operou em regime permanente permitiu a verificação da vazão total e, por conseqüência, a determinação da vazão real em cada trecho ramificado. Os poucos trabalhos teóricos nesta área não comprovam experimentalmente a teoria, não analisam a influência de propriedades físicas e nem estimam a potência do motor. O experimento, portanto, procura comparar os dados coletados com a teoria utilizando fluidos com propriedades físicas diferentes. Este trabalho permitiu comparar os valores teóricos e experimentais com desvio de 12,5 a 20,5%, sendo proposta uma sequência teórica dividida em passos para a determinação do ponto de operação do sistema. O emprego desta sequência proposta permite reduzir os custos de instalação evitando malhas de controle, e os custos operacionais com a redução da energia consumida em sistemas industriais / Abstract: A centrifugal pump is a dynamic machine that can perform only on points on the head capacity curve or curve pump. Consequently, the sum of piping and components resistances during operation must fall exactly on the head capacity curve. The literature for the selection and specification of this equipment feeding only one point as a tank or vessel is large, however is hard to find studies regarding the simultaneous feeding of two or more tanks in different heights and showing the pressure behavior during process and the system curve. This simultaneously feeding is said branched. This study aimed to design and build a pilot-scale experimental unit to determine the system curve and the power consumption of a centrifugal pump when it feeds two tanks in different heights using in fluid viscosity of 1.0 cP, water as fluid reference as well sugar solution to 1.2 cP. The unit consisted of a feed tank of 162.5 L built in acrylic, centrifugal pump with a rotor diameter of 200 mm combined with a balance of motor 2 hp rated power, a frequency inverter to control the engine speed, PVC pipes in a transparent 1 in.nominal discharge of the pump, a flowmeter with a scale from 0 to 12 m3/ h, pressure gauge with a scale from 0 to 4 kgf/cm2, and two tanks of 72 L each in discharge also acrylic installed in different heights. The experimental unit that operated in steady state allowed the verification of the total flow and, consequently, the determination of actual flow in each passage branched. The few theoretical works in this area do not prove the theory experimentally, does not analyze the influence of physical properties and do not estimate the power of the engine. This work allowed us to compare the theoretical and experimental values with deviation of 12,5 to 20,5% being proposed after a theoretical split into steps for determining the operating point of the system. The use of this proposed sequence reduces installation costs by avoiding control loops, and operating costs by reducing the energy consumed in industrial systems / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

Liquid storage tanks are a crucial type of structures. They are used to store various types of liquids and liquefied gases in different situations. In seismic regions, functionality of these structures after severe earthquakes is an important factor in their design. In earthquake-prone regions, the sloshing phenomena has an important role in the design procedure. Current design codes and guidelines (e.g. ACI 350.3 and ASCE 7) are based on analytical studies that in some cases can be inaccurate in prediction of forces and pressures. Since a long time ago scientists have studied the sloshing phenomena in liquid storage tanks with different methods including analytical, numerical and experimental studies. In the current study, rectangular ground-supported tanks are studied and the effect of seismic loading on them is investigated both experimentally and numerically. For the experimental tests, the tanks were placed on a shaking table and using high-speed HD cameras, tests were filmed and later analyzed frame by frame to capture the critical moments. To investigate the bi-lateral effect of base excitation on the tanks, they were oriented on the table with four different angles. In the numerical study, a computational fluid dynamics tool - OpenFOAM - was used to simulate the tank motion and finally the results were compared with the experiment in order to develop a reliable model.

Master of Science