Computational Fluid Dynamics (CFD) is a field that is constantly advancing. Its advances in terms of capabilities are a result of new theories, faster computers, and new numerical methods. In this thesis, advances in the computational fluid dynamic modeling of moving bodies and combustive flows are investigated. Thus, the basic theory behind CFD is being extended to solve a new class of problems that are generally more complex. The first chapter that investigates some of the results, chapter IV, discusses a technique developed to model unsteady aerodynamics with moving boundaries such as flapping winged flight. This will include mesh deformation and fluid dynamics theory needed to solve such a complex system. Chapter V will examine the numerical modeling of a combustive flow. A three dimensional single vane burner combustion chamber is numerically modeled. Species balance equations along with rates of reactions are introduced when modeling combustive flows and these expressions are discussed. A reaction mechanism is validated for use with in situ reheat simulations. Chapter VI compares numerical results with a laminar methane flame experiment to further investigate the capabilities of CFD to simulate a combustive flow. A new method of examining a combustive flow is introduced by looking at the solutions ability to satisfy the second law of thermodynamics. All laminar flame simulations are found to be in violation of the entropy inequality.

Computational Fluid Dynamics (CFD) is a field that is constantly advancing. Its advances in terms of capabilities are a result of new theories, faster computers, and new numerical methods. In this thesis, advances in the computational fluid dynamic modeling of moving bodies and combustive flows are investigated. Thus, the basic theory behind CFD is being extended to solve a new class of problems that are generally more complex. The first chapter that investigates some of the results, chapter IV, discusses a technique developed to model unsteady aerodynamics with moving boundaries such as flapping winged flight. This will include mesh deformation and fluid dynamics theory needed to solve such a complex system. Chapter V will examine the numerical modeling of a combustive flow. A three dimensional single vane burner combustion chamber is numerically modeled. Species balance equations along with rates of reactions are introduced when modeling combustive flows and these expressions are discussed. A reaction mechanism is validated for use with in situ reheat simulations. Chapter VI compares numerical results with a laminar methane flame experiment to further investigate the capabilities of CFD to simulate a combustive flow. A new method of examining a combustive flow is introduced by looking at the solutions ability to satisfy the second law of thermodynamics. All laminar flame simulations are found to be in violation of the entropy inequality.

No description available.

SuperCritical-Water-cooled Reactors (SCWRs) are being developed as one of the Generation-IV nuclear-reactor concepts. Main objectives of the development are to increase thermal efficiency of a Nuclear Power Plant (NPP) and to decrease capital and operational costs. The first objective can be achieved by introducing nuclear steam reheat inside a reactor and utilizing regenerative feedwater heaters. The second objective can be achieved by designing a steam cycle that closely matches that of the mature supercritical fossil-fuelled power plants. The feasibility of these objectives is discussed. As a part of this discussion, heat-transfer calculations have been performed and analyzed for SuperCritical-Water (SCW) and SuperHeated-Steam (SHS) channels of the proposed reactor concept. In the calculations a uniform and three non-uniform Axial Heat Flux Profiles (AHFPs) were considered for six different fuels (UO2, ThO2, MOX, UC2, UC, and UN) and at average and maximum channel power. Bulk-fluid, sheath, and fuel centerline temperatures as well as the Heat Transfer Coefficient (HTC) profiles were obtained along the fuel-channel length. The HTC values are within a range of 4.7 – 20 kW/m2⋅K and 9.7 – 10 kW/m2⋅K for the SCW and SHS channels respectively. The main conclusion is that while all the mentioned fuels may be used for the SHS channel, only UC2, UC, or UN are suitable for a SCW channel, because their fuel centerline temperatures are at least 1000°C below melting point, while that of UO2, ThO2, and MOX may reach melting point. / UOIT

<div>The objective of this research was to develop an efficient simulation of an industrial reheating furnace with a flexible scale formation model and to apply the models to study various conditions within an industrial reheating furnace. This work focused on developing a model capable of considering many different key variables that influence scale formation. The scale formation model was incorporated into the computational fluid dynamics (CFD) software ANSYS Fluent © to solve a coupled steady-state and transient simulation. It was also generalized for a low-carbon steel product, so it may not be adequate to cover the effects of alloying metals on the oxidation process. In order to verify the accuracy of these models, baseline cases were simulated and validated against both industrial data and findings from experiments in published literature.</div><div><br></div><div>A parametric study with two levels of oxygen enrichment implementation in only the preheat zone was undertaken to study the effects on the heat transfer, scale formation, and fluid flow within the reheat furnace. A medium oxygen enrichment case of 46 vol% oxygen and an oxy-fuel case were used for study. Both oxygen enrichment cases showed largely increased heat transfer to the slab in the preheat zone and increased scale formation. Based on these results, 46 vol% oxygen enrichment is recommended for use in a typical industrial reheat furnace with additional firing rate drawback to reduce scaling and to reduce the chance of overheating the steel slab product.</div>

In this master thesis an implementation of an Organic Rankine Cycle (ORC) on a stepping furnace in a steel mill is modeled and proposed. The study is a case study at the company Štore&amp;STEEL d.o.o. with intentions of realization. In a steel mill a stepping furnace is used to preheat the steel billets for later forging. The stepping furnace is gas fired and already has recuperation of the inlet air implemented. Still there is high temperature of the stack after recuperation, which makes application of an ORC worth of researching and modeling.First the flue gas over one year of furnace operation is analyzed in terms of temperature and volumetric flow. Mass flow and heat capacity are calculated. A layout of an ORC is proposed and modeled in IPSEpro for different temperatures of the flue gas resulting in different output powers and efficiencies. For each temperature an economic viability calculation with the method of reference cost of electric energy is done.The results are presented and the best design and conditions are proposed. The results of the thesis proved that further detailed measurements and calculation are worthwhile , as the flue gas from the stepping furnace has satisfactory conditions to make an application of an Organic Rankine cycle viable. Also the least ammount of state support to fulfill the companies conditions on return of investment is calculated and presented. Finally there are additional measurements and calculations suggested.

The repair welding of main steam pipelines, which involves the welding of new material onto service-exposed material, are investigated. This paper investigates the literature and experimental work surrounding this subject. The introduction provides a background to the applicable welding technology. In section two the heat-affected zone is discussed with emphasis on the residual stresses that develop in this zone. The mechanical properties of the heat-affected zone are also investigated. This includes the tensile, toughness and hardness properties as well as inspecting the relevant microstructures. The effect of post weld heat treatment on these properties is also investigated. Section three investigates the phenomenon of creep. Not only is this important due to the high temperatures at which these pipelines operate, but creep is also associated with some failures of these weld during post weld heat treatment. The creep properties of the heat-affected zone are investigated in detail with the use of weld simulation. Sections four and five detail reasons for weld failure after welding due to hydrogen and reheat cracking. Hydrogen cracking is investigated with the use of slow strain rate tensile tests during cathodical charging the specimen with hydrogen. The phenomenon of reheat cracking is investigated with the use of high temperature tensile tests as well as a novel approach in which the stress relief of a welded joint is simulated while measuring crack growth and stress relieved. / Dissertation (MEng)--University of Pretoria, 2014. / gm2014 / Materials Science and Metallurgical Engineering / Unrestricted

No description available.

The aim of this master’s thesis is a retrofit of condensing three case steam turbine K300-170 with reheating. In the first part, the heat balance of the system is calculated for given parameters. The design of the flow section is focused on the combined intermediate pressure and low pressure turbine section and it consists of defining rotor and blading characteristics. In the stress control, the stress of the designed blading is checked and for the conclusion the shaft seal losses and their effect on the overall output power of the turbine are estimated. The drawing of axial section of combined intermediate pressure and low pressure turbine section is also included in the thesis.

No description available.