Today’s telecommunication cabinets use Electro Magnetic Compliance (EMC) screens in order to reduce electromagnetic noise that can cause some miss functions in electronic equipment. Many radio base stations (RBSs) use a 90-degree building architecture: the flow inlet is perpendicular to the EMC screen, which creates a complex flow, with a 90-degree air turn, expansions, compressions, perforated plates and PCBs. It is of great interest to study how the EMC screen interacts with the rest of components and analyze the total pressure drop and how much the flow pattern changes due to the placement of the screen. Velocity, pressure and temperature measurements as well as flow pattern visualizations have been carried out to gain good insight into the flow and heat transfer characteristics in a subrack model of an RBS. Furthermore, these measurements have been very useful for validating detailed CFD models and evaluating several turbulence models. Nowadays, industrial competition has caused a substantial decrease in the time-to-market of products. This fact makes the use of compact models in the first stages of the design process of vital importance. Accurate and fast compact models can to a great extent decrease the time for design, and thus for production. Hence, to determine the correlations between the pressure drop and flow pattern on the PCBs as a function of the geometry and the Reynolds number, based on a detailed CFD parametric study, was one objective. Furthermore, the development of a compact model using a porous media approach (using two directional-loss coefficients) has been accomplished. Two correlations of these directional loss coefficients were found as a function of the geometry and Reynolds number. / QC 20100630

The turbine technology improvements from 1980 onwards have considerably increased mechanical and thermal stresses on turbine oils which, cause oil oxidation and thereby turbine oil degradation (Livingstone et al., 2007; Sasaki & Uchiyama, 2002). If the oil degradation problem is ignored, this might result in serious turbine system erratic trips and start-up operational problems (Overgaag et al., 2009). Oil oxidation by-products, in other words, sludge and varnish contaminants, lead stated turbine operation-tribological problems. Hence, sludge and varnish presence in turbine oil become a major reason for declining turbine reliability and availability. In the power generation industry, heavy-duty gas turbines as well as steam turbines have been lubricated with mineral based turbine oils for many decades (Okazaki & Badal, 2005). First, generally Group I oils (mineral base oils produced by solvent extraction, dewaxing) were used. Nevertheless, this group of oils has lower oxidation resistance. Therefore, modern gas turbines demand oils which have better oil oxidation resistance, and lower sludge and varnish contaminants tendency (Hannon, 2009). Today, there are many turbine lubricants available on the market. Besides Group I oils, more and more Group II oils (mineral base oils produced by hydro cracking and hydro treating) are selected in service, and having increased oil oxidation resistance. However field inspections demonstrate that Group II oils also experience sludge and varnish problems as well as Group I oils. Primary reason for these phenomena is the antioxidant additive packages that are used in Group II oils (Overgaag et al., 2009). In any case with recent oil formulations, oil degradation products still exist in current turbine oils, and will continue to do so in natural process. These sludge and varnish contaminants are less than 1 micron in size. Thus, they can pass turbine oil system standard mechanical filters without obstruction. With regard to keep the turbine systems in best operational conditions, external turbine oil cleaning practices became crucial to remove these less than 1 micron size oil degradation products from turbine oils. Current effective method for removing the sludge and varnish is to use electrostatic oil cleaners (Moehle & Gatto et al., 2007). Since the majority of turbine user and operator population have been shifted to use Group II based oils to counter the increased sludge and varnish problems, traditional oil cleaners became insufficient to remove sludge and varnish from Group II. (Due to Group II oils have different oil characteristics such as oil oxidation stability and solvency capability). With this awareness, thesis project is looking for ways to introduce and develop an Advanced Electrostatic Oil Cleaner to increase the availability and reliability figures of heavy-duty gas turbines against the rising amount of oil degradation products in modern formulated turbine oils. ECC (Electrostatic Cooled Cleaner) is an electrostatic oil cleaner device to clean and cool mineral based turbine oils for heavy-duty gas turbine applications by removing the sludge and varnish - oil contaminants from turbine oils. The basic principle of the ECC is based on the electrostatic force produced by parallel positioned electrodes which are charged with a high D.C. voltage. Oil contaminants- sludge and varnish have polar nature. Therefore, they are attracted by electrostatic forces whose intensity is proportional to the voltage applied. With the oil flowing in parallel to these electrodes, the polar particles in the oil (which is only neutral /no polar) are caught by filter media positioned between these electrodes. Small investments on advanced oil cleaner result in big savings on turbine system performance. Increased turbine availability and reliability predominantly reduce maintenance costs and risks besides, and thus maximizing revenue by extending heavy-duty gas turbine operational life. An introduced prototype of the ECC-D4 model was tested using two Group II and one Group I oils. The amounts of 200 liter (each) test oils were circulated approximately 300 times through the ECC-D4. In each 3 oil cleaning test sessions, it is proved that the oil insolubles content decreased approximately 40% in tested turbine oils within about 240 ECC-D4 operating hours. With taken base of heavy-duty gas turbine characteristics such as 400 MW power production capacity, annually 8000 operating hours, and 15000 liter oil reservoir volume; it is estimated that the ECC-D4 can extend the oil service-life from 24000 to 48000 operating hours (which is approximately the oil service end-life). In addition to that, assuming the ECC-D4 investment cost as 30k€, about 15k€ savings per year through the new turbine oil and component replacement costs, besides turbine operation profit losses. Moreover, the ECC-D4 returns on investment with a rate of 39 % for defined heavy-duty gas turbine. In general perspective of ECC-D4, it makes heavy-duty gas turbine infrastructure innovative, fully integrated and committed to fulfilling the need for clean, efficient, reliable power production practices in an environmental manner.

<p>In aeromechanical design one of the major rules is to operate under High Cyclic Fatigue (HCF) margins and away from flutter. The level of dynamic excitations and risk of HCF can be estimated by performing forced response analyses from blade row interaction forces or Low Engine Order (LEO) excitation mechanisms. On the other hand, flutter stability prediction can be assessed by calculation of aerodynamic damping forces due to blade motion. In order to include these analyses as regular practices in an industrial aeromechanical design process, interaction between the fields of fluid and structural dynamics must be established in a rather simple yet accurate manner. Effects such as aerodynamic and structural mistuning should also be taken into account where parametric and probabilistic studies take an important role.</p><p>The present work presents the development and validation of a numerical tool for aeromechanical design. The tool aims to integrate in a standard and simple manner regular aeromechanical analysis such as forced response analysis and aerodynamic damping analysis of bladed disks.</p><p>Mistuning influence on forced response and aerodynamic damping is assessed by implementing existing model order reduction techniques in order to decrease the computational effort and assess results in an industrially applicable time frame.  The synthesis program solves the interaction of structure and fluid from existing Finite Element Modeling (FEM) and Computational Fluid Dynamics (CFD) solvers inputs by including a mapping program which establishes the fluid and structure mesh compatibility. Blade row interaction harmonic forces and/or blade motion aerodynamic damping forces are inputs from unsteady fluid dynamic solvers whereas the geometry, mass and stiffness matrices of a blade alone or bladed disk sector are inputs from finite element solvers. Structural and aerodynamic damping is also considered.</p><p>Structural mistuning is assessed by importing different sectors and any combinations of the full disk model can be achieved by using Reduced Order Model (ROM) techniques. Aerodynamic mistuning data can also be imported and its effects on the forced response and stability assessed. The tool is developed in such a way to allow iterative analysis in a simple manner, being possible to realize aerodynamically and structurally coupled analyses of industrial bladed disks. A new method for performing aerodynamic coupled forced response and stability analyses considering the interaction of different mode families has also been implemented. The method is based on the determination of the aerodynamic matrices by means of least square approximations and is here referred as the Multimode Least Square (MLS) method.</p><p>The present work includes the program description and its applicability is assessed on a high pressure ratio transonic compressor blade and on a simple blisk.</p> / Turbopower / AROMA

Hotels constitute one of the main, and still expanding, pillars of the tourism sector and are highly unique among other commercial buildings. Resource intensive and frequently inefficient systems and operational routines applied in the sector, result in considerable environmental impact and indicate an urgent need for more environmentally sound practices and products in the hotel industry. A certain level of activity in the area of reducing resource use has been observed for quite some time but the motivation for this was related to cost-benefit issues rather than the environment. Furthermore, most of the initiatives are still considered to be best practice case studies and not daily routines. The constantly increasing prices of basic commodities, such as energy resources and water, encourage the implementation of energy and water efficiency and conservation measures in hotel facilities. To this end, numerous guidelines and initiatives have been produced by hotel-related organisations. The study of attitudes among 610 European hoteliers indicated that, at the moment, the level of environmental awareness among hotel managers is not high enough to introduce significant changes, although attitudes differ depending on the country of origin and the corporate policy. The prospects of significant cost savings, as well as customer demand were identified as the most likely parameters to enhance environmental responsibility among hoteliers. The popularity of CSR reporting and sustainability indices, especially among the larger companies, leads the author to believe that the industry is preparing to change. Many of the companies running hotels are also reporting their environmental management goals and indicators of environmental performance, while benchmarking and all types of comparison league tables are gaining popularity. There is, however, no system or methodology of data collection and monitoring that is universally accepted or applicable throughout the hotel sector. Furthermore, the accuracy and validity of the published performance indicators and benchmarks is widely debated due to large variations in the figures reported. The analyses performed on data from over 180 upscale and mid-market European chain hotels (Hilton International and Scandic) indicated that even among relatively uniform (service-wise) hotels the amenities offered did influence consumption, further complicating the concept and applicability of uniform benchmarking and resource consumption modelling. It was thus concluded that, creating a uniform model for all hotels is almost impossible, or would require a significant amount of very detailed input data, and that the results could still be highly inaccurate. Instead, it was suggested that it might actually be more accurate to develop models for individual hotels. Such an approach would allow for the modelling of the behaviour of all types of hotels with no size, type of services or standard limitations. Multi-variate step-wise regression analyses performed on individual Scandic hotels in Sweden indicated that energy consumption was dependent on the outdoor air temperature/actual heating degree days, while water consumption was mainly influenced by the number of guest-nights sold. Experience gained by the author during the process of the Hilton Environmental Reporting system upgrade allowed for the formulation of a set of rules of thumb that ought to be followed in the design of similar schemes. The experience of various regions and numerous companies also suggests that well designed and implemented environmental and resource management programs bring significant benefits at an individual as well as a corporate level. This study provides an indication of the strategies that can be used by various stakeholders in the process of development and implementation of such programs. This research further suggests that future developments in environmental performance indicators and benchmarking may best be served by disaggregating hotels into modules (such as guest-rooms, catering outlets, conference centres) and developing consumption models and best practice indicators for these particular components. The individual efficiencies/performance indicators should then be combined and weighted to provide a just overall evaluation of a facility that could then be compared to a benchmark (developed in the same manner). In a similar manner, sustainability assessment schemes and indicators for destinations and communities could be developed. However, more accurate and differentiated knowledge of the individual performance of sub-systems is necessary to proceed with such an alternative. In addition, the methodologies for data collection and reporting procedures, at all levels of the company and sector, need to be standardized and detailed / QC 20100818

For the application of minichannel heat exchangers, it is necessary to have accurate design tools for predicting heat transfer and pressure drop. Until recently, this type of heat exchangers was not well studied, and in the scientific literature there were large discrepancies between results reported by different investigators. The present thesis aims to add to the knowledge of the fundamentals of single- and two-phase flow heat transfer and pressure drop in narrow channels, thereby aiding in the development of this new, interesting technology with the possibility of decreasing the size of electronics through better cooling, and of increasing the energy efficiency of thermal processes and thermodynamic cycles through enhanced heat transfer. A comprehensive experimental single-phase flow and saturated flow boiling heat transfer and pressure drop study has been carried out on vertical stainless steel tubes with inner diameters of 1.700, 1.224 and 0.826 mm, using R-134a as the test fluid. The heat transfer and pressure drop results were compared both to conventional correlations developed for larger diameter channels and to correlations developed specifically for microscale geometries. Contrary to many previous investigations, this study has shown that the test data agree well with single-phase heat transfer and friction factor correlations known to be accurate for larger channels, thus expanding their ranges to cover mini/microchannel geometries. The main part of the study concerns saturated flow boiling heat transfer and pressure drop. Tests with the same stainless steel tubes showed that the heat transfer is strongly dependent on heat flux, but only weakly dependent on mass flux and vapor fraction (up to the location of dryout). This behavior is usually taken to indicate a dominant influence of nucleate boiling, and indicates that the boiling mechanism is strongly related to that in nucleate boiling. The test data for boiling heat transfer was compared to several correlations from the literature, both for macro- and mini-channels. A new correlation for saturated flow boiling heat transfer of refrigerant R-134a correlation was obtained based on the present experimental data. This correlation predicts the presented data with a mean absolute deviation of 8%. The frictional pressure drop results were compared to both macro- and mini channel correlations available from the literature. The correlation suggested by Qu and Mudawar (2003) gave the best prediction to the frictional two-phase pressure drop within the studied ranges. A unique visualization study of saturated flow boiling characteristics in a vertical 1.332 mm inner diameter quartz tube, coated with a transparent heater has also been conducted. The complete evaporation process in a heated circular mini-channel has been studied visually in detail using high speed CCD camera. The study revealed the developments of the flow patterns and the behavior from bubble nucleation to the dry out of the liquid film. The bubble departure frequency, diameter, growth rate, and velocity were determined by analyzing the images. Finally, a flow pattern map for boiling flow in microchannels has been developed based on the test data. / QC 20100812

This thesis theoretically and experimentally investigates different aspects of the application of CO2 in supermarket refrigeration. Theoretical analysis has been performed using computer simulation models developed to simulate CO2 indirect, NH3/CO2 cascade, CO2 trans-critical and direct expansion (DX) R404A systems. The models supported the selection of the CO2 system solutions to be tested experimentally and facilitated the design of NH3/CO2 cascade and trans-critical systems test rigs. Performance evaluation and systems’ optimizations have also been carried out. In order to verify the findings of the theoretical analysis an experimental evaluation has been performed whereby a scaled-down medium size supermarket has been built in a laboratory environment. NH3/CO2 cascade and trans-critical systems have been tested and compared to a conventional R404A system installed in the same laboratory environment. Experimental findings have been compared to the computer simulation models. In supermarket refrigeration applications, safety is a major concern because of the large number of people that might be affected in the event of leakage. Therefore, a computer simulation model has been developed to perform calculations of the resulting concentration levels arising from different scenarios for leakage accidents in the supermarket. The model has been used to validate some of the risks associated with using CO2 in the application of supermarket refrigeration. Results of the experiments and the computer simulation models showed good agreement and suggest that the NH3/CO2 cascade system is a more efficient solution than the analyzed conventional ones for supermarket refrigeration. On the other hand, CO2 trans-critical solutions have efficiencies comparable to the conventional systems analyzed, with potential for improvements in the trans-critical systems. From a safety point of view, the analysis of the calculations’ results clearly shows that using CO2 in supermarket refrigeration does not create exceptional health risks for customers and workers in the shopping area. Studies conducted in this thesis prove that the CO2 systems investigated are efficient solutions for supermarket refrigeration. / QC 20100909

<p>ABSTRACT</p><p>Cities throughout Asia have experienced unprecedented economic development over the past decades. In many cases this has contributed to their rapid and uncontrolled growth, which has resulted in a multiplicity of problems, including rapid population increase, enhanced environmental pollution, collapsing traffic systems, dysfunctional waste management, and rapid increases in the consumption of energy, water and other resources. The significant energy use in cities is not very well perceived in Asian countries. Although a number of studies into energy consumption across various sectors have been conducted, most are from the national point of view. Energy demand analysis is not considered important at the level of the city. The thesis is focused on the dynamics of energy utilization in Asian mega-cities, and ultimately aims at providing strategies for maximizing the use of renewable energy in large urban systems.</p><p>The study aims at providing an in-depth understanding of the complex dynamics of energy utilization in urban mega-centers. An initial general analysis is complemented by a detailed study of the current situation and future outlook for the city of Bangkok, Thailand. An integrated approach applied to the study includes identification of the parameters that affect the utilization of energy in mega-cities and a detailed analysis of energy flows and their various subsystems, including commercial, industrial, residential and that of transportation. The study investigates and evaluates the energy models most commonly used for analyzing and simulating energy utilization. Its purpose is to provide a user-friendly tool suitable for decision-makers in developing an energy model for large cities. In addition, a Multi-Criteria Decision-Making (MCDM) process has been developed to assess whether or not the energy systems meet the sustainability criteria.</p><p>A metabolic approach has been employed to analyze the energy flow and utilization in selected Asian mega-cities, including Bangkok, Beijing, Shanghai, and Tokyo. The approach is applied to measure the majority of indirect energy flows or the energy embodied in the flows of goods and services involving the residents of those cities. Since the function of cities is to serve the lives of the residents, indirect energy consumption could be regarded as being of equal importance as that of direct energy use. The essence of embodied energy is that an indirect reflection upon behavior following direct energy consumption. It can illustrate how a city relies on the outside, for example other cities, countries, etc. and provides some interesting information that cannot be easily drawn from the direct energy demand. The study reveals that the indirect energy demand is more significant than the direct energy demand in Bangkok, Shanghai, and Tokyo, while direct energy demand is greater than the indirect energy demand in Beijing. This can be explained by the fact that Bangkok, Shanghai, and Tokyo have a greater reliance upon the outside in terms of energy demand.</p><p>The Long-range Energy Alternative Planning (LEAP) system has been selected to perform Bangkok energy modeling. In a Bangkok case study a range of policy interventions are selected and how these would change the energy development in Bangkok by the year 2025 is examined. Different policies can be grouped by the sectors analyzed. The only supply-side policy considered meets an existing target of having 10% of electricity generated from renewable sources. The study period for the model started in 2005 and ends in 2025, with the year 2000 taken as the base year. The proposed scenarios were evaluated using the MCDM approach to rate their sustainability. Team members found that this method provided a methodology to help decision-makers to systematically identify management objectives and priorities.</p>

The development of new types of offshore wind turbine on floating platforms requires the development of new approaches to modelling the combined platform-turbine system. In this thesis a linearised frequency-domain approach is developed which gives fast but approximate results: linearised models of the structural dynamics, hydrodynamics, aerodynamics and control system dynamics are brought together to find the overall response of the floating wind turbine to harmonic wind and wave loading. Initially, a nonlinear flexible multibody dynamics code is developed and verified, which is then used to provide reference nonlinear simulation results. The structural dynamics of a wind turbine on a moving platform are shown to be nonlinear, but for realistic conditions the effects are small. An approximate analysis of the second-order response of floating cylinders to hydrodynamic loads suggests slow drift motion may be relatively small for floating wind turbines, compared to other floating offshore structures. The aerodynamic loads are linearised using both harmonic and tangent linearisation approaches; the harmonic linearisation gives improved results when stall occurs. The wake dynamics can also be included. The control system behaviour is linearised using the same method, which works well when the wind speed is far from the rated wind speed; close to the rated wind speed the nonlinearity is stronger, but further improvement should be possible. These sub-models are combined to give a simple but complete model of a floating wind turbine, with flexible blades and a flexible tower, but neglecting the control system behaviour, wake dynamics and nonlinear hydrodynamic loads. For the OC3-Hywind turbine, the accuracy of the results is assessed by comparison to nonlinear time-domain simulations using the commercial code Bladed. Peak-peak errors of less than 5 % are achievable for many harmonic wind and wave inputs, but certain conditions lead to larger errors. The effect of including linearised control system behaviour is demonstrated for a subset of conditions. Overall, the results are promising but more work is needed for practical application.

The primary requirements for a modern industrial gas turbine consist of a continuous trend of an increasing efficiency combined with very low emissions in a robust, cost-effective manner. To fulfil these tasks a high turbine inlet temperature together with advanced dry low NOX combustion chambers are employed. These dry low NOX combustion chambers generate a rather flat temperature profile compared to previous generation gas turbines, which have a rather parabolic temperature profile before the nozzle guide vane. This means that the nozzle guide vane endwall heat load for modern gas turbines is much higher compared to previous generation gas turbines. Therefore the prediction of the nozzle guide vane flow field and endwall heat transfer is crucial for the engineering task of the design layout of the vane endwall cooling system. The present study is directed towards establishing new in-depth aerodynamic and endwall heat transfer knowledge for an advanced nozzle guide vane of a modern industrial gas turbine. To reach this objective the physical processes and effects which cause the different flow fields and the endwall heat transfer pattern in a baseline configuration, a combustion chamber variant, a heat shield variant without and with additional cooling air and a cavity variant without and with additional cooling air have been investigated. The variants, which differ from the simplified baseline configuration, apply design elements which are commonly used in real modern gas turbines. This research area is crucial for the nozzle guide vane endwall heat transfer, especially for the advanced design of the nozzle guide vane of a modern industrial gas turbine and has so far hardly been investigated in the open literature. For the experimental aerodynamic and endwall heat transfer research of the baseline configuration of the advanced nozzle guide vane geometry a new low pressure, low temperature test facility has been developed, designed and constructed, since no experimental heat transfer data exist in the open literature for this type of vane configuration. The new test rig consists of a linear cascade with the baseline configuration of the advanced nozzle guide vane geometry with four upscaled airfoils and three flow passages. For the aerodynamic tests the two middle airfoils and the hub and the tip endwall are instrumented with pressure taps to monitor the Mach number distribution. For the heat transfer tests the temperature distribution on the hub endwall is measured via thermography. The analysis of these measurements, including comparisons to research in the open literature shows that the new test rig generates accurate and reproducible results which give confidence that it is a reliable tool for the experimental aerodynamic and heat transfer research on the advanced nozzle guide vane of a modern industrial gas turbine. Previous own research work together with the numerical analysis performed in another part of the project as well as conclusions from a detailed literature study lead to the conclusion that advanced Navier-Stokes CFD tools with the v2-f turbulence model are most suitable for the calculation of the flow field and the endwall heat transfer of turbine vanes and blades. Therefore this numerical tool, validated against different vane and blade geometries and for different flow conditions, has been chosen for the numerical aerodynamic and endwall heat transfer research of the advanced nozzle guide vane of a modern industrial gas turbine. The evaluation of the numerical and experimental investigations of the baseline configuration of the advanced design of a nozzle guide vane shows the flow field of an advanced mid-loaded airfoil design with the features to reduce total airfoil losses. For the hub endwall of the baseline configuration of the advanced design of a nozzle guide vane the flow characteristics and heat transfer features of the classical vane endwall secondary flow model can be detected with a very weak intensity and geometric extension compared to the studies of less advanced vane geometries in the open literature. A detailed analysis of the numerical simulations and the experimental data showed very good qualitative and quantitative agreement for the three-dimensional flow field and the endwall heat transfer. These findings, together with the evaluations obtained from the open literature, lead to the conclusions that selected CFD software Fluent together with the applied v2-f turbulence model exhibits a high level of general applicability and is not tuned to a special vane or blade geometry. Therefore the CFD code Fluent with the v2-f turbulence model has been selected for the research of the influence of the several geometric variants of the baseline configuration on the flow field and the hub endwall heat transfer of the advanced nozzle guide vane of a modern industrial gas turbine. Most of the vane endwall heat transfer research in the open literature has been carried out only for baseline configurations of the flow path between combustion chamber and nozzle guide vane. Such a simplified geometry consists of a long, planar undisturbed approach length upstream of the nozzle guide vane. The design of real modern industrial gas turbines however requires often significant variations from this baseline configuration consisting of air-cooled heat shields and purged cavities between the combustion chamber and the nozzle guide vane. A detailed evaluation of the flow field and the endwall heat transfer shows major differences between the baseline and the heat shield configuration. The heat shield in front of the airfoil of the nozzle guide vane influences the secondary flow field and the endwall heat transfer pattern strongly. Additional cooling air, released under the heat shield has a distinctive influence as well. Also the cavity between the combustion chamber and the nozzle guide vane affects the secondary flow field and the endwall heat transfer pattern. Here the influence of additional cavity cooling air is more decisive. The results of the detailed studies of the geometric variants are applied to formulate guidelines for an optimized design of the flow path between the combustion chamber and the nozzle guide vane and the nozzle guide vane endwall cooling configuration of next-generation industrial gas turbines. / QC 20100917