bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of On-Line Performance Diagnostics Program of a Helicopter Propulsion System
Authors: Ki Jayoung , Kong Changduk , Kho Seonghee , Kim Jaehwan , Ahn Ieeki , Lee Daesung
Published: February 2010

The engine health monitoring system has been generally applied to the aircraft system to improve reliability and durability of the aircraft propulsion system and to minimize its operational cost. The helicopter flies at low altitude level flight mode in its own operational range comparing to other aircraft categories. The low level flight means that the engine operates at variable atmospheric condition such as hot and cold temperature, snow, heavy rain, etc. Furthermore, it may increase the possibility of foreign object ingestion, such as sand, dust, etc., i.e. this operating condition gives rise to damages of engine gas path components. Because types and severities of most helicopter engine faults are very complicate, the conventional model based fault diagnostic approach like the GPA (Gas Path Analysis) method is not adequate to monitor such a complex engine fault condition. An on-line diagnostic program was developed by using SIMULINK, where measurement signals were simulated by an input module. This study proposes a neural network algorithm for calculating variation of mass flow and efficiency in each engine component from measuring data. The neural network was trained by damages at each component such as compressor, compressor turbine or power turbine. The used database for training the neural network was obtained from simulation under various flight conditions. Reliability and capability of the developed on-line diagnostics program were evaluated through application to a helicopter engine health monitoring.
Heat Transfer and Pressure Drop Measurements for a Square Channel With 45Deg Round Edged Ribs at High Reynolds Numbers
Authors: Rallabandi Akhilesh P. , Alkhamis Nawaf , Han Je-Chin
Published: February 2010

Experiments to determine heat transfer coefficients and friction factors are conducted on a stationary 45 deg parallel rib roughened square channel which simulates a turbine blade internal coolant passage. Copper plates fitted with silicone heaters and thermocouples are used to measure regionally averaged heat transfer coefficients. Reynolds numbers studied range from 30,000 to 400,000. The ribs studied have rounded (filleted) edges to account for manufacturing limitations of actual engine blades. The rib height (e) to hydraulic diameter (D) ratio (e/D) ranges from 0.1 to 0.2; spacing (p) to height ratio (p/e) ranges from 5 to 10. Results indicate an increase in heat transfer due to ribs at the cost of a higher friction factor, especially at higher Reynolds Numbers. Round edged ribs experience a similar heat transfer coefficient and a lower friction factor compared to sharp edged ribs, especially at higher values of rib height. Correlations predicting Nu and f as a function of e/D, p/e and Re are presented. Also presented are correlations for heat transfer and friction roughness parameters (G and R).
Effect of Particle Size and Trench Configuration on Deposition From Fine Coal Flyash Near Film Cooling Holes
Authors: Ai Weiguo , Laycock Robert G. , Rappleye Devin S. , Fletcher Thomas H. , Bons Jeffrey P.
Published: February 2010

Particulate deposition experiments were performed in a turbine accelerated deposition facility to examine the effects of flyash particle size and trench configuration on deposits near film cooling holes. Deposition on two bare metal Inconel coupons was studied, with hole spacings (s/d) of 3.375 and 4.5. Two sizes of sub-bituminous coal ash particles were used, with mass mean diameter of 4 and 13 microns, respectively. The effect of a cooling trench at the exit of the cooling holes was also examined in this deposition facility. Experiments were performed at different angles of impaction. Particles were accelerated to a combustor exit flow Mach number of 0.25 and heated to 1183°C before impinging on a target coupon. The particle loading in the 1-hr tests was 160 ppmw. Blowing ratios were varied in these experiments from 0 to 4.0. Particle surface temperature maps were measured using two-color pyrometry based on RGB signals from a camera. Deposits generated from finer particles were observed to stick to the surface more tenaciously than larger particles. The capture efficiency measured for the small particles was lower than for the larger particles, especially at low blowing ratios. However, the finer particles exhibited a greater variation in deposition pattern as a function of hole spacing than seen with larger particles. The effect of trench configuration on deposition was examined by performing deposition tests with and without the trench for the same hole spacing and blowing ratio. The effects of trench configuration on capture efficiency, deposition pattern, and surface topography are reported. Deposition experiments at impingement angles from 45° to 15° showed changes in both deposit thickness and temperature. The trench increased cooling effectiveness, but did not change the particulate collection efficiency because the trench acted as a particulate collector.
Investigations of Pyrolysis Syngas Swirl Flames in a Combustor Model
Authors: Casarsa Luca , Micheli Diego , Pediroda Valentino , Radu Robert
Published: February 2010

An atmospheric combustor model with optical access for confined, non-premixed swirl-stabilized flames was developed in order to investigate the combustion behaviour of gas turbine flames fired with low-caloric syngases. The applied measuring techniques are Particle Image Velocimetry (PIV) for cold aerodynamic analysis, IR thermometry in open flame conditions, thermocouple traverses and global emissions analyzer in confined flame conditions. Two different fuels were chosen: propane and a synthetic mixture of CH4, CO, CO2, H2 having a composition typical of a gas from wood pyrolysis. Thermal powers between ∼5 kW and ∼20 kW were obtained with two different air flow rates and equivalence ratio varied in the range φ = 0.2–1.0. The experimental results constitute a database for the validation of numerical combustion models. Preliminary numerical analysis was carried out with STAR-CD software package.
Self-Acting Clearance Control for Turbine Blade Outer Air Seals
Authors: Justak John F. , Doux Cyrille
Published: February 2010

Tip leakage losses constitute a major source of inefficiency in turbine rotor blades. Blade tip sealing has been a challenge due to the dynamic changes in clearance between the blade tips and the surrounding stationary casing. The variation is due to thermal and mechanical loads on the rotating and stationary structures. Improved sealing in both the high pressure compressor and the high pressure turbine can provide significant reductions in specific fuel consumption and compressor stall margin. Existing seal designs deteriorate. This increase in leakage reduces engine efficiency and thus, the engine burns more fuel to maintain the same power output. Turbine temperatures then rise toward material limits and decrease the overall life of the engine. A novel concept for controlling clearance between rotating blade tips and stationary outer air seal for gas turbine application is presented in this paper. The seal consists of segmented compliant sealing surfaces providing primary sealing, and a flexible sheet metal seal acting on the outer surface of the segments serving as a secondary seal. A commercial computational fluid dynamic (CFD) solver is used for the numerical flow analysis work to simulate the flow characteristics and spatially varying thermodynamic conditions in the flow passage between the blades tip and the primary sealing surface. The results showed that the seal surface geometry has a major impact on the flow field, and several design parameters were identified. A sudden flow contraction (step), as well as gradual converging and diverging seal surface influence differently the flow properties and consequently the seal surface pressures. Also, both pressure difference and clearance were found to be significant factors affecting the flow. The results presented in this study demonstrate the mechanisms which enable the seal to self-balance at a controlled clearance without contacting the blades.
CFD Analysis of the Flameless Combustion in a Micro-Gas Turbine
Authors: Cameretti Maria Cristina , Piazzesi Renzo , Reale Fabrizio , Tuccillo Raffaele
Published: February 2010

The concept of flameless combustion as an effective tool for reducing the nitric oxide emission from micro-gas turbines is worthy of an accurate investigation of the thermo-chemical processes inside the combustor. To this aim the authors, basing on their previous experiences on this subject, present a more detailed analysis of the combustion phenomena in a micro-turbine equipped with an exhaust recirculation system. The CFD calculations are extended to the case of liquid fuelling and employ the boundary conditions provided by a preliminary matching analysis. A three dimensional domain is considered for a better evaluation of the temperature and pollutant distributions. In the final part of the paper, the authors discuss an attempt to approach the same flameless regime by exploiting the exhaust recirculation that takes place inside the combustor.
Single and Two Shaft Gas Turbine Configurations Performance Analysis, Using Different Types of Fuels
Authors: Malkogianni A. K. , Tourlidakis A. , Polyzakis A. L.
Published: February 2010

Coal gas and biofuels as alternative fuels have recently become more attractive, because of their benefits, especially in electrical power industry. The major obstruction to their use is the relatively low calorific values. This paper presents a comprehensive simulation method for calculating the adiabatic temperature of various fuels when they are used in combustion chambers under constant pressure. The adiabatic temperature is presented as a function of combustion fuel air ratios and the fuels low calorific values. In addition, the utilization of various gaseous fuels in single shaft and two shaft gas turbine engines is analyzed. This analysis includes the design point (DP) and off-design (OD) performance of the two engines. The calorific values of the four gases investigated correspond to natural gas (NG) and to fuels with significantly lower calorific values than that of NG (coal synthetic gases, biofuels). Two main conclusions are drawn from this analysis. Firstly, for both single shaft and two shaft engines and for a given turbine entry temperature (TET), both power and thermal efficiency are increasing when fuels with decreasing calorific value are burnt. Secondly, for both single shaft and two shaft engines and for a given power, the thermal efficiency is slightly reduced.
Heat Transfer and Pressure Drop Measurements in Constant and Converging Section Pin and Diamond Pedestal Arrays
Authors: Jaswal I. , Ames F. E.
Published: February 2010

High solidity pin and pedestal arrays are beneficial in reducing temperature gradients and distributing stress across double wall cooling channels such as trailing edge regions. In this study two high solidity (45%) cooling channel geometries were selected and tested in both constant channel height and converging channel configurations. One geometry consisted of a high solidity round pin fin array and the other geometry consisted of a rounded diamond pedestal array designed to minimize pressure drop. Heat transfer rates for both geometries were determined on a row by row basis for both the constant channel and converging channel configurations. Heat transfer and pressure drop measurements were acquired in a bench scale test rig. Reynolds numbers ranged from approximately 3000 to 60,000 for the constant channel arrays and 3500 to 100,000 for the converging arrays based on the characteristic dimension of the pin or pedestal and the local maximum average velocity across a row. The high solidity pin fin array had an axial spacing (X/D) of 1.043 and a cross channel spacing (Z/D) of 1.674. The high solidity diamond pedestal array had an axial spacing of 1.00 and a cross channel spacing of 1.93. The constant section pin fin array had a channel height to diameter of 0.95 while the constant section diamond pedestal array had a height to characteristic dimension of 0.96. The converging pin fin array had an inlet to exit convergence ratio of 2.87 over five heated rows while the converging pedestal array had an inlet to exit convergence ratio of 3.53 over seven heated rows. The constant channel height internal cooling schemes have shown that the high solidity pin fin and the rounded diamond pedestal arrays produce comparable heat transfer and array pressure drop. Both the converging channel arrays show a noticeable (5% to 7%) reduction in heat transfer compared with the constant height channels. Array pressure drop for the two converging geometries was found to be quite consistent.
Gas Turbines Axial Compressor NDE by Eddy Current Probes to Detect Corrosion Pitting
Authors: Ceschini Giuseppe Fabio , Iozzelli Federico
Published: February 2010

Corrosion Pitting is a failure mode that appears in several cases in which there is a combination of Gas Turbines poor Inlet Filtration system (or wrong maintenance of it) and a particularly aggressive environment, characterized by presence of sulfides and chlorides. The corrosion pitting spots can cause crack initiation on the axial compressor blades and, with operation, go on propagating by HCF failure mechanism. This paper describes the application of a new type of Eddy Current probe, suitable to detect those very small spots on the first stage blades, avoiding to disassembly the gas turbine casings, in the very early stage of the corrosion phenomena. A specific experience on some LNG plants is reported.
Compressor Variable Geometry Schedule Optimisation Using Genetic Algorithms
Authors: Gallar L. , Arias M. , Pachidis V. , Pilidis P.
Published: February 2010

Variable geometry blade rows in axial compressors are devised to fulfil different requirements. Main objectives include their role as a “part speed crutch” to push the front stages out of surge at low spool speeds, modulation of the power output in industrial machines — given the fact that the spool needs to run at synchronous speed with the electric generator frequency — and they can also be re-staggered to attain a modified capacity (usually upflowed) of the same baseline compressor. The operating schedule of the variable vanes is typically obtained from expensive and time consuming performance rig tests in which a large number of possible combinations are compared. In principle, the final choice is dictated by the pursuit of high efficiency at high rotational speeds and increased surge margin at low speeds where large excursions away from the design point are expected. The aim of this work is to integrate a validated genetic algorithm optimiser within an industry proprietary mean line compressor performance prediction code to maximise the machine efficiency while keeping an adequate user-defined value of the surge margin. In so doing, an optimised variable geometry schedule is derived, together with a modified range of rotational speeds for each given operating point. Nevertheless, aware of the detrimental consequences to the whole engine performance that the new arrangement can cause, the whole engine response for the new settings has been investigated. In this regard and to a first order, the working line on the compressor map is considered unaffected by the setting of the variable vanes and the effect of the spool speed variation on the turbine operation is accounted for by a reduction in turbine efficiency proportional to any fall in the shaft speed. Results for a state of the art eight stage compressor show a marked improvement for the coupled compressor-turbine efficiency particularly at low spool speeds for a sensible value of the surge margin. Free from the surge margin constraint the efficiency is further increased at the expense of a hindered compressor operational stability. The work is intended to continue with the incorporation of bleeds and power off take in the calculations for the sake of a greater applicability of the tool.
CFD Prediction and Design of Low NOx Radial Swirler Systems
Authors: King Phil T. , Andrews Gordon E. , Kim Myeong N. , Pourkashanian Mohamed , McIntosh Andy C.
Published: February 2010

A radial swirler with vane passage fuel injection using a radial fuel spoke with one fuel hole per passage was investigated using CFD at 0.5 equivalence ratio and 600K inlet temperature at 1 bar. Experimental measurements of the internal flame composition from water cooled gas sample probes were the experimental results used for comparison. Three combustion models were compared: flamelet with two difference kinetic schemes; PDF transport with two step chemistry and finite rate eddy dissipation model. Both models consistently underpredicted the turbulent flame thickness to 90% heat release by a factor of about 2. The PDF model with postprocessing NOx predictions over estimated the NOx emissions considerably and the best model was the flamelet model with full chemistry. The under prediction of the turbulent reaction zone thickness was concluded to be due to inadequate modelling of strained flame quenching for very lean flames with large laminar flame thickness and very low burning velocities. This flamelet model was applied to predict the influence of the radial swirler outlet geometry on the flame development, fuel and air mixing and NOx emissions. A dump expansion from the radial swirler outlet was compared with the addition of a shroud at the outlet and with the addition of a 60mm long outlet throat. The shroud was shown to increase the peak turbulence and confine it very close to the shroud lip. This improved the fuel and air mixing and lowered the predicted NOx from 2.7ppm to 1.2ppm with the shrouded swirler and 0.3ppm with the 60mm outlet throat and mixing length.
Applications of an Interactive Balancing Procedure for Gas Turbines and Other Turbomachinery
Authors: Allison Timothy C. , Simmons Harold R.
Published: February 2010

Least squares balancing methods have been applied for many years to reduce vibration levels of turbomachinery. This approach yields an optimal configuration of balancing weights to reduce a given cost function. However, in many situations, the cost function is not well-defined by the problem, and a more interactive method of determining the effects of balance weight placement is desirable. An interactive balancing procedure is outlined and implemented in an Excel spreadsheet. The usefulness of this interactive approach is highlighted in balancing case studies of a GE LM5000 gas turbine and an industrial fan. In each case study, attention is given to practical aspects of balancing such as sensor placement and balancing limitations.
Evaluating a Three-Dimensional Slot Design for the Combustor-Turbine Interface
Authors: Knost D. G. , Thole K. A. , Duggleby A.
Published: February 2010

As turbine inlet temperatures are pushed ever higher in an attempt to improve efficiency and power, it has become critical to cool component surfaces. One surface that is particularly difficult to treat because of the complex flow field that surrounds it is the nozzle guide vane endwall. Past studies have indicated that leakage bypass flow emerging from the combustor-turbine junction may be effectively harnessed for cooling purposes. When combined with endwall film-coolant injection, component service life may be significantly extended. This paper presents results from a computational study investigating a three-dimensional slot geometry at the combustor-turbine interface. The downstream edge of the slot was scalloped using a simple periodic function intended to enhance thermal benefit to the endwall by manipulating coolant distribution. Effects of varying the slot geometry amplitude and phase were investigated along with the slot nominal width and upstream distance from the vane. Initial results indicate dramatic effects can be realized depending upon the scalloping used.
Effect of Wake-Disturbed Flow on Heat (Mass) Transfer to a Turbine Blade
Authors: Olson S. J. , Sanitjai S. , Ghosh K. , Goldstein R. J.
Published: February 2010

This study investigates the effect of wakes in the presence of varying levels of background freestream turbulence on the heat (mass) transfer from gas turbine blades. Measurements using the naphthalene sublimation technique provide local values of the mass transfer coefficient on the pressure and suction surfaces of a simulated turbine blade in a linear cascade. Experimental parameters studied include the pitch of the wake-generating blades (vanes), blade-row separation, Reynolds number and the freestream turbulence level. The disturbed flow strongly affects the mass transfer Stanton number on both sides of the blade, particularly along the suction surface. An earlier transition to a turbulent boundary layer occurs with increased background turbulence, higher Reynolds number and from wakes shed from vanes placed upstream of the linear cascade. Note that once the effects on mass transfer are known, similar variation on heat transfer can be inferred from the heat/mass transfer analogy.
Novel Turbine Rotor Shroud Film-Cooling Design and Validation: Part 2
Authors: Chana K. S. , Haller B.
Published: February 2010

This paper is part two of a two part paper which considers a shroud film-cooling system design. The design was carried out using test results from a previous two-dimensional (2D) design and optimisation using three-dimensional (3D) CFD. The first cooling design was carried out using a streamline boundary layer approach and tested in the QinetiQ turbine test facility (TTF). The test results showed the design did not function as well as had been predicted and gave a poor performance in terms of film cooling effectiveness. Lessons learnt from the 2D design as well as understanding gained from heat transfer and pressure data taken on the rotor casing led to the formulation of a completely new design philosophy. Accepting, cooling films would not survive rotor passing and therefore concentrating on localised cooling as well as the re-establishment of cooling films between rotor passings. The design concept was validated/optimised with the aid of 3D CFD. Heat transfer instrumentation was implemented in a cooling insert fitted over the test rotor to evaluate the performance of the design. Tests carried out with and without cooling showed an improvement in cooling performance, leading to a 40% reduction in heat transfer rate to the rotor casing across the rotor overtip region. A significant improvement was achieved with the new design over the original with reductions in casing heat transfer rates of up to 44%, with a design coolant mass flow of 1.85% of core flow. Heat transfer data were successfully processed to Nusselt number, allowing the results to be translated to a gas turbine engine design.
Phase Field Approach to Microstructural Modeling and Life Prediction of High Temperature Coatings
Authors: Mohanty R. R. , Sohn Y. H.
Published: February 2010

A mechanism-based methodologies to model microstructural evolution and predict lifetime of oxidation resistance coatings and TBCs using phase-field simulation is presented wherein only fundamental properties of materials such as free energy, atomic mobility and elastic constants are employed. Phase field approach to simulate critical phenomena associated with TBC failure, namely sintering of ytrria-stabilized zirconia (YSZ) topcoat, (t’→f+m) phase transformations in YSZ topcoat, high temperature oxidation (i.e., growth of thermally grown oxide, TGO) of bond coats, multicomponent-multiphase interdiffusion between bond coats and superalloy substrate, and fracture at the YSZ/TGO and TGO/bond coat interfaces are presented based on available literature. Results from simulation of microstructure evolution due to multiphase-multicomponent interdiffusion between bond coat and superalloy substrates are highlighted with an emphasis on composition-dependent interdiffusion. Specifically, a phase field model has been utilized to simulate and predict interdiffusion behavior and evolution of microstructure in multi-phase diffusion couples of binary and ternary systems, e.g. Ni-Al and Ni-Cr-Al. The model was capable of predicting composition profiles, diffusion paths and dissolution kinetics of the second phase, which were in good agreement with the experimental results reported in the literature.
Radiation Characteristics of Promising Algae for CO2 Fixation and Biofuel Production
Authors: Berberog˘lu Halil , Gomez Pedro S. , Pilon Laurent
Published: February 2010

This paper reports experimental measurements of the radiation characteristics of green algae used for carbon dioxide fixation via photosynthesis. Particular attention was paid to three widely used species namely Botryococcus braunii, Chlorella sp., and Chlorococcum littorale. Their extinction and absorption coefficients were obtained from normal-normal and normal-hemispherical transmittance measurements over the spectral range from 400 to 800 nm. Moreover, a polar nephelometer is used to measure the scattering phase function of the microorganisms at 632.8 nm. It was observed that for all strains, scattering dominates over absorption. The magnitudes of the extinction and scattering cross-section are functions of the size, shape, and chlorophyll content of each strains in a non-trivial manner. Absorption peaks at 435, 475, and 676 nm corresponding to chlorophyll a and chlorophyll b have been clearly identified in the three species considered. The results can be used for scaling and optimization of CO2 fixation in ponds or photobioreactors as well as in the development of controlled ecological life support systems.
Low Temperature, All-Inorganic Nanoparticle Solution Process for ZnO Nanowire Network Transistor Fabrication on a Polymer Substrate
Authors: Ko Seung Hwan , Park Inkyu , Pan Heng , Misra Nipun , Grigoropoulos Costas P.
Published: February 2010

All-solution processed, low-temperature zinc oxide nanowire network transistor fabrication was demonstrated by combining 1) source-drain electrode fabrication by direct nanoimprinting of metal nanoparticle solution and 2) zinc oxide nanowire network based channel synthesized by a simple hydrothermal approach in water. This simple process can produce high resolution metal contact transistors with inorganic semiconductor nanowire active material in a fully maskless sequence, eliminating the need for lithographic and vacuum processes. The temperature throughout the processing was under 140°C, which will enable further applications to electronics on low-cost, large-area flexible polymer substrates.
Advanced Transient Plane Source Method for the Measurement of Thermal Properties of High Pressure Metal Hydrides
Authors: Flueckiger Scott , Voskuilen Tyler , Zheng Yuan , Pourpoint Timothe´e
Published: February 2010

Metal hydrides are a promising material type for hydrogen storage in automotive applications, but thermal property data is needed to optimize the necessary heat exchangers. In the present work, the transient plane source method is integrated with a pressure vessel to measure these properties for metal hydride powder as a function of pressure during the hydrogenation process. The properties under investigation include effective thermal conductivity, thermal diffusivity, specific heat, and thermal contact resistance. The results of this work with oxidized Ti1.1CrMn powder provide effective thermal conductivity values similar to data reported in literature for other metal hydride materials. The experimental measurements are also well modeled by the Zehner-Bauer-Schlu˝nder interpretive model for packed beds as a function of gas pressure. Extending the test method and ZBS model to estimate the contact resistance provides values that were two orders of magnitude less than measurements previously reported for other hydride materials.
A Spectrally Accurate 2-D Axisymmetric Photon Monte-Carlo RTE Solver for Hypersonic Entry Flows
Authors: Feldick Andrew , Giegel Josh , Modest Michael F.
Published: February 2010

A two-dimensional axisymmetric ray tracing photon Monte Carlo radiative transfer solver is developed. Like all ray tracing Monte Carlo codes, the ray tracing is performed in 3-D, however, arrangements are made to take advantage of the 2-D nature of the problem, to minimize computational time. The solver is designed to be integrated into finite volume hypersonic flow solvers, and is able to resolve the complex spectral properties of such flows to line-by-line accuracy. The solver is then directly integrated into DPLR, a hypersonic flow solver, and closely coupled calculations are performed.
Analysis of Heat and Mass Transfer of an Adiabatic Cross-Flow Liquid Desiccant Absorber Operating at Low Temperatures
Authors: Pineda Sergio M. , Diaz Gerardo
Published: February 2010

With the rising costs of electricity due to increasing demand of electric power, liquid desiccant systems have received significant attention as a way to reduce latent loads on air conditioning systems. In particular, the performance of liquid desiccant systems in humid climates has shown significant reductions in energy consumption. In general, these liquid desiccant systems are composed by an absorber or dehumidifier and a regenerator that utilizes a heat source to reject the water from the diluted liquid desiccant. As the humidity of the air is absorbed at the dehumidifier, the temperature of the liquid desiccant increases due to the addition of heat from the enthalpy of condensation of the water vapor. Thus, many designs of liquid desiccant absorbers include the flow of a cooling fluid that removes heat from the liquid desiccant. A novel application of liquid desiccant systems corresponds to the localized removal of moisture from the air inside low temperature rooms that contain relatively high levels of humidity such as refrigerated warehouses for the food industry. The purpose is to reduce the formation of ice at the surface of the evaporator. Due to the low temperature of the air inside these rooms, no cooling fluid is necessary for the removal of heat from the liquid desiccant. Thus, the designs of the absorbers differ from the designs used for ambient air temperatures. In this paper, a mathematical model of the heat and mass transfer for an adiabatic parallel-plate absorber for which a thin film of liquid desiccant flows down its walls and dehumidifies the air in cross-flow configuration is developed.
Thermal Performance of the Mini-Loop Heat Pipe (LHP)
Authors: Tanaka K. , Katsuta M. , Ohuchi Y. , Saitho K.
Published: February 2010

In this paper, we describe the outline of experimental manufacture of the LHP. This LHP is made of a copper. The evaporator is φ19×95mm, the vapor tube is φ5×300mm, the condenser is φ3.5×600mm and the liquid tube is φ 3.5×300mm. The wick is made of the sintering copper. The working fluid is methanol. Second, we describe the test result of heat transfer capability of this LHP. Finally, I describe the basic equations that resolve the physical development of the LHP and how to estimate the each temperatures of the LHP.
Porosity Effects on Thermal Behaviour of 10 PPI Aluminum Foam
Authors: Cavallini Alberto , Mancin Simone , Rossetto Luisa , Zilio Claudio
Published: February 2010

Electronic cooling challenge is focused on the high heat flux to be dissipated by the operating fluid. Efficient heat spreaders and dissipators, and compact heat exchangers are in great demand for various applications. In the last decade, cellular structure materials and particularly open cells metal foams have been proposed as possible substitutes for traditional finned surfaces. Several authors have experimentally investigated the thermal performance of different metal foams and periodic heat transfer media. Metal foams present random microstructures that consist in open cells randomly oriented and mostly homogeneous in size and shape. Most commercially available metal foams are based on aluminum, copper, nickel and metal alloys. This paper presents the porosity effects on the thermal behaviour of different 10 PPI (pores per inch) metal foams tested in the experimental facility built at the Dept. of Fisica Tecnica of the University of Padova. In particular, the data points have been collected by varying independently the mass flow rate and the heat flow rate. The measured experimental heat transfer coefficients and the pressure drops for three metal foams with different porosity are compared.
Modeling Hydrogen Release From Doped Borosilicate Glass by Furnace or Lamp Heating
Authors: Kitamura Rei , Pilon Laurent
Published: February 2010

This paper explores the physical mechanisms responsible for so-called “photo-induced hydrogen outgassing”. The latter refers to enhanced hydrogen release rate from doped borosilicate glass samples during incandescent lamp heating compared with furnace heating. Experimentally, the glass sample was placed inside an evacuated silica tube. Both were modeled as plane parallel slabs exposed to diffuse furnace radiation or to collimated lamp radiation. Combined conduction, radiation, and mass transfer were accounted for by solving the one-dimensional transient mass and energy conservation equations along with the steady-state radiative transfer equation. All properties were found in the literature. The experimental observations can be qualitatively explained based on conventional thermally activated gas diffusion and by accounting for the participation of the silica tube to radiation transfer along with the spectral properties of the glass samples.
On the Reduction of Wall Temperature Non-Uniformity of a Three-Dimensional Experimental Apparatus
Authors: Lee P. Y. C. , Leong W. H.
Published: February 2010

This paper presents a detailed analysis that was performed for the design of a “uniform” temperature boundary condition imposed on a boundary of a three-dimensional cubical experimental apparatus for benchmark natural convection heat transfer study. The three-dimensional experimental apparatus was constructed with plates which were assembled to act as boundary conditions to the enclosure walls. Test measurements revealed that temperature non-uniformity along one of the plates (boundary) was significant enough that the benchmark study could not be carried out to the desired accuracy of about 1% error. A subsequent detailed mathematical analysis revealed that the temperature non-uniformity on the plate was a result of the effect of thermal spreading/constriction resistance. Modifications to the original design of the apparatus were made to reduce the temperature non-uniformity on the plate by adding a heat source around the plate where the uniform temperature setting was desired. Before the addition of this heat source, a careful mathematical analysis shows a significant reduction in temperature non-uniformity from about 4% (based on the initial design) to less than 1% (for the modified design). By examining the temperature difference between two locations on the plate, the predicted temperature difference obtained through mathematical analyses show excellent agreement with the measured temperature difference.
Development of a Quantitative Nanoscale Thermal Conductivity Profiling Technique by the Removal of Influence Due to Heat Transfer Through the Air
Authors: Kim Kyeongtae , Chung Jaehoon , Hwang Gwangseok , Kwon Ohmyoung , Lee Joon Sik , Park Seungho , Choi Young Ki
Published: February 2010

We developed a quantitative thermal property profiling technique that measures the thermal property of the sample from the tip-sample heat transfer only using SThM. The principle of the technique is explained rigorously through a theoretical analysis of the heat transfer phenomena. The spatial resolution of this technique was demonstrated by obtaining the thermal conductivity profile of samples in which a thin silicon oxide layer is sandwiched between single crystal silicon layers. For a sample with 1.4 μm thick silicon oxide layer, its thermal conductivity was quantitatively profiled. However, for a sample with 100 nm thick silicon oxide layer, the obtained profile was not quantitative. From the experimental results the quantitative spatial resolution of this technique is estimated to be around 200 nm. In order to further improve the quantitative spatial resolution of this technique, the tip radius of the completed thermocouple SThM probe should be reduced further.
CFD Investigating the Changes of FAC Wear Sites Due to the Power Uprate of Nuclear Power Plant
Authors: Hung Tsun Fu , Ferng Yuh Ming , Lin Bing Hong , Shih Chunkuan , Pei Bau-Shei
Published: February 2010

Changes of flow-accelerated corrosion (FAC) wear sites on the piping due to the power uprate of nuclear power plant are investigated by way of computational fluid dynamics (CFD) models. These models proposed in this paper include the three-dimensional two-phase flow models and appropriate FAC models. The computations are performed using commercial code Fluent 6.2 which is control-volume-based. A boiling water reactor (BWR), located at Taiwan, is selected in the present analytical works. Simulation results clearly reveal that the present model can precisely capture the two-phase phenomena within the piping system. Coupled with the calculated two-phase flow characteristics, the appropriate FAC indictors can predict the local distributions of severe FAC sites. These predicted results show reasonable agreement with the plant measurements. Therefore, the impacts of power uprate on the changes of wear sites can be confidently investigated by the present CFD model. Through the comparisons of predictions for the selected BWRs under 100%, 105%, and 110% power levels, the simulation results clearly reveal that the power uprate does not significantly change the characteristics of FAC wear sites.
Heat Transfer Characteristics of Vertical Rectangular Channel Inserting Copper Wire With High Porosity
Authors: Honma Akira , Takeda Tetsuaki
Published: February 2010

In the Very-High-Temperature Reactor (VHTR) which is the next generation nuclear reactor system, ceramics and graphite are used as the fuel coating material and the core structural material, respectively. Even if the accident occurs and the reactor power goes up instantly, the temperature of the core will change slowly. This is because the thermal capacity of the core is so large. Therefore, the VHTR system can passively remove the decay heat of the core by natural convection and radiation from the surface of the reactor pressure vessel (RPV). From the view point of the safety characteristic, the passive cooling system should be designed for the VHTR as the best way of the reactor and vessel cooling systems (VCS). So, the gas cooling system by natural convection is the one of the candidate systems for the VCS of the VHTR. This study is to develop the passive cooling system for the VHTR using the vertical rectangular channel inserting porous materials. In general, when the high temperature circular or rectangular channels are cooled by forced convection of gas, there are several methods for enhancement of heat transfer such as attaching radial or spiral fins on a channel surface or inserting twisted tape in a channel. The objective of this study is to investigate heat transfer characteristics by forced convection of porous materials inserted into a rectangular channel with high porosity. In order to obtain the heat transfer characteristics of the one-side heated vertical rectangular channel inserting the porous material, an experiment was carried out. From the results obtained in this experiment, it was found that an amount of removed heat by forced convection using porous material (porosity > 0.996) was about 15% higher than that without the copper wire. Furthermore, the ratio between the amounts of heat removed of the rectangular channel with the porous material and without the porous material increases with increasing temperature of the channel wall.
Investigation of the Beltline Welding Seam and Base Metal of the Greifswald WWER-440 Unit 1 Reactor Pressure Vessel
Authors: Schuhknecht Jan , Viehrig Hans-Werner , Rindelhardt Udo
Published: February 2010

The investigation of reactor pressure vessel (RPV) materials from decommissioned NPPs offers the unique opportunity to scrutinize the irradiation behaviour under real conditions. Material samples taken from the RPV wall enable a comprehensive material characterisation. The paper describes the investigation of trepans taken from the decommissioned WWER-440 first generation RPVs of the Greifswald NPP. Those RPVs represent different material conditions such as irradiated (I), irradiated and recovery annealed (IA) and irradiated, recovery annealed and re-irradiated (IAI). The working program is focussed on the characterisation of the RPV steels (base and weld metal) through the RPV wall. The key part of the testing is aimed at the determination of the reference temperature T0 following the ASTM Test Standard E1921-05 to determine the fracture toughness of the RPV steel in different thickness locations. In a first step the trepans taken from the RPV Greifswald Unit 1 containing the X-butt multilayer submerged welding seam and from base metal ring 0.3.1 both located in the beltline region were investigated. Unit 1 represents the IAI condition. It is shown that the Master Curve approach as adopted in ASTM E1921 is applicable to the investigated original WWER-440 weld metal. The evaluated T0 varies through the thickness of the welding seam. The lowest T0 value was measured in the root region of the welding seam representing a uniform fine grain ferritic structure. Beyond the welding root T0 shows a wavelike behaviour. The highest T0 of the weld seam was not measured at the inner wall surface. This is important for the assessment of ductile-to-brittle temperatures measured on sub size Charpy specimens made of weld metal compact samples removed from the inner RPV wall. Our findings imply that these samples do not represent the most conservative condition. Nevertheless, the Charpy transition temperature TT41J estimated with results of sub size specimens after the recovery annealing was confirmed by the testing of standard Charpy V-notch specimens. The evaluated Charpy-V TT41J shows a better accordance with the irradiation fluence along the wall thickness than the Master Curve reference temperature T0. The evaluated T0 from the trepan of base metal ring 0.3.1 varies through the thickness of the RPV wall. T0 increases from −120°C at the inner surface to −104°C at a distance of 33 mm from it and again to −115°C at the outer RPV wall. The KJc values generally follow the course of the MC, although the scatter is large. The re-embrittlement during 2 campaigns operation can be assumed to be low for the weld and base metal.
A Study of Steam-Water Countercurrent Flow Model in TRACE Code
Authors: Cheng Yi-Hsiang , Shih Chunkuan , Wang Jong-Rong , Lin Hao-Tzu
Published: February 2010

This paper studied the countercurrent flow model in the TRACE code version 5.0. Steam and water are chosen as the working fluids that flow counter-currently in a circular pipe. Three types of the countercurrent flow models, the Wallis, the Kutateladze and the Bankoff correlations, are investigated. A single pipe model was built for the studies of the Wallis and the Kutateladze correlations, and the variable in the calculation model is the pipe diameter. A perforated plate model was built to study the Bankoff correlation, and the variables include the pipe diameter, the hole diameter, the number of holes and the plate thickness. The hydraulic diameter of the pipe varies from 2.5–200 mm for validating both the Wallis and the Kutateladze correlations. While validating the Bankoff correlation, the hydraulic diameter of the pipe is of 50 and 200 mm, and the plate thickness changes as 10 and 40 mm. Through this study, we validate the countercurrent flow model in the TRACE code, and provides comments on the application ranges of these three correlations.
Experimental Characterization of Hydraulics in EPR™ Control Rod Guide Assembly: EDF and AREVA Complementary Approaches
Authors: Dolleans Philippe , Muller Thierry , Migot Benoiˆt , Petitjean Se´bastien , Fontes Jean-Philippe , Longatte Elisabeth , Mezoul Bruno
Published: February 2010

The new EPR™ Evolutionary high-Power nuclear Reactor is based on the best design concepts of French and German experiences over the past thirty years in power plant design construction and operation. In the framework of detailed engineering phase of plant construction in Finland (Olkiluoto 3) and in France (Flamanville 3), various investigations were led to improve the knowledge of hydraulics in innovative Reactor Pressure Vessel internals. A specific attention has been paid to hydraulics in Control Rod Guide Assembly (CRGA), which is an innovative component derived from the KONVOI design but adapted to the EPR™ design. In order to assess the hydraulic behavior of the EPR™ CRGA, a complementary experimental approach was developed by EDF and AREVA. Two mock-ups, representative of the full-scale EPR™ Control Rod Guide Assembly, were designed: MAGALY mock-up using real prototype of CRGA within AREVA’s engineering teams and PHACETIE mock-up at same scale but dedicated to a more analytic approach designed by EDF. The aim of the paper is to present the tests performed on two mock-ups to characterize the hydraulic behavior of this innovative EPR™ CRGA. At first, a comparison of the two mock-ups was done. The benchmark showed that the two mock-ups feature similar hydraulic behavior. The head losses evaluated along the experimental devices are practically identical. Moreover, the results showed that the global hydraulic forces applied to the Rod Cluster Control Assembly (RCCA) just up to the Upper Core Plate (UCP) are in a very good agreement. The good comparison between the two mock-ups strengthens the hydraulic characterization methods of the hydraulics in EPR™ CRGA. Specific studies were also led on the two mock-ups. The MAGALY mock-up was used to characterize the impact of the EPR™ operating conditions on the CRGA hydraulics behavior and especially on the vibrations and the drag forces applied to RCCA. Complementary measurements by using Laser Velocimetry techniques (PIV and LDV) were carried out on the PHACETIE mock-up allowing an evaluation of the velocity field inside the CRGA. The results obtained thanks to the two mock-ups allowed AREVA and EDF to have a good knowledge of the hydraulics behavior in the EPR™ CRGA. In a next step, further studies will be performed in order to deepen the knowledge of the vibratory behavior of the RCCA and the control rod drop time.
Integration of Degradation Models Into Generation Risk Assessment (GRA): Challenges and Modeling Approaches
Authors: Jyrkama Mikko I. , Pandey Mahesh D. , Hess Stephen M.
Published: February 2010

The main objective of generation risk assessment (GRA) is to assess the impact of equipment unavailability and failures on the ability of the plant to produce power over time. The system reliability models employed for this purpose are based on the standard fault tree /event tree approach, which assumes failure rates to be constant. However, this ignores the impact of aging degradation and results in static estimates of expected generation loss. Component and equipment degradation not only increases the probability of failure over time, but also contributes to generation risk through increased unavailability and costs arising from greater requirement for inspection and replacement of degraded components. This paper discusses some of the key challenges associated with integrating the results of component degradation models into GRA. Because many analytical and simulation methods are subject to limitations, the methodology and modeling approach proposed in this work builds on the current GRA practice using the fault tree approach. The modeling of component degradation can be done separately at the fault tree cut set level, assuming the cut sets are independent and the component unavailabilities are relatively small. In order to capture the joint contribution of equipment failure and unavailability to generation risk, new risk-based importance measures are also developed using the concept of net present value (NPV).