bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational Study of the Unsteady Flow Structure of the Buoyancy-Driven Rotating Cavity With Axial Throughflow of Cooling Air
Authors: Dweik Zain , Briley Roger , Swafford Timothy , Hunt Barry
Published: February 2010

Buoyancy driven flows such as the one that occurs in the inter-disk space of an axial compressor spool plays a major role in determining the gas turbine engine projected life and performance. Details of the developed flow structure inside these spaces largely impact the operating temperatures on the rotating walls of the compressor hardware and therefore impact the life of the machine. In this paper the impact of engine power condition (Idle, Highpower, and Shutdown) on the flow structure for these rotating cavities is studied under a wide range of operating conditions encountered by realistic turbomachines. A computational analysis is performed using commercially available computational tools for grid generation (ICEM-CFD) and turbulent-flow simulation (CFX). A computational test case was developed to imitate the rig-test conditions of Owen and Powell, and computed results were assessed and validated by comparison with their experimental results. A total of fifteen unsteady CFD cases covering a wide range of operating conditions (Rossby Number Ro, Rotational Rayleigh Number Raφ, and axial Reynolds Number Rez) were analyzed. The computed flow results revealed that the flow structure evolution, starting from a steady state solution, is such that radial arms of different number (according to the engine power condition), surrounded by a co-rotating (cyclonic) and counter-rotating (anti-cyclonic) pair of vortices, start to form at different locations. Cold air from the central jet enters the cavity in these arms under the combined action of the centrifugal buoyancy and the Coriolis forces. As time proceeds, the flow structure tends to become virtually invariant with time in a repeatable pattern. The number of radial arms, strength of recirculation zones, and the degree of invasion of the central cooling air toward the shroud are all dependent on the engine power condition. The computations also revealed that at high rotational speed the flow stabilizes, and the unsteady features of the flow structure (cyclonic and anti-cyclonic recirculation zones surrounding the radial arms, radial invasion of the cooling air in the radial arms, and its final impingement upon the shroud surface) eventually disappear after a threshold value of the rotational speed is reached.
Parametric Study of an Advanced IGCC
Authors: Iki Norihiko , Tsutsumi Atsushi , Matsuzawa Yoshiaki , Furutani Hirohide
Published: February 2010

IGCC achieve high efficiency energy conversion from coal to electricity. However its efficiency is below 50% [HHV]. To achieve higher efficiency, Advanced IGCC was planned by using exergy-recuperation concept. Advanced IGCC requires many breakthroughs in technology. Advanced IGCC achieve high efficiency by using the heat of reformed gas and the application of the autothermal reaction in the gasifier. Authors try parametric study of Advanced IGCC to figure out the desirable consists of Advanced IGCC. The performance of Advanced IGCC depends on coal, gasifier condition, configuration of components, etc. The heat value of the supplied coal is 667MW [HHV]. Foreign subbituminous coal is selected as standard fuel. The adiabatic efficiencies of the compressor, the gas turbine, steam turbine and condensing turbine at standard condition were defined so that the efficiency of IGCC with 1500 °C class gas turbine is 48% [HHV] with high performance gasifier. The efficiency of IGCC reaches to 52% [HHV] by applying autothermal reaction in the gasifier. This system requires the extra heat supply in order to hold the autothermal reaction condition in the gasifier. Therefore the net efficiency of this system is about 44% [HHV]. The net efficiency of the advanced IGCC is 48% [HHV]. On the other hand, 1700 °C class advanced IGCC can achieve 51% [HHV] net efficiency and its gas turbine exhaust high temperature heat to hold autothermal reaction condition. Increase of the adiabatic efficiencies of the compressor and the gas turbine enables the high efficiency of the advanced IGCC. If the adiabatic efficiency of compressor reaches to 87% and adiabatic efficiency of the gas turbine reaches to 92%, 1700 °C class advanced IGCC has the potential of over 60% [HHV].
On Surrogate Fuel Formulation
Authors: Slavinskaya Nadezhda A. , Zizin Anton , Aigner Manfred
Published: February 2010

Calculations of evaporation characteristics (distillation curve, two-phase diagram, critical points) of surrogates are described in detail. The efficiency of some surrogate blends, represented in literature, in reflecting the evaporation characteristics was analysed. Based on the analysis, the chemical capabilities of surrogate models are not linked to their abilities to reflect the phase equilibrium properties of real fuel. It is shown, that blending of pure hydrocarbons must begin with the phase equilibrium and distillation curve calculations. A surrogate mixture was selected which closely matches the boiling-point curve and two phase diagram for Jet-A.
Derivation of an Anisotropic Model for the Pressure Loss Through a Heat Exchanger for Aero Engine Applications
Authors: Yakinthos Kyros , Donnerhack Stefan , Missirlis Dimitrios , Seite Olivier , Storm Paul
Published: February 2010

We present an effort to model the pressure loss together with the heat transfer mechanism, in a heat exchanger designed for an integrated recuperative aero engine. The operation of the heat exchanger is focusing on the exploitation of the thermal energy of the turbine exhaust gas to pre-heat the compressor outlet air before combustion and to decrease fuel consumption and pollutant emissions. Two basic parameters characterize the operation of the heat exchanger, the pressure loss and the heat transfer. The derivation of the pressure loss model is based on experimental measurements that have been carried-out on a heat exchanger model. The presence of the heat exchanger is modeled using the concept of a porous medium, in order to facilitate the computational modeling by means of CFD. As a result, inside the integrated aero engine, the operation of the heat exchanger can be sufficiently modeled as long as a generalized and accurate pressure drop and heat transfer model is developed. Hence, the porosity model formulation should be capable of properly describing the overall macroscopic hydraulic and thermal behavior of the heat exchanger. The effect of the presence of the heat exchanger on the flow field is estimated from experimental measurements. For the derivation of the porous medium pressure loss model, an anisotropic formulation of a modified Darcy-Forchheimer pressure drop law is proposed in order to take into account the effects of the three-dimensional flow development through the heat exchanger. The heat transfer effects are taken also into account with the use of a heat transfer coefficient correlation. The porosity model is adopted by the CFD solver as an additional source term. The validation of the proposed model is performed through CFD computations, by comparing the predicted pressure drop and heat transfer with available experimental measurements carried-out on the heat exchanger model.
Impact of Swirl Fluctuations on the Flame Response of a Perfectly Premixed Swirl Burner
Authors: Komarek Thomas , Polifke Wolfgang
Published: February 2010

Combustion instabilities represent a long known problem in combustion technology. The complex interactions between acoustics and turbulent swirling flames are not fully understood yet, making it very difficult to reliably predict the stability of new combustion systems. For example, the effects of fluctuations of swirl number on the heat release of the flame have to be investigated in more detail. In this paper a perfectly premixed, swirl stabilized burner with variable axial position of the swirl generator is investigated. In experiments, the position of the swirl generator has a strong impact on the dynamic flame response, although it does not influence the time-averaged distribution of the heat release significantly. This phenomenon is further investigated, using computational fluid dynamics combined with system identification. The generation of fluctuations of swirl number, their propagation to the flame, and their effect on the dynamic flame response are examined. A simple model based on convective time lags is developed, showing good agreement with experiments.
Comparison of Detailed and Simplified Optimization Approaches for the Performance Simulation of Cogeneration Plants
Authors: Campanari Stefano , Manzolini Giampaolo , Silva Paolo
Published: February 2010

It is well known that cogeneration can be an effective energy-saving solution, able to achieve relevant reductions in primary energy consumption and pollutant emissions. Generally speaking, obtaining best performances from a cogeneration plant requires a proper design and a careful management, aiming to maximize the plant energy and economic savings. Solving the issue of optimization may require a dedicated simulation tool when the CHP plant faces variable loads (both electrical, thermal and in some cases cooling loads) and electricity tariffs, or significantly changes its efficiency at partial load, or integrates a heat storage which allows to extend the possible plant management strategies. In all these cases, the optimization results may not be easy predictable. However, in other cases also simpler and faster approaches may lead to correctly optimized results, depending on the application features. The purpose of this work is to compare two approaches to the optimization of trigeneration plants: (i) a detailed model already presented in previous works (DCOGEN), able to perform accurate optimization and prediction of annual energy balances but requiring detailed plant definition, accurate specifications of the user demands and a significant computational time, and (ii) a simplified and faster model based on few information and a intuitive optimization strategy. The comparison is carried out for two cases, reflecting the features of industrial CHP applications based on small scale gas turbines and reciprocating engines. Results show the advantages given by the detailed model as well as the limits of simplified approaches.
Active Compressor Stability Management via a Stall Margin Control Mode
Authors: Liu Yuan , Dhingra Manuj , Prasad J. V. R.
Published: February 2010

An active engine control scheme for protection against compressor instabilities such as rotating stall and surge is presented. Compressor stability detection is accomplished via a parameter known as the correlation measure, which quantifies the repeatability of the pressure fluctuations in the tip region of a compressor rotor. This work investigates the integration of the correlation measure with an aircraft engine control system through the use of a stall margin control mode. The development and implementation of the stall margin mode is described. The effectiveness of the overall active control framework—an active compressor stability management system—is assessed using a computer simulation of a high-bypass, dual-spool, commercial-type turbofan engine.
Biomass Gasification Modelling: An Equilibrium Model, Modified to Reproduce the Operation of Actual Reactors
Authors: Damiani Lorenzo , Trucco Angela
Published: February 2010

This paper presents a modified equilibrium simulation model for biomass gasification performance prediction. The model, implemented in the Matlab-Simulink® environment, is able to calculate the reactor main operating parameters, such as reaction temperature, gas composition, gas flow rate and solid product (typically charcoal). The comparison of model output with experimental data puts in evidence the insufficient precision of equilibrium models, due to their incapability of taking into account the non equilibrium effects always present in the gasification process. To obtain a better prediction of measured values the pure equilibrium model has been modified on the basis of literature experimental data, introducing semi-empirical correlations with the aim to consider the most meaningful effects of non-equilibrium. The results demonstrate that this modification leads to an increased precision of the model in reproducing experimental data.
Assessment of the Operational Performance of Fischer-Tropsch Synthetic-Paraffinic Kerosene in a T63 Gas Turbine Compared to Conventional Jet A-1 Fuel
Authors: Bester Nigel , Yates Andy
Published: February 2010

The performance implications of operating on Synthetic-Paraffinic Kerosene (SPK) were investigated using a RR-Allison T63-A-700 Model 250-C18 B gas turbine and compared to conventional Jet A-1. The SPK was aromatic–free and possessed a greater hydrogen/carbon ratio than petroleum derived Jet A-1. The variation in aromatic content had several implications with respect to soot and NOx emissions. Reduced aromatics also implied a reduction in the radiative heat transfer to the combustor liner. A simple model was used to explore the effect of H/C ratio on the adiabatic flame temperature, the combustor exit temperature and the engine efficiency via the impact on the gas properties and these were compared to the experimental data. It was found that operation with SPK changed directionally toward improving energy extraction via a turbine and an overall efficiency gain of about 1.2% was attained with operation on SPK through increased combustion efficiency, a reduction in liner pressure loss and an improvement in the combustion products properties. A modified combustion liner was fitted to enable the thermal loading on the combustor liner to be investigated and the expected trend with the SPK fuel was confirmed and quantified.
Start Fuel Schedule Enhancements for the ETF40B Gas Turbine Engine
Authors: Simonetti Joseph L. , McMurry Joseph H.
Published: February 2010

Gross starting characteristics of the Vericor Power Systems ETF40B gas turbine engine utilizing diesel fuel for the Republic of Korea Navy LSF-II application indicate inconsistent starting performance, especially in cold ambient temperatures. There is also evidence that cold starting inconsistencies exist on the US Navy LCAC installation of the ETF40B engine. The inconsistencies include late light-offs, failed starts, excessive exhaust smoke, detonative ignition and excessive commanded fuel flow by the full authority digital engine control (FADEC). The starting anomalies experienced on US Navy LCAC have ultimately resulted in the addition of starting requirements to the production engine acceptance test procedure. A detailed review of historical information regarding the TF40B fuel system characteristics resulted in the basis for establishing revised LFMV calibration values and revised FADEC engine start fuel scheduling. Additionally, this review indicated the need for fuel system flow/pressure measurements in order to establish current characteristics and to help refine component requirements and changes (as appropriate). These measurements are required over the entire engine starting and operating range. Cold ambient temperature start testing was performed to establish the engine start characteristics on JP5/JET A fuels with the existing and revised LFMV calibrations. A revised start schedule was developed that provided a reliable, stable starting characteristic (reliable first attempt starting, reducing smoking on starts, eliminating detonative ignition, minimizing large variations in commanded fuel flow during starting). The fuel system pressures and flows were fully characterized in the start and operating regime and start testing validation was performed on Diesel Fuel.
Preparing for the Future: Reducing Gas Turbine Environmental Impact
Authors: Cumpsty Nicholas A.
Published: February 2010

In the long term the price of fuel will rise and it is now urgent to reduce carbon dioxide emissions to avoid catastrophic climate change. This lecture looks at power plant for electricity generation and aircraft propulsion, considering likely limits and possibilities for improvement. There are lessons from land-based gas turbines which can be applied to aircraft, notably the small increases in efficiency from further increase in pressure ratio and turbine inlet temperature. Land-based gas turbines also point to the benefit of combining the properties of water with those of air to raise efficiency. Whereas the incentive to raise efficiency and reduce CO2 will force an increase in complexity of land-based power plant, the opportunities for this with aircraft are more limited. One of the opportunities with aircraft propulsion is to consider the whole aircraft operation and specification. Currently the specification for new aircraft of take-off and climb thrust are not fully consistent with designing the engine for minimum fuel consumption and this will be addressed in some depth in the lecture. Preparing for the future entails alerting engineers to important possibilities and limitations associated with gas turbines which will mitigate climate change due to carbon dioxide emissions.
Experimental Apparatus for the Determination of Condensation Heat Transfer Coefficient for R134a and R600a Flowing Inside Vertical and Horizontal Tubes Respectively
Authors: Dalkilic¸ Ahmet Selim , Ag˘ra O¨zden
Published: February 2010

Determination of condensation heat transfer coefficients for HFC-134a in a 7 mm i.d. vertical smooth copper tube and R600a in a 4 mm i.d. horizontal smooth copper tube are experimentally investigated. The test sections are 1 m long horizontal and 0.5 m long vertical counter flow tube-in-tube heat exchangers with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The experiments are performed at average qualities ranging between 0.1–0.99 for the horizontal test section and 0.67–0.99 for the vertical test section. The mass fluxes are ranging between 50–120 kg m−2s−1 and saturation temperatures are between 30–43 °C for the horizontal test section, the mass fluxes are around 29 kg m−2s−1 and saturation temperatures are between 30–36 °C for the vertical test section. The experimental apparatus are designed to capable of changing the different operating parameters such as mass flow rate and condensation temperature of refrigerant, cooling water temperature, and mass flow rate of cooling water etc and investigate their effect on heat transfer coefficients and pressure drops. The ex-proof diaphragm pump for R600a and the gear pump for R134a are used to circulate the refrigerant in these systems. The detailed description of design and development of the test apparatus, control devices, instrumentation, and the experimental procedure are reported and the study of experimental setups from the available literature survey with the existing ones are compared in this paper. The condensation heat transfer coefficients are obtained for two different test sections with various experimental conditions and compared with some well-known correlations in the literature.
Numerical Simulation, Method of Design and Optimization of a Brick Dryer
Authors: Shokouhmand Hossein , Abdollahi Vahid , Vahidkhah Koohyar , Habibi Kaveh , Aria Hatef , Shemirani Farzin M.
Published: February 2010

In the present study, an innovative method for an accurate simulation and design of a chamber dryer used in brick/ceramic industry has been proposed. A thorough investigation of currently used dryers is conducted and the source of losses and optimization criteria are detected and discussed. Three-dimensional modeling of the chamber dryer is done via a commercial CFD Package. In the second step, critical locations in the cell together with the critical values for heat transfer coefficient are obtained from the result of 3D modeling. Then a set of partial differential equations governing heat and mass transport in a single brick (critical) are discretized by Finite difference method. The resulting PDEs together with temperature and humidity boundaries have been solved numerically. These equations are derived by combining conservation laws with Fourier’s law for heat conduction and Darcy’s and Fick’s laws for mass diffusion in porous material. All necessary diffusion coefficients for liquid and vapor have been obtained experimentally via implanting relevant temperature and humidity sensors into the green product situated in a real-scale dryer and by logging the variations in both parameters. Finally an efficient scheme for mounting the air circulation devices, inlet air temperature and humidity, burner characteristics, flow rates and drying process control have been proposed for a sample dryer with a specific dimensions.
Thermal Characterization of Bi-Material Microcantilevers: Thermal Conductance and Microscale Convection
Authors: Narayanaswamy Arvind , Gu Ning
Published: February 2010

Bi–material atomic force microscope cantilevers have been used extensively over the last 15 years as physical, chemical, and biological sensors. As a thermal sensor, the static deflection of bi–material cantilevers due to the mismatch of the coefficient of thermal expansion between the two materials has been used to measure temperature changes as small as 10−5 K, heat transfer rate as small as 40 pW, and energy changes as small as 10 fJ. Bi–material cantilevers have also been use to measure “heat transfer - distance” curves a heat transfer analogy of the force–distance curves obtained using atomic force microscopes. In this work, we concentrate on characterization of heat transfer from the microcantilever. The two quantities that we focus on are the thermal conductance of the cantilever, Gcant (units WK−1), and the thermal conductance due to microscale convection from the cantilever to the ambient fluid, Gconv (units WK−1). The deflection of the cantilever to changes in its thermal environment is measured using the shift in position, on a position sensitive detector, of a laser beam focused at the tip of the cantilever. By determining the response of the microcantilever to (1) uniform temperature rise of the ambient, and (2) change in power absorbed at the tip, the thermal conductance of heat transfer from the cantilever can be determined. When the experiment is performed at low enough ambient pressure so that convection is unimportant (¡ 0.1 Pa), Gcant can be measured. When the experiment is performed at atmospheric pressure the heat transfer coefficient due to convection from the cantilever can be determined.
Experimental Results for Light-Induced Boiling in Water-Based Graphite Nanoparticle Suspensions
Authors: Taylor Robert A. , Phelan Patrick E. , Adrian Ronald J. , Otanicar Todd , Prasher Ravi S.
Published: February 2010

One relatively simple subset of nanotechnology is nanofluids, obtained by the addition of nanoparticles to a conventional base fluid. The promise of nanofluids stems from the fact that at relatively small particle loading (typically <1% by volume) significant enhancement in thermal transport may be possible [1–3]. Since there are a wide variety of nanoparticle materials to choose from, nanofluidic systems can be tuned to fit a number of applications. This research focuses on direct thermal collection of light energy using highly absorptive nanofluids. Experimental tests are conducted using a 0.1% by volume graphite/water (30nm nominal particle diameter) nanofluid exposed to a 130 mW, 532 nm, continuous laser. A lens is placed between the laser and the fluid to achieve a high-energy flux (∼ 490 Wcm−2). Since initially over 99.9% of the light is absorbed in a path length of 0.1 mm, the irradiated portion of the base fluid collects enough energy to vaporize. Heuristic methods of analysis demonstrate this situation incorporates several interesting modes of heat transfer and fluid mechanics. These experiments also reveal the possibility for novel solar collectors in which the working fluid directly absorbs energy and undergoes phase change in a single step.
Fluid Flow and Heat Transfer Characteristics of Ethylene Glycol and Water in Copper-Based Microchannel Devices
Authors: Mei Fanghua , Lu B. , Meng W. J. , Guo S.
Published: February 2010

Metal-based microchannel heat exchangers (MHEs) offer potential solutions to applications demanding high heat flux removal, such as cooling of high-performance microelectronic and energy-efficient lighting modules. Efficient fabrication of metal-based MHEs and quantitative flow and heat transfer measurements on them are critical for establishing the economic and technical feasibility of such devices. Adopting metal-based MHEs in many applications demands quantification of flow and heat transfer performance with application-relevant coolants, e.g. ethylene glycol (EG)/water mixtures rather than pure water. As a first step in this direction, we report here fabrication and assembly of all-Cu MHE prototypes, as well as results of flow and heat transfer testing using pure EG and pure water as the fluid medium. Results of heat transfer testing indicate sensitivity of overall heat transfer performance to entrance length effects, which in the case of pure EG, is significantly influenced by its physical properties under the testing condition.
Second Law Analysis of Slip Flow Heat Transfer in Annulus Microchannel
Authors: Sadeghi Arman , Asgarshamsi Abolhassan , Saidi Mohammad Hassan
Published: February 2010

In the present work, the second law of thermodynamics analysis has been carried out for steady state hydrodynamically and thermally fully developed laminar gas flow in annulus microchannels with asymmetrically heated walls. The rarefaction effects are taken into consideration using first order slip velocity and temperature jump boundary conditions. Viscous heating is also included for both the hot wall and the cold wall cases. Using the velocity distribution obtained in earlier works, the energy equation is solved to get analytically the temperature distribution and consequently to compute the entropy generation rate. The effects of rarefaction and the annulus geometrical aspect ratio on velocity distribution are discussed. The complicated interactive effects of rarefaction, viscous dissipation, the ratio of Brinkman number to dimensionless temperature difference, annulus geometrical aspect ratio and asymmetry on entropy generation rate and Bejan number are shown in graphical form and also discussed in details. The analytical results obtained are compared with those available in the literature and an excellent agreement is observed. It is realized that the effect of the wall heat fluxes ratio on entropy generation is negligible at great values of the ratio of Brinkman number to dimensionless temperature difference, while the effect of increasing values of the annulus geometrical aspect ratio is to severely increase entropy generation. The entropy generation decreases as Knudsen number increases, however the effect of increasing values of Brinkman number and the ratio of Brinkman number to dimensionless temperature difference is to increase entropy generation.
Two and Three-Dimensional Simulations of Enhanced Heat Transfer in Nuclear Fuel Rod Bundles
Authors: Carrilho Leo A. , Khan Jamil , Conner Michael E. , Mandour Abdel , Dzodzo Milorad B.
Published: February 2010

The effects of artificial roughness for the purpose of thermal performance improvement in pressurized water nuclear reactors are investigated. The artificial roughness consists of two-dimensional ribs parallel to the turbulent flow. The fuel rod bundle subchannel is preliminarily modeled as an annulus using the finite element method in ANSYS/FLOTRAN. The Navier-Stokes equations are solved from the SST (Shear Stress Transport) turbulence model for the simulated annulus thermal-flow. The analyses are performed for ribs dimensions and pitch provided by published previous work. It is found that, heat transfer and differential pressure have similar behavior with highest heat transfer occurring at the reattachment point. The finite element model describes well the characteristics of turbulent flow in smooth and rough rod when compared to previous semi-empirical models. Next paper extends the analysis by comparing numerical results with experimental test data and sensitivity analyses for different roughness configurations.
Performance of Hybrid Photovoltaic and Thermal (PV/T) Collector With and Without Electricity Generation
Authors: Yandri Erkata , Miura Naokatsu , Ito Sadsuke , Fujisawa Toru , Yoshinaga Mika
Published: February 2010

This paper presents the experimental results that involve the analysis of a photovoltaic and thermal (PV/T) hybrid collector, which has an integration of the photovoltaic cells and a solar thermal panel into one collector, by focusing on its thermal efficiency when both thermal and electrical energies are generated and when only thermal energy is generated. The experiment was performed at 4 different collector input temperatures, i.e., 12°C, 15°C, 20°C, and 25°C under the condition that the water flow rate was 4 l/min. We analyzed during the period of peak irradiation from 12:00 to 13:00 to obtain the semi-steady-state thermal performance. Besides, in order to remove the differences of the wind environment, the wind heat losses are calculated in the analysis. The result shows that the thermal efficiency of the PV/T collector decreases slightly when only thermal energy is generated as compared to that when both thermal and electrical energies are generated.
Nanoscale Wicking Structures
Authors: Zhang Conan , Hidrovo Carlos H.
Published: February 2010

Heat pipes are ubiquitous in various heat transfer applications due to their low maintenance and lack of moving parts. Their simplicity makes them compact and ideally suited for microelectronics use. Recirculation of the coolant in a heat pipe is done passively by means of a wicking structure that induces capillary-driven flow from the condenser to the evaporator. This fluidic scheme is highly desirable but requires precise optimization of the wicking structure geometry to provide the required coolant flow rates under different heat loads. In this paper we present an ab initio model that simulates the capillary flow within a wicking structure of regular and periodic geometry. An energy formulation incorporating capillary equations for pressure gradient and the Stokes flow equation for frictional dissipation were used in the analysis. The feasibility of using nanostructures for capillary-driven flow was assessed using this theoretical analysis. This model is specifically designed to simulate a nanopillar array wick (or nanowick) but was also extended to incorporate commercially available homogenous wicks through the use of a general Darcy’s flow approach. A Darcy’s flow analysis requires knowledge of the porous structure permeability (κ), which must be empirically determined. However, our first principles approach can be used to estimate the effective permeability of various commercial wicks. Only the characteristic structural dimensions of a wick are needed in our model for an accurate estimate of the permeability and the maximum flow rate the wick can sustain without the necessity for an empirical correlation. The results of the theoretical model were corroborated through experimental measurements of baseline mesh wicks and nanowicks. Since the thermal performance of most heat pipes is usually capped by the capillary limit, this threshold was examined for each wick by measuring the mass flow over time at different heat fluxes. At high heat fluxes, the wick cannot sustain the fluid flow necessary for heat removal and burnout occurs. This phenomenon occurs at the thermal capillary limit. The mass flow ceases to increase in the case of burnout and may actually decrease if a disruptive vapor film is created. Experiments show that the baseline wicks were found to have higher mass flow rates when compared to a nanowick due to the difference in thickness of the wicks. However, when the data were normalized to produce velocity values, the nanowick was found to have a higher velocity than most of the baseline wicks. These experimental results were weighed against the theoretical model results showing very good agreement of the two.
Analysis of Instability for OTSG by Using Multivariable Frequency Domain Method
Authors: Hou Su-xia , Tai Yun , Zhao Fu-yu
Published: February 2010

A new method for analyzing the problem of the thermal-hydrodynamic instability of OTSG (once-through steam generator) with multiple boiling channels is presented in this paper. The mothod is based on modern frequency domain theory and is more efficient for analyzing the instability of OTSG with coupling interactions and complicated boundary conditions than the usually used single variable method. A mathematical model for a OTSG is derived from the foundamental equations by use of the small perturbation and Laplace-transform techniques. The stable boundary and parametric effects on the stability of the system are evaluated with a computer code. Numerical examples are given in the paper and the predictions of the model are in good agreement with the experimental results.
Steady-State Thermal-Hydraulic Analysis of a Particle-Bedded Boiling Water Reactor
Authors: Cai Xiaoyu , Qiu Suizheng , Su Guanghui , Zhao Changyou
Published: February 2010

The current Light Water Reactors both BWR and PWR have extensive nuclear reactor safety systems, which provide safe and economical operation of Nuclear Power Plants. During about forty years of operation history the safety systems of Nuclear Power Plants have been upgraded in an evolutionary manner. The cost of safety systems, including large containments, is really high due to a capital cost and a long construction period. These conditions together with a low efficiency of steam cycle for LWR create problems to build new power plants in the USA and in the Europe. An advanced Boiling Water Reactor concept with micro-fuel elements (MFE) and superheated steam promises a radical enhancement of safety and improvement of economy of Nuclear Power Plants. In this paper, a new type of nuclear reactor is presented that consists of a steel-walled tube filled with millions of TRISO-coated fuel particles (Micro-Fuel Elements, MFE) directly cooled by a light-water coolant-moderator. Water is used as coolant that flows from bottom to top through the tube, thereby fluidizing the particle bed, and the moderator water flows in the reverse direction out of the tube. The fuel consists of spheres of about 2.5 mm diameter of UO2 with several coatings of different carbonaceous materials. The external coating of steam cycle the particles is silicon carbide (SiC), manufactured with chemical vapor deposit (CVD) technology. Steady-State Thermal-Hydraulic Analysis aims at providing heat transport capability which can match with the heat generated by the core, so as to provide a set of thermal hydraulic parameters of the primary loop. So the temperature distribution and the pressure losses along the direction of flow are calculated for equilibrium core in this paper. The calculation not only includes the liquid region, but the two phase region and the superheated steam region. The temperature distribution includes both the temperature parameters of micro-fuel elements and the coolant. The results show that the maximum fuel temperature is much lower than the limitation and the flow distribution can meet the cooling requirement in the reactor core.
Code Acceptance of a New Joining Technology for Storage Containments
Authors: Cannell Gary R. , Grant Glenn J. , Hill Burton E.
Published: February 2010

One of the activities associated with cleanup throughout the Department of Energy (DOE) complex is packaging radioactive materials into storage containers. Much of this work will be performed in high-radiation environments requiring fully remote operations for which existing, proven systems do not currently exist. These conditions require a process that is capable of producing acceptable (defect-free) welds on a consistent basis; the need to perform weld repair, under fully-remote operations can be extremely costly and time consuming. Current closure-welding technologies (fusion welding) are not well suited for this application and will present risk to cleanup cost and schedule. To address this risk, Fluor and the Pacific Northwest National Laboratory (PNNL) are proposing that a new and emerging joining technology, Friction Stir Welding (FSW), be considered for this work. FSW technology has been demonstrated in other industries (aerospace and marine) to produce near flaw-free welds on a consistent basis. FSW is judged capable of providing the needed performance for fully-remote closure welding of containers for radioactive materials. The performance characteristics of FSW, i.e., high weld quality, simple machine-tool equipment and increased welding efficiency, suggest that this new technology should be considered for radioactive materials packaging campaigns. FSW technology will require some development/adaptation for this application, along with several activities needed for commercialization. One of these activities will be to obtain approval from the governing construction code to use the FSW technology. The American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME B&PVC) will govern this work; however, rules for the use of FSW are not currently addressed. A code case will be required to define appropriate process variables within prescribed limits for submittal to the Code for review/approval and incorporation.
Experimental Study on Application of Heat Transfer Enhancement Method Using Porous Material With High Porosity
Authors: Takeda Tetsuaki , Ichimiya Koichi
Published: February 2010

A technology development of a hydrogen production system by nuclear heat is being performed as a heat application system of the Very High Temperature Reactor (VHTR) in worldwide. As for the development of the coupling technology between the VHTR and the hydrogen production system, Japan Atomic Energy Agency had carried out a coupling technology test using a steam reforming process by natural gas. In the hydrogen production system by nuclear heat, the catalyst tube of the steam reformer is heated by the high temperature helium gas from the intermediate heat exchanger (IHX). There are several methods for heat transfer enhancement. For example, there are attaching various fins on the heat transfer surface, processing the surface roughly, and so on. Disk type fins are attached on the outside surface of the catalyst tube. The catalyst tube is inserted into the guide tube to increase an amount of heat transferred from the high temperature helium gas. However, it has to take into consideration the deterioration of the structure strength by attaching the fins on the tube surface with the design of the steam reformer. The objective of this study is to clarify performances of a method for heat transfer enhancement using porous material with high porosity by an experiment. The experiment has been performed using an apparatus which simulated the passage structure of the steam reformer to obtain characteristics of heat transfer.
Mechanistic Prediction of CHF in Fuel Assembly Using the Subchannel Code CAPE
Authors: Yoshida Ryo , Yoshida Kenji , Kataoka Isao , Naito Masanori
Published: February 2010

In order to predict the critical power or void fraction in BWR fuel bundles and the DNB heat flux of PWR fuel assemblies, the boiling transition analysis code called “CAPE” with mechanistic models has been developed in the IMPACT project by NUPEC. The objective of the CAPE code development is to perform with good accuracy the safety evaluation for a new type or improved fuel bundle design of BWR and PWR without full-scale experiments or any tuning parameters in the analysis code. In the present study dryout heat fluxes of BWR fuel assembly were analyzed by the CAPE code and compared with experimental data of BFBT benchmark test carried out by NUPEC. In the CAPE code, mechanistic model of liquid film dryout in annular flow is used considering entrainment and deposition of droplet. In such mechanistic prediction of dryout, the correlations of entrainment and deposition rates play quite important roles and many correlations have been developed. In addition to the original correlations in the CAPE code, several typical correlations, which are widely used in the analysis of annular dispersed flow, were tested for the prediction of dryout. The results indicated that the CAPE code satisfactorily predicted dryout heat fluxes of fuel assembly for wide range of pressure, mass flux, subcooling and bundle geometries obtained in BFBT benchmark test. The accuracy of prediction depends upon the combination of correlations of entrainment and deposition rates. The evaluation of correlations of entrainment and deposition rates was carried out.
Mechanistic Prediction of Void Fraction Distribution in BWR Fuel Assembly Using the Subchannel Code CAPE
Authors: Yoshida Kenji , Yoshida Ryo , Kataoka Isao , Naitoh Masanori
Published: February 2010

In order to predict the critical power or void fraction in BWR fuel bundles and the DNB heat flux of PWR fuel assemblies, the boiling transition analysis code called “CAPE” with mechanistic models has been developed in the IMPACT project by NUPEC. The objective of the CAPE code development is to perform with good accuracy the safety evaluation for a new type or improved fuel bundle design of BWR and PWR without full-scale experiments or any tuning parameters in the analysis code. In the present study void fraction distribution of BWR fuel assembly were analyzed by the CAPE code and compared with experimental data of BFBT benchmark test carried out by NUPEC. The analyses were carried out by changing the operational parameter such as the inlet subcooling, mass flow rate and the power output of the fuel bundles. Resultantly, the thermal equilibrium quality at the outlet ranges 2% ∼25%. Averaged and local void fractions were compared between experiment and analysis. The results indicated that the CAPE code satisfactorily predicted void fraction distribution of fuel assembly for wide range of pressure, mass flux, subcooling and bundle geometries obtained in BFBT benchmark test. However, the detailed analysis showed that in some subchannels, which was surrounded by the heated fuel rods and partially unheated wall such as an unheated rod, a water rod and a separation wall of the channel box, certain difference between experiment and prediction appeared. In the CAPE code, the drift flux model is used for predicting void behavior in fuel assembly. In drift flux model, correlations of drift velocity and distribution parameters are quite important in predictive accuracy of void fraction. In particular, it is considered that distribution parameter plays important role in void distributions in subchannel surrounded by unheated rods. In addition to the original correlations in the CAPE, some typical correlations of drift velocity and distribution parameter were tested for the prediction of void fraction distribution. The evaluations of correlations of drift velocity and distribution parameter were carried out, and some recommendations for improvement of predictive capability of the CAPE code were made.
Design- and Operating-Bases Regional Meteorological Conditions for Permitting New Nuclear Power Plants in the United States
Authors: Wan Ping K. , Carson Alice C.
Published: February 2010

Power generation is well recognized as a major prerequisite for a country’s economic development. Nuclear power has become an increasingly attractive alternative in the power market worldwide due to several factors: growing demand for electric power, increasing global competition for fossil fuels, concern over greenhouse gas emission impacts on global warming, and the desire for energy independence. Protecting people and the environment is of concern to nuclear power generators. Thus, sound engineering design that provides adequate protection against natural and man-made hazards is of utmost importance. Meteorological parameters related to structure design and system operation are the extreme and mean values for wind speed, temperature, humidity, and precipitation, as well as the seasonal and annual frequencies of severe weather conditions such as tornadoes and hurricanes, ice and snow accumulation, hail and lightning. Inherent in ascertaining values for these parameters is the need for reasonable assurance that the chosen values and frequencies will not be exceeded during the expected life of the plant. All regional meteorological and air quality conditions are classified as climate site characteristics for consideration in evaluating the design and operation of a nuclear power plant [1]. This paper discusses the regulatory requirements, methodology and sources of data for development of the design- and operating-basis regional meteorological conditions used in preparing a Combined License Permit Application (COLA) in the United States. Additionally, the differences in methodology for determination of these meteorological conditions by reactor type (i.e., Advanced Passive 1000–AP1000, Advanced Boiling Water Reactor–ABWR, Economic Simplified Boiling Water Reactor–ESBWR, U.S. Evolutionary Power Reactor–U.S. EPR, and Advanced Pressurized Water Reactor–APWR) are explored and summarized.
Numerical Calculations on Countercurrent Air-Water Flow in Small-Scale Models of a PWR Hot Leg Using a VOF Model
Authors: Murase Michio , Utanohara Yoichi , Kinoshita Ikuo , Minami Noritoshi , Tomiyama Akio
Published: February 2010

In the case of loss of the residual heat removal (RHR) systems under mid-loop operation during shutdown of a PWR plant, reflux cooling by a steam generator (SG) is expected, and the generated steam in a reactor core and the condensed water in the SG form a countercurrent flow in a hot leg, which consists of a horizontal pipe, an elbow and an inclined pipe. In order to improve a countercurrent flow model of a transient analysis code, countercurrent air-water tests were conducted using the 1/15th scale model of the PWR hot leg at Kobe University and the authors conducted numerical calculations of the 1/15th scale tests using the thermal-hydraulic analysis code FLUENT6.3.26 and an Euler-Euler model or a VOF model. In the tests and calculations, however, the expansion of the inclined pipe in the PWR hot leg was not simulated. In this study, using the VOF model, the authors conducted numerical calculations for a 1/15th scale model of the PWR hot leg with the expansion of the inclined pipe, which mitigates CCFL (countercurrent flow limitation) there. The calculated flow patterns in the hot leg using the VOF model were quite different with the data for the 1/15th tests without the expansion of the inclined pipe due to underestimation of CCFL characteristics at the upper end of the inclined pipe, but became similar with the observed results for the 1/15th scale model with the expansion of the inclined pipe due to the mitigation of CCFL at the inclined pipe. The results indicate that the VOF model could not correctly calculate air-water two-phase flows at the upper part of the inclined pipe but could calculate two-phase flows in the horizontal pipe.
Temper-Bead Weld by Underwater Laser Beam Welding
Authors: Fukuda Takeshi , Sumiya Rie , Kono Wataru , Suezono Nobuichi , Tamura Masataka , Chida Itaru
Published: February 2010

In repair welding for nuclear reactor vessel, low alloy steels are affected by heat input during welding process. The conventional repair welding for wall steel constructions requires post weld heat treatment (PWHT) to achieve the desired microstructure properties. However, post weld heat treatment is very difficult for some structures in operating plants. In such case, temper-bead welding technique is available as a repair welding method. Temper-bead welding employs a multi-pass deposition of welding metal. Each layer of beads provides heat for thermal treatment of the previous weld bead or layer, which lowers hardness of the heat affected zone (HAZ) and improves mechanical properties like the toughness. Toshiba has developed underwater laser cladding and laser seal welding techniques for reactor components repair welding. In this report, some experimental results of laser based underwater temper-bead welding are presented.