bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical Study on Heat Transfer Characteristics of CO2-DME Mixture Fluid
Authors: Zhang Xin-Rong , Liu Jia , Yamaguchi Hiroshi
Published: February 2010

In response to the call for environment protection, more and more researches have been finding new alternative refrigerants which are of zero Ozone depleting potential (ODP), low global warming potential (GWP) and will be efficient, inflammable, and nontoxic to replace the HCFCs and HFCs refrigerants. Non-azeotropic mixtures of suitable fluids are becoming the important candidates of that search race. In this paper, the flow and heat transfer performance of CO2-DME (dimethyl ether) mixture refrigerants at 8.0 MPa in a horizontal tube was numerically investigated. In particular, this work has been focused upon the laminar heat transfer characteristics of CO2-DME mixture refrigerant flow with Reynolds number ranging from 180 to 1800 and the mass fraction of DME ranging from 21% to 39%. The results show that the heat transfer performance of the mixture fluid can be improved when the mass fraction of DME increases to 30%. Considering both the best heat transfer performance and the safety, the optimum component of CO2-DME (70/30, mass%) has been found in this study. And the mechanisms that are responsible for the heat transfer enhancement are obtained and they are: (1) The temperature gradient of CO2-DME mixture fluid with high mass fraction of DME is larger than that of CO2-DME mixture fluid with low mass fraction of DME; in addition, the temperature gradient increases with the mass fraction of DME; (2) The increase of thermal conductivity for CO2-DME mixtures can enhance the heat transfer performance to a large extent. (3) The self-acceleration characteristic of the supercritical mixture fluid is also beneficial to the heat transfer enhancement. Furthermore, it is found that the heat transfer performance of the mixture fluid can also be improved with Reynolds number. The viscous boundary layer of the fluid becomes thinner when the Reynolds number increases, which leads to an enhancement in heat transfer. In addition, at high Reynolds number, the flow is tend to be turbulent, which is beneficial to the heat transfer performance of mixture fluid. With regard to the flow characteristic of mixtures, first the flowing changes depend on the temperature and the density of fluid to a large extent-the high value of velocity can occur when the fluid has a high temperature and a low density. And secondly, the supercritical CO2-DME mixtures speed up along the tube and make themselves different with water flow. These results of this study have significant implications for the design of high-performance heat exchangers, using CO2-DME mixture as the working fluid.
Tailoring Thermoelectric Properties of Segregated-Network Polymer Nanocomposites for Thermoelectric Energy Conversion
Authors: Choi Kyungwho , Kim Dasaroyong , Kim Yeonseok , Grunlan Jaime C. , Yu Choongho
Published: February 2010

Carbon nanotube (CNT)-polymer composites were prepared by segregated network approach. CNTs were served as conductive fillers in a polymer matrix to synthesize electrically conducting polymer composites. In the segregated network composites, the thermoelectric properties were further improved by replacing Gum Arabic (GA) with electrically conductive stabilizer PEDOT:PSS doped with dimethyl sulfoxide (DMSO). The electrical and thermal conductivities and Seebeck coefficient were measured to determine the thermoelectric property of the polymer composites. The electrical conductivity of the composites with 9.8wt% of CNT was 3191.8 S/m whereas that of 10wt% CNT composite with GA sample was 400 S/m.
Experimental Investigation of Single-Phase Microjet Array Impingement Cooling
Authors: Browne Eric A. , Michna Gregory J. , Jensen Michael K. , Peles Yoav
Published: February 2010

The heat transfer performance of two microjet arrays using degassed deionized water was investigated. The in-line jet arrays had a spacing of 250 μm, a standoff of 200 μm, and diameters of 54 and 112 μm. Average heat transfer coefficients were obtained for 150 < Red < 3300 and ranged from 80,000 to 414,000 W/m2-K. A heat flux of 1,110 W/cm2 was attained with 23 °C water and a surface temperature of 50 °C.
Lumped Parameters Modeling of an Incinerator With Heat Recovery for Energy Production
Authors: Antonelli Marco , Simi Alessio , Martorano Luigi , Lensi Roberto
Published: February 2010

This work shows the modeling of an incineration plant with energy recovery which operates in the vicinity of Pisa, Italy. The plant analysed was built formerly as an incineration plant and was recently refurbished with a heat recovery steam generator to drive a condensing steam turbine. In the foresight of an enlargement of the plant capacity, the Technical Office of the Company asked the Energetica Department of University of Pisa for an analysis of the recovery capability. The Technical Office and the Energetica Department decided to create a lumped parameter model in order to simulate the temperature behavior of the combustion products. This model was created inside Matlab/Simulink environment. The followed procedure led to the reproduction of the system interested by the cycle in steady state conditions in order to obtain a model simple enough but at the same time rigorous of the real behavior of steam cicle. After the description of the plant modeling, model calibration and validation is shown, by means of the comparison between the measured and simulated values of temperatures and mass flows in several load conditions. The model developed is currently used by the Technical Office of the Company for further developments of the plant.
Radiative Properties of Numerically Generated Fractal Soot Aggregates: The Importance of Configuration Averaging
Authors: Liu Fengshan , Smallwood Gregory J.
Published: February 2010

The radiative properties of numerically generated fractal soot aggregates were studied using the numerically accurate generalized multi-sphere Mie-solution method. The fractal aggregates investigated in this study contain from 10 to 600 primary particles of 30 nm in diameter. These fractal aggregates were numerically generated using a combination of the particle-cluster and cluster-cluster aggregation algorithms with fractal parameters representing flame generated soot. Ten different realizations were obtained for a given aggregate size measured by the number of primary particles. The wavelength considered is 532 nm and the corresponding size parameter of primary particle is 0.177. Attention is paid to the effect of different realizations of a fractal aggregate with identical fractal dimension, prefactor, primary particle diameter, and the number of primary particles on its orientation-averaged radiative properties. Most properties of practical interest exhibit relatively small variation with aggregate realization. However, other scattering properties, especially the vertical-horizontal differential scattering cross section, are very sensitive to the variation in geometrical configuration of primary particles. Orientation-averaged radiative properties of a single aggregate realization are not always sufficient to represent the properties of random-oriented ensemble of fractal aggregates.
Analysis of Effectiveness of Parallel Flow Microchannel Heat Exchangers With Heat Transfer From Surroundings
Authors: John T. J. , Mathew B. , Hegab H.
Published: February 2010

The performance of a parallel flow micro channel heat exchanger (MCHX) is examined in this paper with the help of a mathematical model developed for this study. The thermal performance of a balanced parallel flow MCHX is numerically evaluated with the effect of heat transfer from the surroundings taken into consideration. Two non-dimensional governing equations are developed for modeling this MCHXPF. This model also considers a case in which the temperature of surrounding that is adjacent to the hot fluid channel is assumed to be different from that in contact with the cold fluid channel. The equations are numerically solved using the Runge-Kutta-Fehlberg method. MATLAB software is used to develop the program for solving the equations that constitute this model. The axial temperatures along both channels are obtained upon numerically solving the governing equations. The effectiveness of each fluid is then calculated using its inlet and outlet temperatures. The heat transfer between the fluids and that between the surrounding and each fluid are also numerically calculated using the axial temperatures of the fluids. The effectiveness of the fluids depends on the NTU, temperatures of the surroundings, and the thermal resistance between the individual fluids and their corresponding surrounding. When the heat transfer from the surrounding and the respective fluid is increased the effectiveness of the hot fluid decreased and that of the cold fluid increased. The temperature of the surroundings will determine the direction of heat transfer between the individual fluid and its surrounding. When the temperature of the surroundings is higher than the inlet temperature of the hot fluid then there would be degradation of the effectiveness of the hot fluid and an improvement in the effectiveness of the cold fluid. And the opposite trend happens when the temperature of the surroundings are lower than the inlet temperature of the cold fluid.
Advanced Differential Approximation Formulation of the PN Method for Radiative Transfer
Authors: Modest Michael F. , Pal Gopalendu
Published: February 2010

The spherical harmonics (PN) method, especially its lowest order, i.e., the P1 or differential approximation, enjoys great popularity because of its relative simplicity and compatibility with standard models for the solution of the (overall) energy equation. Low-order PN approximations perform poorly in the presence of strongly nonisotropic intensity distributions, especially in optically thin situations within nonisothermal enclosures (due to variation in surface radiosities across the enclosure surface, causing rapid change of irradiation over incoming directions). A previous modification of the PN approximation, i.e., the modified differential approximation (MDA), separates wall emission from medium emission to reduce the nonisotropy of intensity. Although successful, the major drawback of this method is that the intensity at the walls is set to zero into outward directions, while incoming intensity is nonzero, resulting in a discontinuity at grazing angles. To alleviate this problem, a new approach, termed here the “advanced differential approximation (ADA),” is developed, in which the directional gradient of the intensity at the wall is minimized. This makes the intensity distribution continuous for the P1 method and mostly continuous for higher-order PN methods. The new method is tested for a 1-D slab and concentric spheres, and for a 2-D medium. Results are compared with the exact analytical solutions for the 1-D slab as well as the Monte Carlo-based simulations for 2-D media.
The SLW Model: Exact Limit and Relationship to Other Global Methods
Authors: Solovjov Vladimir P. , Webb Brent W.
Published: February 2010

The exact form of the Spectral-Line Weighted-sum-of-gray-gases (SLW) model is developed as a limiting case of the classical SLW method when the number of gray gases in the classical model approaches infinity. Solutions of the Exact SLW RTE are obtained in the case of isothermal media. It is demonstrated that accuracy of the Exact SLW method is limited only by the accuracy of the ALBDF correlations used for characterization of the absorption spectrum. This work also demonstrates theoretically the close relationship between the SLW, ADF, and FSK models. The theoretical foundation is laid for the extension of the exact method to the case of non-isothermal media.
Sweeping Flow Heat Transfer With Piezoelectric Fans Over Vertical Flat Surfaces
Authors: Arik Mehmet , Ulcay Mehmed S.
Published: February 2010

Piezoelectric fans have been investigated for electronics cooling over the last several decades. The primary usage of these meso scale-vibrating fans has been to create sweeping flows over the heated surfaces. In this paper, an experimental study to understand the heat transfer behavior of a thin piezo fan with 7.5 cm length and 1 cm width has been performed for a range of operating conditions and fan-to-heater distance. Results showed that piezo fans consume very small amount of electrical power in return providing considerable COPs. Heat transfer enhancements were found to be over 12 at the resonance frequencies. Later, attention was turned to comparison of this technology with other meso scale cooling devices such as synthetic jets and rotary fans. Volumetric COP and heat transfer characteristics are compared for a range of conditions.
A New Viewpoint to Studying the Condensate Retention and Drainage Process on Air Cooling Coil
Authors: Xu X. G. , Chan M. Y. , Deng S. M.
Published: February 2010

Normally simultaneous air cooling and dehumidification takes place in an air cooling coil. The condensate accumulated on the cooling coil surfaces could significantly affect its thermal and hydraulic performance. The condensate retention and drainage has bee usually regarded as a static process. The total mass of condensate retained was viewed as being influenced by the balance among gravitational, air flow drag forces and surface tension retaining force only. With fixed geometric and surface characteristics and under a constant air Reynolds Number, a cooling coil was therefore considered to have a fixed amount of condensate retained. However, some researches pointed out that the total mass of condensate retained could be influenced by system operating parameters such as temperature and moisture content of inlet air. A previously related study by authors developed a mathematic model and considered this process as being a dynamic but without giving a detailed discussion. In this paper, through a further analysis of data obtained in the previously study, a new viewpoint on condensate retention and drainage process has been suggested in order to better explain the experimental results and to provide a base for proposing some future related research work.
Simulation of Charge Density and Field Distribution of a Gold Nanoparticle Tip-Terminated Scanning Nanowire Waveguide for Molecular Imaging
Authors: Malcolm Nathan , Heltzel Alex J. , Shi Li , Howell John R.
Published: February 2010

A Finite Difference Time Domain (FDTD) simulation is employed to calculate electromagnetic field and charge density distributions at the junction between a gold nanoparticle (NP) tip of a scanning ZnO nanowire and gold NP bio-markers. This three-dimensional simulation calculates the magnetic and electric field components in a large matrix of Yee cells by solving Maxwell’s curl equations. An absorbing boundary condition is included to eliminate reflection back into the simulation chamber. In the specific simulations considered here, a laser pulse of single wavelength is incident on the backside of a transparent silicon dioxide micro-cantilever, and coupled into a ZnO nanowire grown from an opening on a metal coating of the front side of the cantilever. The simulation results reveal local field enhancement between the gold NP tip of the nanowire and only one of three 20 nm gold NPs with a 28 nm empty spacing between two adjacent NPs. The charge density distributions in the gold tip and the gold NP are calculated and correlated with the local field enhancement, which makes the gold tip of the scanning nanowire waveguide attractive for use in imaging gold NP bio-labels on cell membranes.
Forces Acting on Sessile Droplet on Inclined Surfaces
Authors: Annapragada S. Ravi , Murthy Jayathi Y. , Garimella Suresh V.
Published: February 2010

Although many analytical, experimental and numerical studies have focused on droplet motion, the mechanics of the droplet while still in its static state, and just before motion starts, are not well understood. A study of static droplets would shed light on the threshold voltage (or critical inclination) for initiating electrically (or gravitationally) induced droplet motion. Before the droplet starts to move, the droplet shape changes such that the forces acting at the triple contact line balance the actuation forces. These contact line forces are governed by the contact angles along the contact line. The contact angle varies from an advancing angle at the leading edge to a receding angle at the trailing edge of the droplet. The present study seeks to understand and predict these forces at the triple contact line. The droplet shape, as well as the advancing and receding contact angles, is experimentally measured as a function of droplet size under the action of a gravitational force at different inclination angles. The advancing and receding contact angles are correlated with static contact angle and Bond number. A Volume of Fluid - Continuous Surface Force model with varying contact angles along the triple contact line is developed to predict the same. The model is first verified against a two-dimensional analytical solution. It is then used to simulate the shape of a sessile droplet on an incline at various angles of inclination and to determine the critical angle of inclination as a function of droplet size. Good agreement is found between experimental measurements and predictions. The contact line profile and contact area are also predicted. The contact area predictions based on a spherical-cap assumption are also compared against the numerical predictions.
Expedited Freezing of Nanoparticle-Enhanced Phase Change Materials (NEPCM) Exhibited Through a Simple 1-D Stefan Problem Formulation
Authors: Khodadadi J. M. , Fan Liwu
Published: February 2010

An analytic/integral approach is utilized to solve a model 1-dimensional Stefan problem for a nanofluid that undergoes freezing. Initially, the isothermal nanofluid is contained in a finite slab. During the freezing process, the traveling interface separates the liquid and solid phases that possess their respective thermophysical properties. The most favorable feature of this model is that the thermal property jumps between the liquid and solid phases are accounted for. The problem is made dimensionless and is shown to depend on the thermal conductivity ratio, thermal diffusivity ratio, Stefan (Ste) and subcooling numbers. The energy equation within the solid layer is solved exactly and that of the liquid layer is solved using the integral method. The instantaneous interface position and the moving front velocity are obtained and the total freezing time is then determined. Combinations of two base PCM (water and cyclohexane) and four nanoparticles (alumina, copper, copper oxide and titanium oxide) are chosen for demonstration purposes. The thermal properties of the resulting nanofluids as a function of the volume fraction were determined using models proposed in the literature. The results show that the dimensionless freezing time is independent of the nanofluid constituents and only depends on the volume fraction. Keeping everything else the same, the freezing time is shown to decrease as the volume fraction of the nanoparticle is raised.
Use of the Linear Driving Force Approximation in Adsorption Heat Pump and Chiller Modeling
Authors: Raymond Alex , Garimella Srinivas
Published: February 2010

Adsorption heat pumps and chillers can utilize solar or waste heat to provide space conditioning, process heating or cooling, or energy storage. In these devices, accurate modeling of intraparticle adsorbate mass transfer is an important part of predicting overall performance. The linear driving force (LDF) approximation is often used for modeling intraparticle mass transfer in place of the more detailed Fickian diffusion (FD) equation for its computational simplicity. This paper directly compares the adsorbate contents predicted by the conventional LDF approximation, an empirical LDF approximation proposed by El-Sharkawy et al. [1], and the FD equations for cylindrical adsorbent fibers such as activated carbon fiber (ACF). The conditions under which the LDFs agree with the FD equation are then evaluated. It is shown that for a given working pair, agreement between the LDF and FD equations is affected by the diffusivity, particle radius, half-cycle time, initial adsorbate content, and equilibrium adsorbate content. The maximum possible error in adsorbate content predicted by the LDF approximation compared with the FD solution is then calculated for the ACF (A-20)-ethanol working pair. Although the maximum error will be different for other cases, the technique used in this paper can be reproduced to determine the greatest possible LDF error for any working pair.
Application of Data Analytics to Heat Transfer Phenomena for Optimal Design and Operation of Complex Systems
Authors: Sharma Ratnesh K. , Marwah Manish , Lugo Wilfredo
Published: February 2010

Heat transfer phenomena in complex physical systems like multiphase environments, multidimensional geometries can be difficult to capture in terms of correlations, analytical functions or numerical models using conventional techniques. Such systems are designed based on approximations, thumb-rules or semi-empirical correlations between parameters based on averaged values and are operated likewise using another set of rules derived from bulk thermodynamic performance parameters. With the development of nano-scale sensors and advanced data aggregation techniques, there is a need for analytical techniques that can discover the complex interrelationships between the thermodynamic parameters of the process, geometry constraints and the governing outcomes of the process. Such techniques can leverage the possibility of deployment of thousands of sensors to extract the key relationships that drive the transport phenomena for advanced development of process control tools and methodologies. Heat and mass transfer equipment design and operation can benefit from knowledge discovered through analytics applied on thermo-physical data obtained from real time processes. We present illustrative use cases of application of data analytics and knowledge discovery techniques to a richly instrumented data center where computer room air conditioning (CRAC) units provide cooling for IT equipment arranged in rows of racks. Sensors located at each rack provide temperature measurements which are analyzed in real-time and also archived. Rack temperatures, together with operating parameters of CRAC units such as supply air temperature (SAT), and variable speed drive (VFD) settings, are analyzed together to derive design insights and detect anomalies.
Analysis of Single-Phase Convective Heat Transfer and System COP at Higher Power Levels in Thermoelectric-Based Hydronic Cooling and Heating Device
Authors: Kazmierczak Michael J. , Gupta Abhishek
Published: February 2010

Experiments were performed on a heat exchanger equipped with multiple thermoelectric (TE) modules. The TE-HX serves as the basic system component in a simple hydronic modular Peltier heat pump system designed to provide chilled or hot water for domestic use (or supplementary building climate control) of small residences [1]. The present work focuses on the detailed convection analysis inside the TE-HX component when 10 thermoelectric modules are utilized. The local heat transfer coefficient at different points along the channel are measured at steady-state, first, when a continuous heater is installed and then when replaced with 10 TE modules. The experimental heat transfer coefficients obtained are compared with available empirical correlations for “transition” (3000 < ReDh < 7000) turbulent flow inside the channel with fair-to-good results. Next, the resulting coefficient-of-performance of the TE heat pump system is measured with its value depending both on system input power and water flow rate. Testing showed that performance degradation, i.e. reduced COPs, occurred when operated at higher power levels but remains satisfactory for up to 688 Watts with higher flow rate.
A Tunable Magnetomechanical Thermal Switch for Thermal Management Purposes
Authors: Bulgrin Katherine E. , Ju Y. Sungtaek , Carman Greg P. , Lavine Adrienne S.
Published: February 2010

This work proposes a new design for a thermal switch that exploits the temperature dependence of a ferromagnetic material situated between a hot and cold surface. A numerical model is presented which predicts the behavior of the thermal switch. It is shown that with modifications to the physical structure, the device can be tuned to turn on at different heat source temperatures. The time-averaged heat flux and effective conductance compare favorably to existing thermal switch technologies over a range of heat source temperatures. Additionally, it is shown that the contact conductance of the surfaces has a large influence on the device performance.
Reduced-Order Investigation of Synthetic Jet Cooling for Electronic Applications
Authors: Dhananjaya Rao G. , Rao Ajay , Utturkar Yogen , Arik Mehmet
Published: February 2010

Synthetic jets are meso-scale devices operating at zero-net-mass-flux principle. These devices produce periodic jet-like streams, which have local velocities 10–20 times greater than the average fan velocities. As a result, positioning one or more of these jets close to a heat sink causes high-velocity air currents in tightly spaced fin gaps and enhances the surface heat transfer. A reduced-order modeling (ROM) approach was followed in simulating the heat transfer analysis of commercial heat sink with synthetic jet. Unsteady state results are matched with steady state results as part of the ROM approach. The methodology is implemented on two problems (i.e canonical problem of jet impinging perpendicularly on a flat plate and jet blowing on a commercial heat sink). Results from ROM for two cases are validated against experimental results. It is found that, this approach provides 90% time saving within ±5% accuracy. Modeling via ROM is much faster and cheaper computationally; hence this approach can be used for studying the system-level convective heat transfer enhancement of heat sinks using synthetic jets.
Steam Ejector Used as a Substitute for Cooling Tower in the Ethanol Production Process
Authors: Lopez Luiz Antonio Negro Martin , Ting Daniel Kao Sun , Alvim de Castro Alfredo Jose´
Published: February 2010

Nowadays petroleum dependency in transportation is widely discussed all over the world. Atmospheric pollution and global warming are deleterious consequences of gasoline consumption. Ethanol is a natural substitute fuel that has been increasingly used. One of the most important raw materials used for ethanol production is the sugar cane. The exothermic fermentation reaction of the sugar cane juice in the ethanol production process requires a rigorous temperature control. This control is usually made by using cooling water from cooling towers. The heat released from cooling towers not only has an economical cost as well as it contributes to the global heating. Steam ejectors can substitute cooling towers thus improving the ethanol production plant efficiency and reducing world heating. Furthermore, steam ejectors are smaller, cheaper and are very simple equipment when compared with cooling towers. Furthermore, its use provides an improved thermal efficiency of the production plant resulting in the reduction of the global warming effects. In this work the use of steam ejector is proposed for the fermentation cooling of a typical Brazilian sugar and ethanol production plant. The steam which feeds the steam ejector is obtained from the plant utilities and the low temperature obtained from steam expansion within the ejector is used for sugar cane fermentation process cooling. The steam ejector discharge heat is recovered as it is used to sugar and ethanol production process heating. The sugar and ethanol production plant overall energy fluxes either using cooling towers as well as using steam ejectors are presented and the results are compared and discussed.
An Extension of the Large-Cell Radiation Model for the Case of Semi-Transparent Nonisothermal Particles
Authors: Dombrovsky Leonid A.
Published: February 2010

The recently developed model for thermal radiation in multiphase flows typical of melt-coolant interactions is generalized to account for transient temperature profile in large semi-transparent particles of solidifying melt. A modification of the Large-Cell Radiation Model (LCRM) is based on approximate solution for coupled radiation and conduction in optically thick spherical particles of a refractive material. The simplicity of the suggested approximation enables one to implement the modified model in a multiphase CFD code. The LCRM extension makes possible the use of this approach not only for the core melt in nuclear fuel-coolant interactions (FCI’s) but also for other melt substances which are widely used in the laboratory experiments. The numerical data demonstrate an effect of absorption coefficient of the particle substance on the rate of particle cooling and solidification.
Overview of Radiative Transfer in Cellular Porous Materials
Authors: Viskanta R.
Published: February 2010

Highly porous cellular materials capable of absorbing, emitting and scattering radiation are finding use at low and high temperatures in a range of traditional and modern technologies. The motivation for use of cellular materials is attributed to the high volumetric heat transfer rate (i.e., large surface area to volume ratio, high volumetric heat transfer coefficient), and large mixing rate due to the tortuosity of open cell foams. A brief overview of simulating heat transfer in cellular materials is presented and most important modeling parameters are identified, but the focus of the discussion is on heat transfer in cellular materials in the presence of radiation environment. Several examples involving radiation, conduction and radiation as well as convection and radiation for different technological applications are discussed, and the models are assessed by comparing the predictions with experimental data.
STP Risk Managed Technical Specification Software Design and Implementation
Authors: Yilmaz Fatma , Kee Ernie , Richards Drew
Published: February 2010

STP uses a custom enterprise software application called RICTCal to calculate risk informed completion times (RICTs). Besides providing the end user interface to the calculation engine, the software also creates electronic regulatory-required reports that are automatically filed in the plant records management system. In addition to regulatory-required information on risk informed completion times and risk managed action times (RMATs), the software provides additional configuration risk information such as risk for reactor trip. The computation methodology and design of the software is described as well as required input data to support the calculation.
Sensitivity Study of Lower Plenum Boron Injection in a BWR
Authors: Yan Jin , Mallner Andrew
Published: February 2010

Boiling water reactors (BWRs) are equipped with a standby liquid control system (SLCS). The SLCS is used to inject boron to shutdown the reactor from full power condition in the event that the control rods fail to insert. In order for the SLCS system to shut down the reactor, adequate mixing of the borated solution with the reactor coolant is necessary. In BWRs prior to BWR 5, the boron injection points are located in the lower plenum. The objective of this project is to evaluate the impact of the operating conditions on the boron injection based on the understanding of the behavior of multi-species flow in typical pre-BWR 5 reactors by using computational fluid dynamics (CFD). The project is divided into two phases. At the first phase, a CFD model based on the test configurations of GE 1/6 scale test program was established. The results were validated against measurements conducted by GE during the 1/6 scale test program performed in 1981. The validation shows that the CFD can give accurate predictions of the boron mixing. The technical approach employed in the CFD model was adequate to capture the boron mixing process in the BWR lower plenum. The second phase of the project is the sensitivity study based on the same technical approach developed in the first phase. However, a simplified BWR lower plenum model was used due to the time constrain. In the sensitivity study, the baseline case and four additional cases with different operating conditions were investigated using the same CFD approach.
SCDAP/RELAP5 Analysis of Progression of Severe Accident in CANDU 6 Plant
Authors: Dupleac Daniel , Mladin Mirea , Prisecaru Ilie
Published: February 2010

The CANDU system design has specific features which are important to severe accidents progression and require selective consideration of models, methods and techniques of severe accident evaluation. Moreover, it should be noted that the mechanistic models for severe accident in CANDU system are largely less validated and, as a consequence, the level of uncertainty remains high in many instances. Unlike the light water reactors, for which several different computer codes to analyze severe accidents exist, for CANDU severe accidents analysis only two codes were developed: MAAP4-CANDU and ISAAC. However, both codes started by using MAAP4/PWR as reference code and implemented CANDU 6 specific models. Thus, the two codes have many common features. Recently, a joint project involving Romanian nuclear organizations and coordinated by Politehnica University of Bucharest has been started. The purpose of the project is the assessment and adaptation of the SCDAP/RELAP5 code to CANDU 6 severe accidents analysis. The present work investigates the progression of a severe accident in CANDU 6 reactor starting from a LBLOCA and a subsequent loss of all heat sinks. The paper provides details concerning the methodology and nodalisation used, and interprets the results obtained. Comparisons of the SCDAP/RELAP5 simulations with the MAAP4-CANDU and the ISAAC codes reported results are presented. Also, some insights are given on possible reasons for the discrepancies between the SCDAP/RELAP5, MAAP4-CANDU and ISAAC codes predictions.
Development of Short Stroke Shearing Technology for FBR Fuel Pins
Authors: Higuchi Hidetoshi , Koizumi Kenji , Hirano Hiroyasu , Tasaka Masayuki , Washiya Tadahiro , Kobayashi Tsuguyuki
Published: February 2010

The short stroke shearing tests with simulated fuel pin bundle were carried out in engineering scale. The shearing device was designed to handle the simulated Monju (FBR prototype reactor) type fuel pin bundle. Monju type and Commercial reactor type simulated fuel pins were used for the test. The length of sheared pin and the opening ratio of sheared section were measured under several shearing settings such as the pressure to hold pin bundle, the shearing speed and the filling-ratio of pins in the pin magazine. Both types of fuel pin were able to be sheared accurately at the length of about 10mm, and the opening ratio of sheared section was not significantly reduced. As the results, fundamental data of the short stroke shearing characteristics were obtained and that shearing method was confirmed to be promising with the reliable shearing device.
Development of Multifunction Laser Welding Head as Maintenance Technologies Against Stress Corrosion Cracking for Nuclear Power Reactors
Authors: Chida Itaru , Mukai Naruhiko , Kono Wataru , Miura Takahiro , Yoda Masaki
Published: February 2010

Multifunction laser welding head has been developed. The head is able to perform not only underwater laser welding as repair, but also laser peening as preventive maintenance and laser ultrasonic testing as inspection. By using the effect of color aberration with optics, laser beam was focused to the ideal spot size on each process. Underwater laser welding was carried out onto EDM slit with the developed head and sealing ability with deposited weld metal was confirmed. As preventive maintenance, laser peening was also performed on the material surface with the developed head, and stress improvement ability was confirmed. For inspection with the developed head, a new method of visualizing weld defects in water by laser-ultrasonics has developed. Furthermore, developing synthetic aperture focus technique for visualized inspection surfaces 2-dementionally, the inspection result like penetrant testing despite underwater environment was achieved. Therefore, practicality of the developed head on each process was confirmed.
A Performance Test Result of Chordal Type Flowmeter Using High Reynolds Number Facility in NMIJ
Authors: Furuichi Noriyuki , Terao Yoshiya , Takamoto Masaki
Published: February 2010

In this paper, test result of two performance tests of the “Chordal Type” ultrasonic flowmeter made by Cameron inc. using NMIJ’s high Reynolds number calibration facility will be presented. This type flowmeter have been introduced to nuclear power plant in USA to MUR uprating. First test is the investigation of the effect of the inner roughness of the upstream pipe. In this test, the difference of the K-factor, which is one of correction factors of a flowmeter, between Ra = 1.7 (mm) and 14.2 (mm) is about 0.1%. To obtain the high efficiency of MUR uprating, actual flow calibration is recommended. Second test is the investigation of the relationship between “Profile Factor” and “Velocity Ratio”. As a result, the correlation obtained by calibration for many upstream conditions at Re = 3.0 × 106 can estimate “Profile Factor” at Re = 1.4 × 107 within ±0.25%. However, the correlation with Reynolds number does not behave as expected by theorem. To obtain the correction factor of flowmeter with high accuracy and reliability, the actual flow calibration under the same Reynolds number at the actual plant condition is the only effective method.
Experimental Study of the Influence of Roughness Change in a Piping on the Flow Measurement
Authors: Nishi Yoshihisa , Eguchi Yuzuru , Nishihara Takashi , Kinoshita Izumi , Inada Fumio , Nagashima Kazufumi
Published: February 2010

In measurement of an ultrasonic flowmeter, the flow rate in piping is obtained using some measurement signals along the “chord” of the circular cross section of the piping. As for the “Chordal type ultrasonic flowmeter”, the flow rate is obtained by four (or eight) “chords”. The wall roughness influences the velocity profile. To evaluate the influences of roughness change on the measurement using four velocity points, a water test was performed. The Reynolds (Re) number of the test ranges from 4×105 to 3×106. It was suggested that high precision measurement in the range of high Re number can be expected in the smooth pipe. In the wall where sand of 0.1mm diameter was pasted, no difference in the velocity profile with the smooth wall was observed. A change in the velocity profiles appeared in the rough surface pipe where sands of 0.6mm and 0.2mm diameter has been pasted. Bias error (ESL) was used to estimate the uncertainty of the flow rate measurements using four velocity points. The difference of each ESL value based on the influence of roughness tended to diminish as the Re number increased. And the Re number dependency of ESL is small, especially in the high Re number side. It suggests that an actual flow rate test for the high Re number to confirm the influence of roughness would not be necessary.
FAST Code System: Review of Recent Developments and Near-Future Plans
Authors: Mikityuk Konstantin
Published: February 2010

The FAST (Fast-spectrum Advanced Systems for power production and resource ManagemenT) project is an activity performed in the Laboratory for Reactor Physics and Systems Behaviour of Paul Scherrer Institut in the area of fast-spectrum reactor behaviour with an emphasis on the comparative analysis of Generation IV systems.
Risk-Informed, Technology-Neutral Design and Licensing Framework for New Nuclear Plants
Authors: Chapman Jim , Hess Stephen M.
Published: February 2010

The regulatory framework for the current generation of operating plants and advanced light water reactors (ALWRs) planned for near term construction has evolved over several decades to permit effective regulation of the light water reactor (LWR) designs. To address other reactor types, development of a framework that possesses the attributes of being technology neutral, risk-informed and performance-based with corresponding processes (regulations and guidance) is ongoing by several U.S. and international organizations. There are different visions for a revised design and licensing framework applicable to advanced (i.e. Generation III “Plus” and IV) reactors. The dominant visions are represented by activities underway at the US Nuclear Regulatory Commission (NRC), at two gas cooled reactor vendors and by the American Nuclear Society (ANS). To support development of a revised framework, the Electric Power Research Institute (EPRI) conducted research to identify and assess specific elements of possible technology neutral, risk-informed, performance based frameworks; to develop a preliminary integrated reference framework based on the results of this evaluation; and to provide recommendations in areas where additional development and testing would appear to be most beneficial. In the research discussed in this paper the key features of these various proposed frameworks were reviewed and combined into an integrated reference framework. This integrated reference framework includes elements that are intended to provide the roadmap for successfully designing and licensing an advanced reactor design if such an approach is used. The results of this research are being used to support Industry efforts to develop standards and guidance for advanced plants with safety characteristics which differ from existing and advanced LWRs.
Heat Transfer to Supercritical Water in Vertical Annular Channel and 3-Rod Bundle
Authors: Razumovskiy V. G. , Pis’mennyy Eu. N. , Koloskov A. Eu. , Pioro I. L.
Published: February 2010

The results of heat transfer to supercritical water flowing upward in a vertical annular channel (1-rod channel) and tight 3-rod bundle consisting of the tubes of 5.2-mm outside diameter and 485-mm heated length are presented. The heat-transfer data were obtained at pressures of 22.5, 24.5, and 27.5 MPa, mass flux within the range from 800 to 3000 kg/m2·s, inlet temperature from 125 to 352°C, outlet temperature up to 372°C and heat flux up to 4.6 MW/m2 (heat flux rate up to 2.5 kJ/kg). Temperature regimes of the annular channel and 3-rod bundle were stable and easily reproducible within the whole range of the mass and heat fluxes, even when a deteriorated heat transfer took place. The data resulted from the study could be applicable for a reference estimation of heat transfer in future designs of fuel bundles.
Non-Intrusive Experimental Investigation of Flow Behavior Inside a 5X5 Rod Bundle With Spacer Grids Using PIV and MIR
Authors: Dominguez-Ontiveros Elvis , Estrada-Perez Carlos , Hassan Yassin
Published: February 2010

The validity of the simulation results from Computational Fluid Dynamics (CFD) are still under scrutiny. Some existing CFD closure models for complex flow produce results that are generally recognized as being inaccurate. Development of improved models for complex flow simulation require an improved understanding of the detailed flow structure evolution along with dynamic interaction of the flow multi-scales. Thus, the goal of this work is to contribute to a better understanding of presupposed and existent events that could affect the safety of nuclear power plants by using state-of-the-art measurement techniques that may elucidate the fundamental physics of fluid flow in rod bundles with spacer grids. In particular, this work aims to develop an experimental data base with high spatial and temporal resolution of flow measurements inside a 5×5 rod bundles with spacer grids. The full-field detailed data base is intended to validate CFD codes at various temporal-spatial scales. Measurements were carried out using Dynamic Particle Image Velocimetry (DPIV) technique inside an optically transparent rod bundle utilizing the Matching Index of Refraction (MIR) approach. This work presents results showing full field velocity vectors and turbulence statistics for the bundle under single phase flow conditions.
Risk Assessment of Hydrogen Production System by Dimethyl Ether Steam Reforming With the Use of Nuclear Power
Authors: Koguchi Kazuo , Kasai Shigeo , Takahashi Makoto , Wakabayashi Toshio
Published: February 2010

Hydrogen is regarded as a clean fuel because it does not pollute when burned with air. In the case of commercial use, there is a need to research how to produce hydrogen more efficiency and large scale. Although there are some methods of hydrogen production, it can be considered that the heat of the nuclear reactor is promising method. In the recent studies on the hydrogen production with nuclear power, there has focused on the technical issues. Therefore, the object in this paper is to perform the risk assessment for a system of hydrogen production plant by Dimethyl Ether (DME) steam reforming with the use of nuclear power. First, one of the suitable systems with the DME steam reforming plant was selected PWR. A FMEA (Failure Mode and Effects analysis) was performed to identify initiating events. After identifying initiating events, event tree analysis (ETA) was performed to quantify the average frequency of an accident at this system. The result of the PSA, the safety of DME steam reforming plant with nuclear power depends on a rupture of reformer and heat exchanger between hydrogen and DME by the result of FMEA. Event tree analysis shows that the average frequency of hydrogen or DME explosion is 7.7×10−7 year−1 in the case of the rupture of the reformer and 1.9×10−8 year−1 in the case of the break of the heat exchanger.