bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Humidity on PEM Fuel Cell Performance: Part II — Numerical Simulation
Authors: Shimpalee S. , Dutta S. , Lee W. K. , Van Zee J. W. 
Published: December 2021

Abstract
Experiments have shown that the inlet humidity has a significant influence on the performance of a polymer electrolyte membrane (PEM) fuel cell, and theory indicates that the ionic resistivity of the electrolyte membrane is dependent on the activity of water at the membrane surface. Water flux and activities change along the flow field direction. To understand the inner flow and mass transfer processes, a numerical model is developed to predict the flow inside a single fuel cell. Detailed velocity fields, pressure profiles, and current density distributions are obtained and predictions from the full-cell model are compared with the experimental data. Predictions indicate that flow inter-linkage between side-by-side flow channels occurs through the porous diffusion layer. Results also indicate that the diffusion of hydrogen is aided by the flow toward the membrane in the anode side and diffusion of oxygen is opposed by the flow direction present in the cathode side.
An Investigation of Local Degassing Effects on Heat Transfer During Gas-Saturated Boiling From a Small Cylinder
Authors: Hong Y. S. , Ammerman C. N. , You S. M. 
Published: December 2021

Abstract
Boiling heat transfer from a 50-μm-diameter wire immersed in FC-72 is examined. Effects of pressure, subcooling, and dissolved gas concentration on nucleate boiling heat transfer and critical heat flux (CHF) are investigated. The current study is an ongoing effort to systematically quantify dissolved gas content effects on boiling heat transfer. The present investigators previously determined that gas-saturated boiling efficiency is affected by local degassing of the working fluid near the heater surface. This local degassing effect is further investigated in the present study using helium, air, and carbon dioxide as dissolved gases. In addition, the limits of gas-saturated boiling enhancement are determined by varying system pressure.
Stability of Heat Pipes in Vapor-Dominated Systems
Authors: Amili Pouya , Yortsos Yanis C. 
Published: December 2021

Abstract
We study the linear stability of a two-phase heat pipe zone (vapor-liquid counterflow) in a porous medium, overlying a superheated vapor zone. The competing effects of gravity, condensation and heat transfer on the stability of a planar base state are analyzed in the linear stability limit. The rate of growth of unstable disturbances is expressed in terms of the wave number of the disturbance, and dimensionless numbers, such as the Rayleigh number, a dimensionless heat flux and other parameters. A critical Rayleigh number is identified and shown to be different than in natural convection under single phase conditions. The results find applications to geothermal systems, to enhanced oil recovery using steam injection, as well as to the conditions of the proposed Yucca Mountain nuclear waste repository. This study complements recent work of the stability of boiling by Ramesh and Torrance (1993).
Prediction of Frost Height on Heat Exchanger Fins
Authors: Chen Hong , Thomas Leena , Besant Robert W. 
Published: December 2021

Abstract
Frost growth on heat exchanger fins under freezer operating conditions reduces the heat rate and increases the airflow pressure drop across heat exchangers.
In this paper, a numerical model is presented to predict the height of frost growing on the heat exchanger fins under freezer operating conditions where the frost is treated as a porous media and includes coupling with heat conduction in the fins. The simulation results are compared to the experimental data for frost height measured using a specially designed laser scanning system. The frost height data on two-dimensional fins agree well with the simulation results and are generally within the experimental uncertainty.
NMR Technique for Multiphase Fluid Study Involving Melting Phenomena
Authors: Ni Q. , King J. D. , Tao Y.-X. 
Published: December 2021

Abstract
Nuclear magnetic resonance (NMR) sensors are used to determine the time variation of solid mass for a packed ice bed in an experiment of convective melting under non-thermal equilibrium conditions. The paper describes the basic experimental technique for NAFTM apparatus and feasibility for determining the solid volume fraction and ultimately the melting rate. The NMR technique provides an effective, non-destructive method for multiphase fluid study where phase change is one of the important physical phenomena. The results show a good agreement of data obtained by the NMR method with those from image-analysis method.
Micro Thermal Engines: Is There Any Room at the Bottom?
Authors: Peterson Richard B. 
Published: December 2021

Abstract
Richard P. Feynman introduced the field of microscale and nanoscale engineering in 1959 by giving a talk on how to make things very small. Feynman’s premise was that no fundamental physical laws limit the size of a machine down to the microscopic level. Is this true for all types of machines? Are micro thermal devices fundamentally different than mechanically-based machines with respect to their scaling laws? This paper demonstrates that micro thermal engines do indeed suffer serious performance degradation as their characteristic size is reduced. A micro thermal engine, and more generally, any thermally-based micro device, depends on establishing a temperature difference between two regions within a small structure. In this paper, the performance of a micro thermal engine is explored as a function of the characteristic length parameter, L. In the development, the important features of thermal engines are discussed in the context of developing simple scaling laws predicting the dependency of the operating efficiency on L. After this is accomplished, a general model is derived for a heat engine operating between two temperature reservoirs and having both intrinsic and extrinsic sources of irreversibility, i.e. thermal conductances and heat leakage paths for the heat flow. With this model and typical numerical values for the conductances, micro heat engine performance is predicted as the characteristic size is reduced. This paper demonstrates that under at least one particular formulation of the problem, there may indeed be some room at the bottom. However, heat transfer does play a critical role in determining micro engine performance and depending on how the heat transfer through the engine is modeled, vanishingly small efficiencies can result as the characteristic engine size goes to zero.
Temperature Dependent Thermal Conductivity of Symmetrically Strained Si/Ge Superlattices
Authors: Borca-Tasciuc Theodorian , Liu Jianlin , Zeng Taofang , Liu Weili , Song David W. , Moore Caroline D. , Chen Gang , Wang Kang L. , Goorsky Mark S. , Radetic Tamara , Gronsky Ronald 
Published: December 2021

Abstract
Experimental evidence for a significant thermal conductivity reduction has been reported in recent years for GaAs/AlAs, Si/Ge, and Bi2Te3/Sb2Te3 superlattices. Previously reported experimental studies on Si/Ge superlattices are based on samples grown by metal oxide chemical vapor deposition (MOCVD) on GaAs substrates with Ge buffers. In this work, we present experimental results on the temperature dependent thermal conductivity of symmetrically strained Si/Ge superlattices grown by molecular beam epitaxy (MBE) as a function of the superlattice period and the growth temperature. Thermal conductivity measurements are performed using a differential 3ω method. In this technique, the temperature drop across the superlattice film is experimentally determined and used to estimate the thermal conductivity of the film. Transmission electron microscopy (TEM) is employed to study the quality of the superlattice and the influence of the growth temperature on the superlattice structure. For all the superlattices studied, the measured thermal conductivity values are lower than that of the Si0.5Ge0.5 alloy. Furthermore, the measured thermal conductivity of a 40Å period Si/Ge superlattice with high dislocation density is comparable to the calculated minimum thermal conductivity of the constituent bulk materials.
Theoretical and Experimental Study of Heating/Drying of Paper Sheet With Gas Heated Infrared Emitter
Authors: Husain A. Nadir , Seyed-Yagoobi Jamal , Wirtz Jefferson W. 
Published: December 2021

Abstract
Infrared (IR) radiation is used for heating/drying of moist paper owing to its penetration characteristic inside porous media, and a high absorptivity of water in the infrared wavelength range. A series of experiments has been conducted along with the development of a theoretical model to study IR drying characteristics. Paper samples are instrumented with thermocouples in the thickness direction to obtain transient temperature profiles along with moisture data. The experimental results confirm IR energy penetration into the paper sheet. The numerical model predicts the experimental transient temperature profile for thinner samples fairly well but tends to under predict the temperatures with progressively thicker samples. Theoretical depth of IR penetration, as a function of sample initial moisture content, has been calculated and was found to decrease with increasing moisture content.
Direct Numerical Simulation of Mixing of a Passive in Decaying Turbulence
Authors: Deb P. , Majumdar Pradip 
Published: December 2021

Abstract
Research on turbulent mixing processes is of great interest to those working on turbulent-reactive flows. In this paper, a detailed study has been performed for the evolution of scalar fields of different initial integral scales in decaying, homogeneous and isotropic turbulence using DNS technique. Passive scalar mixing in a cubical decaying, homogeneous, isotropic turbulence field is considered. The three-dimensional incompressible Navier-Stokes equations together with scalar equation are solved using Fractional Step Method. The convective and diffusive terms in governing equations are discretised by Compact Finite Difference Scheme. The 32 × 32 × 32 uniform staggered grids are used. The present simulation is performed at Taylor Reynolds number of 28.83. In this paper, the evolution of scalar RMS and scalar dissipation rate for different integral length scales has been presented. The initial velocity vector and Probability Density Function (PDF) of scalar at different eddy turn over time have also been presented.
Design Analysis of an Electroless Plating Bath Using CFD Technique
Authors: Lee Tien-Yu Tom , Lin Jong-Kai 
Published: December 2021

Abstract
The fluid field of the electroless plating bath was analyzed using a Computational Fluid Dynamics Tool. By solving continuity and momentum equations, the pressure and velocity distributions in the plating bath were predicted. The analysis was performed under various design options: flow direction, flowrate, diffuser plate design, and wafer cassette design. It was found that with the reverse flow option; it seems to deliver uniform flow as compared to the forward flow option. Flow pattern was similar among different flowrates and diffuser designs. Low velocity flow always existed at the top portion of the wafer and near the last row of the wafer cassette. With the hypothesis that slower flowrate results in higher plating rate; a qualitative agreement has been observed between the predicted flow pattern and the plated nickel height uniformity.
Temperature/Heat Flux Errors Caused by High Temperature Resistive Shunting Along Mineral-Insulated, Metal-Sheathed Thermocouples
Authors: Gill Walter , Nakos James T. 
Published: December 2021

Abstract
Commercially manufactured, mineral-insulated, metal-sheathed (MIMS) thermocouples (TCs) have been used at Sandia National Laboratories (Sandia) and other experimental laboratories for many years to measure temperatures in fires and high-temperature (e.g., 1200°C) radiant-heat environments. These TCs are rugged and relatively inexpensive, which make them ideal for large-scale outdoor testing where factors such as weathering and rough handling are important.
A particularly insidious source of TC error is thermal shunting of the TC assembly. This error is caused by a sharp drop in the electrical resistivity of the mineral insulation at elevated temperatures. When a TC assembly is subjected to high temperature along its length, the lower resistivity of the mineral insulation can cause shorting or shunting to occur.
This paper describes several cases demonstrating the seriousness of the shunting problem at temperatures previously thought to be immune. Some preliminary experiments designed to clarify the thermal shunting problem are presented. A model developed under previous work but modified specifically for Type K TCs is discussed. Comparisons of measured and predicted temperature error data in additional thermal shunting experiments provide some degree of confidence in the model’s predictive capability. Predictions for several common field test configurations used in Sandia experiments are shown in the hopes of sensitizing other researchers in the field to this problem.
Design and Uncertainty Analysis of a Second-Generation Convective Heat Flux Calibration Facility
Authors: Holmberg David G. , Womeldorf Carole A. , Grosshandler William L. 
Published: December 2021

Abstract
The National Institute of Standards and Technology has developed a convective heat flux facility to allow calibration of heat flux sensors. The facility consists of a small wind tunnel that produces a two-dimensional laminar boundary layer across a heated isothermal copper plate. Sensors are mounted flush in the copper plate alongside a reference to measure the heat leaving the plate. Convective calibrations up to 5 kW/m2 are possible. Sensor output is compared with the reference value, and contrasted with a standard radiation calibration. Recognizing that many sensors are used in mixed radiation and convection environments, this facility provides a unique opportunity to assess a sensor’s convective response. This report describes a second-generation heated plate and provides an analysis of the system uncertainty. Redundant references, improved sensor heating and mounting, improved reference isolation, and a minimized radiation component has reduced the combined relative expanded uncertainty of the reference to ±2.5 %. The benefits of an embedded temperature sensor in the heat flux sensor are described. The facility is available for comparative calibrations and for heat transfer studies by individual researchers.
Survey of Research Activities for Passive Safety System of AC600
Authors: Chen Bingde , Yang Zhumao , Ji Fuyun 
Published: December 2021

Abstract
The use of passive safety system in AC600, the Chinese advanced 600 MWe PWR proposed by NPIC, together with other improvements, such as simplification and advanced I&C etc., makes the plant more safe, economic and reliable. The core damage frequency (CDF) decreases from less than 10−4 of conventional PWR to less than 10−5 to 10−6 and the plant available factor increases to ∼90%.
The passive safety system of AC600 consists of three complete independent systems. They are passive containment cooling system (passive CC system), passive core residual heat removal system (passive CRHR system) and passive safety injection system (CMT). To verify and demonstrate the AC600’s innovative passive safety features and to obtain an experimental database for system design modification and optimizing, and for computer code development and assessment, the experimental studies on these systems were finished in NPIC during the eighth national Five Year period under the national support.
In this paper, the experimental research activities on passive containment cooling system, passive CRHR system and CMT injection system, including test rigs and main results are summarized. These experiments proved the design of all these passive systems are feasible and reliable and can meet basically the required safety functions. Some undesired thermal hydraulic phenomena, for example, “water hammer”, which may have bad impacts on its safety functions and to which high attention should be given, was found and identified in these studies. All data obtained have already been used in the design improvement and next R&D program planning.
An Experimental Correlation of Quenching Temperature Under Top-Down Reflooding in a Vertical Tube
Authors: Huang Yanping , Lang Xuemei , Chen Bingde 
Published: December 2021

Abstract
A quenching experiment under top-down reflooding in a vertical tube was performed by adopting the transient hot block quenching test technique. The temperature history on the inner wall of test tube was calculated by using a quasi-steady-state two-dimension numerical technique, and the intersection of double tangent lines was used to determine the location and the time of the quench front. Based on some theoretical models of quenching temperature, at the same time, the effect of flow parameters in the tube during quenching was taken into account, a semi-empirical correlation for quenching temperature under the low pressure and low mass flow rate is presented in this paper. It is as follows:Tq−TsTo−Ts=11.8362(Ts−Tf,inTo−Ts)−0.0714[(cρk)w]0.2938×G0.0251×(Ts−Tf,in)−0.3145 The parameter range of this correlation is as follows: system pressure: 0.31∼0.88MPa: mass flux: 17.7∼902.kg/m2s; inlet subcooling: 3∼77°C; initial hot-wall temperature: 450∼600 °C.
A Method for Estimating Acoustic Implosion Efficiencies for Collapsing Cavities in Nuclear Reactor Systems
Authors: Kullberg C. M. 
Published: December 2021

Abstract
For the last several decades, condensation induced water hammer events have been a concern i n the nuclear industry. With the arrival of passive reactor designs, concerns have arisen about the natural inception of vapor cavity formation in these systems. Several aspects of subcooled bubble cavity implosions are examined. In particular, this paper will focus on spherical cavity implosion transients. Numerical scoping calculations were performed with the compressible version of the Rayleigh-Plesset equation. The calculations revolved around predicting two key parameters, the peak pressure and the net acoustic energy release. Both of these parameters are relevant in quantifying the damage potential of a spherical water hammer event.
Approximate Temperature Profiles and Companion Heat Transfer Rates of Uniform Annular Fins Using Finite-Differences Instead of Bessel Functions
Authors: Campo Antonio 
Published: December 2021

Abstract
The temperature variation along annular fins of uniform thickness and constant thermal conductivity is governed by a differential equation of second order with variable coefficients which is called the modified Bessel equation of zero order. This educational paper addresses a simplistic finite-difference procedure for solving this kind of Bessel equation employing a reduced system of algebraic equations. Approximate temperature distributions and companion heat transfer rates have been computed with the elimination of unknowns by hand and also with the Gauss elimination method using the symbolic algebra software Maple V (Char et al., 1991) on a personal computer. Instructors and students of heat transfer courses may benefit from this alternative computational procedure that seeks to avoid the use and operations with Bessel functions and still produce numerical results of good quality. Rudimentary knowledge of numerical techniques is the only mathematical background that students need to possess in order to implement the computational scheme explained here.
Rheological Measurements on Molten Metals
Authors: Bakhtiyarov Sayavur I. , Overfelt Ruel A. 
Published: December 2021

Abstract
The rotational measurement technique has been developed to measure the dynamic viscosity of liquid metals. A special procedure is accomplished to eliminate both end and eccentricity effects. The technique was calibrated and tested with liquids of known rheology. The apparent viscosity of low melting alloy composite is measured by means of the technique.
Plastic Flow in Confined Porous Media of Complex Contours
Authors: Letelier Mario F. , Rosas César E. 
Published: December 2021

Abstract
A theoretical study of the fully developed fluid flow through a confined porous medium is presented. The fluid is described by the Bingham plastic model for small values of the yield number. The analysis allows for many admissible shapes of the wall contour. The velocity field is computed for several combination of relevant parameters, i.e., the yield number, Darcy resistance coefficient and the boundary perturbation parameter. The wall effect is especially highlighted and the characteristics of the central plug region as well. Plots of isovel curves and velocity profiles are included for a variety of flow and geometry parameters.
Elasto-Plastic Finite Element Analysis of Metal-Matrix Composite Plates With Hole Under Plane Loading
Authors: Okumuş Fuat , Turgut Aydın , Sancaktar Erol 
Published: December 2021

Abstract
The elasto-plastic stress analysis of composite plates with hole has been carried out by the finite element method.
For this purpose, an isoparametric rectangular element with nine nodes has been chosen and the lagrange polynomial has been used as interpolation function. Steel-aluminum composite has been manufactured by using mould under the action of 30 MPa pressure and heating up to 600 °C. Mechanical properties and yield strength of the composite material have been obtained experimentally by using a strain gauge in the tensile testing machine. The composite plates in various dimensions have been. obtained by changing the diameter of the hole. The various tension loads which are increased step by step from beginning of the yield have been applied to these plates. The expansions of plastic regions have been illustrated for various cases. According to orientation angle and applied loads, elastic, plastic and residual stresses have been obtained.
Stress Analysis of Bolted Joints of Flat Cover With Tap Bolts in a Pressure Vessel
Authors: Sawa Toshiyuki , Karasawa Akihiro , Shimizu Akihiro 
Published: December 2021

Abstract
Bolted joints with gaskets have been designed empirically, and the sealing performance is not made clear by theoretical analyses because the contact stress distribution between the gasket and the flanges are not clarified when an internal pressure is applied to the joint. The present paper, discusses the distribution of contact stresses in the bolted joints fastened with tap bolts, when a clamped part with a gasket is the cover of a pressure vessel and is a circular flange. The distribution of contact stresses is analyzed as a three-body contact problem, using the three-dimensional theory of elasticity. Moreover, the contact stress is measured by means of ultrasonic waves. In addition, the load factor (the ratio of an increment of the axial bolt force to an external load) and the maximum stress caused in bolts are analyzed taking into account the bending moment. For verification, experiments are carried out, and the analytical results are found in fairly good agreement with the experimental ones. It was found that the sealing performance was improved when Young’s modulus of the gaskets was decreased and the gasket thickness was increased.
Examining Multiaxial Impact Behavior of Polymer Materials
Authors: Lawrence G. E. , Saigal A. , Zimmerman M. A. , Greif R. , Duan Y. 
Published: December 2021

Abstract
The analysis of multiaxial impact of polymer disks is considered. The calculation of impact displacements and stresses is provided. Finite element simulation results are compared to experimental data. The results from simulations of various impact velocity and mass are given for a constant disk thickness. Results from simulations of various disk thickness for constant impact mass and velocity are shown as well. The plasticity failure model used in FEA simulation of impact is quantified for the application with the tested polymers. It is shown that strain rate material dependence is an important factor in accurately modeling impact response of polymers.