bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling the f and j Characteristics of the Offset Strip Fin Array
Authors: Muzychka Y. S. , Yovanovich M. M.
Published: December 2021

New models for predicting the thermal-hydraulic characteristics of offset strip fin arrays are developed. These models are developed by combining the asymptotic behaviour for the laminar and turbulent wake regions. Models in these two regions are developed by considering the offset strip fin as an array of short ducts or channels. The proposed models are compared with published experimental data for nineteen configurations of the rectangular offset strip fin. Model predictions are within ± 20 percent for 96 percent of friction factor data and 82 percent for Colburn j factor data. Extension of the new models for offset strip fins having non-rectangular subchannels is also discussed.
Laminar Mixed Convection in the Entrance Region of a Helical Pipe
Authors: Zheng B. , Lin C. X. , Ebadian M. A.
Published: December 2021

A fully elliptic numerical study is performed to investigate the buoyancy-affected, three-dimensional laminar flow and heat transfer in the entrance region of a helical pipe at a constant wall temperature. The Control Volume Method with second-order accuracy is used to numerically solve the three-dimensional fully elliptic governing equations for the problem. The O-type non-uniform structure grid system is adopted to discretize the computation domain (two complete turns of a helical pipe) in this study. The Bossinesq approximation is applied to deal with the buoyancy effect caused directly by density difference. The developments of flow and temperature fields, profiles and characteristics at different Gr/Re2 are given and discussed. The computed results reveal that the entrance region of heat transfer is increased rapidly when buoyancy force is considered. In the meantime, the buoyancy effect on the average Nusselt number and friction factor is greater at the entrance region of the helical pipe, but it gradually becomes weaker further downstream.
Natural Convection Heat Transfer in a Vertical Air Layer Partitioned Into Cubical Enclosures of Finite Wall Thermal Conductivity and Thickness
Authors: Yamaguchi Y. , Asako Y.
Published: December 2021

Three-dimensional natural convection heat transfer characteristics in a vertical air layer partitioned into cubical enclosures of finite wall thermal conductivity and finite thickness were obtained numerically. The outer surfaces of the enclosure are prescribed at different temperatures. These walls are often encountered in applications such as door panels and thermal insulation boards. The analyses were performed for finite wall thickness and conductivity, for Ra = 104 and 105 and for a wide range of wall thickness and thermal. The results were presented in form of temperature distributions and contour plots of Num and Qwall/Qtotal. From comparison of the results with ideal boundary conditions, a correlation for heat transfer for partitioned walls was developed. It was shown from the results that the ratio of heat transfer into the partition walls to the total heat transfer from the hot wall is a function of the product of wall thermal conductivity and thickness.
Computation of Discrete-Hole Film Cooling by a Near-Wall Second-Moment Turbulence Closure
Authors: Chen Hamn-Ching , Wei Gengsheng , Han Je-Chin
Published: December 2021

A multiblock Favre-Averaged Navier-Stokes (FANS) method has been developed in conjunction with a chimera domain decomposition technique for investigation of flat surface, discrete-hole film cooling performance. The finite-analytic method solves the FANS equations in conjunction with a near-wall second-order Reynolds stress (second-moment) closure model and a two-layer k-ε model. Comparisons of flow fields and turbulence quantities with experimental data clearly demonstrate the capability of the near-wall second-moment closure model for accurate resolution of the complex flow interaction bewteen the coolant jet and the mainstream. The near-wall second-moment anisotropic model provides better agreement in adiabatic film effectiveness prediction than the two-layer k-ε model.
Energy Conversion in Multilayer Thin-Film Structures for Thermionic Cooling
Authors: Zeng Taofang , Chen Gang
Published: December 2021

A new type of multilayer thermionic coolers with varying barrier heights is proposed in this article. Based upon the assumption of ballistic electrons in the filters and thermalized electrons in the bases, we analyzed the energy balance at each stage. As the heat flux increases at later stages, the barrier height should also increase. The optimum structure is obtained by a trial-and-error method. Calculation results show that the coefficient of performance does not change significantly with the number of stages of the thermionic cooler. The heterojunction structure with varying barrier heights have a slightly higher COP than the one with a fixed barrier height.
Experimental Correlation of a Thermal / Fluid Dynamic / Electrical Performance Model of a Multiple-Tube, Vapor-Anode AMTEC Cell
Authors: Hendricks Terry J. , Huang Chendong , Giglio Joseph C.
Published: December 2021

An AMTEC (Alkali-Metal Thermal-to-Electric Conversion) cell performance analysis model described by Hendricks et al. (1998) has been correlated with experimental data by comparing its predictions for Beta” alumina solid electrolyte (BASE) and evaporator temperatures, voltage, power output, and conversion efficiency with experimental measurements on two versions of a PX-6 AMTEC cell. The critical features of this AMTEC cell model, the PX-6 experimental set up and testing, and the model correlation PX-6 test data are discussed in this work. Model prediction/test data comparisons are presented across a wide range of current-voltage conditions and hot side temperatures for two significantly different cell lengths. Cell model predictions demonstrate good agreement with experimental PX-6 test data in simultaneously predicting BASE tube and evaporator temperatures, the onset of sodium (Na) condensation in the BASE tubes, current-voltage characteristics, and power output in high current ranges (i.e., > 1.5 A). The model also has demonstrated good capability to predict cell conversion efficiency at high currents when Na is not condensing in the BASE tubes. The good model prediction/test data comparisons have demonstrated the progress in developing this cell performance model and increased confidence in its technical foundations, algorithm implementation, and capability to predict AMTEC cell performance. The AMTEC cell model’s capability to simultaneously predict many critical cell performance parameters across a wide range of hot side temperatures, at high current conditions, and different cell lengths demonstrates the progress that has been made in its development. It has demonstrated good predictive capability, utility, and flexibility as a performance design and analysis tool for sophisticated AMTEC cell design. Testing limitations prevented testing at low current levels (i.e., < 1.5 A), so future experimental validation studies should focus on correlating model predictions at low currents.
A New Model for Two Phase Multicomponent Displacements Honouring Ganglia and Droplets
Authors: Bedrikovetsky Pavel
Published: December 2021

During two-phase flow through porous media, a non-wetting phase may be present simultaneously as a continuous phase and as trapped isolated ganglia. Mass exchange between these two parts of the non-wetting phase is going on by dissolution and diffusion of components through the wetting phase, the compositions of the non-wetting phase in both parts being different. Nevertheless, the traditional mathematical model for two-phase multicomponent transport through porous media assumes that the distribution of all components in the overall non-wetting phase is homogeneous.

This paper derives a new set of equations governing two-phase, three-component flow through permeable media that honours the isolated nature of a trapped residual phase. The solutions of these equations compare favourably to the results of laboratory tests. An analytic solution of the equations of the displacement of oil and water by the mixture ‘water-miscible gas’ (water-alternating-gas process) shows that a significant amount of oil remains after a miscible displacement. This observation is in contrast to the ‘traditional’ fractional flow model that predicts complete recovery of oil from the portions of the medium swept by the solvent.
Interaction Coefficient Between Ice Particles in Convective Melting of Granular Packed Bed
Authors: Jiang J. , Tao Y.-X.
Published: December 2021

To numerically simulate the convective melting of packed bed it is necessary to determine the thermophysical properties or their constitutive equations. One of the most uncertain values among them is the solute interaction coefficient of solid particles, which represents the interaction force between solid particles and is equivalent to the viscosity term in Navier-Stokes equations if the dirty fluid model is applied. It was found from the previous study that the solute (solid particle) interaction coefficient, μs, characterizes the solubility such as the melting rate, the distribution of ice volume fraction, the velocity of ice particle, and the melting time. In this study, a parametric study based on the two-dimensional model for the convective melting of granular packed beds (Jiang et al. 1999) is conducted to determine the sensitivity of interaction coefficient to the model prediction. The packed bed considered here is collection of ice particles of various shapes. Warm water at a constant temperature enters horizontally the bed where melting takes place. Two cases are considered. One is to consider μs as constant, and the other is to consider it as a function of the ice volume fraction. The melting rate, fluid flow velocity and ice volume fraction distribution are discussed for different interaction coefficient values. An “optimal” interaction coefficient between ice particles is determined by comparing the simulation data with experimental data (Tao et al. 1998). It is found that the melting results are most sensitive to the value of constant interaction coefficient rather than to whether it is a constant or as a function of the ice volume fraction.
A Theoretical Treatment of Critical Heat Flux on Metal-Graphite Composite Heating Surfaces
Authors: Yang Wen-Jei , Zhang Nengli
Published: December 2021

This paper presents a theoretical treatment of the critical heat flux on metal-graphite composite surfaces. A previous study found that the tips of graphite-fibers act as bubble nucleation sites. Throughout the transition boiling regime, vapor rises into liquid on the nodes of the Taylor waves in reference to the Rayleigh-Taylor instability theory. At the critical (i.e., maximum) heat flux, this rising vapor forms into jets. These jets come from the graphite fiber tips that are arranged in an equilateral triangular grid in the metal matrix. The basic spacing of the grid is the two-dimensional Taylor wavelength, which is the spacing of the most basic module of jets. At the peak heat flux, the Kelvin-Helmholtz instability causes the jets to become unstable and brings about burnout. In other words, this instability theory predicts when the vapor velocity in the jet will reach a critical value to cause the vapor jets to cave in. The existing empirical results indicate that the nucleate pool boiling curves for metal-graphite composites of different graphite concentrations (i.e., area fractions) congregate near the critical heat flux of the composite for the optimum performance as the degree of superheat increases. With this particular graphite-fiber concentration known, a balance of the heat flux by the latent heat carried away in the jets when the liquid is saturated yields the maximum (i.e., critical) heat flux equation. Both copper-graphite and aluminum graphite composites are treated.
Study on Enhancement of Critical Heat Flux by Supplying Liquid-Jets to Heating Surface
Authors: Ohtake Hiroyasu , Yamamoto Noriyuki , Koizumi Yasuo
Published: December 2021

The enhancement of a critical heat flux in pool boiling was investigated by supplying liquid-jets to a heated surface, as a proposal of the high heat removal technology for future. Experiments were conducted using a pure copper block and saturated water for a pool condition at atmospheric conditions. Two or three jet-nozzles were set away a certain distance from the test surface for supplying liquid-jets to the heated surface. In the present study, the effects of the distance between the nozzles and the test surface, the diameter of jet-nozzles, the liquid flow rate and the jet-velocity on the enhancement rate of the critical heat flux were examined experimentally.

The critical heat flux obtained in the present experiments was enhanced a factor of about two for the flow rate per nozzle of 2.5 × 10−6 m3/s by supplying two liquid-jets. However, it was little affected for the supplied liquid when the distance between the jet-nozzles and the heated surface was 15 mm. The enhancement rate increased with the liquid flow rate and liquid jet velocity except for the 15 mm nozzle distance. The dependency of the enhancement rate on the flow rate for the nozzle-diameter of 0.9 mm was similar to that for the 0.5 mm in diameter. The dependency on the jet-velocity for the case of 0.9 mm, however, was difference to that of 0.5 mm. In other words, the enhancement rate of the critical heat flux is related to the flow rate of the liquid-jets. These results suggest that the enhancement of the critical heat flux is affected additionally by the quantity of supplied liquid to the macrolayer on the heated surface.
Numerical Study of Spray Parametric Effects on Gas Turbine Combustion Performance
Authors: Su K. , Zhou C. Q.
Published: December 2021

A numerical study was conducted to determine the effects of fuel spray characteristics on the gas turbine combustion performance including the combustion efficiency and the overall temperature distribution factor (OTDF) at the exit of the combustor using the KIVA-3V code. A model of a typical annular combustor was used in the computations. Operating conditions were varied with inlet pressure from 0.1 to 1.2 MPa, inlet temperature from 400 to 650 K, and air fuel ratio from 0.015 to 0.024. A log-normal spray distribution was assumed to simulate a real fuel spray distribution at injection. The droplet mean diameter as well as injection velocity and angle were independently varied to distinguish the separate effects of variables involved. Flow fields and temperature distributions in the combustor were analyzed. The results reasonably agreed with those from a semi-empirical approach. It is found that the overall temperature distribution deteriorates as the Sauter mean diameter of fuel spray increases. There is an optimum range of the Sauter mean diameters for the efficient combustion of fuel sprays. The overall temperature distribution is improved as the injection velocity of fuel sprays increases, but the combustion efficiency does not change much with it. It appears that the KIVA-3V code can be used to guide the design and improvement of the gas turbine combustor.
An Unstructured-Mesh Methodology for Computation of Reacting Sprays in Industrial Combustors
Authors: Giridharan M. G. , Sheu J. C. , Bayyuk S. A. , Presser C.
Published: December 2021

This paper reports the progress made in developing a state-of-the-art, unstructured-mesh code for simulating reacting two-phase flows for general-purpose industrial applications. The code has been created by combining a finite-volume solver for computing flow, heat-transfer, and chemical reaction in the gas phase with a new object-oriented module specifically designed and developed to provide a framework for solving the system of equations governing the motion of spray droplets and their interactions with the gas phase. The gas phase equations are solved in an Eulerian frame while the droplet equations are solved in a Lagrangian frame. The paper presents the equations for droplet transport and behavior, describes the coupling models between the gas and liquid phases, and outlines the overall solution technique. Much of the paper is devoted to verification and validation of the computational models. The verification studies include comparison of computational results for particle motion under the influence of gravity and for solutions. The validation studies include comparison of predictions with published experimental data on behavior of evaporating and non-evaporating sprays. All comparisons show good qualitative and quantitative agreement. A 2-D axisymmetric simulation of methanol combustion in the N1ST reference spray combustor is also presented, and the results are compared with the NIST flow visualization data. Relevant ongoing work and future plans for incorporation of advanced spray models are briefly described.
Fabry-Perot Resonators Built With YBa2Cu3O7-δ Films on Si Substrates
Authors: Kumar A. Ravi , Boychev Vladimir A. , Zhang Zhuomin M. , Tanner David B.
Published: December 2021

Fabry-Perot (F-P) resonators were built from two superconductive YBa2Cu3O7-δ (YBCO) films separated by a spacer. Each film of 35 nm thickness was deposited on a Si substrate ≈0.2 mm thick. A slow-scan Michelson interferometer was employed to measure the transmittance of the resonator in the far-infrared frequency region from 10 to 90 cm−1 at temperatures between 10 and 300 K. Measurements showed that in the normal state the peak (or resonant) transmittance decreases with temperature, whereas in the superconducting state it can increase with decreasing temperature. The transmittance of the resonator was calculated using properties of individual reflectors obtained previously. When the effect of partial coherence is taken into consideration, the calculated transmittance is in good agreement with the experiments. Furthermore, the maximum possible resonant transmittance was predicted based on an optimization analysis considering the interference effects. The effect of the YBCO film thickness on the transmittance peaks was also studied, showing that the resonant transmittance decreases but the finesse increases as the film thickness is increased. This study should help improve the future design of F-P resonators based on HTSC thin films.
Computations of Low Pressure Fluid Flow and Heat Transfer in Ducts Using Direct Simulation Monte Carlo Method
Authors: Yan Fang , Farouk Bakhtier
Published: December 2021

High Knudsen (Kn) number flows are found in vacuum and micro-scale systems. Such flows are characterized by non-continuum behavior. For gases, the flows are usually in the slip or transition regimes. In this paper, the direct simulation Monte Carlo (DSMC) method has been applied to compute low pressure, high Kn flow fields in partially heated channels. Computations were carried out for nitrogen, argon, hydrogen, oxygen and noble gas mixtures. Variation of the Kn is obtained by reducing the pressure while keeping the channel width constant. Nonlinear pressure profiles along the channel centerline are observed. Heat transfer from the channel walls is also calculated and compared with the Graetz solution. The effects of varying pressure, inlet flow and gas transport properties (Kn, Reynolds number, Re and the Prandtl number, Pr respectively) on the wall heat transfer (Nu) were examined. A simplified correlation for predicting Nu¯ as a function of Pe¯ and Kn¯ is presented.
Experimental and Numerical Study of Conjugate Heat Transfer in a Horizontal Channel Heated From Below: Applications to CVD Processing
Authors: Chiu Wilson K. S. , Richards Cristy J. , Jaluria Yogesh
Published: December 2021

A detailed experimental and numerical study is carried out to investigate conjugate heat transfer in a horizontal channel with a heated section which simulates Chemical Vapor Deposition (CVD) processing. Since film quality, uniformity and deposition rate have strong dependence on temperature, the role of conjugate heat transfer in influencing temperature distribution is significant in thin film production. Experimental data obtained from this study provides physical insight into conjugate heat transfer effects and allows for comparison and validation of numerical conjugate heat transfer models. The basic characteristics of the flow and the thermal transport are studied. The numerical model is used to perform a parametric study of operational parameters, allowing for the characterization of conjugate heat transfer effects on temperature at the susceptor surface, reactor walls and the gas phase. The study yields valuable guidelines for the thermal design of CVD reactors.
A Study of Particle Growth Using Light Scattering and Local Sampling in Flame Synthesis of Nano Particles
Authors: Cho Jaegeol , Lee Jeonghoon , Kim Hyun W. , Choi Mansoo
Published: December 2021

The growth of silica particles in coflow diffusion flames has been studied experimentally using light scattering and local thermophoretic sampling techniques. The number densities and volume fractions of both aggregates and spherical particles have been determined calculated by a novel method of using the scattering cross section measured from 90° light scattering with the combination of particle sizes and morphology measured from the localized sampling and TEM image analysis under the assumption of monodisperse distribution of primary particles in an aggregate. Rayleigh-Debye-Gans and Mie theories have been applied to the calculations for fractal aggregates and spherical particles, respectively. Of particular interests are the effects of carrier gas flow rates on the evolution of silica particles and the roles of radial heat and H2O diffusion have been studied when using N2 or O2 as a carrier gas.
Benchmark Boundary Element Solutions for Some Problems Governed by the Boussinesq Equations
Authors: Grigoriev Mikhail M. , Dargush Gary F.
Published: December 2021

The boundary element formulation developed previously by the authors for incompressible isothermal viscous fluid flows is extended for non-isothermal flows governed by Boussinesq equations. The new boundary element method is applied to the classical Rayleigh-Benard problem and to a stratified flow over a backward-facing step. In all cases, the boundary element results are in good agreement with published finite element solutions. However, in some instances, the boundary element solutions are more accurate, particularly in terms of resolving surface tractions and heat fluxes.
Wavelets and the Numerical Solution of Heat Transfer Problems: A Discussion of Two Methods
Authors: Sowayan A. S. , Bénard A. , Díaz A. R.
Published: December 2021

Two methods for solving heat transfer problems using wavelets are reviewed and discussed, namely the so-called “Fictitious Boundary” and “Fictitious Domain/Penalty” methods. Evaluation of the two methods is performed by solving simple two-dimensional heat conduction problems using fixed scale expansion of the unknowns. A discussion on the implemention of the boundary conditions and the ease of solving the resulting system of equations is presented. For each problem the error is computed so that the accuracy of the solution can be evaluated. It is found that the Fictitious Domain/Penalty method shows better agreement with the exact solutions than the Fictitious Boundary method as it introduces less computational errors due the methodology used to implement the boundary conditions in the extended domain.
Simulation of Flow and Heat Transfer With Phase Boundaries and Complex Geometries on Cartesian Grids
Authors: Udaykumar H. S. , Mittal R. , Shyy W.
Published: December 2021

This paper is an extension of our previous work on simulation of complex phase front evolution in the diffusion-dominated situation. The Navier-Stokes equations are solved using a finite-volume method based on a second-order accurate central-difference scheme in conjunction with a two-step fractional-step procedure. The key aspects that need to be considered in developing such a solver are imposition of boundary conditions on the immersed boundaries and accurate discretization of the governing equation in cells that are cut by these boundaries. A new interpolation procedure is presented which allows systematic development of a spatial discretization scheme that preserves the second-order spatial accuracy of the underlying solver. The presence of immersed boundaries alters the conditioning of the linear operators and this can slow down the iterative solution of these equations. The convergence is accelerated by using a preconditioned conjugate gradient method where the preconditioner takes advantage of the structured nature of the underlying mesh. The accuracy and fidelity of the solver is validated and the ability of the solver to simulate flows with very complicated immersed boundaries is demonstrated. The method will be useful in studying the effects of fluid flow on the evolution of complex solid-liquid phase boundaries.
Three-Dimensional Thermal Model of Resistance Spot Welding in Aluminum
Authors: Kabir A. A. S. Arefin , Khan Jamil A. , Broach Kirk
Published: December 2021

A 3-D thermal model for resistance spot welding in aluminum is presented. The numerical model, validated with experimental findings, considers phase change and the associated weld-pool convection. A parametric study is performed to determine the influence of welding features such as faying surface (work-piece contact surface) contact resistance, current, electrode-work-piece surface-thermal-contact-conductance and electrode tip diameter. These parameters have significant effects on the nugget and heat-affected-zone geometry. The phase change morphology, including melting and solidification rates and weld pool dynamics, is also significantly influenced by the parameters studied. The strongest convection was observed at the center of the molten pool in a plane aligned with gravity. Although two prominent convection cells develop, the phase change morphology is not significantly affected due to the short welding time (less than 0.05 seconds) and low fluid velocity (smaller than 1 × 10−2 mm/s). The nugget grows nonlinearly with increasing current and faying surface contact resistance while diminishing with increasing electrode work-piece surface-thermal-contact-conductance. The influence of faying surface contact resistance on nugget size is less than that of the other parameters. Optimum selection of electrode tip diameter provides the best possible nugget. The duration of weld pool existence increases with the increasing current but decreases with the increasing electrode work-piece surface-thermal-contact-conductance.
Data Reduction Methodology for Fast-Response Schmidt-Boelter Heat-Transfer Gages
Authors: Adams John C. , Kidd Carl T.
Published: December 2021

Transient heat-transfer data have recently been obtained in hypersonic wind tunnels at the Arnold Engineering Development Center (AEDC) with miniaturized fast-response Schmidt-Boelter gages. These sensors have time constants in the 10- to 15-msec range, but have response characteristics that are usually less than first-order. This presents a requirement for a general data reduction method to prevent degradation of the accuracy of the experimental data. A consistent nonambiguous data reduction methodology for fast-response Schmidt-Boelter heat-transfer gages is presented which is easy to implement in an algorithmic fashion. Timewise correction of measured Schmidt-Boelter gage heat flux is no more difficult than that involved in a classical first-order system (Gardon gage), and only involves the determination of a characteristic time measure of the integrated energy deficiency inherent in the gage response. This characteristic time measure is easily determined from the gage response characterization to a step input heat flux by numerical integration of the response versus time data.
A Comparison of Radiation Versus Convection Calibration of Thin-Film Heat Flux Gauges
Authors: Smith D. E. , Bubb J. V. , Popp O. , Diller T. E. , Hevey Stephen J.
Published: December 2021

A transient, in-situ method was examined for calibrating thin-film heat flux gauges using experimental data generated from both convection and radiation tests. Also, a comparison is made between this transient method and the standard radiation substitution calibration technique. Six Vatell Corporation HFM-7 type heat flux gauges were mounted on the surface of a 2-D, first-stage turbine rotor blade. These gauges were subjected to radiation from a heat lamp and in a separate experiment to a convective heat flux generated by flow in a transonic cascade wind tunnel. A second set of convective tests were performed using jets of cooled air impinging on the surface of the gauges. Direct measurements were simultaneously taken of both the time-resolved heat flux and surface temperature on the blade. The heat flux input was used to predict a surface temperature response using a one-dimensional, semi-infinite conduction model into a substrate with known thermal properties. The sensitivities of the gauges were determined by correlating the semi-infinite predicted temperature response to the measured temperature response. A finite-difference code was used to model the penetration of the heat flux into the substrate in order to estimate the time for which the semi-infinite assumption was valid. The results from these tests showed that the gauges accurately record both the convection and radiation modes of heat transfer. The radiation and convection tests yielded gauge sensitivities which agreed to within ±11%.
Instability of Flame Spread in Microgravity
Authors: Oravecz Lisa M. , Wichman Indrek S. , Olson Sandra L.
Published: December 2021

Results from the first part of an experimental study of flame spread instability are presented. The instabilities were investigated in the NASA drop facilities because the particular instabilities being examined were most pronounced in microgravity, when the influences of buoyancy were minimized. The flame front over thin cellulosic samples broke apart into separate flamelets which interacted with one another and oscillated (frequency ∼ 1 Hz). Different heat-sink backings, which were used to promote flame instability and flamelet productions are examined and described. Preliminary experiments in the NASA 5 second drop tower (Zero-G) drop facility are discussed.
Thermal Analysis of an Absolute Radiometer Designed for the Future Satellite Mission of Total Solar Irradiance Measurement
Authors: Shen Y. J. , Chen D. H. , Zhang Z. M.
Published: December 2021

This work employs finite element (FE) software to perform a thermal modeling of a proposed absolute radiometer designed for the future satellite mission of total solar irradiance measurement. Both steady-state and transient analyses have been performed to obtain the temperature distribution and history. The cavity-type absolute radiometer employs the electrical-substitution technique and active temperature control to determine the radiant power entering the receiving cavity. The nonequivalence between the shutter-open mode and shutter-closed mode due to different temperature distributions is a major factor that affects the radiometric accuracy. The steady-state analysis shows that the nonequivalence is a function of sensor positions and can be minimized by properly choosing the electrical heating method and the temperature sensor location. The transient analysis provides the temperature response for a step power input. In order to reduce the computational time, simplified lumped-heat-capacity models have been developed by applying the least-squares fitting technique to the transient result of the FE model. The two-lumped-heat-capacity model demonstrates a better accuracy than the single-lumped-heat-capacity model and will facilitate the controller design.
Surface Deformation and Thermal Convection in Electrostatically-Positioned Droplets Under Microgravity
Authors: Song Suping , Li Ben Q.
Published: December 2021

Electrostatically positioned droplets are very useful for the fundamental study of solidification phenomena and the measurement of thermal physical properties. This paper descries a numerical analysis of surface deformation and surface tension driven flows in electrostatically positioned droplets in microgravity. The analysis is based on a fully coupled boundary element and finite element solution of the Maxwell equations, the Navier-Stokes equations and the energy balance equation. Results show that an applied electrostatic field results in a nonuniform electric stress distribution along the droplet surface, which, combined with surface tension, causes the droplet to deform into an ellipsoidal shape in microgravity. Laser heating induces a non-uniform temperature distribution in the droplet, which in turn produces Marangoni convection in the droplet. It is found that the viscous stress contribution to the deformation is small for a majority of cases. Also, a higher temperature gradient produces a stronger Marangoni convection in droplets with higher melting points that require more laser power. The internal recirculating flow may be reduced by more uniform laser heating. During the undercooling of the droplet, both temperature and fluid flow fields evolve in time such that the temperature gradient and the tangential velocities along the droplet surface subside in magnitude and reverse their directions.
Safety Analyses at the Idaho National Engineering and Environmental Laboratory Test Reactor Area: Past to Present
Authors: Ambrosek Richard G. , Ingram Fred W.
Published: December 2021

Test reactors are unique in that the core configuration may change with each operating interval. The process of safety analyses for test reactors at the Idaho National Engineering and Environmental Test Reactor Area has evolved as the computing capabilities, software, and regulatory requirements have changed. The evaluations for experiments and the reactor have moved from measurements in a set configuration and then application to other configurations with a relatively large error to modeling in three-dimensions and explicit analyses for each experiment and operating interval. This evolution is briefly discussed for the Test Reactor Area.
Thermal Margin Evaluation for FELI Fuel Assemblies During an Accidental Vessel Draining
Authors: Ambrosek Richard G. , Ingram Fred W. , Hawkes Grant L. , Sterbentz Jim W.
Published: December 2021

Safety requirements many times require specific evaluations for experiment operating conditions during periods of postulated off-normal operation. A unique experimental facility in the Advanced Test Reactor was designed for enhancement of the neutron flux in an irradiation position, large “I”, in the reflector region. Requirements for the facility necessitated analysis of the enhancement fuel to demonstrate that melting of the fuel element cladding would not occur during a loss of coolant event during reactor shutdown. The response of the fuel elements was evaluated using computer software that allowed detailed evaluations of the gamma heating magnitude and deposition fraction, natural convection cooling, prediction of heat transfer coefficients, and detailed finite element modeling for prediction of the temperature magnitudes and profile.
Experimental Laboratory Research on Computer-Aided System for Determining Fluid Flow Patterns in Air-Water Two-Phase Flow
Authors: Keska Jerry K. , Smith Michael D. , Dolan Quinn F.
Published: December 2021

Measurements and monitoring of flow patterns are one of the most important parameters in many industrial processes such as mass transfer in all types of reactors, heat exchangers, and tribo systems. The objective of this paper is to report and analyze the experimental data obtained in the process of development of Computer-Aided Measurement System of flow patterns based on in-situ mixture dynamic parameters. The measurement systems of in-situ parameters are interfaced with a Computer-Aided-Data-Acquisition-System (CADAS). The developed apparatus allowed measurement of the in-situ flow parameters of the mixture simultaneously including concentration and pressures monitored in large and small time scales. Using a previously developed computer-aided-measurement system and electronic sensors, experimental data of in-situ spatial concentration, in-situ gas/liquid velocities, pressures, and other parameters were obtained for steady-state conditions in an adiabatic two phase air-water flow system which consisted of a small square vertical channel.
Cooperative Learning in an Introductory Heat Transfer Class
Authors: Boehm Robert F.
Published: December 2021

A description is given of an introductory heat transfer class offered in a “cooperative learning” format. The emphasis of the course was to develop analysis skills of the class members. Groups of three students spent most of the class time working problems collectively. Various aspects of arranging this type of course are summarized, including the steps to be taken prior to the beginning of the term, as well as those elements that were handled on a day-today basis. The benefits and drawbacks of this type of approach are outlined.
Feasibility Study of a Hybrid Combustion-Fuel Cell Cogeneration Plant: A Senior Design Project Case Study
Authors: Manno Vincent P. , Friend Katherine K. , Nelson Emilie R.
Published: December 2021

This paper is a case study of a senior level project on cogeneration for the Tufts University Medford, MA campus. Eight students were involved — six in the BSME program and two in the BSEnvE program. Through brainstorming and collaborative planning, students developed a “Proposal Document” which defined the study objectives, milestone schedules and deliverables. The student team was then divided into technical and project functional groups. Electronic communication was utilized but “face-to-face” meetings were crucial for maintaining progress. The student team evaluated whole campus and part-campus possibilities taking into account thermal and electrical demand profiles and local infrastructure. The outcome design featured a hybrid conventional combustion/molten carbonate fuel cell system to supply all electrical and partial thermal demands for a complex of buildings housing classrooms, gymnasium facilities and a new field house. Engineering specifications were developed and civil engineering and siting constraints were analyzed. Technology selection was driven not only by engineering constraints but also by student interest in exploring emerging technologies (fuel cells). The team presented written and oral reports to student peers, faculty, university personnel and outside experts.

The paper provides an analysis of outcomes, assessments and satisfaction level. High course satisfaction and above average workloads were reported. The paper concludes with an elucidation of lessons learned including project execution, team makeup and background, the proper focus of design project courses, and the synthesis and integration of knowledge. Even in this small, relatively homogeneous mix of students, attention to bridging interdisciplinary gaps was required. Experience from this and similar courses indicate that the goal of capstone “synthesizing” experiences is flawed if the tendency towards “disciplinarity” in undergraduate education continues.
Critical Radius for Radial Heat Conduction: A Necessary Criterion but Not Always Sufficient
Authors: Kulkarni M. R.
Published: December 2021

Use of the critical radius for radial heat conduction in thermal insulation systems has been widely reported in the literature. When it is desirable to increase heat dissipation, this critical radius can be used in a definitive manner to maximize the heat dissipation. However, if it is desirable to decrease heat gain or heat loss, the critical radius only serves as a necessary condition, but it is not sufficient. To address design of such thermal systems, a new crossover radius is introduced. A crossover radius is a radius greater than the critical radius and is defined such that the heat transfer with the corresponding amount of insulating material is equal to that of the bare thermal system. Both cylindrical and spherical systems are considered.
Snap-Lock Beads Danger Analysis
Authors: Brickman Dennis B.
Published: December 2021

A tragic accident occurred when a 16 month old child fell face down and an oblong plastic toy snap-lock bead lodged in his throat obstructing his airway. Approaches utilized in the danger analysis include safety and medical literature review, codes and standards research, accident statistics survey, and evaluation of alternative snap-lock beads designs. Results of the danger analysis indicate that there are technically and economically feasible design alternatives which prevent the snap-lock beads from blocking the user’s airway.
Ohio River Mainstem Systems Study Lock and Dam Risk and Reliability
Authors: Schaaf David M.
Published: December 2021

The Ohio River is one of the busiest inland waterways in the world. It stretches from Pittsburgh, Pennsylvania to its confluence with the Mississippi River, a reach of 981 river miles (1579 km). Over 240 million tons (217,724 million kg) of cargo are shipped on the Ohio River annually. Additionally, a large number of recreational and other craft use the river. There are 19 high-lift lock and dams on the Ohio River of various ages and capacities.

The U.S. Army Corps of Engineers (USACE) is presently conducting the Ohio River Mainstem Systems Study (ORMSS). Lock and dams are generally designed for a 50-yr service life. As projects approach the end of their initial design life, USACE investigates the need for rehabilitation of the existing project to extend their service life. The study will address a master funding plan for all 19 lock and dams along the Ohio River for the time period 2000–2060. Because of the variation in ages, traffic levels, and maintenance history at the different projects along the Ohio River, the study will use both engineering and economic modeling to determine when and where improvements should be implemented during the study period.
Fire Safety in Nuclear Power Plants: A Risk-Informed and Performance-Based Approach
Authors: Azarm Mohamed A. , Travis Richard J.
Published: December 2021

The consideration of risk in regulatory decision-making has long been a part of NRC’s policy and practice. Initially, these considerations were qualitative and were based on risk insights. The early regulations relied on good practices, past insights, and accepted standards. As a result, most NRC regulations were prescriptive and were applied uniformly to all areas within the regulatory scope. Risk technology is changing regulations by prioritizing the areas within regulatory scope based on risk, thereby focusing on the risk-important areas. Performance technology, on the other hand, is changing the regulations by allowing requirements to be adjusted based on the specific performance expected and manifested, rather than a prior prescriptive requirement. Consistent with the objectives of risk-informed and performance-based regulatory requirements, BNL evaluated the feasibility of applying risk- and performance-technologies to modifying NRC’s current regulations on fire protection for nuclear power plants.(1) This feasibility study entailed several case studies (trial applications). This paper describes the results of two of them. Besides the case studies, the paper discusses an overall evaluation of methodologies for fire-risk analysis to support the risk-informed regulation. It identifies some current shortcomings and proposes some near-term solutions.
Analysis of the Convergent Channel as an Extensional Rheometer
Authors: Souza Mendes P. R. , Thompson R. L. , Nieckele A. O.
Published: December 2021

An important aspect while designing an “R2 z = constant” convergent channel as an extensional rheometer is the appropriate choice of the geometrical parameters and of the Reynolds number range of operation. The higher is the Reynolds number value, the thinner will be the boundary layer where the undesirable no-slip effect is confined, as discussed in the literature. However, if the Reynolds number, Re, is too large, then shear-related pressure losses become important, which is also undesirable in rheometry. Therefore, one design task is to find a range of Re within which the boundary layer is thin enough, and the velocity field in most of the domain is reasonably close to the desired kinematics. In this work we obtained numerical solutions for the flow of Newtonian and viscoelastic fluids through a convergent channel, for representative ranges of Re, dimensionless channel length, L, and dimensionless axial coordinate of inlet section, z0. For all cases, we determined fields of flow type, where regions of shear and of extension can be visualized. Among other findings, it is shown that, depending on the geometrical and flow characteristics, most of the mechanical energy dissipated can be due to shear effects, so that the extensional viscosity cannot be determined via pressure drop measurements.
Multiparticle Settling in Non-Newtonian Fluids
Authors: Zhu Qinsheng , Clark Peter E.
Published: December 2021

The settling of particles in non-Newtonian fluids is an important topic in industries from pharmaceuticals and foods to mineral extraction and construction. A large body of experimental work is available on single particle settling in both Newtonian and non-Newtonian fluids. Multi-particle systems are less well studied. Most reported work in multiparticle systems has been in Newtonian fluids. Recently, there has been increasing interest in multiparticle settling in non-Newtonian fluids. This paper will review some of the more important of these studies and present some new data on periodic motion observed in systems of three or more particles.
Anomalous Wall Effects in Parallel Plate Torsional Flow of Highly Concentrated Emulsions
Authors: Pal Rajinder
Published: December 2021

The rheological behaviour of a highly concentrated oil-in-water emulsion (75.1% by volume oil) was studied employing parallel plate torsional flows, with main emphasis on the wall effects. The steady shear and oscillatory shear data were collected with a controlled stress rheometer using smooth and serrated parallel plate geometries. The effect of the gap-height (between the parallel plates) on the rheological properties was also determined. When a serrated parallel plate geometry is used, the wall (slip) effects are found to be negligible. The data obtained by employing various gap heights overlap with each other. However, in a smooth parallel plate geometry, the emulsion behaviour is strongly affected by slip at the wall. The data obtained by employing various gap heights are different. In the absence of wall effects, the emulsion exhibits a highly nonlinear behaviour characterized by yield stress and high values of storage modulus.