bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phase Discrimination Techniques for Phase Doppler Measurements in Dispersed, Bubbly Flows
Authors: Stanley K. N. , Nikitopoulos D. E. 
Published: March 2022

Abstract
A combined Phase-Doppler Anemometry (PDA) and video imaging measurement technique for non-intrusive measurements in dispersed bubbly flows is presented. A one-component Phase-Doppler Velocimetry system has been employed to measure liquid seeding particle size and velocity as well as bubble size and velocity non-intrusively. Measurable flow quantities include: (1) mean velocities and RMS velocity fluctuations for bubbles and liquid; (2) local bubble diameter, and (3) local bubble passage frequency. Non-intrusive local measurement of seeding particle and bubble size is an advantage over techniques used previously (Laser-Doppler Velocimetry, Hot-Film Anemometry). Visual data collected simultaneously with the light-scattering measurements and analyzed with the aid of image processing are used to verify the trends portrayed by the light-scattering measurements. A multi-level phase discrimination technique based on velocity, diameter, and relative data rates between the carrier and dispersed phases is employed to minimize bias from bubble signals when measuring liquid phase data in dilute flows. An amplitude discrimination technique for the Phase-Doppler system is proposed for higher volume fraction flows. The proposed method enables local non-intrusive measurement of liquid phase velocity as well as local bubble size characteristics, velocity, and concentration.
Wall Heat Transfer Measurements in Saturated Pool Boiling of FC-72 on a Small Heated Area
Authors: Rule Toby D. , Kim Jungho 
Published: March 2022

Abstract
Local wall heat flux measurements of saturated pool boiling of FC-72 on a small heated area held at constant wall temperature were made. An array of 96 temperature controlled heaters was used to measure the heat flux distribution on this surface. Array-averaged heat flux, RMS variations in heat flux, and local heat flux information is presented. Local heat flux variations are shown to be three to six times larger than variations in the spatially averaged heat flux.
Simulation of 3-D Mold-Filling and Solidification Processes on Distributed Memory Parallel Architectures
Authors: Ilinca Florin , Hétu Jean-François , Audet Martin , Bramley Randall 
Published: March 2022

Abstract
This work presents industrial mold-filling applications of a three-dimensional stabilized finite element solver on distributed memory parallel architectures. The paper focuses on the solution algorithm and parallel implementation for complex multiphasics problems involving high Reynolds number flows with free surfaces, turbulence modeling and heat transfer. Standard domain decomposition methods (Chaco, Metis) are applied to the graph of nodes obtained from the finite element mesh, and a distributed-memory MPI programming model is used. An implicit time integration scheme and a segregated iterative algorithm are used to solve the momentum, energy, turbulence variables and front tracking equations. The equations are dis-cretized using a stabilized SUPG finite element method on linear elements. The resulting sparse system of linear equations is solved using parallel preconditioned iterative methods.
Moisture Induced Failures of Plastic Packages of IC Devices: State-of-the-Art and Crucial Needs
Authors: Feng Y. , Raju V. R. , Suhir E. 
Published: March 2022

Abstract
This review addresses the current status of understanding of the mechanical behavior of plastic microelectronics packages and the ability to predict and prevent moisture induced failures in them. While significant progress has been made during the last decade to improve the reliability of plastic packages, moisture related failures are still a major concern to both the manufacturing and user communities. The current procedures used in the industry to alleviate this problem are identified and discussed. These include controlling moisture content in the packages, improving geometrical designs, developing new molding compounds with higher strength and/or lower thermal stresses and treating material surfaces for better interfacial adhesion, etc. Understanding derived from theoretical modeling based on structural and fracture mechanics is also discussed. Some unsolved problems crucial in helping to find an ultimate solution to eliminate moisture induced failures in plastic packages are also addressed.
A Mechanical Reliability Evaluation of Several Electrically Conductive Epoxies: Part III — Fracture Properties
Authors: Rafanelli Anthony J. 
Published: March 2022

Abstract
Electrically conductive epoxies have become attractive alternatives to traditional tin-lead solder as bonding media for electronic interconnections. However, these materials, being of a different nature than solder, have not undergone as extensive material and mechanical characterization as the latter. Subsequently, a comprehensive, multi-phase evaluation is warranted prior to approving a direct substitution. Such an evaluation would include several key mechanical studies such as basic material properties, fatigue, creep, and fracture. This paper reports on results of fracture property studies, namely determination of the J-Integral on samples of conductive adhesive epoxies. In addition, testing was also performed on eutectic or near eutectic solder, to provide a benchmark for comparison.
A Study on Reliability of Pb40/Sn60 Solder Joints Under Dynamic Loading
Authors: Basaran Cemal , Chandaroy Rumpa 
Published: March 2022

Abstract
Solder interconnects are commonly used in surface mount technology microelectronics packaging. It is well known that the dominant failure mode for solder joints is thermal fatigue. When semiconductor devices are used in vibrating environment such as in automotive and military applications, dynamic stresses contribute to the failure mechanism of the solder joint and in certain circumstances they can become the dominant failure cause. In this paper a unified constitutive model for Pb40/Sn60 solder joints is developed and then implemented in a finite element dynamic analysis procedure. The purpose of the material model and the implementation is to study the contribution of vibration induced strains to the fatigue life of solder interconnects in low-cycle and high cycle fatigue. The proposed material model, which is based on the Disturbed State Concept (DSC), is used for dynamic analysis of a solder joint.
In Situ Sensing System for Rapidly Spreading Microdroplets During Droplet-Based Manufacturing
Authors: Kim Ho-Young , Qiu Taiqing , Chun Jung-Hoon 
Published: March 2022

Abstract
Deposition of microdroplets is fundamental to many emerging technologies. The strongly coupled droplet spreading and cooling processes have profound impact on the quality of droplet-formed structures. This work developed a microsensor for characterizing rapidly spreading microdroplets on a substrate after the impact. The sensor consists of fine conducting lines made of Au and Ti two-layered structure with both width and spacing 2 μm. Transient droplet contact diameters were measured with the sensors of 8 μm spatial and 1 μs temporal resolutions. Two different regimes of spreading were discovered: an extremely fast initial spreading process followed by slow spreading. The results are important for achieving a better understanding of rapid solidification and formation of novel microstructures in droplet-based manufacturing processes.
Numerical Modeling for Rotational Molding of Thermoplastics
Authors: Olson Lorraine G. , Gogos George , Pasham Venkataramana , Liu Xuejun 
Published: March 2022

Abstract
A thermal model for rotational molding is presented which includes heat transfer from the oven to the mold, through both the mold and gradually depositing plastic layer, and to the unmelted but well-mixed powder. The problem is addressed numerically for the first time using Arbitrary Lagrangian Eulerian finite element methods. One dimensional results (spherically symmetric) show excellent agreement when compared with more limited numerical models, and when compared with experimental results from the literature and with the trends observed in practice. Extending these finite element techniques to axisymmetric cases may make accurate wall-thickness predictions possible.
Study on Propagative Collapse of a Vapor Film of Film Boiling: Effects of Liquid Subcoolings on Characteristics of Propagative Collapse
Authors: Sakamoto Yasuyoshi , Ohtake Hiroyasu , Koizumi Yasuo 
Published: March 2022

Abstract
Using a platinum wire of 1 mm in diameter and 160 mm in length, pool film-boiling experiments were performed for saturated and subcooled water at atmospheric pressure and the propagative collapse of the vapor film was examined. The temperature of a local-cooled spot which was suspected to have a large effect on the collapse of the water film was varied systematically in the experiments.
The experimental results showed that the propagation velocity of the vapor film collapse decreased and the surface temperature at the collapse increased with decreasing the cold-spot temperature. In particular, when the cold-spot temperature was below the thermodynamic limit of superheat of water, the surface temperature at the collapse increased remarkably. The propagation velocities of the collapse of the vapor film were similar to the rewetting velocities by a falling-film.
Effect of Fluid Properties on Electrohydrodynamically Enhanced Heat Transfer in Pool Boiling
Authors: Hardesty John T. , Raghupathi Priya , Seyed-Yagoobi Jamal , Bryan James E. , Wawzyniak Markus 
Published: March 2022

Abstract
The effect of fluid properties on electrohydrodynamically enhanced heat transfer in pool boiling was studied using R-123, R-134a, and R-407c as the working fluids at various pool temperatures. Two experimental boiling apparatuses were used, one electrically heated and suitable for high pressure refrigerants, and the other water heated, suitable only for low pressure refrigerants. In both cases, the pool boiling consisted of a single horizontal copper tube with the same surface finish, heated length, and outer diameter. The electrode design consisted of eight straight wires spaced radially at equal angles around the tube. The electrical properties of working fluids as a function of temperature were measured using a unique test cell.
Results show that of the three refrigerants, R-123 and R-134a both demonstrate significant EHD enhancement at 4 °C and 20 °C pool temperatures. Enhancements at 4 °C are larger than those at 20 °C for both refrigerants. Measured electric charge relaxation time and estimated bubble departure time indicate that negligible enhancement should be realized with R-407c at 4 °C pool temperature, while some enhancement should be achieved at 20 °C and 35 °C pool temperatures. Experimental results confirm this and clarify the relationship between bubble departure time and electric charge relaxation time.
Electrohydrodynamic (EHD) Enhancement of Boiling Heat Transfer With a Lo-Fin Tube
Authors: Han Sang-Houn , Na Min-Kyun , Oh Si-Doek , Kwak Ho-Young 
Published: March 2022

Abstract
The effect of D.C electric field on nucleate boiling heat transfer for refrigerants of R-11, HCFC-123 and FC-72 was investigated experimentally by using a single lo-fin tube shell/tube heat exchanger. The lo-fin tube which brings two times increase in the heat transfer area provided about 150% of boiling heat transfer enhancement compared to that of smooth surface. Experimental study has revealed that the electrical charge relaxation time is an important parameter for the boiling heat transfer enhancement under electric field. Boiling heat transfer enhancement was obtained up to 40% for R-11 which has moderate relaxation time of 1.3 s. However remarked boiling heat transfer enhancement has been obtained up to three fold increase (300%) for HCFC-123 which has the electrical charge relaxation time of 0.89 × 10−3 s. For FC-72 having longer relaxation time than the bubble detachment one, no appreciable effect on the nucleate boiling heat transfer was observed.
Wavelet and Fractal Analyses of Fluidized Bed Heat Transfer
Authors: Ross Kristen A. , Pence Deborah V. 
Published: March 2022

Abstract
The present study examines hydrodynamics and heat transfer in a gas-fluidized bed using wavelet and fractal analyses. Wavelet analysis provided the opportunity to investigate time-varying heat transfer simultaneously from both a time and frequency (scale) perspective. As a result, intermittent periods of local bubble formation were discovered to occur at the stagnation point on the cylinder for fluidization ratios 50 percent greater than those required for minimum fluidization. In addition to physical insight, the time-frequency plots (scalograms) revealed what is believed to be fractal characteristics of these time-varying data. The fractal nature of these signals was confirmed using Hurst’s rescaled range analysis, which was employed to estimate the fractal dimension of each time series. For the present investigation, time-varying local heat transfer from a heated horizontal cylinder to a cold bubbling bed of 345 μm particles was measured as a function of angular position and flow rate.
Numerical Solution of the Effect of Vibration on Melting of Unfixed Rectangular Phase-Change Material Under Low-Gravity Environment
Authors: Shirvanian A. , Faghri M. , Zhang Z. , Asako Y. 
Published: March 2022

Abstract
This paper presents a numerical method for simulating the melting process in a cavity in the presence of wall vibration. An enthalpy method is employed to solve the governing equations associated with melting of an unfixed solid Phase Change Material (PCM) in a low gravitational environment. In this method, the problem is solved in one domain. The PCM, initially at its melting temperature, is placed inside a rectangular enclosure. The enclosure walls are then exposed to a uniform temperature under a specified amplitude and frequency of vibration. Melting begins from all sides, and due to natural convection, the PCM would not retain its initial shape. The governing equations are discretized by using a control-volume based finite difference method and are solved in together with solid PCM’s equation of motion. The results are presented in the form of a parametric study of the effects of aspect ratio, Stefan number, Strouhal number and dimensionless frequency or period of vibration, on the melt thickness, the solid PCM velocity and the volume of solid PCM. The melt thickness and solid PCM velocity are found to vibrate at the same frequency as of the exciting vibration. The melting rate increases with increase in Strouhal number while decreases with increase in dimensionless frequency of vibration. As seen from the results, for very high frequencies of vibration the melt thickness and molten volume fraction essentially approach those for without vibration. The results show that for the range of parameters investigated, vibration can enhance the melting rate up to 15%.
Guidelines for Preliminary Thermal Design of Convectively Cooled Printed Circuit Boards
Authors: Park Hyunjae , Nigro Nicholas , Elkouh Abdel , Gollhardt Neil , Lee Ping 
Published: March 2022

Abstract
This paper discusses the development and use of an approximate analysis model for predicting the temperature distribution on a Printed Circuit Board (PCB) containing imbedded heat dissipating electronic components which are being cooled by laminar air flow induced by a fan. The direction of the air flow is parallel to the PCB. Temperature results obtained from the model are presented in dimensionless curves as a function of the PCB design parameters including the board dimensions, air velocity (or flowrate), and number, position and heat dissipation of the components. These curves enable the engineer to quickly select the optimal values of the design parameters which meet the design specification imposed on the maximum allowable board wall temperature. Information gained from these curves is employed to establish a set of guidelines (steps) for the preliminary thermal design and layout of the PCB and components.
Inflow and Outflow Effects on Natural Convection in Partially Heated Vertical Parallel Plate Channels
Authors: Campo Antonio , Manca Oronzio , Morrone Biagio 
Published: March 2022

Abstract
In a vertical uniform wall heat flux channel in natural convective flow, the adiabatic. extensions can ameliorate or worsen the chimney effect and the corresponding heat transfer characteristics. The investigation set up in this paper is devoted to the detailed analysis of the aforementioned problem, by numerically solving the elliptic equations in an enlarged I-shaped computaional domain. The results presented herein have the aim to ascertain the discrepancies between the two investigated configurations, i.e. heated inlet and unheated inlet. The results are reported in terms of maximum wall temperatures and nondimensional induced flow rates. Further, some thermal and flow fields are shown. The channel Rayleigh number ranged between 102 and 105 and the adiabatic extension between 0.0 and 19.0. The I-shaped domain allowed to evaluate the discrepancies in terms of stream function and thermal fields, particularly at the exit section. Moreover, it is shown the less the channel Rayleigh number the greater the influence of the adiabatic extensions. This influence is relevant up to four times the adiabatic extension respect to the heated section.
Diagnosis of Gas Species Concentrations and Temperatures in Laminar Flames
Authors: Zhu Yingjie , Sivathanu Yudaya R. , Gore Jay P. 
Published: March 2022

Abstract
The structure of premixed laminar methane/air flames at atmospheric pressure was studied in this paper. In the post-flame region of these flat flames, the emission specctroscopy was used to obtain the temperature and gas species concentrations information which are very important in the study of combustion. Based on the thermal emission by gas molecules in lean flames, the emission data obtained by using the multiwavelength infrared detection method were operated in an iterative algorithm to get the gas species moles fractions and temperatures. At the same positions in the flames, temperature measurements were also obtained from thermocouple and H2O and CO2 concentrations were obtained from gas chromatography. The emission spectroscopy provided accurate temperature and mole fractions data compared to the theoretical value with the consideration of reasonable heat loss.
Simultaneous Measurement of Velocity, Size and Temperature of Burning Coal Particles in Swirl-Stabilised Vitiated Air Flames
Authors: Prassas Ilias , Taylor Alex M. K. P. , Whitelaw J. H. 
Published: March 2022

Abstract
The velocity, size and volume flux of individual burning and non-burning particles were measured simultaneously in the near-burner region of a natural-gas supported 8 kW swirl burner for swirl number 0.68, using in the secondary stream unheated air as well as preheated vitiated air as oxidant, with oxygen mole fraction of 0.165 and 0.177, at 400 and 350 °C preheat temperatures respectively. An optical instrument based on a combined shadow Doppler velocimeter instrument (for sizing particles of arbitrary shape) and spatially-precise two-colour pyrometry was developed for the measurements. The results at axial distance z/D = 2.6 which lay within the recirculation zone showed that the fraction of burning particles (defined as the ratio of detected burning particles and the total measured) decreased with increasing radial distance in all flow conditions. The maximum fraction of burning particles decreased as a function of decreasing oxygen mole fraction from about 94% at a 0.21 mole fraction to 28% and 12% at oxygen mole fractions of 0.177 and 0.165 respectively and, as a consequence, the volume flux of burning particles was an order-of-magnitude smaller than the volume flux of the ensemble.
Fuel Preheat Effects on Soot Formation in Soot-Emitting Laminar Microgravity Jet Diffusion Flames
Authors: Konsur Bogdan , Megaridis Constantine M. , Griffin DeVon W. 
Published: March 2022

Abstract
An experimental investigation conducted at the 2.2s drop tower of the NASA Lewis Research Center is presented to quantify the influence of moderate fuel preheat on soot formation within 0-g laminar gas jet diffusion flames. The experimental methodology implements jet diffusion flames of nitrogen-diluted acetylene fuel burning in quiescent air at atmospheric pressure. Fuel preheat in the 0-g laminar jet diffusion flames is found to reduce soot loadings on the annular region but causes an increase in soot volume fractions on the centerline. In addition, fuel preheat reduces the spatial extent of the soot field in 0-g. The results also show that the soot growth stage is shortened when elevated fuel temperatures are used. Finally, an attempt is made to provide an explanation for the pronounced annular character of the soot field in 0-g.
Ignition Analysis of SHS Processes Subjected to a Constant Heat Flux
Authors: Escobar-Vargas Sergio , Hernandez-Guerrero Abel , Baltazar-Cervantes Juan C. 
Published: March 2022

Abstract
The research presented here deals with the minimum ignition times for a Ti+C (graphite) powder mixture. A family of curves from the simulation of the ignition process involves the application of radiant heat to a cylindrical sample. Some non-dimensional parameters of the process are varied such as the Damköhler number (Da), as well as Zeldovich (A) and Stefan (H) numbers. The initial composition of the mixture was varied from the non-stoichiometric to the stoichiometric case. The minimum ignition time was used to develop an ignitability curve which directly relates the applied radiant heat flux with the Da number. These curves define the ignition/non-ignition zone for the reactants considered.
Influence of Fuel-Air Ratio on Horizontal Flame Spread Rates
Authors: Litton Charles D. , Hwang Charles C. 
Published: March 2022

Abstract
Flame spread along horizontal surfaces in the presence of a forced convective airflow depends primarily upon the transfer of radiant energy to downstream surfaces from a flame front that is tilted in the direction of flow. The soot in the flame serves as the primary source of radiation but the soot that emerges from the flame and mixes with the forced airflow also serves to attenuate the radiation thereby decreasing the radiant flux at the downstream surfaces. There is, then, a complex interaction between the quantity of soot produced and the radiative heat transferred to the downstream surfaces. It has also been shown that when flames transition from over-ventilated to under-ventilated conditions, the soot yield increases while both the total combustion efficiency and the convective fraction of the combustion efficiency begin to decrease. This transition occurs when the flame is unable to entrain sufficient air to burn either at the stoichiometric fuel-air ratio or on the over-ventilated side of stoichiometric. When the total and convective combustion efficiencies do not decrease at the same rate, the radiative fraction tends to increase at equivalence ratios in the range of 1 to 1.3. This results in an increase in radiative heat transfer to the downstream surfaces that causes the flame spread rate to accelerate. A flame spread model was developed to quantify these processes. Predictions from the model are in excellent agreement with experimental data for flame spread along surfaces of styrene-butadiene rubber conveyor belts in a largescale fire gallery where the transition to under-ventilated combustion occurs when the flames begin to impact the roof of the gallery.