bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heat Transfer Characteristics of Single Droplet Cooling Using a Microscale Heater Array
Authors: Lee Jungho , Kim Jungho , Kiger Kenneth T. , Horacek Bohumil 
Published: November 2021

Abstract
Heat transfer by phase change is an attractive method of cooling since large amounts of heat can be removed with relatively small temperature differences. Droplet cooling is one method whereby very high heat transfer rates coupled with good temperature uniformity across surfaces can be provided, which is important in microelectronics where even small temperature gradients across the chip can cause component failure. In this study, time and space resolved heat transfer characteristics for a single droplet striking a heated surface were experimentally investigated. The local wall heat flux and temperature measurements were provided by a novel experimental technique in which 96 individually controlled heaters were used to map the heat transfer coefficient contour on the surface. Significant time and space resolved variations in wall heat fluxes were exhibited during boiling and evaporation. The droplet behavior with wall interaction was simultaneously viewed using a high-speed digital video camera. Local heat transfer measurements can provide much needed information regarding the relevant wall heat transfer mechanisms by pinpointing when and where large amounts of heat are removed. This study should result in benchmark data against which numerical calculations can be compared.
Simulation of Thermal Plasma Spraying of Partially Molten Ceramics: Effect of Carrier Gas on Particle Deposition and Phase Change Phenomena
Authors: Ahmed I. , Bergman T. L. 
Published: November 2021

Abstract
A 3D simulation of the thermal plasma spraying process is reported. In particular, the effect of the radial injection of a carrier gas is taken into account for a dilute spray. The thermal history of powder particles of different sizes is predicted. It is shown that introduction of a carrier gas can lead to a significant modification of the plasma jet, and can have an effect on the thermal histories of the injected particles. The study is motivated by the processing of non-traditional materials, specifically nanostructured ceramics.
A Heat Flux Correlation for Spray Cooling in the Nucleate Boiling Regime
Authors: Cabrera E. , Gonzalez J. E. 
Published: November 2021

Abstract
In this work an experimental study of spray cooling using monodispersed droplet sprays impinging on a flat and heated surface is reported. The aim of the work was to formulate an empirical model describing the heat flux (HF) for the nucleate boiling regime. Monodispersed water droplets with a known diameter and velocity, produced by a droplet generator, were directed toward a heated surface and the heat transfer was registered using a data acquisition system. The resulting high heat flux was investigated as function of the droplets’ diameter and velocity, mass flow rate, ambient pressure, subcooling degree and surface roughness. The resulting matrix of variables investigated in the experiments included; mass flux rate (340 &lt; ṁ″ &lt; 750 kg/m2s), subcooling degree (25 &lt; Tsub &lt; 78 °C), ambient pressure (1 &lt; P &lt; 1.8 bar), and surface roughness (79 &lt; Rt &lt; 5 μm). A generalized correlation was developed for the dimensionless HF as function of the dimensionless mass flow rate, temperature, surface roughness and pressure, along with the Jacob number. The form of the correlation is q ˙ ″ ρ V h f g = 0.245 ( Ja ) 1.038 ( Δ T sub Δ T sat ) 0.491 ( ρ σ m ˙ μ 3 ) 0.133 ( R t D ) 0.0213 ( P P 0 ) 0.291 having a confidence level greater than 95%, the differences between predicted and experimental HF were less than ±19%.
A Fully Eulerian Approach to Particle-Laden Compressible Flows
Authors: Dolatabadi Ali , Mostaghimi Javad , Ivanovic Mihajlo 
Published: November 2021

Abstract
Dense particles in highly compressible gas flows are analyzed using the Eulerian-Eulerian approach. Simulations are applied to a High Velocity Oxy-Fuel (HVOF) thermal spray torch. In this analysis, by using a fully Eulerian approach, the dispersed flow like the continuous flow is considered in the Eulerian frame whereby most of the physical aspects of the gas-particle flow in the HVOF process can be incorporated. These two phases are coupled through momentum and energy exchanges that are expressed in the form of source terms appearing in the governing equations. The numerical simulations show large variations in gas velocity and temperature both inside and outside the torch due to flow features such as mixing layers, shock waves, and expansion waves. The characteristics of the particles such as velocity and temperature are analyzed.
From Sub-Channel Analysis to Two-Phase Flow CFD: Improving Thermal-Hydraulics Analysis of Nuclear Reactor Cores
Authors: Clerc Sebastien , Agee Lance , Harrison Jim 
Published: November 2021

Abstract
For safety analyses of nuclear reactor cores, a correct prediction of the thermal-hydraulic characteristics is crucial. These predictions are all the more difficult as the flows generally involve liquid and vapor phases simultaneously. Moreover, the geometry of nuclear cores is often quite complex. The typical situation is that of a rod bundle, the characteristic length of the gap between two rods being much smaller than the size of the bundle.
The traditional approach to the simulation of such flows is called the sub-channel analysis. The flow is assumed to have a privileged direction, and the cross-flow inertia effects are neglected. Moreover, a lumped-geometry approach is generally adopted, whereby a single discretization cell is used to represent the volume between several rods. This leads to efficient solution methods but forbids a precise description of local or global three-dimensional effects.
As the computational power of modem computers steadily increases, a finer description of the flows in nuclear reactor cores becomes possible. Indeed, there is a current trend in the nuclear industry toward a CFD-like description of these flows as shown by Paillère, et al., (1998) and Rautaheimo, et al., (1999). However, the numerical method used for the simulation must satisfy some specific requirements:
• The use of unstructured meshes must be possible to allow an easy description of the geometry between the rods.
• The numerical method must be suitable for variable density (thermally expandable) flows.
Cavendish, Hall, and Porsching (1994) present a covolume method designed to meet these requirements. This method relies on the construction of a dual or Voronoi mesh. The pressure and the thermodynamic variables are computed at the vertices of the primal mesh. Additionally, the velocities are computed in the normal direction to each face of the primal mesh, or, equivalently, along each edge of the dual mesh. The continuity equation is integrated by parts on the dual polytopes, while the momentum equations are discretized by finite differences on the primal mesh.
This Cavendish, Hall, and Porsching covolume numerical method has been used to solve typical problems of nuclear reactor thermal-hydraulics analysis. The physical models are those of the CORETRAN code (1999). The first numerical results demonstrate the efficiency of the method and validate the new approach.
ATR Flow Blockage Tests and CFD Simulations
Authors: Oh Chang H. , Atkinson Steve A. 
Published: November 2021

Abstract
Steady state flow channel blockage tests were conducted at the Idaho National Engineering and Environmental Laboratory (INEEL) as part of the safety basis upgrade program for the Advanced Test Reactor (ATR). The tests were sponsored by the U.S. Department of Energy (DOE). This study was aimed at carrying out flow blockage tests, establishing a base case to compare test results with numerical results using a computational fluid dynamics code, calculating temperature profiles for blockage cases, and determining whether or not the ATR core would be exposed to core melting due to blockage of the inlet of a fuel cooling channel.
The test section consisted of three parallel channels and two side channels along the side plate. Three cases were selected to evaluate flow blockage events in the channels. A base case with all the channels open, Case 1 where the inlet of the middle channel is blocked, and Case 2 where both the middle channel and the side channel are blocked.
Laser Doppler anemometer (LDA) was used to measure velocities in the channel. Velocities were measured at 2.54-mm intervals in the channel width, and every 1.27-mm around side windows in the flow direction for three parallel channels.
LDA measured velocity profiles for the base case and Case 1 indicated good agreement with predicted velocity profiles from the CFD model. The channel velocity in the blocked channel is about 70% of the velocity in the unblocked, adjacent channel in between the top and second side channel vents. Additional flow redistribution occurs into the blocked channel at the second side channel vent.
Temperature calculations for the base case were made to compare with benchmark temperatures calculated with the ATR SINDA model and CFD calculations underpredicted benchmark plate temperatures by less than 10% while it predicted bulk temperatures very well. The same heat flux and boundary conditions were incorporated for Case 1 and Case 2. The results for both cases indicated that core melt would not occur in the postulated ATR flow channel blockage events simulated for this study. Peak fuel plate temperature is about 20% greater than the peak temperature for the unblocked case just upstream of the second side channel vent.
Numerical Study of Transient Conjugate Heat Transfer in a Long Two-Phase Pipeline
Authors: Fairuzov Yuri V. , Arvizu Dal Piaz Hector 
Published: November 2021

Abstract
A growing number of multiphase technology applications stimulate the development of reliable methods for modeling transient processes in two-phase systems in which the temperature field in the moving fluid and the temperature field in the bounding walls are directly dependent on each other. This situation presents a conjugate heat-transfer problem since the heat-transfer rate at the wall-fluid interface and local fluid conditions are not known a priori, and therefore need to be simultaneously calculated. Examples of such processes include the direct heating of multiphase pipelines, a change of heat load in evaporators of two-phase thermal control systems, startup or shutdown of systems with a two-phase working fluid. In this paper, direct electrical heating of a long two-phase pipeline has been modeled. The modeling of transient two-phase flow and heat transfer in the pipeline is based on two different mathematical formulations. In the first formulation, the transient heat conduction and the forced convection effects are rigorously taken into account. The second formulation assumes that the pipe wall and the fluid are in local thermal equilibrium. The effect of the thermal capacity of the pipe wall is taken into account by an additional term in the energy equation for the fluid flow. Such an approach allows significant simplifying the problem and reducing the computer running time. Numerical simulation of the sudden heat input to the pipe wall has been performed using both formulations of field equations. The practical significance of the results obtained is discussed.
Steady-State Operation of a Loop Heat Pipe With Analytical Prediction
Authors: Watson Heather , Gerhart Charlotte , Mulholland George , Gluck Donald 
Published: November 2021

Abstract
The steady-state performance of an 800W, sintered nickel powder wick, loop heat pipe (LHP) has been analyzed using a modified Dynatherm LHP Thermal Model. Results from characterization tests of this LHP performed at the Air Force Research Laboratory in Albuquerque, NM are used as the basis for comparison and discussion of results for the analytical model. The analytical predictions gave excellent correlation to the measured data for power levels ranging from 50 to 1500W at condenser chiller settings between −40°C and 20°C, with the LHP in a horizontal orientation.
Passive Cooling of Permafrost Foundation Soils Using Porous Embankment Structures
Authors: Goering Douglas J. 
Published: November 2021

Abstract
Permafrost (permanently frozen ground) underlies approximately 25% of the world’s land surface. Construction of surface facilities in these regions presents unique engineering challenges due to the alteration of the thermal regime at the ground surface. Even moderate disturbance of the pre-existing ground surface energy balance can induce permafrost thawing with consequent settlement and damage to buildings, roadways, or other man-made infrastructure.
The present work examines the thermal characteristics of embankments constructed of unconventional, highly porous materials. Using these materials, a passive cooling effect can be achieved due to the unstable density stratification and resulting natural convection that occur during winter months. The convection enhances transport of heat out of the embankment, thus cooling the lower portions of the embankment and underlying foundation soil and preserving the permafrost layer. Numerical results obtained with an unsteady two-dimensional finite element model are compared to experimental measurements taken in full-scale field installations for the cases of open and closed (impermeable) side-slope boundary conditions.
Multi-Mode Heat Transfer in a Randomly Packed Bed of Cylindrical Rods Using a Finite Volume Scheme
Authors: Murthy J. Y. , Mathur S. R. 
Published: November 2021

Abstract
In this paper, calculations of mixed-mode heat transfer in beds of randomly-packed cylinders are presented. An unstructured finite volume method is employed. Random packing is addressed by meshing a periodic module, and creating the bed by stacking and random lateral translation of modules. The ability of the finite volume scheme to employ arbitrary polyhedra is exploited in addressing the resulting non-conformal interfaces. Conduction and radiation are considered, but convection is ignored. Results are presented for conducting and semi-transparent cylinders for a range of fluid and solid conductivities and solid refractive indices and establish the viability and versatility of the method.
A Hybrid Finite Volume/PDF Monte Carlo Method to Capture Sharp Gradients in Unstructured Grids
Authors: Li Genong , Modest Michael F. 
Published: November 2021

Abstract
The hybrid finite volume/PDF Monte Carlo method has both the advantages of the finite volume method’s efficiency in solving flow fields and the PDF method’s exactness in dealing with chemical reactions. It is, therefore, increasingly used in turbulent reactive flow calculations. In order to resolve the sharp gradients of flow velocities and/or scalars, fine grids or unstructured solution -adaptive grids have to be used in the finite volume code. As a result, the calculation domain is covered by a grid system with very large variations in cell size. Such grids present a challenge for a combined PDF/Monte Carlo code. To date, PDF calculations have generally been carried out with large cells, which assure that each cell has a statistically meaningful number of particles. Smaller cells would lead to smaller numbers of particles and correspondingly larger statistical errors. In this paper, a particle tracing scheme with adaptive time step and particle splitting and combination is developed, which allows the PDF/Monte Carlo code to use any grid that is constructed in the finite volume code. This relaxation of restrictions on the grid makes it possible to couple PDF/Monte Carlo methods to all popular commercial CFD codes and, consequently, extend existing CFD codes’ capability to simulate turbulent reactive flow in a more accurate way. To illustrate the solution procedure, a PDF/ Monte Carlo code is combined with FLUENT to solve a turbulent diffusion combustion problem in an axisymmetric channel.
Feature Variation and Its Impact on Structural Acoustic Response Predictions
Authors: Cunefare Kenneth A. 
Published: November 2021

Abstract
This paper presents a screening technique to assess the impact on model fidelity introduced by variations in the properties or positions of features in harmonically forced fluid-loaded structural acoustic models. While fluid-loading is included, it is not a requirement or restriction to the methods presented. The perspective taken is one of knowledge of a reference state, with a desire to determine the impact on the total radiated acoustic power due to perturbations in the reference state. Such perturbations change the predicted resonance frequencies of a structure under consideration, and hence, change the predicted response amplitudes. The method uses a single degree of freedom response model in the local region of each fluid-loaded resonance, coupled with eigenvalue sensitivities or variations, to estimate the perturbation impact. The SDOF model argues for the use of proportional bandwidth analyses. Elements of the analysis method are not necessarily restricted to model perturbations nor acoustic power, rather they may be used to assess the perturbation of any quadratic response quantity of interest due to changes in resonance frequency. The SDOF analysis method is limited by its assumption of constant modal forcing between the reference and perturbed states.
An Investigation of Power Flow in the Mid-Frequency Range for Systems of Co-Linear Beams Based on a Hybrid Finite Element Formulation
Authors: Zhao Xi , Vlahopoulos Nickolas 
Published: November 2021

Abstract
A hybrid finite element analysis (hybrid FEA) is employed for investigating power flow characteristics for systems of co-linear beams in the mid-frequency range. The importance of capturing power re-injection and power re-radiation effects in the solution is demonstrated. The dependency of the power flow characteristics of a system in the mid-frequency range on the rigidity, mass, and damping properties of its components is determined. Both the hybrid FEA and analytical solutions are employed for analyses in order to establish the viability of the hybrid FEA as a simulation technology in the mid-frequency range.
A Hybrid Finite Element Formulation for Mid-Frequency Analysis of Systems With Excitation Applied on Short Members
Authors: Zhao Xi , Vlahopoulos Nickolas 
Published: November 2021

Abstract
A hybrid finite element method for computing mid-frequency vibrations is presented. In the mid-frequency region a system is comprised by some members that contain several wavelengths and some members that contain a small number of wavelengths within their dimensions. The former are considered long members and they are modeled by the Energy Finite Element Analysis (EFEA). The latter are considered short and they are modeled by the Finite Element Analysis (FEA). In this paper the excitation is considered to be applied on the short members. The hybrid formulation computes the response of the entire system. The characteristics of the long members affect the behavior of the short members and the amount of power flow between the members of the system. The resonant characteristics of the short members and the boundary conditions imposed by the long members determine the amount of input power into the system. The interaction between members is described by a set of equations between the FEA and the EFEA primary variables at the interfaces between long and short members. The equations for the short and the long members and the interface equations are solved simultaneously. A theoretical formulation and a numerical implementation for systems that contain one wave type is presented. Analytical solutions for several co-linear beam configurations are compared to numerical results produced by the hybrid finite element method. Good correlation is observed for all analyses.
Laser-Induced Acoustic Waves for Measurement and Imaging
Authors: Li Wen , Roy Ronald A. , Cleveland Robin O. , Berg Lawrence J. , DiMarzio Charles A. 
Published: November 2021

Abstract
A short pulse of laser light can act as a source of acoustic energy for acoustic imaging. Although there are a number of mechanisms by which the light pulse may generate sound, all require a pulse of high peak power density and short duration. In this work, we address examples where the material is highly absorbing at the laser wavelength, and the sound is generated near the surface. In these cases, there exist two different mechanisms which can convert the light to sound. The first is heating followed by expansion, and the second is generation of a plasma in the air above the surface. In the first case, sound generation occurs in the medium of interest and the energy efficiency can be very high, in the sense that no reflection losses occur. We present two applications from our own research.
Vibration and Acoustic Evaluation of a Large Centrifugal Wastewater Pump, Part 2: Modeling and Interpretation
Authors: Abbot Philip , Gedney Charles , Morton David , Celuzza Stephen , Dyer Ira , Ehlers Peter , Vaicaitis Rimas , Brown James , Guinzburg Adiel , Hodgson William 
Published: November 2021

Abstract
In Part 1, an extensive series of vibration and acoustic measurements conducted on a large centrifugal wastewater pump at a municipal pump station was discussed. In Part 2, the vibration data are evaluated with a physics-based model to estimate the individual contributions from the pump and an acoustic resonance. The results of the measurements, combined with the model, suggest that the primary mechanisms for the pump bearing vibration are: the near-field hydrodynamic pressures generated by the pump itself within the volute, and to a lesser extent, the acoustic resonance excited by the pump’s BPF.
Field Demonstration of a Boiler Feedwater Pump Upgraded to Reduce Vibration and Acoustic Emissions Without Compromising Performance
Authors: Marchi John F. , Bush R. Frank 
Published: November 2021

Abstract
The high-energy boiler feedwater pump is the heart of the steam-generation cycle in modern high-pressure boiler systems. These multi-stage centrifugal pumps are engineered to produce system pressures from 12 MPa (1800 lb/in2) to 45 MPa (6500 lb/in2) at temperatures ranging from 150°C (300°F) to 312°C (600°F).
To optimize pump hydraulic performance, pump designers have focused on impeller and diffuser vane angles, hydraulic passageway shapes and minimized impeller-to-diffuser vane clearances to maximize performance within a narrow range of operation. This was the approach that had been applied successfully on lower energy pump design of an earlier era.
However, in the mid-1980s, in response to market forces, operators began to cycle and operate plants over a wide range of loads, which was contrary to the original plant designs. This new operating paradigm has resulted in unacceptable vibration and acoustic emissions that are often attributable to impeller-to-diffuser vane interaction (a result of the minimized clearances referenced previously). Efforts to reduce these emissions by changing the design must always be balanced with the potential impact on hydraulic performance.
This paper uses operating field data taken from boiler feedwater pumps to prove that by:
• optimizing hydraulic passageways and
• changing the internal geometry, specifically, impeller-to-diffuser vane combinations,
vibration and acoustic emissions are reduced without compromising hydraulic performance.
Computational Methods for the Detection of the Source of Acoustical Noise
Authors: DeLillo Thomas , Isakov Victor , Valdivia Nicolas , Wang Lianju 
Published: November 2021

Abstract
Computational methods for the inverse problem of detecting the source of acoustical noise in an interior region from pressure measurements in the nearfield are discussed. The methods are based on a single layer potential representation of solutions to the Helmholtz equation. Regularization is peformed using the singular value decomposition and the conjugate gradient method.