bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Origin of the Dynamic Growth of Vapor Bubbles Associated With Vapor Explosions
Authors: Lee Ho Sung , Merte Herman 
Published: July 2023

Abstract
An explosive type of vapor bubble growth was observed during pool boiling experiments in microgravity using R-113, where heater surface superheats as high as 70 °C were attained at nucleation. This corresponds to approximately 65% of the computed superheat limit of the fluid, compared to the approximate 30% observed at earth gravity for the same system. Photographs and measurements of the vapor bubble growth provide evidence for rates of growth not accountable by conventional models. The photographs reveal that the liquid-vapor interface of the explosive bubbles become wrinkled and corrugated, leading to the conclusion that some type of instability mechanism is acting.
The classical hydrodynamic instability theories of Landau and Rayleigh-Taylor, used in conjunction with a model of the early growth of spherical vapor bubbles developed by the authors, predict that the early growth should be stable. These theories do not consider the effects of heat transfer at the interface, which is believed responsible for the observed instability of the evaporating surface. This was confirmed by the mechanisms proposed by Prosperetti and Plesset which, although including the effects of heat transfer, required that the unperturbed liquid temperature distribution be known at the moment of onset of the instability. This is generally unknown, so that no comparisons with experiments were possible up to this point. The present pool boiling experiments conducted in microgravity, some of which result in the explosive vapor bubble growth referred to, permit the precise determination of the unperturbed liquid temperature distribution using a model of the early vapor bubble growth along with the measurement of heater surface temperature at nucleation. The limited results to date provide good agreement with the mechanisms proposed by Prosperetti and Plesset.
Linear Stability Analysis of Thermocapillary Convection in a Liquid Bridge With Encapsulation by Inverse Iteration Algorithm
Authors: Li Minwei , Sun Zequan , Zeng Danling 
Published: July 2023

Abstract
Linear stability theory was applied in the present paper to analyze the stability of the basic state solution of thermocapillary convection in a liquid bridge with liquid encapsulation. Discretizing the linearized disturbance equations by using finite-difference approximation, stability analysis is evolved to a complex generalized eigenvalue problem with a complicated band structure of matrix. The influence of dimensionless parameters on the stability of the system is revealed through solving the complex generalized eigenvalue problem by inverse iteration. The results provide a theoretical and numerical foundation for crystal growth by float-zone method and for other engineering applications.
Thermal Contact Conductance of Sintered Copper Coatings on Ferro-Alloy
Authors: Marotta E. , Fletcher L. S. , Aikawa T. , Maki K. , Aoki Y. 
Published: July 2023

Abstract
This experimental investigation presents heretofore unpublished thermal contact conductance data of sintered powder copper disks which were hot-pressed onto a sintered powder Ferro-alloy proposed for automotive valve-seat applications. The sintered copper disk acts as an enhancement coating to decrease the surface imperfections and increase the rate of heat transfer across the valve seat/engine block interface. The experimental interface temperature was varied between 100 to 200 °C (212 to 392°F) while the interface pressure was varied between 2.5 to 25 MPa (363 to 3625 psi). These experimental parameters approximate some of the conditions (such as interface pressure) that exist at a valve seat/engine block interface of an internal combustion engine. The thermal contact conductance values for an uncoated Ferro-alloy/cast aluminum alloy interface, and for 0.2, 0.5, 1.0, and 2.0 mm sintered copper coatings were obtained over the range of interface temperatures and pressures.
Thermal Contact Conductance of a Paper/Elastomer Interface
Authors: Mohr J. W. , Seyed-Yagoobi J. , Wirtz J. W. , Price D. C. 
Published: July 2023

Abstract
A better understanding of the parameters associated with the heating of paper during copying and printing processes would permit more accurate design and control of the process. One parameter affecting the heat transfer from an elastomer covered roller to the paper sheet is the thermal contact conductance at the interface between the paper sheet and the roller. The main objective of this work was to measure the thermal contact conductance of an elastomer/paper sheet interface. Two types of elastomers (A and B) were considered.
The thermal contact conductance values for elastomer A varied from 217 W/m2K to 258 W/m2K within the applied pressure range of 34.5 kPa to 344.7 kPa. This pressure range is representative of the pressures encountered in typical printing and copying processes. The corresponding thermal contact conductance values for elastomer B were 803 W/m2K and 2,072 W/m2K. The thermal contact conductance values for elastomer B were significantly higher than those for elastomer B due to a combined effect of the higher thermal conductivity and more uniform surface flatness characteristics of elastomer B compared to elastomer A.
A Transient Experimental Method for the Indirect Measurement of Thermal Contact Conductance
Authors: Hook Randy C. , Clements Randy A. , Crane Roger A. 
Published: July 2023

Abstract
A study has been completed to illustrate the use of an experimental apparatus for the implicit measurement of transient thermal contact conductance between dissimilar metals The two metals selected for a trial evaluation are 304 stainless steel and 6061-T6 aluminum. An inverse heat transfer method is used, which employs the analytic solution for a one dimensional heat flow between dissimilar metals to calculate the contact conductance by sequential function estimation. Relevant programs for the collection and reduction of data have been developed and are available. Sample test results are presented.
Heat Flux Determination at the AWJ Cutting Zone Using IR Thermography and Inverse Heat Conduction Problem
Authors: Mohan Ram S. , Kovacevic Radovan , Beardsley Heather E. 
Published: July 2023

Abstract
In abrasive waterjet (AWJ) cutting, the cutting tool is a thin stream of high velocity abrasive waterjet slurry which can be considered as a moving line heat source that increases the temperature of the narrow zone along the cut kerf wall. A suitably defined inverse heat conduction problem which uses the experimentally determined temperature histories at various points in the workpiece, is adopted to determine the heat flux at the cutting zone. Temperature distribution in the workpiece and the cutting nozzle during AWJ cutting is monitored using infrared thermography. A suitable strategy for on-line monitoring of the radial and axial wear of the AWJ nozzle based on the nozzle temperature distribution is also proposed.
Thermal Stress Limits of Plates Subjected to Extremely High Heat Flux
Authors: Lienhard John H. , Napolitano Dominic S. 
Published: July 2023

Abstract
For heat fluxes in the range of 20 MW/m2 to 400 MW/m2, solid surfaces usually experience large thermal stresses and degradation of mechanical properties. The resulting mechanical failure of such surfaces is a primary limitation to the design of thermal systems at extremely high heat flux. This paper is an investigation of the general mechanical behavior of plates operated at extremal fluxes. Two prototypical configurations are considered. Several candidate materials are examined, accounting for the temperature dependence of thermal and mechanical properties. The elastic performance of plates at high flux is investigated and conditions for yielding are identified for various materials, mechanical restraints, and heat source distributions. Plastic behavior, which is characteristic of higher flux levels, is also examined. New material figures of merit are developed, taking account of the temperature dependence of thermal, elastic, and/or plastic properties.
Combined Heat and Mass Transfer by Natural Convection in a Saturated Thermally Stratified Porous Medium
Authors: Angirasa D. , Peterson G. P. , Pop I. 
Published: July 2023

Abstract
A numerical study is presented for the combined heat and mass transfer by natural convection adjacent to a vertical surface embedded in a stably thermally stratified, fluid-saturated, low porosity medium. A wide range of thermal stratification levels is considered in flows with both aiding and opposing buoyant forces. The thermal stratification was shown to have a profound influence on the heat and mass transfer rates, and the direction of flow and transport. The underlying physical phenomena are explained while providing the Nusselt and Sherwood number data.
An Experimental and Numerical Study of Natural Convection From a Horizontal Cylinder With Longitudinal Baffles
Authors: Facas George N. , Zhang Yan , Brown Harry L. , Ruff Gary A. 
Published: July 2023

Abstract
Laminar natural convection over an isothermal horizontal cylinder with multiple longitudinal baffles has been experimentally and numerically studied. The effect of multiple longitudinal baffles on the heat transfer, in terms of the Nusselt number, has been established over the range 2 × 104 ≤ Ra ≤ 8 × 104. The numerical results are in excellent agreement with the experimental data. For the cases considered in this study, both the experimental and numerical results show that the heat lost from a horizontal cylinder can be reduced by 30% when six baffles are used. The energy savings are about 10% when two baffles are used.
Measurements of Turbulent Natural Convection Flow Over a Vertical Backward-Facing Step
Authors: Abu-Mulaweh H. I. , Armaly B. F. , Chen T. S. 
Published: July 2023

Abstract
Measurements of turbulent natural convection boundary-layer air flow over a two dimensional, vertical backward-facing step are reported. The upstream and downstream walls of the step were heated to a constant and uniform temperature, while the step is kept adiabatic. The experiment was carried out for a step height of 22 mm and a temperature difference ΔT = 30°C between the heated walls and the ambient air. Laser-Doppler velocimeter and cold wire anemometer were used, respectively, to measure simultaneously the mean turbulent velocity and temperature distributions and their turbulent fluctuations. Measurements of the mean velocities and temperature distributions along with the distributions for turbulent intensities, turbulent heat fluxes, and Reynold stress are presented at various axial locations upstream and downstream of the step. These detailed measurements can serve as benchmark data for testing the accuracy of turbulence models in predicting numerically the flow and heat transfer characteristics in this geometry and flow conditions.
Air Cooling of a Vented Enclosure by Combined Conduction, Natural Convection and Radiation
Authors: Yu Enchao , Joshi Yogendra K. 
Published: July 2023

Abstract
A three-dimensional investigation of combined conduction, natural convection and radiation in vented enclosures is carried out. A discrete flush type heat source mounted on a vertical substrate is used to simulate an electronic component. A uniform volumetric generation rate is assumed within the heat source. Combined natural convection in the air, conduction in the heat source, the substrate and the enclosure walls, and surface radiation are solved for Rayleigh numbers at 2.6 × 106 and 2.0 × 107. Radiation is incorporated based on the radiosity/irradiation approach. The resulting flow and temperature patterns are discussed, focusing on radiation and three-dimensional effects. The relative contributions of natural convection and radiation are investigated for different emissivities of internal surface of the substrate. Heat transfer rates from the substrate and other internal walls are presented to illustrate conjugate heat transfer due to combined modes. The numerical solutions are found in reasonably good agreement with the experimental data.
Experimental Studies of Interfacial Area in a Horizontal Slug Flow
Authors: Riznic Jovica R. , Lewis Steven P. , Kojasoy Gunol 
Published: July 2023

Abstract
The internal flow structure of horizontal slug flow has been experimentally investigated by measuring the local interfacial area concentration, void fraction and interfacial velocity distribution. The four-sensor electroresistivity probe was used to detect the instantaneous interface velocities and interfacial area. Experimental studies were performed on the plug/slug flow regimes with an air-water system. Data were acquired at the axial location of L/D = 253 from the mixing chamber. Four different liquid flow rates in combination with five different gas injection rates were studied. The superficial liquid velocity was varied between 0.55 and 2.20 m/s and gas velocity between 0.27 and 2.20 m/s. With these experimental conditions, the total void fraction, including contributions from small and large slug bubbles, ranged from 10 to 70%. The void fraction measurements were checked against the raw signal data, high speed video recordings, and measurements obtained by the hot film anemometer probe. The agreement between the data was very good, confirming that the four-sensor probe measurements can be performed with a high degree of confidence. In the region of transition between plug and slug flow regime, with an increase in the gas flow rate, the number and contribution of the small follow-up bubbles increased. The increase in the liquid flow rate produced similar effects. The slug bubble frequency also increased with an increase in the gas velocity and also slugs are longer at higher gas flow rates.
Total interfacial area concentration profile includes the contribution from both slugs and small follow-up bubbles. Experimental data showed higher interfacial area concentration in the lower part of a slug bubble, with a larger curvature of interface. This is expected, since along the steeper curvature a ratio of local surface area to volume is increasing. Radial profiles of interfacial area concentration for slug bubbles show almost a flat profile in the upper part of slug bubble. The larger values of the total interfacial area concentration indicates that the contribution from the small bubbles is increasing. Experiments showed that in the plug/slug flow regime, contribution from the increasing number of small bubbles to the interfacial area concentration is substantial in upper part of the horizontal channel.
Water-Droplet Cooling Process in a Steam-Turbine Bypass Flow
Authors: Amano R. S. , Draxler G. R. , Golembiewski J. M. 
Published: July 2023

Abstract
This paper presents a study of the numerical simulations of a steam flow and heat transfer behavior when subjected to a cooling water spray in the pipe downstream from a high-pressure turbine bypass valve. The structure of a cooling water spray injected into a steam flow was studied for the purpose of developing a physical model to investigate the dissipation and evaporation processes of the cooling water droplets in a high temperature, high turbulent steam flow passage. Heat transfer rates were calculated for a better understanding of the temperature variations in the entire system. A dispersed two-phase model was incorporated for the particle tracking of the droplets injected into the steam flow and the water evaporation process was observed. Further, this study was continued by installing a perforated plate in the pipe section downstream from the water cooling injections. The results of the calculations are quite reasonable, and show a physically sound state.
Local, Instantaneous Heat Transfer in Pulse-Stabilized Fluidization
Authors: Pence Deborah V. , Beasley Donald E. 
Published: July 2023

Abstract
The Pulsed Atmospheric Fluidized Bed Combustor (PAFBC), a hybrid combustor concept that couples a pulsed combustor with an atmospheric bubbling fluidized bed, has technical advantages in energy efficiency and emissions. The present study examines the effect of an opposing oscillatory flow on the local, instantaneous heat transfer in a laboratory scale bubbling gas-fluidized bed. This opposing secondary flow consisted of a steady mean component and an oscillating component thereby modeling the flow in the tailpipe of a pulsed combustor.
Spectral and contact time analyses of local, instantaneous heat flux measurements from a heated, submerged horizontal cylinder clearly indicate that the bed hydrodynamics were significantly altered by the opposing secondary flow. These heat flux measurements were accomplished by employing an isothermal platinum film heat flux gage. For the present investigation, data were acquired for a monodisperse distribution of particles with a mean diameter of 345 μm and total fluidization ratios ranging from 1.1 through 2.7.
Heat transfer observed under conditions of secondary flows with a superimposed waveform exhibit characteristics of globally dominated, as opposed to locally dominated, hydrodynamics. For low primary and secondary flow rates and a forcing frequency of 5 Hz, a substantial enhancement in heat transfer was observed. Increases in the bubble phase and emulsion phase heat transfer coefficients were identified as the primary contributors to the observed increases in time-averaged local heat transfer coefficients.
Combined Concentration and Temperature-Induced Marangoni Convection in a Binary Mixture
Authors: Suzuki Yuji , Noguchi Suguru , Longtin Jon P. , Hijikata Kunio 
Published: July 2023

Abstract
In binary and multi-component mixtures, surface-tension-driven flow, i.e., Marangoni convection, can arise from both concentration and temperature gradients at the liquid surface. Depending on the liquids, concentration effects can complement or oppose temperature effects, which is important for many areas of engineering interest, e.g., mixing, solidification, evaporation, and drying. This work experimentally investigates combined temperature and concentration-induced Marangoni convection for an ethanol-water binary mixture in an enclosed cell with heated and cooled walls. Velocity profiles are obtained using a photochromic dye technique, and concentration variation at the liquid surface is measured using an interferometric technique. The results indicate that concentration effects dominate at 50/50 and 80/20 ethanol-water volume percent mixtures, resulting in a large surface velocity in the opposite direction to the bulk flow. Concentration effects can be arrested by exposing the free liquid surface to non-condensable gas at atmospheric pressure.
Critical Heat Flux During Subcooled Flow Boiling in Narrow Rectangular Channels
Authors: Nakajima Ryo , Ramanujapu Naresh K. , Dhir Vijay K. 
Published: July 2023

Abstract
The critical heat flux during subcooled flow boiling in narrow one-side heated rectangular channels was investigated experimentally using fluorinert liquid PF-5060 as a coolant. Three channel widths were examined, that is 1.3mm, 2.0mm, and 3.0mm. The heating surface was 10mm wide and 200mm long and only vertical upflow was experimented. Experiments were conducted at nearly atmospheric pressure under the following conditions: subcooled coolant mass velocity 2000–5000 kg/m2s; inlet temperature 24–47 °C; exit pressure 1.0–1.4 bar; equilibrium quality at channel exit −0.58 to −0.28.
Critical heat flux under the above experimental conditions was found to increase with increase in mass velocity, with decrease in the channel width, and with increase in the inlet subcooling. Visual observations showed that bubbles were small and had diameter less than 100μm. A comparison of the data with correlations reported in the literature showed that the correlations generally tended to overpredict the data. The correlations also do not show a proper trend with respect to the effect of channel width on critical heat flux. A new correlation based on dimensional analysis has been proposed. The correlation proposed can predict experimental data within 20% uncertainty.
Phase Distribution Measurements in Liquid-Liquid Pipeline Flows Using an Impedance Probe
Authors: Angeli Panagiota , Hewitt Geoffrey F. 
Published: July 2023

Abstract
A high frequency impedance probe was used for volume fraction distribution measurements and flow pattern identification in oil-water flow. The signal processing technique was based on a method by van der Welle (1985) that attributes to the beginning of the signal rise or fall the contact of the interface with the probe tip. The experiments were performed in two 1 inch nominal bore horizontal test sections made from stainless steel and acrylic resin. Measurements were made for mixture velocities from 1.3 m/s to 1.7 m/s and input oil volume fractions from 25% to 85%. Under these conditions different complex flow patterns exist, whose discrimination with visual observation is difficult. The results revealed that the mixing of the liquid phases is much greater in the rougher steel pipe than in the acrylic pipe under the same conditions and also helped to clearly identify the three layer, the stratified mixed and the fully mixed flow patterns.
On Some Approach for the Problem of Heat Transfer in Bubbly Liquids
Authors: Khabeev Nail S. 
Published: July 2023

Abstract
Transfer processes in a multiphase flows are determined by the distributions of microparameters near inhomogeneties. For an analysis not to be too complicated, one has to make use the models that could considerably simplify the microprocess equations. The simplest is two-temperature model, but the main problem is to determine the effective value of heat transfer coefficients that would be valid for a certain class of process. It seems natural that the effective heat transfer coefficients be selected from the condition that these should ensure the same heat dissipation as that of the exact solution for the problem of heat exchange between single bubble and liquid. In the present work the propagation of small perturbations in liquid with vapor bubbles has been studied on the basis of this approximate approach for the heat transfer problem in bubbly liquids. The results of calculations are in good agreement with the solutions, obtained by using much more complicated models.
Waves and Instabilities in Inclined Gas-Liquid Pipe Flow
Authors: Grolman Eric , Fortuin Jan M. H. 
Published: July 2023

Abstract
The Modified Apparent Rough Surface (MARS) model (Grolman et al., 1996) successfully predicts liquid holdup and pressure gradient for wavy gas-liquid pipe flow in slightly inclined pipes, up to the transition to slug (intermittent) flow. Additional equations are used to predict the transition from wavy-to-intermittent flow and for the velocity of waves on the gas-liquid interface.
In this paper, Linear (stability) Theory is compared with the MARS model, on the basis of measurements in horizontal and slightly inclined (0° ⩽ β ⩽ 6°) pipes. Viscous terms in the linear analysis require estimates of shear stresses. Using the MARS model for the interfacial and liquid-to-wall friction factors, stability can be predicted to within reasonable degree of accuracy. Credible wave velocities are also obtained, provided the interfacial waves are not assumed to be marginally stable.
Earlier semi-theoretical equations (MARS model) still provide better estimates of both stability and wave velocity and are much easier to handle than Linear Theory. However, the use of good friction factor equations, i.e. those capable of predicting liquid holdup and pressure gradient, has significantly improved the results obtained with Linear Theory. This opens the way to further studies into the mechanisms determining the velocity, growth and instability of waves in gas-liquid pipe flow.