bluuebunny/crossref_metadata_2025 huggingface dataset:
An Optimum Step Design for Centering of Pistons
Authors: Etsion I.
Published: November 2010

A stepped lands piston enclosed within a tight circular cylinder of uniform bore and subjected to unequal upstream and down-stream boundary pressures is analysed for the case of incompressible fluid. Performance characteristics are given for small eccentricity ratios as a function of the step height and location, and a design parameter which relates the leakage and the centering force is defined. It is shown that piston performance can bo optimized by selecting a proper step design.
Microbubble Spectra and Superheat in Water and Sodium, Including Effect of Fast Neutron Irradiation
Authors: Pyun J. J. , Hammitt F. G. , Keller A.
Published: November 2010

The microbubble spectrum in a sample of tap water was measured by the Coulter counter technique under various conditions, and at the same time the tensile strength (i.e., “superheat” capacity) of the tap water was measured by the ultrasonic cavitation technique. It was observed in this experiment that the microbubble population and size increased and the superheat decreased for increasing temperature and under fast neutron irradiation. Finally the generalized Noltingk-Neppiras equation was solved numerically for selected initial microbubble radii, and the suppression pressure (or superheat) determined by this numerical solution was compared with the experimental result. Apparent inconsistencies in experimental results may be primarily due to the neglect of the rectified diffusion effect in the present analysis.
Calculation of Velocity Profiles in Drag-Reducing Flows
Authors: Tiederman W. G. , Reischman M. M.
Published: November 2010

A calculation procedure for predicting mean velocity profiles in drag-reducing flows is presented. The procedure is based upon the eddy diffusivity model of Cess and it requires only pressure drop, flow rate and geometry information. The predictions show excellent agreement with experimentally measured profiles in both Newtonian and drag-reducing flows.
Prediction of the Trajectory of a Turbulent Jet Injected Into a Crossflowing Stream
Authors: Sucec J. , Bowley W. W.
Published: November 2010

A semianalytical prediction of the trajectory of a turbulent jet issuing at various angles to the horizontal into a crossflowing stream is presented. The predictive technique utilizes the basic conservation equations, in conjunction with idealizations instigated by experimentally observed jet behavior, to arrive at two-dimensional trajectories in either a uniform or a spatially variable mainstream crossflow. Comparisons of the predictions with available experimental data yield good agreement over a range of jet to crossflow velocity ratios of two to eighteen.
Shear Effects in Hot-Wire Measurements
Authors: So Ronald M. C.
Published: November 2010

When a circular cylinder is placed in a two-dimensional shear flow, a lift force is experienced by the cylinder. In the case of hot-wire measurements in the viscous sublayer, this will give rise to a displacement of the wire from its true position. The resultant measurements are found to be in error if the wire length to diameter ratio is > 300 and the shear gradient of the flow is large.
A Hybrid Marching Integration Procedure for the Prediction of Two-Dimensional Supersonic Boundary Layers
Authors: Issa R. I. , Lockwood F. C.
Published: November 2010

An economical, “parabolic/hyperbolic hybrid,” numerical prediction procedure, employing marching integration, is presented for the computation of supersonic flows of the boundary layer class in which embedded pressure waves are present. The hyperbolic component is based on the method of characteristics, while the computational procedure of Patankar and Spalding constitutes the parabolic component. The method is evaluated against analytic solutions for inviscid flows and against experiment for laminar and turbulent near-wall flows. Calculations for laminar and turbulent free shear flows are also presented. The method performs well when the viscous/wave interaction is not strong enough to induce significant “upstream influence.”
Self-Excited Aeroelastic Instability of a Bridge Deck
Authors: Be´liveau J. G.
Published: November 2010

The self-excited loads due to the response of a suspension bridge are critical to the stability of the motion. Although buffeting loads due to the random components of the wind enter into the mean square of the response, the response is dominated by the inherent instability of the system near the critical velocity. In this study of a particular deck, experimental information in the form of quasisteady aerodynamic coefficients of an actual bridge deck is used to determine the flutter speed. This is compared to the critical speed obtained by a general unsteady aerodynamic formulation. Finally, the inability of classical airfoil theory to determine the flutter speed is demonstrated.
Fluid Elastic Whirling of Tube Rows and Tube Arrays
Authors: Blevins R. D.
Published: November 2010

Models are developed for the fluid force coefficients that determine the onset of whirling of tube rows and tube arrays. A control volume momentum analysis is employed. The results are in agreement with the available experimental data.
Transient Cooling of a Sphere in Space
Authors: Ayers D. L.
Published: November 2010

A method is presented for determining the transient temperature distribution of a solid sphere cooling in space. The sphere is assumed initially to be at a uniform temperature and then instantaneously subjected to the radiation sink of space at time zero. This nonlinear problem was solved by using finite-difference computing techniques. Results are presented in dimensionless graphical form over a wide range of variables. This facilitates calculation of the transient temperature history at several points in the sphere.
A Numerical Method for Calculating Fully Developed Laminar Velocity Profiles From Temperature Profiles
Authors: Billig L. O. , Galle K. R.
Published: November 2010

It is noted that the velocity profile has a significant effect on the temperature profile that develops in a fluid flowing through a tube. A numerical method for retrieving the velocity profile from a temperature profile is given and the computer program written to implement the method is described. The method retrieved velocity profiles of reasonable accuracy from temperature profiles calculated from the Graetz solution and by Kays’ numerical method. The results of a study to estimate the effects of possible experimental errors from several possible sources on the calculated velocity profiles are included.
An Experimental Investigation Into the Oscillatory Motion of the Mixture-Vapor Transition Point in Horizontal Evaporating Flow
Authors: Wedekind G. L.
Published: November 2010

A horizontal tube evaporator in which complete vaporization takes place can be divided into two distinct regions: a two-phase region and a super heat region. The mixture-vapor transition point refers to the boundary between these two regions. Experimental evidence indicates that, during steady as well as transient flow conditions, the motion of the mixture-vapor transition point is of an oscillatory nature. This study is concerned with the statistical characteristics of these oscillations, the physical mechanisms causing them, and the influence of various evaporator parameters. Experimental data are presented which indicate that the statistical characteristics of the transition point oscillations can be described by a transformed Rayleigh distribution, and that the inlet flow quality and evaporator heat flux have a considerable influence on this distribution.
Thermocouple Response Characteristics in Deflagrating Low-Conductivity Materials
Authors: Suh Nam P. , Tsai C. L.
Published: November 2010

The transient thermocouple response characteristics in deflagrating low-conductivity materials with high temperature gradients were investigated theoretically and experimentally. The theoretical model considers the thermocouple bead and lead wires separately, and the two resulting partial differential equations are solved simultaneously by a finite difference technique. The experimental results are obtained by embedding various size thermocouple wires in double-base solid propellants and consequently measuring the temperature profiles and the surface temperatures. The theoretical model is used to predict the experimentally measured temperatures. There is good agreement. The experimentally measured values are smaller than the correct surface temperature, corresponding to the model prediction for zero wire diameter, by at least 20 percent even when 1/2-mil thermocouple wire is used. Both the experimental and theoretical results show a plateau when the thermocouple bead emerges from the solid into the gas phase. The theoretical results also show that there is an optimum ratio of. the thermocouple bead diameter to the wire diameter, which is found to be close to three
Frequency Response of Pool Boiling Plants
Authors: Chiu P. C. , Poon K. L.
Published: November 2010

Dynamic analysis of a pool boiling plant is accomplished by using small perturbation technique. Mass and energy balance equations are established by basing on the dynamic model constructed and considering additional factors such as steam voids in the liquid phase, water droplets in the steam phase, and the heat transfer behavior at heating surface. Analytical methods for the steam void and dryness fraction dynamics are developed so that their approximate numerical solutions may be readily obtained. Two small boiler plants were constructed and experimental work was carried out by varying the heat input and the valve position in a sinusoidal manner. The experimental results of pressure, steam flow, and water level frequency responses were found to be in closer agreement with the analytical results obtained from the present model than those obtained from the simple mass and energy equations.
Base Heat Transfer in Two-Dimensional Subsonic Fully Separated Flows
Authors: Mitchell John W.
Published: November 2010

An experimental investigation of the heat transfer from the base of a two-dimensional wedge-shaped body to the separated-flow region was conducted in a low-speed wind tunnel. The Stanton number has been determined as a function of Reynolds number for two geometries that are representative of heat-exchanger surfaces. The heat transfer is found to be comparable in magnitude to that for attached flows. An analysis based on the mechanisms of vortex shedding and boundary-layer behavior is developed. The analysis agrees fairly well with the data and indicates the parameters governing base heat transfer.
Radiative Energy Transfer Within a Nonisothermal Air Plasma
Authors: Mandell David A.
Published: November 2010

The object of the present work is to study the mechanism of radiative heat transfer within a nonisothermal air plasma. The problem of an air plasma bounded by two parallel black boundaries, and within which there is a uniform heat source, is studied. Local thermodynamic equilibrium and linearized radiation are assumed. Centerline temperature results are presented for boundary temperatures of 5000 deg K, 10,000 deg K, and 15,000 deg K, and for densities from 10 times normal to 0.01 times normal density. The results show that for higher densities, the optically thin, optically thick, and differential approximation results differ significantly from the general solution over a large range of surface spacings.
Freeze-Drying of Spheres and Cylinders
Authors: Cox C. C. , Dyer D. F.
Published: November 2010

A quasi-steady analysis is presented for freeze-drying spheres and cylinders of beef, taking into account the diffusional and bulk flow of a binary gas mixture inside the food product. A variation in the interface temperature is accounted for by solving the mass-transfer equations with property data from previous investigations. This analysis involves the solution of the coupled equations of continuity, momentum, energy, and specie concentration. The effects of controllable freeze-drying parameters are considered. Drying times for the two models are compared. The interface position and temperature are calculated. Drying time is predicted as a function of chamber condition and particle size. Typical temperature profiles in the product are given. The diffusional contribution to the total flow is determined. Results indicate that drying time increases with chamber pressure and chamber water concentration, and with the square of the diameter of the particle. The interface temperature increases nonlinearly during drying. More than half the total flow is found to be diffusional under some chamber conditions.
Preservation of Blood Components at Cryogenic Temperatures
Authors: Rowe Arthur W.
Published: November 2010

The application of cryogenic technology to medical problems has resulted in the development of methods for freeze-preserving two of the cellular components of blood. Cryopreservation of different cell types, e.g., nucleated leukocytes and non-nucleated erythrocytes, cannot be achieved successfully unless techniques designed to prevent cellular damage induced by freezing are used. Unprotected cells can, depending upon the rate of freezing, be damaged in a variety of ways, principally through dehydration, solute effects, and ice-crystal formation. When cryoprotective compounds, such as glycerol, DMSO, etc. are used and the cooling rate is controlled, cell damage can be circumvented, however. A slow cooling rate with an intracellular additive has been found better for preserving nucleated white blood cells, whereas very rapid freezing techniques have in general proven more successful for preserving non-nucleated red blood cells for transfusion. Ultra-rapid freezing of blood in the form of droplets is a useful means of preserving red cells for blood-group studies. Storage and prolonged preservation of biological specimens have been more successful at cryogenic temperatures (e.g., −196 deg C) than at higher storage temperatures (e.g., −85 deg C).
Volume Interchange Factors for Nonhomogeneous Gases
Authors: Edwards D. K. , Balakrishnan A.
Published: November 2010

Interchange factors describing the radiation heat transfer between two gas-volume elements or between one such element and a wall element are shown to be convenient for treating a variety of engineering problems, such as those involving combustion chambers, furnaces, and plumes. When the gas is not homogeneous in temperature, composition, or pressure, gas-volume interchange factors are found to be complex functions of the geometrical arrangement and the temperature, composition, and pressure fields which affect the radiant properties in the gas within and between the elements. A simplified expression is derived for the rapid calculation of such factors, and comparisons are made with exact numerical computations. Both take into account nongray spectral variations in gas properties. The case of adjoining elements is shown to require special treatment, and results are presented. Volume interchange factors and the machine time necessary to compute them are reported to demonstrate the relative ease with which such factors can be obtained using the approximations developed in this paper.
Optimization of a Heat Pipe with a Wick and Annulus Liquid Flow
Authors: Hwang-Bo H. , Hilding W. E.
Published: November 2010

An analytical model has been formulated for the parametric study of liquid flow characteristics in the heat pipe, which consists of a porous tube, a closed outer container tube, and an annulus between them. The analytical model includes the effect of the rate of change of momentum, surface tension forces, the frictional forces in the body of wicking material and at the wall, as well as the axial variation of static pressure supporting the capillary meniscus at the liquid–vapor–wick interface in the vapor passage. The length of the condenser of the heat pipe was optimized as a function of the radial heat flux rate and the ratio of the liquid flow rate in the annulus to that within the wick, Wa/Ww. The effect of pressure loss and recovery in the vapor passage of the heat pipe on the optimum length of condenser was investigated.
A Study of the Liquid–Vapor Phase Change of Mercury Based on Irreversible Thermodynamics
Authors: Adt R. R. , Hatsopoulos G. N. , Bornhorst W. J.
Published: November 2010

The object of this work is to determine the transport coefficients which appear in linear irreversible-thermodynamic rate equations of a phase change. An experiment which involves the steady-state evaporation of mercury was performed to measure the principal transport coefficient appearing in the mass-rate equation and the coupling transport coefficient appearing in both the mass-rate equation and the energy-rate equation. The principal transport coefficient σ, usually termed the “condensation” or “evaporation” coefficient, is found to be approximately 0.9, which is higher than that measured previously in condensation-of-mercury experiments. The experimental value of the coupling coefficient K does not agree with the value predicted from Schrage’s kinetic analysis of the phase change. A modified kinetic analysis in which the Onsager reciprocal law and the conservation laws are invoked is presented which removes this discrepancy but which shows that the use of Schrage’s equation for predicting mass rates of phase change is a good approximation.
Heat Pipes in the Magnetic-Field Environment of a Fusion Reactor
Authors: Carlson G. A. , Hoffman M. A.
Published: November 2010

Heat pipes have been proposed for use in environments where there are strong magnetic fields such as in controlled fusion reactors. The presence of a magnetic field can influence the performance of a heat pipe significantly, depending on the heat-pipe geometry, its orientation in the magnetic field, the heat-pipe materials and fluid properties, as well as the magnetic-field strength. A liquid-metal heat pipe, specifically designed to operate in a magnetic field, will employ a compound wick structure with the optimum liquid-flow passage size larger and the vapor flow passage proportionately smaller than for the no-magnetic-field design. The basic conclusion is that the presence of a magnetic field always results in a lower maximum heat-flux capability, but the detrimental effects of the magnetic field can be greatly reduced by using a heat-pipe geometry optimized for operation in the specific magnetic-field environment.
Radiation Heat Transfer between Closely Spaced Metal Surfaces at Low Temperature: The Impact of Discrete Modes of the Radiation Field
Authors: Caren R. P.
Published: November 2010

The present analysis shows that for closely spaced metal surfaces at low temperature, the heat transfer due to traveling waves greatly exceeds the results of classical theory. The origin of this nonclassical behavior is due to the fact that for closely spaced metal surfaces the density of normal modes of the radiation field greatly exceeds Jeans’ number. This higher modal density results in a greater than classical energy density in the cavity and thus greater heat transfer. The results of this theory are shown to be consistent with the experiments of Domoto, Boehm, and Tien on heat transfer between closely spaced metal surfaces at low temperatures.
Transient Laminar Free Convection in Closed Spherical Containers
Authors: Whitley H. G. , Vachon R. I.
Published: November 2010

The transient laminar free-convection heat and mass transfer of fluids in closed spherical containers is studied analytically. The coupled nonlinear partial differential equations for conservation of mass, energy, and momentum are solved simultaneously. Finite-difference approximations of the governing equations are organized for an iterative numerical-integration scheme which yields temperature and mass flux as a function of time and space. A computational procedure is given and results from application of the model are presented.
Heat Transfer during Vessel Discharge: Mean and Fluctuating Gas Temperature
Authors: Landram C. S.
Published: November 2010

A gas, discharging from its container through an orifice to the atmosphere, is shown to experience a temperature history that is strongly dependent upon the heat transfer from the container wall. Using a quasi-steady free-convection model for the instantaneous conductance between the wall and gas, a satisfactory correlation results between experimental and analytical mean gas-temperature response during discharge. For the special case of choked orifice flow and constant wall temperature, the mean temporal temperature of the gas remaining within the vessel is shown to depend upon just two parameters. The onset of the oscillating component of gas temperature is shown to occur at times which correspond to the dramatic growth of the diffusional thermal boundary layer on the wall, and this finding is in agreement with the Malkus theory of turbulence. The relative size of the temperature oscillations during discharge is shown to reach a maximum at the time when the scale of dimensionless temperature, a parameter essentially dependent on the instantaneous mean gas temperature, is a maximum.
Conduction through Droplets during Dropwise Condensation
Authors: Hurst Charles J. , Olson Donald R.
Published: November 2010

An experimental investigation was undertaken in which dropwise condensation was caused to occur on the upper side of a 0.001-in-thick horizontal copper condensing surface. The lower side of the condensing wall was convectively cooled, and the cooled-side temperatures under growing droplets were measured using infrared-radiation techniques. Temperature measurements showed good agreement with the results of a finite-element analysis of the droplet and condensing surface. Both experimental and analytical results pointed to the existence of an area of very high heat transfer right around the droplet perimeter, and to the importance of the condensing wall as a heat-diffusing mechanism in dropwise condensation.
Laminar Film Condensation on a Sphere
Authors: Yang J. W.
Published: November 2010

A boundary-layer analysis is made for laminar film condensation on a sphere. Similarity transformations are made for two cases. The first case includes both the inertia forces and heat convection; the solutions are valid in the upper stagnation region. The second case excludes the inertia forces; the solutions are valid over the entire surface for high Prandtl numbers. Results of heat-transfer rate, condensation rate, and film thickness are presented. Comparisons with a vertical plate and a horizontal cylinder are discussed.
The Effects of Vibration and Pulsation on Metal Removal by a Plasma Torch
Authors: Dyos G. T. , Lawton J.
Published: November 2010

An experimental study has been carried out on the effects of workpiece vibration and gas pulsations on metal removal rates using plasma jets. In the case of workpiece vibration, increases in removal rates of up to 30 percent were found, which can be accounted for in terms of capillary waves set up in the melt. The influence of pulsation of gas flow velocity and arc current at modulation levels of 10 percent was found to be negligible. A theoretical model has been developed which explains the results in terms of the development of resonance capillary waves in the molten metal and predicts the average depth of the layer of molten metal.
Finite Amplitude Longitudal Convection Rolls in an Inclined Layer
Authors: Clever R. M.
Published: November 2010

For the case of a large Prandtl number, buoyancy driven flow in an inclined fluid layer, it is shown that all longitudinal-coordinate-independent solutions of the governing equations are obtainable from a knowledge of the existing results for two-dimensional convection in a horizontal layer, heated from below. The rescaling here yields results which compare favorably with those of existing experimental heat transport values.
A Technique for Determining the Transient Heat Flux at a Solid Interface Using the Measured Transient Interfacial Temperature
Authors: Anderson S. A. , Hale L. A. , Hunt H. H. , Pulley P. E.
Published: November 2010

A method for determining the transient heat flux across a solid interface, based on experimentally acquired interfacial temperature-time data, is presented. This method results from the application of Duhamel’s integral method to a third order natural splined fit of the discrete data. General case closed form equations that result from splined and least-squares modeling of the experimental data are developed, presented and illustrated.
Thermal Boundary Conditions and Some Solutions for Laminar Duct Flow Forced Convection
Authors: Shah R. K. , London A. L.
Published: November 2010

The importance of laminar flow forced convection theoretical solutions for the design of compact heat exchangers has been well realized. Many of these theoretical solutions published in the literature are difficult to interpret by a designer, because thermal boundary conditions used in the analysis are generally not defined clearly and consistently. The objective of this paper is to clarify this situation by a systemized presentation. Starting with a general classification, nine specific thermal boundary conditions are categorized for singly connected ducts. At the end, the most useful fully developed laminar flow solutions for some important duct geometries are summarized for the designer.
The Effects of Radiative Heat Transfer Upon the Melting and Solidification of Semitransparent Crystals
Authors: Abrams M. , Viskanta R.
Published: November 2010

Employing the assumptions of one-dimensional energy transfer, equilibrium phase change, and negligible convection in liquid regions, the time-dependent conservation of energy equation is formulated for the general situation of n semitransparent contiguous liquid and solid phases. The dimensionless parameters governing phase change are identified and the effects of their variation are ascertained by a finite difference solution of the rigorously formulated energy and radiative transfer equations. The chief conclusions of this investigation are that for the range of parameters encountered in the melting and solidification of many optical materials, radiant transfer has a significant effect, and that during solidification, radiation can force the temperature profile within the liquid phase to assume a shape which leads to unstable interfacial growth.
Sublimation in a Porous Continuum Developed From Nonequilibrium Thermodynamics
Authors: Burghardt M. D. , Bowley W. W.
Published: November 2010

The case of sublimation dehydration of a porous continuum is analyzed from the viewpoint of nonequilibrium thermodynamics. The general energy and mass transport equations are shown and the application of sublimation is illustrated.
Experimental Determination of Sodium Superheat Employing LMFBR Simulation Parameters
Authors: France D. M. , Carlson R. D. , Rohde R. R. , Charmoli G. T.
Published: November 2010

Sodium superheat experiments were performed in a forced convection facility employing system parameters in the range of interest for application to loop and pot-type liquid metal cooled fast breeder reactors. The test section was representative of a single reactor fuel element with sodium flowing vertically upward in an annulus heated indirectly from the inside wall only. Steady-state operating parameters prior to a flow coast down approach to boiling included: velocity, 17 fps; heat flux, 7 × 105 Btu/hr-ft2; test section inlet, 600 deg F; test section outlet to plenum, 900 deg F; plenum, 15 psia at 900 deg F and 700 deg F. Other important system variables controlled included sodium inert gas content and system pressure-temperature history. The axial location of boiling initiation in the test section was measured. Five test series encompassing 33 test runs were performed. Applicable superheat results were compared to predictions of the pressure-temperature history model including inert gas effects.
Development and Evaluation of a Remote Sensing Technique for Determining the Temperature Distribution in Semitransparent Solids
Authors: Chupp R. E. , Viskanta R.
Published: November 2010

A technique is presented for recovering the temperature profile in semitransparent solids from remotely sensed spectral emission data. The temperature distribution is determined by iteratively solving the equation governing the emerging spectral emission to recover the profile to best match the emission data. The technique is evaluated using both analytical and experimental emission data. Analytical results show the effect of data error, number of data points, method of representing the temperature profile, and optical thickness range. The method is verified experimentally using Corning Code 7940 fused quartz by comparing recovered temperature profiles with those predicted by a combined conduction-radiation heat-transfer analysis.
Experimental Frequency Response Characteristics for Diabatic Two-Phase Flow in a Vertical Monotube Vapor Generator
Authors: Paul F. W. , Riedle K. J.
Published: November 2010

This paper presents experimental data on the dynamic behavior of diabatic two-phase flow in a vertical tube with Refrigerant-11 as the working fluid. A detailed description is included of the experimental test facility as well as the instrumentation used for monitoring the variables of pressure, flow, heat flux, and void fraction. Experimental data are presented in frequency response form for inlet impedance (ΔP1/ΔW1) and exit void fraction (Δα3/ΔW1) at constant heat flux over a frequency range of 0.01 to 10.0 Hz. The data cover inlet subcooling conditions of 14°F and 79°F and two heat flux levels. The experimental results show that the inlet impedance characteristics have fluctuations in amplitude and phase lag with frequency which lead to resonant peaks in the overall frequency response behavior. Exit void fraction characteristics show similar resonant behavior with large phase lag at frequencies above 1 Hz.
Microwave Induced Temperature Rises in Rabbit Eyes in Cataract Research
Authors: Emery A. F. , Kramar P. , Guy A. W. , Lin J. C.
Published: November 2010

Microwave power deposition patterns and temperature distributions were measured for rabbit eyes exposed to localized near zone 2450 MHz radiation and good agreement was obtained between the measured and predicted transient temperature fields. The lenses were biomicroscopically examined to determine the minimum exposure times necessary to produce posterior lens opacity (cataracts) and these times are correlated with the temperature calculations to suggest that a threshold temperature level exists.
An Experimental Investigation of Boundary Layer and Heat Transfer in the Region of Separated Flow Downstream of Normal Injection Slots
Authors: Foster R. C. , Haji-Sheikh A.
Published: November 2010

An experimental investigation was conducted to determine the flow characteristics, heat transfer coefficients, and film cooling effectiveness in the region immediately downstream of flush, normal injection slots. Air was injected through these slots into a turbulent primary flow produced by a small wind tunnel. Velocity measurements and tuft studies indicated that there was a significant region of separated flow immediately downstream of the slot. The heat transfer coefficients were appreciably increased as a result of this flow separation, and the film cooling effectiveness was decreased in comparison to previous studies involving no flow separation.
An Experimental Study of Vertical Buoyant Jets Discharged Into Water of Finite Depth
Authors: Pryputniewicz R. J. , Bowley W. W.
Published: November 2010

This paper presents an experimental study of turbulent buoyant jets discharged vertically through a single circular submerged pipe into a large body of stagnant nonstratified water of finite depth. The experiments were carried out in laboratory facilities consisting of a closed system capable of maintaining steady-state conditions. The temperature characteristics of a hot rising plume were obtained, for numerous flows, as a function of discharge Froude number and discharge depth. The governing equations to predict jet characteristics are also presented, using an integral approach. A computer was used for reduction of experimental data and the numerical solution to the governing equations. The experimental and theoretical results compared favorably.
Radiation Effects on Heat Transfer in the Reactor Core and Heat Exchangers of an HTGR
Authors: Mori Y. , Hijikata K. , Yamada Y.
Published: November 2010

A general and fundamental study of the effect of radiation between duct walls on the heat transfer performance of duct flows of nonradiating gas such as helium is made by an approximate analysis and numerical calculations. Laminar and turbulent flows in a duct simulating a coolant passage in an HTGR and flows in counterflow and parallel-flow heat exchangers in an HTGR heat transfer system are investigated. An approximate analytical solution, based on the assumption that radiation from a point of duct wall produces an effect only on the narrow region opposite the point, agrees well with numerical results. The increase of radiative heat transfer causes a decrease of temperature difference between the duct walls and improves the heat transfer performance. For heat exchangers the heat transfer effectiveness is shown to depend on three nondimensional parameters and can be improved by the increase of these parameters.
Experimental Study on Natural Convection Heat Transfer With Density Inversion of Water Between Two Horizontal Concentric Cylinders
Authors: Seki N. , Fukusako S. , Nakaoka M.
Published: November 2010

An experimental investigation concerning the effect of density inversion on steady natural convection heat transfer of water between two horizontal concentric cylinders with diameter ratio ranging from 1.18 to 6.39 is carried out. Water, as a testing fluid, has the maximum density at 4°C. Temperature of the inner cylinder is maintained at 0°C, while temperatures of the outer cylinder are varied from 1 to 15°C, with Grashof number ranging from 3.2 × 101 to 2.7 × 105. Photographs and qualitative description of the flow patterns, temperature profiles, local and average Nusselt number are presented. From the present experimental investigation, it is demonstrated that the effect of density inversion is unexpectedly large and the average Nusselt number is a peculiar function of temperature difference between outer and inner cylinder, unlike the previous results on common fluids without density inversion.
Molecular Gas Radiation in a Laminar or Turbulent Pipe Flow
Authors: Wassel A. T. , Edwards D. K.
Published: November 2010

The temperature profile and the radiative and convective wall-heat fluxes for a hydro-dynamically established flow of a nongray gas in a cylinder are calculated numerically for laminar or turbulent flow. Turbulent eddy viscosity is represented by a two-region model having a near-wall-region and a far-from-wall region. Gas properties are represented by the exponential-winged band model. The controlling parameters are Nrm, the ratio of radiation conductance to molecular conductance, τR,i, the maximum spectral optical depth of the radius for the ith gas band, Wi, a measure of the importance of the ith band, and Rt, the turbulent Reynolds number. Qualitatively the results for a gas with a single major band agree with a previous solution for a cylinder with internal heat generation. Radiative Nusselt number NuR increases nearly linearly with Nrm. Radiative flux increases with τR rapidly at first and then only slowly. Increasing Rt increases markedly the convective Nusselt number NuC and appreciably NuR. The gas layer effective transmissivity was found to increase with increasing Rt and decrease with increasing τR. Quantitative comparisons with the constant-volume-heat-source case show discrepancies of up to 10 percent in NuR and up to 25 percent in NuC.
A Continuum Model for Diffusion in Laminated Composite Media
Authors: Maewal A. , Bache T. C. , Hegemier G. A.
Published: November 2010

Using a method developed for studying wave propagation problems, a continuum theory is developed for diffusion-type processes in a laminated composite with periodic micro-structure. Construction is based upon an asymptotic scheme in which a typical macrodimension is assumed large compared to a microdimension. The order of truncation of the asymptotic sequence so obtained defines a hierarchy of models. Solutions are given for the lowest-order models and compared with the results from a finite difference code. For most cases the zeroth-order “effective conductivity” theory yields good results. For exceptional problems requiring a higher-order theory, a modified version of the first-order theory is shown to suffice. For many applications these elementary equations may offer an attractive alternative to other means for obtaining solutions.
Effect of Thermal Instability on Thermally Developing Laminar Channel Flow
Authors: Kamotani Y. , Ostrach S.
Published: November 2010

Results are reported of an experimental investigation in the thermal entrance region of a horizontal parallel-plate channel when the lower plate is heated and the upper one is cooled. The experiments covered a range of Rayleigh numbers between 103 and 3.1 × 104 and Reynolds numbers between 30 and 1100 using air. Measurements of Nusselt numbers and temperature distributions indicate much higher critical Rayleigh numbers than the theoretically predicted values. Beyond critical Rayleigh numbers second-type vortex rolls are predominant and the local Nusselt number increases gradually with the Rayleigh number. The thermal-entrance length as determined from temperature profiles does not show appreciable change with the Rayleigh number.
Flow and Heat Transfer in Convectively Cooled Underground Electric Cable Systems: Part 1—Velocity Distributions and Pressure Drop Correlations
Authors: Chato J. C. , Abdulhadi R. S.
Published: November 2010

Velocity distributions and pressure drop correlations have been obtained experimentally for a wide range of physical, flow, and thermal parameters in three models of oil-cooled underground electric cable systems. The flow can be considered as consisting of several, interconnected, parallel channels. If one of these is significantly larger in cross section, it will dominate the behavior of the entire system with velocities up to an order of magnitude greater than in the other channels. Laminar, fully developed flow exists at a dimensionless entrance length as low as x/DH = 100. The turbulent velocity profiles are essentially uniform in the larger, main channel, but not in the small channels with lower velocities. Laminar friction factors can be correlated with an equivalent Reynolds number, based on the main flow channel alone, as fe·Ree = 30. Turbulent friction factors increase with increasing skid wire roughness ratios and approach the asymptotic values of 0.013 and 0.021 for roughness ratios 0.0216 and 0.0293, respectively. Cable heating had no noticeable effect on the friction factor correlations.
Flow and Heat Transfer in Convectively Cooled Underground Electric Cable Systems: Part 2—Temperature Distributions and Heat Transfer Correlations
Authors: Abdulhadi R. S. , Chato J. C.
Published: November 2010

Temperature distributions and heat transfer correlations have been obtained experimentally for a wide range of physical, flow and thermal parameters in three models of oil-cooled underground electric cable systems. The results show that in the laminar range, with the oils used, the thermal boundary layer thickness around the heated cables is only of the order of 2–3 mm over the entire length of the test section. Consequently, the best correlation of the heat transfer results is obtained if the Nusselt number, based on the cable diameter, is plotted against Re·Pr0.4, where the Reynolds number is based on the overall hydraulic diameter of the cross section of the flow. For laminar flows, the oil temperatures in the restricted flow channels between three cables or two cables and the pipe wall are about 11°C higher than corresponding bulk temperatures. As the flow becomes turbulent, the thermal boundary layer tends to vanish and the oil temperature becomes uniform over the entire flow cross section. Laminar Nusselt numbers are independent of the skid wire roughness ratio and the flow Reynolds number, but increase with increasing Rayleigh number and axial distance from the inlet, indicating significant natural convection effect. The range of laminar Nusselt numbers was 5–16. Turbulent Nusselt numbers increase with increasing roughness ratios. The Nusselt numbers at Re = 3000 are 30 and 60 for roughness ratios of 0.0216 and 0.0293, respectively.
Shape of Two-Dimensional Solidification Interface During Directional Solidification by Continuous Casting
Authors: Siegel R.
Published: November 2010

An analysis was made of the two-dimensional solidification of an ingot being cooled and withdrawn vertically downward from a mold consisting of parallel walls of finite length. In some metallurgical solidification processes the liquid metal is maintained superheated so that it transfers heat into the solidification interface as a means of controlling the metal structure during solidification. This energy plus the latent heat of fusion is removed by the coolant along the sides of the ingot. Increasing the ingot withdrawal rate or the heat addition at the solidification interface causes the interface to move downward within the mold and have a nonplanar shape as a result of the curved paths for heat flow into the coolant. This distortion of the interface in the case of directional solidification leads to an undesirable metallic structure. The present heat transfer analysis shows how the flatness of the interface is related to the ingot thickness, the withdrawal rate, the heat addition from the superheated liquid metal, and the temperature difference available for cooling. This provides an understanding of the conditions that will yield a maximum rate of casting while achieving the desired flatness of the interface. The results are interpreted with respect to the conditions for obtaining an aligned eutectic structure by directional solidification. In this process an additional constraint must be included that relates the ingot withdrawal rate and the heat transfer rate from the liquid metal to the solidification interface.
Evaporation From a Capillary Tube
Authors: Preiss G. , Wayner P. C.
Published: November 2010

The heat transfer characteristics of an evaporating ethanol meniscus formed at the exit of a glass capillary tube were studied experimentally. The meniscus profile was photographed and was found to be a function of the evaporation rate and the initial hydrostatic head. The meniscus was found to be stable over a wide range of evaporation rates.
Physical Modeling of Combined Forced and Natural Convection in Wet Geothermal Formations
Authors: Schrock V. E. , Laird A. D. K.
Published: November 2010

Wet geothermal formations or reservoirs are of great current interest as a new energy source. Such formations have the potential for large quantities of energy at temperatures of interest for power production and other uses. In these reservoirs the ground water usually contains dissolved solids in such high concentration as to pose a serious disposal problem. For this reason and also to maintain the water table, in most cases, the water will be reinjected into the reservoir after the useful energy has been extracted. Efficient utilization of the potential of a given reservoir requires optimum location of costly producing and reinjection wells. Selection of well location must be based upon an understanding of the heat and mass flows within the reservoir. In this paper, we present some general considerations for physical modeling as well as the results obtained from a laboratory model having two wells to simulate a geothermal energy extraction loop.
Characteristics of Hollow Glass Microspheres as an Insulating Material and an Opacifier
Authors: Sparrow E. M. , Cur N.
Published: November 2010

Thermal conductivity measurements were performed to determine the characteristics of hollow glass microspheres as an insulating material and as an opacifying agent for other insulations. The experiments were carried out with a radial flow heat transfer apparatus especially designed to suppress extraneous heat transfers, both internal and external to the heated section, and to provide uniform temperatures on the bounding surfaces. Three types of microsphere insulations were investigated, differing in bulk density and in the presence or absence of an aluminizing coating. The thermal conductivity of the microsphere insulations was found to be about one and a half times that of stagnant air over a wide temperature range. Additional experiments, involving the use of an opacifier (powdered silicon), demonstrated that radiative transfer has a minor effect on the thermal conductivity of microsphere insulations. This finding was corroborated by the fact that the high-temperature conductivity of the aluminized microspheres was not appreciably different from that of the uncoated microspheres. Another set of experiments was performed in which microsphere insulation was added to opacify silica aerogel, a fine powder insulation that is markedly affected by radiative transfer. The presence of the microspheres brought about reductions in conductivity of almost a factor of two at an optimum mixture ratio of the constituents. Furthermore, it was found that the conductivity of such a mixture was lower than that of either constituent, thereby illustrating their synergistic interaction.
Effect of Rotation and Coolant Throughflow on the Heat Transfer and Temperature Field in an Enclosure
Authors: Sparrow E. M. , Goldstein Leonardo
Published: November 2010

Measurements were performed to determine the local heat transfer coefficients along the heated shroud of a shrouded parallel disk system. The temperature field within the enclosure formed by the shroud and the disks was also measured. One of the disks was rotating, whereas the other disk and the shroud were stationary. Coolant air was introduced into the enclosure through an aperture at the center of the stationary disk and exited through a slot at the rim of the rotating disk. The coolant entrance-exit arrangement differed from that of previous studies, with the additional difference that the incoming coolant stream was free of rotation. The coolant flow rate, the disk rotational speed, and the aspect ratio of the enclosure were varied during the experiments. The heat transfer coefficients were found to be increasingly insensitive to the absence or presence of rotation as the coolant flow rate increased. There was a general increase of the transfer coefficients with increasing coolant flow rate, especially for low rotational speeds. The temperature field in the enclosure differed markedly depending on the relative importance of rotation and of coolant throughflow. When the latter dominates, the temperature in the core is relatively uniform, but in the presence of strong rotation there are significant nonuniformities. A comparison was made between the present Nusselt number results and those of prior experiments characterized by different coolant entrance—exit arrangements. The positioning of the coolant exit slot relative to the direction of the boundary layer flow on the shroud emerged as an important factor in the comparison.
Thermal Aspects of Cryosurgery
Authors: Comini G. , Del Giudice S.
Published: November 2010

Tissue reactions to cryosurgical procedures depend on temperature variations and on rates of temperature variations induced by freezing probes. In this paper thermal responses of biological systems undergoing freezing are obtained through the application of the finite element method to the solution of the nonlinear bio-equation. This model allows realistic predictions of isotherm fields and of rates of freezing in practically any cryosurgical procedure.