bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Development of a Low Emission Combustor for a Car Gas Turbine
Authors: Holzapfel I. , Meyer F. J.
Published: November 2010

The limit levels for pollutant emissions of automotive vehicles of 0.41 g/mile HC, 3.4 g/mile CO and 0.4 g/mile NOx which have been set in the USA up to the 80s may be likely achieved or even bettered by an appropriately designed gas turbine. Premixing of the fuel with air and its prevaporization before entering the combustion zone, in conjunction with continuous adjustment of the fuel/air ratio in this zone to the respective operation condition, seems to be the favorable approach for attaining this goal. Losses in output and economy are not to be expected; but as compared to spark-ignition and diesel engines, competitive fuel economy can only be reached at turbine inlet temperatures higher than presently obtainable, which call for ceramic components. The problems which are to be solved are treated and the results of the evaluation of a variable geometry combustor are presented on the basis of projected pollutant concentrations along a steady-state turbine operating line. The methods of water channel and electrical analogies which have been applied for optimizing the flow-contours in the premixing and combustion zones and their results are discussed, and the various principles investigated for mixture preparation are described in brief. In the second part, the results of experiments and measurements which have been performed, and the influences of the various parameters on pollutant emissions are shown in detail. Finally, results of particle and aromatic compound measurements are reported. The aim of the work is a combustor whose pollutant emissions at a specified maximum permissible pressure loss do not exceed the half-limit levels of the Muskie Standards at any steady-state point of operation.
The Use of Gravity Fractionation Techniques for Assessing Slagging and Fouling Potential of Coal Ash
Authors: Borio R. W. , Narciso R. R.
Published: November 2010

This paper presents a novel approach toward a fundamental understanding of ash deposit phenomena and describes a laboratory bench-scale technique for assessing the slagging and fouling potential of mineral matter in coal in a boiler firing pulverized fuel. Coal ash deposits collected from boiler tube surfaces have been found to differ from the composition of the coal ash as fired; i.e., selective deposition has occurred. Data are presented to show that analysis of the distribution of mineral matter in the coal matrix can account for this difference. The technique that has been developed consists of a gravity fractionation of pulverized coal so that the ash can be analyzed in groups of particles that are capable of unique behavior in the boiler. The collective behavior of individual ash particles during combustion is not necessarily equivalent to the behavior of a mixture of all ash particles as would be determined by conventional ASTM tests.
Effect of a Heat-Conducting Well Casing on Temperature Distribution in an Observation Well
Authors: Closmann P. J. , Jones E. R. , Vogel E. A.
Published: November 2010

The effect of heat conduction on temperature along the wall of a well casing has been determined by solution of the equations of heat conduction. The casing was assumed to pass vertically through a planar heat source of constant temperature. The casing and formation were assumed to be in perfect thermal contact. Numerical results were obtained for two sizes of steel casing and one size of aluminum casing. At any given distance from the heat source, the casing temperature differs most at early times from the formation temperature computed in the absence of casing. This difference decreases rapidly with time. Furthermore, the maximum difference occurs at greater distances from the heat source as time increases. In general, after about three months of heating, errors in measured temperatures due to conduction along the casing wall are negligible.
Fatigue Analysis of Offshore Structures
Authors: Wallis J. R. , Bayazitoglu Y. O. , Mangiavacchi A. , Chapman F. M.
Published: November 2010

As the offshore industry moves into deeper water, the dynamic behavior of structures becomes a very important parameter in the overall design procedures. In particular, the cyclic nature of wave loads has a significant effect on the fatigue life of the structure. This paper presents a procedure for fatigue analysis where the dynamic response of the structure is analyzed through a spectral approach. The sea waves which constitute the forcing function acting on the structure are represented as energy spectra; the response is obtained in spectral terms and is subsequently interpreted according to probabilistic concepts. As part of this study we have considered the characteristics of the distribution of the response. In the usual approach to fatigue analysis one assumes that the peaks of the response follow a Rayleigh distribution. This assumption is valid if the Cartwright-Longuet-Higgins’ measure of bandwidth (ε) is equal to zero. However, in practical fatigue applications, this idealization is rarely, if ever, encountered. Thus, in order to better characterize narrow-banded phenomena, we have investigated descriptions which do not assume ε = 0. An investigation of caisson designs indicates that fatigue using the more accurate response distributions can differ appreciably from those obtained with the Rayleigh distribution.
Functional Dependence of Torque Coefficient of Coaxial Cylinders on Gap Width and Reynolds Numbers
Authors: Bilgen E. , Boulos R.
Published: November 2010

Dimensional considerations on the torque coefficient of coaxial cylinders, inner one rotating and outer one at rest, result in the expression CM = f(T/Ri, Re) where Re is the Couette Reynolds number, T is the clearance between the cylinders, and Ri is the inner radius. Experimental data published in the literature and additional data obtained by the authors are analyzed to determine the above functional relationship. It is shown that, depending on the Couette Reynolds number and dimensionless gap width, four different regimes exist and that the fractional characteristics of a coaxial cylinder can accordingly be optimized.
An Assessment of Three-Dimensional Turbulent Boundary Layer Prediction Methods
Authors: Wheeler A. J. , Johnston J. P.
Published: November 2010

Predictions have been made for a variety of experimental three-dimensional boundary layer flows with a single finite difference method which was used with three different turbulent stress models: (i) an eddy viscosity model, (ii) the “Nash” model, and (iii) the “Bradshaw” model. For many purposes, even the simplest stress model (eddy viscosity) was adequate to predict the mean velocity field. On the other hand, the profile of shear stress direction was not correctly predicted in one case by any model tested. The high sensitivity of the predicted results to free stream pressure gradient in separating flow cases is demonstrated.
Field Investigation and Reduction of Wicket Gate Vibration in a Francis-Type Reversible Pump/Turbine
Authors: O’Brien J. T. , Swift W. L.
Published: November 2010

The profiles of three wicket gates on a Francis-type reversible pump/turbine were modified in the field to reduce vibration levels in the pumping and generating modes of operation. This paper describes the modification and the field tests employed to monitor the changes in the gate torque chracteristics. Static and dynamic components of gate torque were reduced significantly.
Improvement of the Performance of Conical Diffusers by Vortex Generators
Authors: Senoo Y. , Nishi M.
Published: November 2010

Vortex generators, which consist of small blades, are applied to conical diffusers the divergence angles of which are 8, 12, 16, 20, and 30 deg, respectively. The area ratio of each diffuser is four. The experiment covers the influence of various parameters, such as the arrangement of blades, inlet boundary layer thickness, and location of vortex generators relative to the conical diffuser, on the pressure-recovery coefficient. The experiment shows that the vortex generators prevent the flow in a conical diffuser from separating up to a divergence angle of 16 deg, and that the pressure-recovery coefficient is approximately equal to that of conventional best conical diffusers.
A Note on the Transition Observations on an Axisymmetric Body and Some Related Fluctuating Wall Pressure Measurements
Authors: Arakeri V. H.
Published: November 2010

Boundary layer transition on an axisymmetric body up to Reynolds number of 1.26 × 106 was observed by schlieren method of flow visualization developed for water tunnel use. The spectrum of the flush mounted pressure transducer signal showed a dominant frequency to exist at transition and further, this frequency was in close agreement with the predicted critical frequency by Smith’s approximate method of transition calculation based on linear stability theory.
Review—Complex Turbulent Flows
Authors: Bradshaw P.
Published: November 2010

“Complex” turbulent flows are those which cannot be predicted with acceptable accuracy by methods developed in classical thin shear layers. This is a subjective and time-dependent definition but even at its narrowest it includes a large class of engineering and environmental flows. Examples include shear layers which interact, in pairs or larger numbers, and shear layers which have been perturbed by body forces, such as buoyancy, or extra rates of strain such as longitudinal curvature or lateral divergence. This review assesses our current knowledge of complex turbulent flows and our ability to predict them. It also assesses the usefulness of the boundary layer approximation in engineering flows and suggests methods of extending it.
New Analytical Method for Calculating Water Level Oscillations in a Simple Surge Tank Under Load Rejection
Authors: Jonckheere R. E.
Published: November 2010

A new analytical method is presented, allowing direct, easy and accurate computation of the nonlinear waterlevel oscillations occurring in a simple surge tank under instantaneous load rejection. The method yields several design equations and is also applicable in the case of instantaneous load demand and to other types of surge tanks.
A Note on the Empirical Constant in the Kolmogorov-Prandtl Eddy-Viscosity Expression
Authors: Rodi W.
Published: November 2010

The transport equation for the Reynolds stress is simplified to yield the Kolmogorov-Prandtl eddy viscosity expression, and the conditions are studied under which the empirical factor cμ in this expression can be a constant. By reference to experimental data, it is shown that these conditions are not generally satisfied. The measured variation of cμ is given for various thin shear layers. Those flows are identified, which can be calculated with a constant value of cμ.
A Nonlinear Design Theory of Supercavitating Cascades
Authors: Yim B. , Higgins L.
Published: November 2010

A nonlinear method of finding two-dimensional supercavitating sections in a cascade is developed. The load distribution is taken from linear theory for low drag super-cavitating foils in a cascade. The double spiral vortex model is used for the cavity termination. Linear and nonlinear theories are compared with special emphasis put on analyzing the blunt leading edge. The foil-cavity shape, the cavity drag and the cavitation number can be obtained by a computer program from the given cavity length and geometrical parameters of the cascade.
Performance of a Supercavitating Jet-Flapped Hydrofoil Operating at Arbitrary Submergence
Authors: Oba R. , Sato K.
Published: November 2010

The flow around an arbitrary supercavitating, jet-flapped hydrofoil operating at an arbitrary submergence is analyzed by a second order theory and the following results are obtained; (i) The hydrofoil performance data are shown for various submergences and jet operating conditions. (ii) The flap effects are highly dependent on the submergence as well as the hydrofoil shape. (iii) Operation of the jet flap results in an increase in the cavity thickness so that the hydrofoil thickness can be increased. (iv) Especially at the shallower submergences, the performance, as well as the flow pattern, changes strikingly with changes in submergence.
Decaying Annular Swirl Flow With Inlet Solid Body Rotation
Authors: Scott C. J. , Bartelt K. W.
Published: November 2010

An experimental investigation of a low-speed turbulent swirling flow in a stationary, concentric, annular duct was made. The experiment involved isothermal air as the working fluid in an annulus with a diameter ratio di/d0 = 0.4, an average axial Reynolds number of 72,000, and an average axial velocity of 15 m/s. The swirl profile initially induced at the inlet was of the forced-vortex type. The rate of swirl, or the magnitude of the tangential velocity relative to the axial component, decayed axially from the inlet. Three different swirl rates were considered, one being straight flow. Extensive measurements were made of the velocity field with a cylindrical pressure probe at seven stations located 1.7 to 32.7 equivalent diameters from the entrance. The specific goals were experimental data on the axial decay of angular momentum and inferred values of the effective turbulent tangential viscosity. Results show a uniform axial decay of angular momentum and a profile shape independent of axial location. An empirical model using tangential eddy diffusivities that vary over the cross-section gave the best description of experimental data. The tangential profile shape and tangential viscosity distribution and magnitude did not depend on the initial rate of swirl.
A Reynolds Stress Model for Turbulent Corner Flows—Part II: Comparisons Between Theory and Experiment
Authors: Gessner F. B. , Po J. K.
Published: November 2010

The applicability of the Reynolds stress model developed in Part I to fully developed rectangular duct flow is investigated. Two sets of experimental data are analyzed in order to prescribe a representative mixing length variation and appropriate values for the constants in the model. Predicted Reynolds stress values are in good agreement with their experimental counterparts for both sets of data. These results are compared with predictions referred to an alternate model in order to explain discrepancies observed in a previous study. Possible extensions of the proposed model to increase its flexibility are discussed.
Entry Flow in Curved Channels
Authors: So Ronald M. C.
Published: November 2010

Entry flow in curved channels is investigated by an approximate method analogous to that used by Pohlhausen in his treatment of boundary layer flows. Constant total pressure across the channel at the entrance is assumed. Therefore, if the upstream influences of viscosity have been neglected, the initial condition is given by a nonuniform velocity right at the entrance to the curved channel. The boundary layer in the entrance region is estimated by assuming a velocity profile that approaches the near parabolic profile when the flow becomes fully developed. As a result of wall curvature, entrance length becomes longer and the pressure drop along the inner wall is different from that along the outer wall.
An Approximate Method for Curved Shear Layers
Authors: So Ronald M. C.
Published: November 2010

Steady, incompressible two-dimensional laminar boundary layers on curved surfaces with spanwise rotation are investigated using an approximate method. A fourth-degree polynomial is assumed for the velocity profiles and they are found to constitute a three-parameter family of curves characterized by a pressure factor, a curvature parameter and a rotational parameter. The results obtained for constant surface velocity flow with/without rotation on plane/curved surfaces are found to be consistent with those reported in the literature.
Forces on Cylinders Near a Plane Boundary in a Sinusoidally Oscillating Fluid
Authors: Sarpkaya Turgut
Published: November 2010

The in-line and transverse forces acting on circular cylinders placed near a plane boundary in a sinusoidally oscillating fluid in a U-shaped vertical water tunnel have been measured. The period parameter UmT/D was varied from about 2 to 40, the Reynolds number from 4000 to 25,000, and the gap between the cylinder and the plane boundary from 0.01 D to 1.0D. The drag and inertia coefficients for the in-line force have been determined through the use of the Morison’s equation and the Fourier analysis, least squares method, and a modified least squares method. The transverse force coefficients have been obtained for the forces toward the wall and away from the wall. The results show that the in-line and transverse forces could acquire very large magnitudes and give rise to serious oscillations. For very small values of the period parameter, effects of flow separation become negligible and the inertia coefficient for the in-line force and the lift coefficient for the transverse force approach those predicted by the potential theory.
Forces on Unstaggered Airfoil Cascades in Unsteady In-Phase Motion
Authors: Kemp N. H. , Ohashi H.
Published: November 2010

Incompressible flow through an unstaggered cascade in general, unsteady, in-phase motion is considered. By methods of thin-airfoil theory, using the assumptions of wakes trailing back at the through-flow velocity, and the Kutta condition, exact analytical expressions are derived for loading, lift and moment. As application, harmonic motion is considered for plunging, pitching, and sinusoidal gusts. Numerical values of lift and moment for these three cases are given graphically (tables are available from the authors). The results show strong analogies with isolated unsteady thin-airfoil theory. They should prove useful as simple examples of unsteady effects in cascades, and as check cases for other approximate or purely numerical analyses.
Performance of Hydraulic Gas Compressors
Authors: Rice W.
Published: November 2010

A hydraulic gas compressor has no moving parts and compresses gas at the expense of hydraulic energy by means of entrainment in a downward moving column of liquid with subsequent separation of gas and liquid at depth. Documentation is cited giving the history and performance data for large hydraulic air compressors built around 1900. An analysis is presented based on one-dimensional bulk parameter modeling of the flow, which enables computerized calculation of the performance of hydraulic gas compressors. The results of small-scale experiments are presented showing agreement with analytical results. It is further shown that the analytical results agree with reported performance data for old large-scale compressors. Unique capabilities of the compressor for transducing and transforming energy are described and application studies are suggested in several areas. Calculated results are presented as an example, for the design and performance of a large air compressor, showing the effect on performance of varying the applied hydraulic head.
A Single Formula for the Complete Velocity Profile in a Turbulent Boundary Layer
Authors: Dean R. B.
Published: November 2010

An expression for the wake deficit g(Π, y/δ) in a turbulent boundary layer is combined with a function f(U+) for the inner layer to yield a single formula for the complete velocity profile in the form y+ exp {Kg(Π, y/δ)} = f(U+). Close agreement is shown with data from boundary layers in a wide range of pressure gradients and beneath a turbulent free stream. The formula will be particularly useful for integral and differential calculation methods.
Simple Predictions for the Sonic Conditions in a Real Gas
Authors: Thompson P. A. , Sullivan D. A.
Published: November 2010

The steady isentropic flow of a fluid which satisfies an arbitrary equation of state is treated, with emphasis on the prediction of pressure, density, velocity, and massflow at the sonic state. The isentrope P(v) is described by a limited number of thermodynamic parameters, the most important ones being the soundspeed c and fundamental derivative Γ. Using this description, an application of the Bernoulli equation and appropriate thermodynamic relations yields simple closed-form predictions for the sonic state. These predictions are recognizable as generalizations of well-known ideal gas formulas, but are applicable to fluids very far removed from the ideal gas state, even including liquids. Comparisons in several cases for which precise independent solutions are available suggest that the methods found here are accurate. A derived similarity principle allows the accurate prediction of sonic properties from any single given sonic property.
The Time Domain of Centrifugal Compressor and Pump Stability and Surge
Authors: Dean R. C. , Young L. R.
Published: November 2010

New evidence about the time domain operation of centrifugal compressors and pumps in compliant systems is presented. Data from Toyama [1,2] plus unpublished data from another compressor indicate that the flow rate oscillates continuously, at large amplitudes, when a compressor is operating in its supposedly stable regime. A tentative flow model predicts similar oscillations. The model assumes that the compressor operation at all times is described by its quasi-steady characteristic; no hysteresis or complex aerodynamic phenomena have been invoked.
Impeller Stalling as Influenced by Diffusion Limitations
Authors: Rodgers C.
Published: November 2010

Relatively small stable flow ranges experienced on some high Mach number centrifugal compressors, triggered by the inability of stationary vaned diffusers to operate at flows below their maximum recovery point, have focused considerable research effort on the diffuser component. With improved impeller stability, vaned diffusers can be assisted to operate to lower flows where impeller stalling becomes predominant. The results of tests on a small high Mach number centrifugal compressor are presented to suggest that in certain applications the primary factor affecting compressor surge could be the impeller inlet-to-exit velocity diffusion ratio, with specific diffuser types, Mach numbers, and incidence considerations becoming secondary in importance.
A Length-Scale Model For Developing Turbulent Flow in a Rectangular Duct
Authors: Gessner F. B. , Emery A. F.
Published: November 2010

A three-dimensional mixing length model is proposed for modeling local Reynolds stress behavior in rectangular ducts of arbitrary aspect ratio. The model is applicable to both developing and fully-developed flows, and can be applied to other 90-degree corner flows with mild streamwise pressure gradients. Comparisons between theory and experiment show that all components of the Reynolds stress tensor are modeled reasonably well, both in the vicinity of a corner and in two-dimensional regions away from the corner.
Roughness Element Geometry Required for Wind Tunnel Simulations of the Atmospheric Wind
Authors: Gartshore I. S. , De Croos K. A.
Published: November 2010

Using a data correlation for the wall stress associated with very rough boundaries and a semi-empirical calculation method, the shape of boundary layers in exact equilibrium with the roughness beneath them is calculated. A wide range of roughness geometries (two- and three-dimensional elements) is included by the use of equivalent surfaces of equal drag per unit area. Results can be summarized in a single figure which relates the shape factor of the boundary layer (its exponent if it has a power law velocity profile) to the height of the roughness elements and their spacing. New data for one turbulent boundary layer developing over a long fetch of uniform roughness is presented. Wall shear stress, measured directly from a drag plate is combined with boundary layer integral properties to show that the shear stress correlation adopted is reasonably accurate and that the boundary layer is close to equilibrium after passing over a streamwise roughness fetch equal to about 350 times the roughness element height. An example is given of the way in which roughness geometry may be chosen from calculated equilibrium results, for one particular boundary layer thickness and a shape useful for simulating strong atmospheric winds in a wind tunnel.
Theoretical Investigation of Pressure Distributions Along the Surfaces of a Thin Blade of Arbitrary Geometry of a Two-Dimensional Centrifugal Pump Impeller
Authors: Kumar T. C. Mohana , Rao Y. V. N.
Published: November 2010

The flow through a two-dimensional centrifugal pump impeller with thin blades of arbitrary geometry is investigated using the hydrodynamic method of singularities. A theoretical analysis is developed to determine the impeller head and pressure distributions along the blade surfaces. The convergence of the numerical procedure is discussed. These results are compared with the theoretical and experimental results reported by Acosta. There is excellent agreement between the theoretical values of the impeller head and the pressure distributions obtained by both methods. Discrepancies in the theoretical and experimental pressure distributions are attributed to the effects of viscosity, inlet turn, blade thickness and inlet stall which are neglected in the analysis.
Turbulent Heat Transfer in Concentric Annuli With Constant Wall Temperatures
Authors: Quarmby Alan , Anand R. K.
Published: November 2010

The problem of turbulent heat transfer in concentric annuli is analyzed for the case in which one wall has a constant temperature while the other is insulated. The solution is given for both, the thermal entrance region and the fully developed situation with heating at either one of the annular surfaces. The description of the velocity profile properly takes into account the Reynolds number and radius ratio dependence of the nondimensional turbulent velocity profile in concentric annuli. Results are presented for radius ratios 2.88, 5.625, and 9.37 with the Reynolds number range from 20,000 to 240,000 and for Prandtl numbers 0.01, 0.7, and 1000. The calculated Nusselt numbers for the constant wall temperature boundary condition are smaller than the corresponding result for a uniform heat-flux boundary condition. The available experimental evidence for concentric annuli is insufficient to provide a direct test of the analysis. However some calculated results for the radius ratios 1.05 and 50 are in agreement with available theory and experiments for the parallel plate channel and circular tube, respectively. There is also good agreement, between the calculated results for the extension of the analysis to the case of a linear rise in wall temperature and experiments for a uniform heat-flux boundary condition for the annuli considered.
The Effects of Gravity and Surface Tension Gradients on Cellular Convection in Fluid Layers With Parabolic Temperature Profiles
Authors: Debler Walter R. , Wolf Louis W.
Published: November 2010

The effects of surface tension and buoyancy on the convection stability of fluid layers with a mean parabolic temperature distribution is examined. A variety of free-surface, thermal boundary conditions are used. Quantitative values for the effect on the critical Rayleigh number of the free-surface boundary condition, fluid depth, and physical properties are given. The role of the mean temperature profile is also discussed. The results should be of value in judging experiments where a free surface is used to enhance the flow visualization. The numerical procedure used to find the eigenvalues was effective and easily altered to obtain results for similar stability problems.
An Analysis of Cell Freezing and Dehydration
Authors: Ling G. R. , Tien C. L.
Published: November 2010

A quantitative picture of the effect of low-temperature exposure on the survival of living cells is presented through discussion of solutions to a differential equation relating the volume of intracellular water to the temperature, the cooling rate, and various cell parameters. It is found that for a given cell, a single parameter which depends on the cooling rate governs the behavior of the cell when it is exposed to low temperatures. The analysis develops relationships between solutions to the differential equation and the phenomena affecting cell survival, namely, intracellular freezing and cell dehydration. Theoretical predictions are found to agree well with existing experimental observations.
Temperature in Semi-Infinite and Cylindrical Bodies Subjected to Moving Heat Sources and Surface Cooling
Authors: DesRuisseaux N. R. , Zerkle R. D.
Published: November 2010

The theory of moving heat sources is applied to two models to determine the effect of convective surface cooling on temperature distributions. The models chosen consist of a translating semi-infinite body and a rotating cylindrical body, each having a band heat source acting on a portion of the surface and convective cooling acting over the entire surface. The analytical results can be utilized to predict temperature distributions occurring in certain machining processes or other processes involving heat sources.
The Effect of Swirl, Inlet Conditions, Flow Direction, and Tube Diameter on the Heat Transfer to Fluids at Supercritical Pressure
Authors: Shiralkar B. , Griffith P.
Published: November 2010

An investigation has been made of the factors governing the heat transfer coefficient to supercritical pressure fluids, particularly at high heat fluxes. The deterioration in heat transfer to supercritical carbon dioxide has been experimentally studied with reference to the operating conditions of mass velocity and heat flux, tube diameter, orientation, tape induced swirl, inlet temperature, and pressure. A detailed comparison has been made with the apparently contradictory results of other investigators, and operating regions, in which the heat transfer coefficient behaves differently, have been defined. The terms used to describe these regions are the Reynolds number, a heat-flux parameter, and a free-convection parameter.
Pseudoboiling Heat Transfer to Supercritical Pressure Water in Smooth and Ribbed Tubes
Authors: Ackerman J. W.
Published: November 2010

Investigations of heat transfer to supercritical pressure fluids have been going on for some time, and correlations have been developed for both free and forced-convection conditions. In these investigations, unpredictable heat transfer performance has sometimes been observed when the pseudocritical temperature of the fluid is between the temperature of the bulk fluid and that of the heated surface. The unusual performance has been attributed to many causes, but one for which more evidence is being collected is that of a pseudofilm-boiling process similar to film boiling which occurs at subcritical pressures. This paper, which is an extension of work reported earlier on forced-convection heat transfer to supercritical pressure water, presents experimental evidence which suggests that a pseudofilm-boiling phenomenon can occur in smooth-bore tubes. During the period from 1963–1966, tubes with ID’s from 0.37 to 0.96 in. were tested at pressures from 3300–6000 psia and at heat fluxes and mass velocities in the range of interest in steam-generator design. The effects of heat flux, mass velocity, tube diameter, pressure, and bulk fluid temperature on both the occurrence and characteristics of pseudofilm boiling are discussed. Results of a second series of tests conducted in 1967, which show that ribbed tubes suppress pseudofilm boiling at supercritical pressure much like they do film boiling at subcritical pressures, are also discussed.
The Heat Transfer and Pressure-Drop Characteristics of Gas Flow Inside Spirally Corrugated Tubes
Authors: Kidd G. J.
Published: November 2010

Heat transfer and pressure-drop experiments have been performed for gas flow inside nine, 1/2-in-OD, 0.035-in. wall thickness, A-nickel, spirally corrugated tubes. The corrugations, which varied from 0.003–0.028 in. deep, were formed by pulling the tubes through a rotating head containing four embossing tools; corrugation-spacing-to-corrugation-depth ratios (P/e) ran from 16–41. The data, for heat transfer to nitrogen, at approximately 200 psig, were correlated by an expression of the form NNu,B (NPr,B)−0.4 × (Tw/TB)0.5 = A(NRe,B)m, where all the physical properties were evaluated at bulk gas conditions. The exponent, m, on the Reynolds number was observed to be consistently greater (0.854–0.900) than the value of 0.8 found for smooth tubes; the constant, A, varied from 0.0095–0.0195 with no apparent correlation with P/e. Friction factors, measured with adiabatic airflow, were found to be up to 1.7 times that for smooth tubes. Tubes of this geometry were found to be very effective in enhancing heat transfer. On an equal pumping power basis, for example, a tube with P/e = 22 had a heat transfer coefficient 22 percent greater than a smooth tube.
An Experimental Study of Radiation Heat Transfer From Parallel Plates With Direction-Dependent Properties
Authors: Black W. Z. , Schoenhals R. J.
Published: November 2010

An experimental study of radiation heat transfer from opposing parallel plates is described. Surfaces composed of many small grooves were used to fabricate plates having direction-dependent radiation properties. These plates possessed a collimated emission pattern which was found to influence significantly the heat transfer rate, the largest observed effects being approximately 40 percent. It appears that somewhat larger alterations could be achieved with further effort. The measurements obtained in this study establish the potential value of specially prepared surfaces for certain applications requiring improved thermal performance.
An Investigation of the Liquid Distribution in Annular-Mist Flow
Authors: Pogson J. T. , Roberts J. H. , Waibler P. J.
Published: November 2010

The results of an experimental investigation of the average liquid film thickness are presented for vertical upward annular-mist two-phase flow, with and without heat transfer. The effects on the film thickness for variations in vapor flow rate, liquid flow rate, vapor density, and heat transfer are described. A correlation equation is presented for the local time-averaged thickness and for the droplet size distribution. In addition, an equation is given for the liquid film flow rate as a function of the average film thickness.
A Numerical Solution for Natural Convection in Cylindrical Annuli
Authors: Powe R. E. , Carley C. T. , Carruth S. L.
Published: November 2010

The results of a finite-difference solution for natural convection within horizontal cylindrical annuli for Prandtl numbers near 0.7 (air) are presented. The ranges of Rayleigh number and inverse relative gap width over which such a solution yields valid results are investigated. It is shown that this solution, though formulated for steady flow, can be used to obtain an indication of the Rayleigh number at which transition from a steady to an unsteady flow will occur for a wide range of inverse relative gap widths (2.8–12.5). A recent experimental investigation has shown that steady secondary cellular flows occur immediately prior to transition for this range of inverse relative gap widths, and the Rayleigh number at which these secondary flows occur is accurately predicted by the numerical solution, thereby yielding a good indication of the Rayleigh number at which transition to an unsteady flow occurs. Flow patterns predicted by the numerical solution near transition are compared with photographs of the flow, and excellent qualitative agreement is noted. It is thus shown that this numerical technique gives, at least qualitatively, valid results for all Rayleigh numbers at which the flow is steady for the range of inverse relative gap widths under consideration. Heretofore unavailable data on temperature profiles, radial and angular velocity components, and local Nusselt numbers for Rayleigh numbers near the transition value are presented. It is found that the foregoing parameters (velocity, temperature, and Nusselt number) are little affected by the appearance of the secondary flow for the smaller inverse relative gap widths considered, whereas for the larger inverse relative gap widths a pronounced increase in magnitude of temperatures and velocity components is noted. The overall or mean Nusselt number is not affected by the appearance of these secondary flows for any of the inverse relative gap widths considered.
The Solution of Three-Dimensional, Composite Media Heat Conduction Problems by Synthesis Methods
Authors: Yasinsky J. B.
Published: November 2010

A method, known as synthesis, is applied to the task of obtaining approximate solutions to the static heat conduction equation for three-dimensional, composite media problems with mixed boundary conditions. The method is based upon an expansion in terms of known two-dimensional solutions of the problem of interest. These known two-dimensional solutions (trial functions) are blended over the remaining dimension by unknown mixing coefficients which are defined by means of variational techniques. A modified canonical variational principle is derived which permits the use of discontinuous trial functions, which expands the class of problems to which the synthesis method can be applied. The equations defining the mixing coefficients are derived in some detail, and the results of several test problems display the potential of this method for analyzing realistic heat conducting systems.
Boiling-Curve Measurements From a Controlled Heat-Transfer Process
Authors: Peterson W. C. , Zaalouk M. G.
Published: November 2010

Feedback has been introduced around a boiling heat-transfer process in such a way that stable operation of the process has been obtained in all boiling regions including the transition region, in which, as is well known, the process itself is unstable. This system makes it possible to obtain much new information concerning both the steady-state and dynamic characteristics of boiling heat-transfer processes. Pool-boiling data which were obtained by the use of this system are presented. Accurate measurements of heater voltage and current were obtained by a new technique involving the use of digital instruments. These data are presented in the form of plotted experimental points in the nucleate, transition, and film boiling regions. The new measurement technique is described. Values of n in the equation q/As = CTdn are determined for all three boiling regions, where q = Btu/hr, As is heater surface area, and Td is temperature difference between heater surface and ambient liquid. The ambient liquid is distilled water maintained at saturation temperature under atmospheric pressure.
An Experimental Investigation of the Enthalpy of Saturated Heavy-Water Liquid
Authors: Nowak E. S. , Chan J.
Published: November 2010

Measurements on the enthalpy of saturated heavy-water liquid were made for temperatures ranging from 90 to 350 deg F by means of a non-flow, continuous-heating calorimeter. Based on confirmatory tests conducted on light water, it is estimated that the heavy-water enthalpy measurements obtained in this paper are accurate to ±0.5 percent. The experimental data of this research is in reasonable accord with the data obtained by other investigators. It was also found that the difference between the heavy-water enthalpy-change values and the corresponding values for light water is a strong function of temperature varying from about 0.2 percent at 100 deg F to 3.5 percent at 350 deg F.
On the Conjugate Problem of Laminar Combined Free and Forced Convection through Vertical Non-Circular Ducts
Authors: Iqbal M. , Aggarwala B. D. , Khatry A. K.
Published: November 2010

The present analysis deals with the conjugate problem of combined free and forced convection through vertical non-circular ducts. The equations coupling heat conduction in the walls with the convection inside the fluid are solved to establish the influence of peripheral wall conduction, using variational technique. Fully developed laminar flow with uniform axial heat input and constant fluid properties, except for the small variation of density in the buoyancy term of the momentum equation, is assumed. The problem has been solved in a generalized way and the results have been presented for rectangular ducts. It is found that large values of the free convection effects and/or of the conduction parameter tend to minimize the asymmetries in circumferential wall temperature.
Fundamental and Higher-Mode Density-Wave Oscillations in Two-Phase Flow
Authors: Yadigaroglu G. , Bergles A. E.
Published: November 2010

This paper treats the oscillatory two-phase flow instabilities commonly referred to as density-wave oscillations. A dynamic analysis of the single-phase region of a boiling channel, accounting for wall heat capacity and the effect of pressure variations on the movements of the boiling boundary, is summarized. Experiments conducted with a Freon-113 channel at atmospheric pressure revealed the existence of “higher-mode” oscillations. These appeared at high subcoolings and low power levels and were characterized by unexpectedly short periods that were fractions of the transit time. The presence of the higher modes and other observations are explained in terms of the dynamic behavior of the boiling boundary.
Computer Methods for Simulation of Multidimensional, Nonlinear, Subsonic, Incompressible Flow
Authors: Fox Douglas G. , Deardorff J. W.
Published: November 2010

This review attempts to summarize the current state of fluid flow simulations with particular regard to numerical discretization techniques, treatment of large Reynolds numbers, and past and future accomplishments of the simulation methodology. Three alternative mathematical representations of the flow are presented and compared for an idealized two-dimensional flow, namely, use of the velocity and pressure as dependent variables (primitive equation), use of vorticity and stream function as dependent variables, and expansion of either of these in a truncated set of orthogonal eigenfunctions of the boundary-value problem (whose coefficients become the dependent variables). Various classes of finite-difference algorithms are discussed with regard to their conditional stability as well as their ability to preserve invariants of the continuous equations. Methods of removing aliasing of high-frequency solutions are discussed. Parameterization and other techniques for dealing with the high-Reynolds-number regime in which solutions exhibit a wide range of scales are considered in depth. We conclude that certain types of information can be better obtained by numerical simulation than by other techniques.
Transient Free Convection in a Bingham Plastic on a Vertical Flat Plate
Authors: Kleppe J. , Marner W. J.
Published: November 2010

A theoretical investigation of transient free convection in a Bingham plastic on a vertical flat plate with constant wall temperature is presented. Except for a linear variation of density with temperature in the body force term, all fluid properties are assumed to be constants. The parameters of the problem are the Prandtl number Pr and a dimensionless group involving the Hedstrom and Grashof numbers, He/GrL3/4. Solutions to the governing boundary-layer equations are obtained using an explicit finite-difference procedure. Mean Nusselt numbers NuL are presented for a range of the parameters, along with representative velocity profiles, temperature profiles, and friction coefficients. Flow in the Bingham plastic does not start until the buoyancy forces become sufficiently large to cause a shear stress in the material which exceeds the yield stress. Thus, for short times heat is transferred by one-dimensional transient conduction, which has the well-known solution expressed in terms of the complementary error function. A temporal minimum, which becomes more pronounced with increasing He/GrL3/4, is noted in the mean Nusselt number. Steady-state NuL values are higher for Bingham plastics than for Newtonian fluids, but the maximum increase, which decreases with increasing Pr, is noted to be less than 15 percent. Due to the behavior of the velocity gradient at the wall, which reaches a maximum before steady-state conditions are reached, a temporal maximum is observed in the mean friction coefficient. Bingham-plastic friction coefficients are significantly higher than for Newtonian fluids; however, this increase is due primarily to the yield stress rather than as a consequence of a steeper velocity gradient at the wall.
Viscous Non-adiabatic Laminar Flow through a Supersonic Nozzle: Experimental Results and Numerical Calculations
Authors: Back Lloyd H. , Massier Paul F.
Published: November 2010

Flow and thermal regimes found in relatively low Reynolds-number flows of high-temperature gases in cooled convergent divergent nozzles used in propulsion systems and in research facilities are investigated by a combined experimental and numerical approach. The experiments were conducted with argon at temperatures up to 14,200 deg R, and the throat Reynolds number ranged from 2200 to 2800. The numerical calculations involved the laminar-flow equations in differential form. Taken together, the experiments and the numerical calculations provide information on the pressure, heat-flux, and shear-stress distributions along internal flows with heat transfer, and on the velocity and enthalpy distributions across the flow as well as along the flow. The influence of heat conduction and of the viscous shear extended to the centerline all along the nozzle.
Transient Combined Conductive and Radiative Heat Transfer
Authors: Doornink D. G. , Hering R. G.
Published: November 2010

Transient simultaneous conductive and radiative transfer in a plane gray layer bounded by black walls is studied. The analytical development yields a nonlinear integro-differential equation which is numerically solved for a layer initially at a uniform temperature when the temperature of one wall is suddenly decreased. Instantaneous temperature and flux distributions illustrate the conduction–radiation interaction during cooling for a wide range of values for the influencing parameters which include layer optical thickness τ0 and the conduction–radiation interaction parameter N. Results are compared to those for an optically thin and optically thick medium, as well as to those for purely conductive and purely radiative transfer.
Heat Transfer by Natural Convection between Vertically Eccentric Spheres
Authors: Weber N. , Powe R. E. , Bishop E. H. , Scanlan J. A.
Published: November 2010

Natural convection to a cooled sphere from an enclosed, vertically eccentric, heated sphere is described in this paper. Water and two silicone oils were utilized in conjunction with four different combinations of sphere sizes and six eccentricities for each of these combinations. Both heat-transfer rates and temperature profiles are presented. The effect of a negative eccentricity (inner sphere below center of outer sphere) on the temperature distribution was an enhancement of the convective motion, while a positive eccentricity tended to stabilize the flow field and promote conduction rather than convection. As for concentric spheres, a multicellular flow pattern was postulated to explain the thermal field observed for the largest inner sphere utilized. In all cases the heat-transfer rates were increased by moving the inner sphere to an eccentric position, and the utilization of a conformal-mapping technique to transform the eccentric spheres to concentric spheres enabled the application of existing empirical correlations for concentric spheres to the eccentric-sphere data. It is significant to note that this technique yields a single correlation equation, in terms of only keff/k and a modified Rayleigh number, which is valid for an extremely wide range of diameter ratios, eccentricities, Rayleigh numbers, and Prandtl numbers.
An Approximate Analysis of the Diffusing Flow in a Self-controlled Heat Pipe
Authors: Somogyi D. , Yen H. H.
Published: November 2010

Constant-density two-dimensional axisymmetric equations are presented for the diffusing flow of a class of self-controlled heat pipes. The analysis is restricted to the vapor space. Condensation of the vapor is related to its mass fraction at the wall by the gas kinetic formula. The Karman–Pohlhausen integral method is applied to obtain approximate solutions. Solutions are presented for a water heat pipe with neon control gas.