bluuebunny/crossref_metadata_2025 huggingface dataset:
The Reversed Brayton Cycle Heat Pump—A Natural Open Cycle for HVAC Applications
Authors: Sisto F.
Published: November 2010

Using reasonable assumptions for turbomachinery efficiencies and heat exchanger effectivenesses, the Coefficient of Performance (COP) and Specific Heating Effect (SHE) of the regenerated and unregenerated cycles are computed and optimized. Only heating data are presented and both open and closed cycles are considered. An effort is made to indicate those cases where (the working fluid being air) the cycle may be appropriately open to combine the heating function with ventilation. When driven by an appropriately small direct Brayton cycle prime mover, the total potential for a new and widespread gas turbine application of literally millions of units becomes defined.
Study of Bolted Joint Integrity and Inter-Tube-Pass Leakage in U-Tube Heat Exchangers—Part II: Applications
Authors: Singh Krishna P.
Published: November 2010

The formulation for “Three Element Bolted Joints” pertinent to removable bundle U-tube Heat Exchangers developed in an earlier work is herein extended to compute inter-tube-pass leakage rates. Design concepts aimed to reduce the leakage flows are proposed and their impact on the stress fields in the structural elements (tubesheet and flanges) is studied. Evaluation of stresses in the tubesheet and mating flanges in a typical example problem reveals potentially severe inadequacies in the existing design codes and standards. Practically feasible remedial design measures are proposed and examined as to their merits and limitations. In particular, the concept of “controlled” metal-to-metal contact beyond the bolt circle, introduced in an earlier work, is explored in depth. Effective use of this concept is shown to significantly alleviate stresses in the elements of the joints.
Experimental Study on Diffusers for Mixed-Flow Machines
Authors: Sakai T. , Sanbe M. , Nakayama T.
Published: November 2010

As a result of examining a relationship between inlet and inside flow patterns in the pure conical mixed-flow diffuser, it was disclosed that a comparatively uniform flow in the diffuser would be obtained resulting in a good pressure recovery. Also to find out an optimum configuration that would enable a stable and effective flow, tests on some model diffusers were made and the following was found: the skewed flow in the pure conical diffuser was rectifiable by means of fitting some guide fences on the face of the diffuser inner wall; though a little twist was observed in the main flow between the inner and outer walls, a curved diffuser gave a slight improvement on the recovered pressure over the case of pure conical one.
Particulate Emissions From Residual Fuel Fired Boilers: Influence of Combustion Modification
Authors: Goldstein H. L. , Siegmund C. W.
Published: November 2010

Studies were carried out in a residual fuel fired package boiler to assess the effect of various combustion modification procedures on the amount and size distribution of particulate emissions. It was found that application of moderate levels of either two stage combustion or flue gas recirculation did not have much effect on particulate loading. Severe staging as well as use of interstage heat transfer to cool the gases between stages produced significantly more particulate. Likewise, higher levels of flue gas recirculation produced substantially more particulate. In both techniques the change in size distribution was mainly in the >10- and 1–10-μm ranges. Emulsified oil containing up to 30 percent water reduced particulate loading primarily in the coarse size ranges. Satisfactory combustion could be obtained using a preheat temperature and excess air level below that required for the straight residual fuel oil.
Measurements of Torsional Dynamic Characteristics of The San Juan No. 2 Turbine-Generator
Authors: Ramey D. G. , Harold P. F. , Maddox H. A. , Starnes R. B. , Knickerbocker J. L.
Published: November 2010

The San Juan Generating Station, jointly owned by Public Service Company of New Mexico and Tucson Gas & Electric Company, is located in the northwestern part of New Mexico. Expansion plans for the transmission system include the addition of series capacitors on lines leaving the plant, necessitating a detailed study of potential subsynchronous resonance problems. A field test was performed on the San Juan No. 2 turbine-generator to obtain measured data for use in these studies. The required data included measurements of torsional resonant frequencies below 60 Hz, mode shapes, and damping characteristics. Test procedures and measurement techniques for obtaining these data are described. The results show that the disturbances caused by line switching in transmission systems can be closely calculated. They also show the correlation between calculated and measured torsional frequencies and mode shapes. The damping coefficient for the first torsional mode is shown to be strongly influenced by electrical system parameters as well as machine loading.
Weak Extinction Limits of Turbulent Flowing Mixtures
Authors: Ballal D. R. , Lefebvre A. H.
Published: November 2010

An equation has been derived for predicting the weak extinction limits of stabilized flames supplied with turbulent, flowing mixtures of uniform composition. Experiments have been conducted to investigate the influence on weak extinction limits of wide variations in inlet air pressure, temperature, velocity, and turbulence level. The apparatus comprised a flameholder, in the form of a hollow cone, which was mounted at the center of a circular pipe with its apex pointing upstream. Fourteen, geometrically similar, conical baffles were manufactured to various sizes and used in conjunction with three different pipe diameters in order to allow the effects of baffle size and blockage ratio to be studied independently over a fairly wide range. The fuel employed was gaseous propane. The experimental results obtained on weak extinction limits were found to be in close agreement with the corresponding predicted values.
The Effect of Water Chemistry on the Reliability of Modern Large Steam Turbines
Authors: Bussert B. W. , Curran R. M. , Gould G. C.
Published: November 2010

The results of a survey of 50 once-through steam generators and 60 drum boiler steam supplies for modern large steam turbines are presented in this paper. A questionnaire was circulated and the information gathered was used to assess current industry practices related to feedwater treatment, boilerwater chemistry and steam purity measurements. Further information was gained by visiting 28 of the surveyed power plants and developing more information concerning their water chemistry practices. The results of the survey and visitation information are then related to individual cases of major corrosion damage that have occurred in the turbines of the participating utilities: The once-through steam generators provide the best measure of steam purity because, in general, the steam purity is equal to the feedwater purity. Major corrosion damage, in many instances stress corrosion cracking, appears to be related to upset conditions of steam purity and water chemistry.
Condensate Reheating and Separate Reheating Hotwells for Central Station Main Condensers
Authors: Harris L. , Bornstein B.
Published: November 2010

Condensate reheating of main condenser effluent with exhaust steam can be used to increase cycle efficiency. This may be accomplished through the use of main turbine exhaust steam; under certain circumstances, this may be accomplished through the use of a Separate Reheating Hotwell that utilizes the exhaust steam from a turbine driving a plant auxiliary. The physical requirements for both of these condensate reheating methods are considered, and their effect on operating in conjunction with multipressure condensers are evaluated and assessed. Separate Reheating Hotwells operating in conjunction with single pressure condensers are investigated too.
Effect of Composition on Melting Behavior of Coal Ash
Authors: Vorres K. S.
Published: November 2010

The design of coal combustion and conversion equipment must consider the behavior of coal ash in the temperature region of application. Correlations of different chemical parameters, including base-to-acid ratio have been made with slagging and fouling behavior. The ionic potential, or ratio of cation valence to cation radius is used as a measure of acid or base behavior. The role of an acid as a polymer former or oxide ion acceptor and a base as a polymer breaker or oxide ion donor is described. The gaseous environment can determine either an acid or base role for iron. Correlations involve concentrations in mole percentages.
Aeroelastic Stability Analysis of Supersonic Cascades
Authors: Strada J. A. , Chadwick W. R. , Platzer M. F.
Published: November 2010

This paper presents three solutions for the analysis of supersonic flow past oscillating cascades with subsonic leading-edge locus. A quite elementary solution is first developed for the case of slowly oscillating finite and infinite flat plate cascades which provides simple analytical expressions for the unsteady pressure distributions. Comparisons with other solutions show generally excellent agreement. Furthermore, a previously developed linearized characteristics solution for finite flat plate cascades is applied to the case of superresonant blade motions. Again, the unsteady blade loading distributions are found to be in good agreement with Verdon’s recent infinite cascade solution for this case. Finally, a nonlinear method of characteristics solution for finite cascades is described which permits the analysis of blade thickness effects on flutter. At this time, only the inlet and passage flow computations have been completed which are compared with the available experimental information.
Sulphur Neutralization by Lignite Ash: Pilot-Scale Combustion Experiments
Authors: Brown T. D. , Lee G. K. , Bambrough H. A.
Published: November 2010

A pilot-scale research boiler (750 kg steam/hr) has been used to study the degree of sulphur neutralization during combustion experiments with three lignites. A series of four closely controlled experiments showed that sulphur balances close to 100 percent could be achieved in the pilot-scale system burning Gascoyne lignite; in these experiments the sulphur retained in solid phase residues varied between 21 and 24 percent of the input sulphur. It was also demonstrated with Utility lignite that external recirculation of flue-gas was moderately effective in reducing nitric oxide emissions at the expense of major increased in the carry-over of unburnt carbon. However, sulphur dioxide neutralization by the coal-ash cations remained essentially unchanged as the recirculation ratio increased. Enhancement of sulphur neutralization by dry lime addition to Poplar River lignite was only found to be effective at addition rates above 1/2 percent lime by weight. The effectiveness of the lime was found to increase as the excess-air level increased.
Electrical Production From Moderate Temperature Geothermal Brines
Authors: Jacobs H. R. , Boehm R. F.
Published: November 2010

Direct contact binary cycles may be used to develop electrical power from moderate temperature geothermal brines. For a simple Rankine cycle using direct contact heat exchangers isobutane is preferred as a working fluid for brines at temperatures greater than 138°C. Pentane appears more attractive at lower temperatures. For all moderate temperature application, however, the use of bottoming cycles, multi-turbine, multi-fluid cycles, yields significantly better performance.
Plane Strain Solutions for Large Diameter Thick Submersible Cylindrical Shells
Authors: Dzialo F. J.
Published: November 2010

Utilizing general stress functions expressed in polar coordinates, plane strain solutions are developed for large diameter thick cylindrical shells. The solutions provide field stresses and strains which consider the effect of gravity body forces, and arbitrary boundary loadings expressed in terms of a Fourier series. To illustrate the theory and its application, a Fourier series expansion is given for a set of boundary stresses partially distributed and in equilibrium. An example is also presented which considers a long cylindrical shell subjected to a gravity body force, a nonuniform hydrostatic pressure, and an arbitrary counterbuoyancy force at the inner boundary. Field stresses and numerical results are provided for the given loading condition.
Measurement of the Auroral-Induced Current in the TransAlaska Pipeline
Authors: Merritt R. P.
Published: November 2010

The aurora and other geophysical phenomena are associated with disturbances in the magnetosphere. Measurement of the potential distribution along the surface of the earth and the current flowing in the earth, i.e., telluric current, have been studied for many years. The presence of a large conductor crossing the region of Alaska with the most active aurora has led to the development of a current monitoring system to measure the total current in the pipeline and measure if any current enters or leaves the pipe in a buried section under test.
A Transformation for the Numerical Solution of Two-Dimensional Free Mixing Flow Problems
Authors: Elassar R. J.
Published: November 2010

A coordinate transformation which removes the variation of the mixing layer width is introduced. The boundary layer equations are then solved in the new coordinate plane using a multilevel difference scheme. The calculated results for two-dimensional symmetric mixing and free shear layer flows for turbulent flow are compared with experimental data and with other solutions.
An Upper Bound on the Stress in Plane Couette Flow
Authors: Nickerson E. C.
Published: November 2010

An absolute upper bound on the momentum number in turbulent plane Couette flow is obtained proportional to the two-thirds power of the Reynolds number. The derivation is based upon the energy integral and the specification of an internally consistent constraint on the fluctuating velocity field. A boundary layer approximation for the mean velocity profile is also obtained and the results are found to be consistent with the two-thirds power law.
Turbulent Jets in a Confined Crossflow
Authors: Stoy R. L. , Ben-Haim Y.
Published: November 2010

An experimental and analytical study of the deflection and impingement of turbulent jets in a confined crossflow, a geometry which occurs in gas turbine blade impingement cooling schemes, is presented. The range of jet and crossflow Reynolds numbers investigated is directly applicable to turbine blade configuratons. A simple one-dimensional analysis using the basic conservation equations is developed to predict jet trajectory, average jet properties, and impingement point for spatially variable crossflow velocity profiles. The simplicity of the one-dimensional analysis makes it more suited to design calculations than two-dimensional jet analyses. Other crossflow velocity profiles are studied and jet development is successfully predicted by the analysis for all cases.
Three-Dimensional Flow Field in Rocket Pump Inducers—Part 1: Measured Flow Field Inside the Rotating Blade Passage and at the Exit
Authors: Lakshminarayana B.
Published: November 2010

The measurement of the flow field within the rotating passages as well as three-dimensional characteristics of the exit flow of an inducer model is reported in this paper. The flow within the inducer is probed by means of rotating pitot probe and pressure transfer device and at the exit by means of three hot wires located in three coordinate directions. In a high solidity inducer (4 bladed), considerable boundary layer growth is observed from hub to mid radius, while the flow from mid radius to tip is found to be highly complex, due to interaction of pressure and suction surface boundary layers and the resulting radial inward flow. The flow losses and wall shear stress derived from these measurements are found to be considerably higher than the corresponding stationary channel. The radial velocities are found to be of the same order of magnitude as axial velocities. Considerable improvement in the flow field is observed when the number of blades is decreased from four to three.
Flow Regime Definition for Flow Between Corotating Disks
Authors: Pater L. L. , Crowther E. , Rice W.
Published: November 2010

Experimental data and results are presented for the flow of an incompressible Newtonian fluid, with full admission, between closely spaced corotating disks, and for both radially inward and radially outward throughflows. The data consist of the measured radial pressure distribution together with flow visualization by means of injected dye, over a very wide range of parameters descriptive of the flows. From the data, the combinations of the parameters corresponding with laminar and with turbulent flow are determined; that is, the data are sufficient to define the flow regimes. Furthermore, for laminar flow, both the pressure distribution data and the flow visualization data confirm the adequacy of earlier analytical results for use in the design of practical devices incorporating these flows, such as multiple disk pumps and turbines.
Dynamic Characteristics of Annular Fluid Transmission Lines
Authors: Healey A. J. , Nicholson J. A.
Published: November 2010

Automatic control of an oil well drilling process requires the knowledge of the dynamics of signal propagation through the annulus formed between the drill and the casing. This paper extends work previously done for circular lines to the annular case. Attenuation and phase speed are presented for various radius ratios as a function of signal frequency. For the liquid case, the results are correlated through the use of an equivalent radius.
Comprehensive Design of Axisymmetric Wind Tunnel Contractions
Authors: Morel T.
Published: November 2010

Design charts for wind tunnel contractions are developed using an inviscid, incompressible flow analysis. A contour formed of two cubic arcs joined smoothly together was found to be a good choice for a wall shape. Therefore, it was selected as the basis for a one-parameter family of wall shapes, which was then investigated in detail. The design chart parameters are the maximum wall pressure coefficients at the inlet (as an indicator of the danger of separation at the inlet end) and at the exit (which is related to the exit velocity nonuniformity). For any choice of these two parameters the charts yield the shape parameter and the nozzle length for this particular family of shapes. The charts may be used to design nozzles with no local separation at the inlet, and with any desired exit velocity uniformity. When the two pressure coefficients are chosen so that separation at both ends is just avoided, the exit boundary layer thickness should be near its minimum.
A Short Diffuser With Low Pressure Loss
Authors: Adkins R. C.
Published: November 2010

A new design concept for gas turbine diffusers is presented and its potential verified by experimental data. The data were obtained from a series of research diffusers, both tubular and annular, with a range of area ratios from approximately 1.9:1 to 3.2:1 and with diffuser entry Mach number and velocity-profile distortion levels which simulated those encountered in engine systems. Measurements for all conditions tested are successfully correlated. From the correlations it is predicted that, in an engine, a pressure recovery in excess of 80 percent may be obtained with diffuser lengths only one-third that required by current design techniques, providing a bleed-off rate of approximately 3 percent of the main airflow can be tolerated at the diffuser throat. It is suggested that the bleedoff will be suitable for turbine cooling purposes.
Effects of Major Design and Operating Parameters on Achieving Low Emissions From Gas Turbine Combustors
Authors: Demetri E. P.
Published: November 2010

The results of a research program involving the design and performance testing of two low-emission combustors for vehicular gas turbine applications are described. The novel features of the combustor designs tested include the use of airblast fuel nozzles, a relatively high value of pressure-loss factor to promote vigorous mixing, and variable geometry to control the liner air flow distributions. Particular emphasis is placed on describing the relative effects of primary-zone equivalence ratio, combustor inlet temperature and pressure, residence time, and the uniformity of the fuel/air distribution in the primary zone. Guidelines for the future design of low-emission combustors based on the observed effects are also presented. The major conclusion reached is that essentially conventional combustor configurations have the capability of achieving the specified emission goals.
Exact Supercavitating Cascade Theory
Authors: Furuya O.
Published: November 2010

A nonlinear exact theory to investigate a steady two-dimensional supercavitating flow past a cascade of arbitrarily shaped blades is presented. The solutions obtained by numerically solving a system of nonlinear, functional equations are compared with the available experimental data for flat-plate cascades and with linearized theories for both flat-plate and circular arc cascades. The force coefficients calculated with the present method show considerably smaller values than those of the linearized theories, as is expected.
Two-Dimensional Base-Vented Hydrofoils Near a Free Surface: Influence of the Ventilation Number
Authors: Rowe A. , Michel J. M.
Published: November 2010

The method of matched asymptotic expansions is used to analyze the flow around a base-vented lifting foil with rounded nose beneath a free surface. The foil is defined numerically. Results concerning the lift and drag coefficients and the limiting values of incidences without cavitation are compared with experiments. The relation between the cavity length and the ventilation number at several depths of submergence is given in the case of a symmetrical wedge: it agrees with the experimental one except by a nearly constant coefficient.
Gravity and Free Surface Effects on a Fully Cavitating Flow
Authors: Young A. C. H. , Song C. C. S.
Published: November 2010

Two-dimensional open channel flow with a steady and fully developed cavity forming at a step on the bottom of the channel was analyzed according to potential flow theory using a re-entrant-jet model. The effects of gravity and the free water surface were fully considered. Cavity profiles and other flow characteristics were found to be significantly different depending upon whether the flow was subcritical or supercritical with a discontinuity at the critical point. The classic solution for an infinite fluid in a nongravitational field was shown to be the limiting case of the subcritical regime. The theory compares favorably with a limited number of existing data in the supercritical regime.
The Effect of Gas Diffusion on the Flow Coefficient for a Ventilated Cavity
Authors: Billet M. L. , Weir D. S.
Published: November 2010

The results of an experimental investigation into the effect of gas diffusion on the volume flow-rate of gas needed to sustain a ventilated cavity are presented. Gas diffusion was found to have a significant effect on the ventilated flow rate required to sustain a cavity of a given size. An analysis for the gas diffusion effect was conducted based on a mathematical model of diffusion proposed by Brennen. The results compare favorably with experimental data. Also, an empirical scaling relationship is proposed for ventilated cavity flows.
An Improvement in the Calculation of Turbulent Friction in Rectangular Ducts
Authors: Jones O. C.
Published: November 2010

Frictional pressure drop in rectangular ducts is examined. Using correspondence between theory and experiment in laminar flow as a means for acceptance of published data, turbulent flow data for smooth rectangular ducts were compared with smooth circular tube data. Data for ducts having aspect ratios between unity and 39:1 were obtained in the literature and, in conjunction with new experimental data, were examined for deviations from the smooth circular tube line (smooth Moody). It was found that at constant Reynolds number based on hydraulic diameter the friction factor increases monotonically with increasing aspect ratio. It was thus concluded that the hydraulic diameter is not the proper length dimension to use in the Reynolds number to insure similarity between the circular and rectangular ducts. Instead, it was determined that if a modified Reynolds number Re* was obtained so that geometric similarity was provided in laminar flow by the relation f = 64/Re* for all geometries, that this Reynolds number also provided good similarity in fully developed turbulent flow within a ∼ 5 percent scatter band about the smooth tube line. By using this “laminar equivalent” Reynolds number, Re*, it is demonstrated that circular tube methods may be readily applied to rectangular ducts eliminating large errors in estimation of friction factor.
Potential Flow Solution for Crossflow Impingement of a Slot Jet on a Circular Cylinder
Authors: Miyazaki H. , Sparrow E. M.
Published: November 2010

A closed-form solution has been obtained for the potential flow about a circular cylinder situated in an impinging slot jet. Among other results, the potential flow solution yields the free stream velocity for the boundary layer adjacent to the cylinder surface. A basic feature of the solution is the division of the flow field into subdomains, thereby making it possible to employ harmonic functions that are appropriate to each such subdomain. The boundary conditions on the free streamline and the conditions of continuity between the subdomains are satisfied by a combination of least squares and point matching constraints. Numerical evaluation of the solution was carried out for cylinder diameters greater or equal to the nozzle width and for a range of dimensionless separation distances between the nozzle and the impingement surface. Results are presented for the velocity and pressure distributions on the cylinder surface, for the position of the free streamline, and for the velocity gradients at the stagnation point. The latter serve as input information to the Nusselt number and skin friction expressions that are given by boundary layer theory. Comparisons were made with available experimental results for the pressure distribution, velocity gradient, and Nusselt number, and good agreement was found to prevail in the stagnation region.
Losses in Radial Inflow Turbines
Authors: Khalil I. M. , Tabakoff W. , Hamed A.
Published: November 2010

A study was conducted to determine experimentally and theoretically the losses in radial inflow turbine nozzles. Extensive experimental data were obtained to investigate the flow behavior in a full-scale radial turbine stator annulus. A theoretical model to predict the losses in both the vaned and vaneless regions of the nozzle was developed. In this analysis, the interaction effects between the stator and the rotor are not considered. It was found that the losses incurred due to the end wall boundary layers can be significant, especially if they are characterized by a strong crossflow. The losses estimated using the analytical study are compared with the experimentally determined values.
Influence of the Axisymmetric Contraction Ratio on Free-Stream Turbulence
Authors: Ramjee V. , Hussain A. K. M. F.
Published: November 2010

The effect of axisymmetric contractions of a given shape and of contraction ratios c = 11, 22, 44.5, 64, and 100 on the free-stream turbulence of an incompressible flow has been studied experimentally with hot-wires. It is found that the longitudinal and lateral kinetic energies of turbulence increase along the contraction. The monotonic increase of the longitudinal turbulent kinetic energy with increasing c is in contrast with the linear (Batchelor-Proudman-Ribner-Tucker) theory. The variation of the lateral turbulent kinetic energy with c is in qualitative agreement with the theory; however, the increase is much lower than that predicted by the theory. The linear theory overpredicts the decrease in the longitudinal turbulence intensity with increasing c and under-predicts the decrease in the lateral turbulence intensity with increasing c. For the given flow tunnel, it is found that a contraction ratio c greater than about 45 is not greatly effective in reducing longitudinal turbulence levels further; the lateral turbulent intensity continues to decrease with increasing c. In the design of a low turbulence-level tunnel, the panacea for the reduction of the turbulence level does not lie in an indefinite increase of the contraction ratio alone. Studies with various upstream screens and a given contraction of c = 11 suggest that the exit turbulence intensities are essentially independent of the Reynolds number based on the screen-mesh size or screen-wire diameter of the upstream screen.
Laser-Doppler Measurements in a Subsonic Jet Injected Into a Subsonic Cross Flow
Authors: Rudinger George , Moon Lamar F.
Published: November 2010

The flow field of a small nitrogen jet (5 mm diameter) injected into a cross flow of air at a momentum-flux ratio of 16 was explored in the plane of the trajectory by means of a laser-Doppler technique. Several traverses were made at right angles to the jet center line obtained from schlieren photographs of light and heavy gases. Velocities were measured in the direction of the traverse and at right angles to it. The locus of the maximum velocity in the direction of the jet trajectory is close to the photographic center line. The vortex center line was derived from the measurements by iteration, and results are in good agreement with those obtained by other investigators with different techniques on a much larger scale. The excess of the center line velocity over the parallel cross stream component decreases faster than for a jet without cross flow, and jet width increases linearly with distance from an effective origin about one jet diameter upstream of the injection point if distances are measured along the trajectory. Velocity profiles exhibit the same similarity as jets injected into stagnant gas.
Semiempirical Analysis of Cavitation in the Wake of a Sharp-Edged Disk
Authors: Arndt Roger E. A.
Published: November 2010

Previously published inception data for cavitation in the wake of sharp-edged disks are reanalyzed. The boundary layer characteristics at the face of the disk are found to play a major role. Good correlation between theory and experiment is achieved when the boundary layer is laminar.
Turbulent Boundary Layer and Flow Resistance on Plates Roughened by Wires
Authors: Furuya Y. , Miyata M. , Fujita H.
Published: November 2010

The flow resistance in a plate roughened by equally spaced wires at right angles to the flow direction was investigated experimentally by measuring the turbulent boundary layer developing along it. Measurements of pressure distribution around a roughness element revealed that the pressure drag accounts for a large portion of the surface resistance and remaining skin frictional part is almost equal to that of a smooth plate. Measurements were also made for plates having three-dimensional roughness. These plates were roughened by short wires in a staggered manner. In this case, the boundary layer was found to have a three-dimensional structure due to accompanying secondary currents.
Flow Distribution Manifolds
Authors: Bajura R. A. , Jones E. H.
Published: November 2010

Flow distribution in the lateral branches of dividing, combining, reverse, and parallel flow manifold systems is studied both analytically and experimentally. Predictions for the flow rates and pressures in the headers of any of the above four basic manifold configurations are obtained from the solution of two first order differential equations involving the flow rate and the pressure difference across headers (pressure-flow equation set), or by the solution of a second order, nonlinear ordinary differential equation involving the flow rate alone (flow distribution equation). Experimental results are presented for various manifold designs having different lateral/header area ratios, lateral flow resistances, and length/diameter ratios. Good agreement is obtained between the analytical and experimental results. Dimensionless parameters which affect flow distribution are identified and discussed with respect to the generalized coefficients of the analytical model. The present method of analysis is proposed for general application in evaluating the performance of flow distribution systems.
An Analysis of Laminar Flow and Pressure Drop in Complex Shaped Ducts
Authors: Zarling John P.
Published: November 2010

An analytical method is presented for solving the governing equation for fully developed, steady, incompressible laminar flow through ducts of constant cross-section having a complex geometry. The technique uses the Schwarz-Neumann alternating method along with least squares point matching. The method is applied to a complex shaped duct and the resulting velocity series solution is used to calculate the flow rate and pressure drop (f•Re) for a range of duct sizes. Numerical results are presented and compared with experimentally determined friction factors for a duct of similar geometry.
An Experimental Study of Surge in Centrifugal Compressors
Authors: Toyama Kosuke , Runstadler P. W. , Dean R. C.
Published: November 2010

Results of high-response measurements in a high-pressure-ratio centrifugal compressor during surge operation are presented. The interpretation of the data provides improved understanding of the flow mechanism of surge and the phenomena which apparently trigger surge. The mass flow throughout the compressor was observed to oscillate in synchronism during supposedly “stable” operation. Surge of the test compressor occurred when a flow perturbation, during “stable” operation, exceeded an apparent limit. When the instantaneous value of diffuser-inlet pressure recovery factor, Cp2*–4, reached approximately 0.40–0.45, the diffuser inlet flow was badly deteriorated and surge occurred. However, gross separation of the diffuser inlet boundary layer was not observed before surge commencement. It is concluded that instantaneous operating states must be recognized for competent surge prediction. Further, doing so will probably require analysis of the entire compressor system including piping, vessels, flow resistances, etc.
Statistical Improvement in Differential Producer Type Flowmeters
Authors: Head V. P.
Published: November 2010

First steps have been taken to demonstrate the feasibility of reducing uncertainties in the use of differential producers. Given a suitable flow conditioner, discharge coefficients are shown to be a highly reproducible function of approach length L/D. In the case of venturis and throat-tap flow nozzles, large effects of excessively small pressure tap diameter ratio δ/d are demonstrated and correlated, and much of the scatter and the premature roll-off of the coefficient with decreasing Reynolds number are thus accounted for. Some influence of throat length ratio x/d upstream of a throat tap is shown.
High-Speed Impact Between Curved Liquid Surface and Rigid Flat Surface
Authors: Hwang J.-B. G. , Hammitt F. G.
Published: November 2010

The impact process of a cylindrical, a spherical and a conical water drop upon a rigid plane is studied with numerical methods. Time variation of drop cross-section, pressure and velocity distribution are presented. The maximum pressure remained at the center of the contact area for the cylindrical drop, but expanded outward with the edge of the contact area for the spherical and conical drops. The peak pressure for both cylindrical and conical drop reached approximately the value predicted by a one-dimensionless analysis. The pattern of pressure distribution on the liquid-solid boundary compared favorably with the existing experimental data.
An Experimental Study of Choked Flow in Short Pipes With Low Air Water Mass Fractions
Authors: Ilic V. , Bryant R. A. A.
Published: November 2010

Using steady flow of air/water at low mass ratios, choking was obtained in short pipes by reducing the back pressure well below atmospheric pressure. Variation of flow parameters affected the choked mass flow-rate, but showed no appreciable effect on the flow pattern; this remained annular with air/water mixture on the outside and water in the core of the pipe.
Optimum Step Design for Centering of Pistons Moving in an
Incompressible Fluid
Authors: Etsion Izhak , Hamrock B. J.
Published: November 2010

Hydrodynamic effects are analyzed for a stepped piston moving within a tight clearance tube filled with an incompressible fluid. Together with the hydrostatic effects that were analyzed in an earlier paper, a complete solution is obtained and an optimum step design for centering of the piston is suggested. The axial speed resulting from an axial driving force is calculated, and some experimental results for pistons falling in a water filled tube are presented.
An Experimental Study of Three-Dimensional Characteristics of
Propeller Wakes Under Stalling Conditions
Authors: Favier Daniel , Rebont Jean , Maresca Christian
Published: November 2010

The three-dimensional flow field of a four-bladed propeller wake has been investigated by use of an anemometric hot film technique. The paper does not deal with the measuring procedure, which has been previously described by the authors, but describes the results obtained for the three-dimensional wake. To gain insight into the process by which local blade stalling influences the wake structure, four advance ratios (λ) have been investigated. The two lower values of λ correspond to a local blade stalling which first affects the blade tip and grows towards the hub with decreasing values of λ. The resultant velocity profiles of u, v, w in the azimuthal direction are investigated and compared at different advance ratios and at various radii. These experimental results reveal that a local flow separation has considerable influence on the three velocity components. It is concluded that for an advance ratio with rotor stalling, the flow separation increases the rotational wake speed effect generated by an increasing tangential component u. The radial flow diminishes as shown by the v velocity profiles. A sharp thickening of the blade wake is also observed from the axial component w.
Solution of the Incompressible Turbulent Boundary-Layer Equations With Heat Transfer
Authors: Cebeci T. , Smith A. M. O. , Mosinskis G.
Published: November 2010

The boundary-layer equations for laminar and turbulent incompressible flows about two-dimensional and axisymmetric flows are solved by an implicit finite-difference method. An eddy-viscosity concept is used to eliminate the Reynolds shear-stress term, and an eddy-conductivity concept is used to eliminate the time mean of the product of fluctuating velocity and temperature. Several flows have been computed by this method, and comparisons with experimental data and with the Bradshaw-Ferriss method are made. In general, the agreement is quite good.
A Dynamic Programming Approach to Stabilize Forced-Convection Two-Phase Flow Systems With “Pressure-Drop” Oscillations
Authors: Maday C. J.
Published: November 2010

Optimization theory is applied to a forced-convection two-phase flow system with heat addition described by a second-order system of differential equations. The mathematical model describes a physical system in which low-frequency pressure-drop oscillations occur, and these oscillations may either grow or decay with time depending on whether the system is stable. The dynamic programming approach is applied to obtain a suboptimal feedback control system which is very stable and exhibits no oscillatory behavior. A system is synthesized whereby pressure and temperature fluctuations are used to control heat-input fluctuations in order to provide stability.
Heat Transfer and Draft Loss Performance of Extended Surface Tube Banks
Authors: Ackerman J. W. , Brunsvold A. R.
Published: November 2010

New heat transfer and draft loss data are presented for one extended surface geometry which was investigated in five staggered and one in-line bank arrangements. In these tests, 1-7/8-inch OD tubes with 1-in. long elliptical studs were investigated. The tube banks, which were in a clean condition, were either 8 or 10 rows deep and covered ratios of transverse spacing to diameter (ST/D) from 2.1 to 3.2 and longitudinal spacing to diameter (ST/D) from 1.7 to 2.4. Heat transfer was from air to the tube banks, with Reynolds numbers ranging from 13,700 to 46,400. Correlations with suitable arrangement factors are shown to adequately describe the performance of the surface investigated. The relative heat transfer, draft loss performance of all arrangements is shown to depend upon the basis of comparison used.
Effect of Buoyancy on Forced Convection in Vertical Regular Polygonal Ducts
Authors: Iqbal M. , Ansari S. A. , Aggarwala B. D.
Published: November 2010

Laminar combined free and forced convection through vertical regular polygonal ducts has been studied. All fluid properties are considered constant, except variation of density in the buoyancy term. Heat flux is considered uniform in the flow direction while in the transverse direction two wall conditions have been considered; Case 1—uniform circumferential wall temperature, and Case 2—uniform circumferential heat flux. A solution by point matching method in terms of a series containing Bessel functions has been obtained. Nusselt numbers, local heat flux, local shear stress, and pressure drop have been investigated. The condition of Case 1 results in higher Nusselt number values compared to the condition of Case 2. However, these differences in Nusselt number diminish as the number of sides of the polygon are increased. In each case at higher values of the Rayleigh number, the Nusselt number is less sensitive to the number of sides. When Nusselt numbers against number of sides are considered, in Case 1, the Nusselt numbers reach asymptotic value at lower number of duct sides compared to Case 2. At low values of buoyancy effect, in Case 1, the maximum circumferential heat flux results at the centre of the wall, while at higher values of the same, the local heat flux becomes uniform over a substantial portion of the wall. Under Case 1 buoyancy effect increases the heat flux ratio at the duct corners. In three-sided polygon at higher values of the buoyancy parameter the maximum shear stress is no longer incident at the wall center. As the number of sides is increased, however, the maximum shear stress again takes place at the wall center. The Case 1 produces higher shear stress values near the wall center, while the Case 2 produces higher shear stress values near the duct corner. When the buoyancy parameter is high and the number of sides is not large, Case 2 results in higher values of pressure drop parameter compared to Case 1.
Thermal Design of High-Altitude Balloons and Instrument Packages
Authors: Kreith Frank
Published: November 2010

The vertical motion of balloon systems depends critically on the heat transfer to and from the gas inside because the temperature and pressure of the gas determines the lift of the balloon and its payload. In the past the thermal design of high-altitude balloons has largely been based on a combination of experience, empirical data, and approximate calculations. Recent advances in heat-transfer research have made it possible, however, to calculate the temperature of the lifting gas as a function of altitude and to predict the vertical motion with the aid of high-speed computers. This review presents the results of heat-transfer experiments and theory pertinent to the processes which affect the calculations of balloon performance and the thermal design of their instrument packages.
Small Spacing Analysis of Radiative Transfer Between Parallel Metallic Surfaces
Authors: Boehm R. F. , Tien C. L.
Published: November 2010

An attempt is made on the basis of electromagnetic theory to predict spacing effects on the radiative transfer between two closely-spaced, semi-infinite metals separated by a nonconducting dielectric. Electromagnetic energy transmission factors are derived for a general, three-medium system and their simplification for the metal-dielectric-metal system is shown. The net energy flux is calculated with these transmission factors and the estimated intensities in the metals. Numerical results are given which exhibit the effects of metal spacing, metal type, temperature level, and type of dielectric. Variations in the heat flux of several orders of magnitude are shown to exist in a system whereas the Stefan-Boltzmann relation indicates a constant flux, independent of spacing.
Heat Transfer to the Highly Accelerated Turbulent Boundary Layer With and Without Mass Addition
Authors: Kays W. M. , Moffat R. J. , Thielbahr W. H.
Published: November 2010

Experimental heat transfer data are presented for a series of asymptotic accelerated turbulent boundary layers for the case of an impermeable wall, and several cases of blowing, and suction. The data are presented as Stanton number versus enthalpy thickness Reynolds number. As noted by previous investigators, acceleration causes a depression in Stanton number when the wall is impermeable. Suction increases this effect, while blowing suppresses it. The combination of mild acceleration and strong blowing results in Stanton numbers which lie above the correlation for the same blowing but no acceleration. Velocity and temperature profiles are presented, from which it is possible to deduce explanations for the observed behavior of the Stanton number. A prediction scheme is proposed which is demonstrated to quite adequately reproduce the Stanton number results, using correlations derived from the profiles.
An Experimental Study of Vigorous Transient Natural Convection
Authors: Mollendorf J. C. , Gebhart B.
Published: November 2010

External natural convection transient response leading to transition and established turbulent flow is determined experimentally and compared with the laminar double-integral theory predictions for processes wherein all transient effects are important. The theory is shown to give very accurate predictions during the laminar portion of the transient, and temperature overshool is not observed experimentally. In addition, several unexpected and very interesting observations were made concerning the stability of the flow as it proceeds to turbulence. The first main observation is that the propagating leading edge effect serves as a very effective moving boundary layer trip and triggers the resulting turbulence. Also for the less extreme condition (less vigorous transient) there is a relaminarization of the boundary layer. Explanations of these observations are proposed in the light of recently acquired results of linear stability theory analysis for small disturbances.
Quasi-Developed Turbulent Pipe Flow With Heat Transfer
Authors: McEligot D. M. , Smith S. B. , Bankston C. A.
Published: November 2010

Available literature on wall friction and heat transfer for gas flow strongly heated in the downstream region of tubes shows disagreement between analysis and experiments. Possible explanations are examined quantitatively, then the governing equations are treated in more complete form than in previous analyses. Results compare favorably with existing experiments for nonreacting, high-Reynolds-number, turbulent flow of a gas with negligible natural convection and with a constant wall heat flux imposed.
Anode Heat Flux Density of High-Current Arcs
Authors: Shih K. T. , Dethlefsen R.
Published: November 2010

The anode heat flux density of high-current arcs was determined by measuring the time from striking an arc to the onset of surface melting. Data were taken using argon and nitrogen with different metals, pressures, and anode surface temperatures. The anode heat flux density was found to be between 104 and 106 w/cm2 for arc currents of 50 to 2000 amp; these values increased with increasing arc current and gas pressure and were higher in nitrogen than in argon. The initial anode surface temperature also had a strong effect on the anode attachment spot.