bluuebunny/crossref_metadata_2025 huggingface dataset:
Working Mechanism of Suction Ring and Effects of Its Geometry
Authors: Murai H. , Narasaka T.
Published: November 2010

The working mechanism of a suction ring and the mechanism in which a geometry of suction ring controls flow patterns inside a turbomachine and the performance of the turbomachine are clarified through the analyses of characteristics curves and oil-flow patterns obtained by the experiment performed with respect to an axial-flow pump equipped with suction rings of systematically changed geometry, the axial clearance from impeller blades, radial clearance from the casing and the length. A guide to determine a geometry of suction ring is presented.
Improved Expansion Factors for Nozzles, Orifices, and Variable-Area Meters
Authors: Head V. P.
Published: November 2010

An explicit equation is developed for calculating jet area increase due to compressibility when the incompressible coefficient is known. If the latter is dependent on Reynolds number, Y must be also. When adiabatic theory is applied to this new jet area, instead of to the aperture as measured by solid boundaries, agreement between theory and experiment is much improved. Orifice data on natural gas and variable-area data on air are analyzed in the light of such theory and revised values of Y are proposed. Pursuit of the methods described should lead to improvement of an order of magnitude in the accuracy of fluid flow measurement with nozzles, orifices, and variable-area meters in the sub-critical compressible regime. The author recommends that all expansion factors, theoretical and experimental, should be based on the stagnation temperature as well as on a statement of the particular pressure to be used with stagnation temperature in determining the density to be used in calculating the flow. In any event, no expansion factor can be meaningful unless accompanied by a definition of the temperature and pressure instrumentation used in experiment or assumed in theory.
On Fluffing of Cards
Authors: Desai S. M.
Published: November 2010

When a stack of identical thin cards is placed in a straight rectangular channel so that the planes of the cards are parallel to the channel axis and an air flow is started, it is observed that under suitable conditions the cards get separated from the walls and each other if they are free to do so. This is called fluffing of cards. A two-dimensional analysis based on an application of the principle of minimum dissipation to viscous flows through card gaps is presented to explain the dynamical behavior of the fluffed cards. It is found that the state of uniform distribution is not only the state of static equilibrium but also, the state of absolute minimum viscous energy dissipation. The analysis determines the forces tending to separate the cards and then the equations for small amplitude oscillations of the cards about the state of uniform distribution. These equations are solved for corresponding modes and frequencies.
An Investigation of the Corner Secondary Flows Generated in Planar Nozzles
Authors: Wagner W. B. , Owczarek J. A.
Published: November 2010

An experimental study was made of the total pressure distribution in the corner secondary flow generated in two planar nozzles having different contours. Also, an analysis was made of the extent of the sidewall boundary layer migration caused by the cross flow and of its accumulation in the corner between the sidewall and horizontal nozzle walls at exits of planar nozzles. A comparison of the calculated and experimental results was made. Reasonably good agreement was found between the analytical and experimental results. The Reynolds numbers considered in this study, based on the average flow speed at nozzle exits and on the nozzle widths, were 5000, 10,000, and 20,000. The nozzle aspect ratios were 4 and 2.
Unsteady Flow in Cavitating Turbopumps
Authors: Kim J. H. , Acosta A. J.
Published: November 2010

Unsteady flow in a cavitating axial inducer pump is analyzed with the help of a simple two-dimensional cascade model. This problem was motivated by a desire to study the effect of unsteady cavitation on the so-called POGO instability in the operation of liquid rocket engines. Here, an important feature is a closed loop coupling between several different modes of oscillation, one of which is due to the basic unsteady characteristics of the cavitation itself. The approaching and leaving flow velocities up- and downstream of the inducer oscillate, and the cavity-blade system participates dynamically with the basic pulsating flow. In the present work, attention is focused on finding a transfer matrix that relates the set of upstream variables to those downstream. This quantity, which is essentially equivalent to cavitation compliance in the quasi-static analyses, is found to be complex and frequency dependent. It represents the primary effect of the fluctuating cavity in the system. The analysis is based on a linearized free streamline theory.
Effect of Polymer Additives on Jet Cavitation
Authors: Hoyt J. W.
Published: November 2010

Cavitation in a fluid jet discharged under the surface of a similar fluid was studied using water and dilute solutions of poly(ethylene oxide), a drag-reducing polymer. The addition of a few parts-per-million of poly(ethylene oxide) to the fluid reduced the cavitation-inception index to about one-half the pure-water value. Upstream turbulence increased the cavitation inception index with water but had little effect on cavitation inception with polymer solutions. The viscosity, air content, nuclei number, and tensile strength of the polymer fluid was found to be essentially the same as water, and the surface tension lowered; hence an explanation of the reduced cavitation-inception index observed in polymer solutions must be sought in the changed fluid dynamics of the polymer jet. Photographs of polymer jets discharging in air are presented to aid in the explanation.
A Transient Response Approximation for Noncircular Fluid Transmission Lines
Authors: Moore E. F. , Karam J. T. , Franke M. E.
Published: November 2010

A method is given for determining the transient response approximation for noncircular fluid transmission lines. The results are presented in terms of a characteristic frequency which depends only on the laminar viscous steady flow resistance and inductance of the noncircular line. The components of an equivalent circuit based on standard transmission line theory are analyzed, and approximations of the series impedance, shunt admittance, propagation operator, and characteristic impedance are presented. These circuit parameters are transformed into the time domain to give a simple approximation for the step response of noncircular fluid-filled lines. The solution is expressed as a single complementary error function. Results are shown for air at 27°C. The results are restricted to laminar flow conditions.
The Force Acting on a Particle and a Bubble in a Spherically Oscillating Inviscid Liquid
Authors: Marmur A. , Rubin E.
Published: November 2010

The force acting on a particle and a bubble in a spherically oscillating inviscid liquid is computed and proved to be directed toward the center of the spherical motion. The theoretical solution is analytic for rigid particles and partly numerical for gas bubbles. Results show that under appropriate conditions this force is of the order of magnitude or greater than the gravity force, and it is greater for bubbles than for rigid particles. The use of this phenomenon as a means of separation and controlling particle motion in both gravitational and nongravitational fields is suggested.
An Optimum Stepped Piston for Cylinders Working With Compressible Fluid
Authors: Etsion I.
Published: November 2010

A stepped piston, enclosed within a tight circular cylinder of uniform bore and subjected to unequal upstream and downstream boundary pressures, is analyzed for the case of a compressible fluid. Performance characteristics are given for small eccentricity and high boundary pressure ratio as a function of step size and location, and a design parameter that relates the leakage and the centering force is defined. It is shown that piston performance can be optimized by suitable step design.
Some Experiments on Wet Steam Flow Visualization in Large Steam Turbine Blading
Authors: Krzyz˙anowski J. , Weigle B.
Published: November 2010

In a series of experiments aimed at the visualization of the wet steam flow in the exhaust part of a 200 MW condensing steam turbine a set of periscopes and light sources was used. The aim of the experiment was: 1 – The investigation of the liquid-phase flow over the last stage stator blading of the turbine mentioned. 2 – The investigation of the gaseous-phase flow through the last stage blading at full and part load. The first part of the program partially failed due to the opaqueness of the wet steam atmosphere for the turbine load higher than 10–20 MW. The detailed experimental conditions will be described. An assessment of the primary droplet size will also be given. The preliminary results of the second part of the program will be outlined. The advantages and disadvantages of the equipment used will be discussed.
Methods for Reducing Losses Across Fluid Metering Nozzles
Authors: Benedict R. P. , Gleed A. R.
Published: November 2010

This paper concerns the pressure losses involved in measuring flow rate. These losses can be large and affect the choice of pump or flow metering section to be used. Solutions are developed for predicting these losses for various fluid meter arrangements. Several methods are described for reducing fluid meter loss, including the use of a new step diffuser. Experimental results are given which verify the theoretical solutions. Design curves are presented to aid in the optimum choice of the flow metering section.
Three-Dimensional Flow Field in Rocket Pump Inducers—Part 2: Three-Dimensional Viscid Flow Analysis, and Hot Wire Data on Three-Dimensional Mean Flow and Turbulence Inside the Rotor Passage
Authors: Lakshminarayana B. , Gorton C. A.
Published: November 2010

This paper reports the measurement and prediction of the three-dimensional flow field in an axial flow inducer operating at a flow coefficient of 0.065 with air as the test medium. The experimental investigations included measurement of the blade static pressure and blade limiting streamline angle, and measurement of the three components of mean velocity, turbulence intensities and turbulence stresses at locations inside the inducer blade passage utilizing a rotating three-sensor hot-wire probe. Analytical investigations were conducted to predict the three-dimensional inviscid flow and to approximately predict the three-dimensional viscid flow by incorporating the dominant viscous terms into the exact equations of motion in rotating coordinate system. Radial velocities are found to be of the same order as axial velocities and total relative velocity distributions indicate a substantial velocity deficiency near the tip at mid-passage. High turbulence intensities and turbulence stresses are concentrated within this core region. Evidence of boundary layer interactions, blade blockage effects, radially inward flows, annulus wall effects and back-flows are all found to exist within the long, narrow passages of the inducer, emphasizing the complex nature of inducer flow which makes accurate prediction of the flow behavior extremely difficult.
The Effect of Rotor Blade Wakes on Centrifugal Compressor Diffuser Performance—A Comparative Experiment
Authors: Baghdadi Samy
Published: November 2010

A vortex nozzle facility for testing radial vaned diffusers independently of any rotor has been developed [1, 2]. This paper describes a comparative experiment designed to evaluate the applicability of results obtained on this facility to actual rotating compressors. Geometrically scaled diffusers were tested in the vortex nozzle facility and in an actual rotating compressor rig, and the results are compared and shown to be very similar in terms of both performance and stability limits. The implications of these results are that blade wake mixing and unsteadiness do not significantly affect diffuser performance.
The Particle-Source-In Cell (PSI-CELL) Model for Gas-Droplet Flows
Authors: Crowe C. T. , Sharma M. P. , Stock D. E.
Published: November 2010

The analysis of gas-droplet flows is complicated by the need to account for the mass, momentum, and energy coupling between phases. The concept of regarding the droplet phase as a source of mass, momentum, and energy to the gaseous phase is described and incorporated into a computational model. A steady two-dimensional spray-cooling problem is analyzed to illustrate the applicability of the model. The predicted temperature and velocity flow field for the gas and droplet phase aptly illustrate the capability of the model to treat the complex phenomena associated with multiphase flows.
Effect of Wind-Tunnel Walls on the Flow Past Circular Cylinders and
Cooling Tower Models
Authors: Farell César , Carrasquel Saul , Güven Oktay , Patel V. C.
Published: November 2010

The effect of wind tunnel walls on the mean pressure distributions on rough-walled circular cylinders and on cooling tower models fitted with longitudinal ribs is studied experimentally in the range of Reynolds-number independence. For circular cylinders the results are compared with analytical corrections based on formulae of Allen and Vincenti, and of Maskell, which are found to be generally applicable in this Reynolds number range. For cooling towers, a correction procedure is proposed using the base pressure coefficient, Cpb, and the dimensionless pressure rise to separation, Cpb–Cpm, where Cpm is the minimum value of the pressure coefficient. The base pressure coefficient Cpb for cooling towers is (in the Reynolds-number-independent range) a function of the boundary geometry: model shape, tunnel type (open or closed jet) and blockage, and is independent of surface roughness. The difference Cpb–Cpm, on the other hand, is mainly a function of surface roughness for both cylinders and cooling towers and is very little, if at all, affected by tunnel blockage for blockages less than, say, 15 percent.
Response of a Turbulent Pipe Flow to a Change in Roughness
Authors: Siuru W. D. , Logan E.
Published: November 2010

Measurements of mean longitudinal velocities, static pressure, turbulence quantities and Reynolds shear stress were made in the region between fully-developed smooth wall and rough wall flows in a circular tube. The rough tube was formed by placing rectangular cross-sectioned rings inside a smooth pipe. A phenomenological model was developed to describe the flow in the region of change. The longitudinal pressure gradient responds very rapidly (within a couple of diameters) to the new wall roughness. The effect on the mean and fluctuating velocity parameters was found to grow with the half-power of the longitudinal distance from the start of the roughened tube for the case when the initial roughness element is upstanding.
A Preliminary Study of Flow and Acoustic Phenomena in Tube
Banks
Authors: Fitzpatrick J. A. , Donaldson I. S.
Published: November 2010

Experiments have been performed in a low turbulence wind tunnel to investigate the effect of tube pitch to diameter ratios, depth of bank, and Reynolds number on the parameters associated with resonant acoustic vibration in in-line tube banks. Results indicate that the depth of a bank is a significant factor in acoustic response characteristics and both the vortex shedding hypothesis and the turbulent buffeting hypothesis are shown to be inadequate for certain configurations. A combination of both hypotheses together with energy levels in the turbulence spectrum is suggested, although no definitive proof is offered.
Quasi Two-Dimensional Analysis of Flow Through a Centrifugal Pump
Impeller
Authors: Kumar T. C. Mohana , Rao Y. V. N.
Published: November 2010

A quasi two-dimensional method of singularities is developed for the analysis of flow through a centrifugal pump impeller of varying width. The theory is applied to a double suction centrifugal pump impeller and the results are compared with those obtained by existing two-dimensional and empirical methods. The suggested analysis gives satisfactory results at regimes close to the best efficiency point.
Derivation of Turbulent Transport Coefficients From Turbulent
Parameters in Isotropic Turbulence
Authors: Abdel-Gayed Ramzy G. , Bradley Derek
Published: November 2010

A survey of experimental work on mass, momentum, and energy transport at the axis of pipes relates the ratio of turbulent diffusivity to kinematic viscosity, ε/ν, to the flow Reynolds number. A single relationship is applicable for all three transport processes. Measurements of turbulent parameters also are surveyed and related to the flow Reynolds number. From a combination of the two sets of results a correlation is obtained between ε/ν and the turbulent Reynolds number, Rl, which is possibly of general validity for isotropic turbulence. The results are based upon transport transverse to the flow (“y” direction) and yield εy/ν = 11 Rly0.65 for Rly > 100.
Lift on a Rotating Porous Cylinder
Authors: So Ronald M. C.
Published: November 2010

Two-dimensional flow past a rotating circular cylinder with uniform suction at the surface is considered. The method of solution follows closely that used by Glauert [1] and the problem is solved for the case in which there is no viscous flow separation from the cylinder surface. Expressions in terms of the ratio of the cylinder peripheral velocity and a suction parameter are obtained for the lift and torque. The results show that uniform suction has a limited effect on the lift; however, the torque increases with suction. Possible application of these results to wind power generation is briefly discussed.
The Coupling of Conduction With Laminar Natural Convection From a Vertical Flat Plate With Arbitrary Surface Heating
Authors: Zinnes A. E.
Published: November 2010

A method has been developed for coupling conduction in a solid with natural convection in a surrounding fluid. The problem investigated is that of steady, constant-property, two-dimensional, laminar natural convection from a vertical, heat-conducting flat plate of finite thickness with an arbitrary heating distribution in its surface. Using this method it is possible to predict the variation of temperature in the plate and the velocity and temperature profiles in the boundary layer as a function of the heating distribution and the thermal properties of the plate and fluid. The equations for conduction in the plate and convection in the boundary layer are written in finite difference form, coupled through the common heat flux at the plate-fluid interface, and solved numerically by an iterative technique. Experimental corroboration of the numerical results is provided by measuring temperatures, both with thermocouples and a laser holographic interferometer, along ceramic and glass plates heated by thin film resistance heating elements vacuum deposited on their surface. The results indicate that the degree of coupling between conduction in the plate and natural convection in the fluid is greatly influenced by the plate-fluid conductivity ratio.
The Departure From Nucleate Boiling in Rod Bundles During Pressure Blowdown
Authors: Cermak J. O. , Farman R. F. , Tong L. S. , Casterline J. E. , Kokolis S. , Matzner B.
Published: November 2010

Tests were performed in a high pressure heat transfer loop to determine the behavior of transient DNB during pressure blowdown in rod bundles. Water flowed along a 21 rod, 5-ft-long electrically heated rod bundle with a radially nonuniform heat flux distribution. Both steady-state and transient DNB tests were conducted over the following range of operating parameters: 1 Pressure—750 to 1500 psia; 2 Inlet temperature—480 to 540 deg F; 3 Mass velocity—1 × 106 to 3 × 106 lb/hr ft2; 4 Grid configurations—2. The data were analyzed using calculated subchannel local velocity and enthalpy as a function of time with proper allowance for the mixing and cross flow within the bundle. Results show that the inception of transient DNB during pressure blowdown can be predicted on the basis of steady-state data.
Depth of Penetration During Electron Beam Welding
Authors: Tong H. , Giedt W. H.
Published: November 2010

An examination of available solutions for the penetration depth for electron beam welding revealed that they have been based on mathematical models which are not truly representative of the physical phenomena. The deposition of electron beam energy has been represented by a steady line source. Experimental evidence, however, shows that due to an oscillating flow of the molten material, the electron beam energy is deposited on a surface which varies from close to horizontal to the sides of a cone-shaped cavity. To account for this a cylindrical constant temperature boundary condition was proposed. Results based on this model were found to agree within 20 percent with available depth of penetration data.
Experimental Hydrodynamics of the Accelerated Turbulent Boundary Layer With and Without Mass Injection
Authors: Julien H. L. , Kays W. M. , Moffat R. J.
Published: November 2010

Mean velocity-profile data are reported for blown, unblown, and sucked accelerated turbulent boundary layers. The pressure gradients investigated are those corresponding to constant values of the pressure-gradient parameter K=νU∞2dU∞dx The two values of K considered in detail are 0.57 × 10−6 and 1.45 × 10−6. For each pressure gradient, the surface boundary conditions cover a range of constant blowing and sucking fractions from F = −0.002 to +0.004. Velocity profiles corresponding to these accelerated flows are shown to differ substantially from those characteristic of zero-pressure-gradient flows. For each case of a constant K acceleration, sequential values of the momentum-thickness Reynolds number approach a specific constant, and the velocity distributions near the wall are similar in both wall coordinates and outer coordinates. Results obtained here can be reproduced by a numerical integration of the boundary-layer equations using a modification of the van Driest damping factor, A+, derived from the data presented here. The A+ correlation is presented.
Superheat Layer Thickness Measurements in Saturated and Subcooled Nucleate Boiling
Authors: Wiebe J. R. , Judd R. L.
Published: November 2010

An experimental study of temperature profiles in water boiling on a horizontal copper surface is reported for incipient boiling conditions and for 20,000, 50,000, and 100,000 Btu/hr-ft2 heat flux at various levels of subcooling ranging from 0 to 105 deg F. The extrapolated superheat layer thickness results for the incipient boiling conditions lend support to Hsu’s mathematical model for bubble nucleation. Increasing heat flux and decreasing subcooling were observed to result in a decreasing extrapolated superheat layer thickness. Analysis of some additional results for Freon-113 boiling on a glass surface indicated that the thickness of the extrapolated superheat layer was governed by the bubble flux density which was influenced by both heat flux and subcooling.
Radiation Energy Density and Radiation Heat Flux in Small Rectangular Cavities
Authors: Caren R. P.
Published: November 2010

The present paper investigates the impact of one or more small cavity dimensions on the radiation energy density and radiation heat flux in rectangular metallic cavities. The emphasis of the present analysis is the exact treatment of the modal structure of the electromagnetic field in a small cavity in determining the properties of the thermal radiation field in the cavity. The excitation spectrum of the modes is assumed to be given by the Planck distribution function. The Poynting theorem is invoked in order to determine the radiative heat flux absorbed by the walls from the radiation in the cavity. Variation of the dimensions of the rectangular cavity allows the effects of cavity size and shape on the radiant energy density and radiant heat transfer to be assessed, particularly in several interesting limiting cases. It is found that significant deviations from the classical theory occur whenever any of the cavity dimensions satisfy the inequality lT ≤ 1 cm-deg K. It is further found that, when two or more of the cavity dimensions satisfy the above inequality, the radiant energy density and radiant heat transfer are significantly reduced in comparison to the results of classical theory. However, when only one dimension is limited, as in the case of a closely spaced parallel-surface geometry, the radiant energy density and radiant heat transfer are significantly increased compared to the classical theory.
Theory of Heat Transfer in a Two-dimensional Porous Cooled Medium and Application to an Eccentric Annular Region
Authors: Siegel R. , Goldstein M. E.
Published: November 2010

A class of incompressible solutions has been obtained for the heat-transfer characteristics of a two-dimensional porous cooled medium. The particular type of geometry considered herein is a doubly connected region. To illustrate the application of this class of solutions, it is applied to an eccentric annular region. The two boundaries of the porous medium are each at a different constant pressure, and hence can each be regarded as having a constant velocity potential. As a result, the porous region occupies a rectangle in a potential plane. The energy equation is transformed into a separable equation in potential-plane coordinates, and general solutions are obtained for an arbitrary surface temperature or heat flux. Conformal mapping can then be used to transform the solution into the physical plane.
Laminar Gravity-Flow Film Condensation of Binary Vapor Mixtures of Immiscible Liquids
Authors: Marschall E. , Hickman R. S.
Published: November 2010

The condensation of a binary vapor mixture of immiscible liquids has been studied. The general formulation of this condensation problem includes the application of the conservation laws to both liquid and vapor phase, along with the boundary and interface conditions. The results indicate that only for small condensation rates, that is, for small temperature differences across the liquid film, do transport processes in the vapor boundary layer play an important role. For large condensation rates, heat and mass transfer can be calculated without the solution of the boundary equations of the vapor flow as long as the condensate film is laminar.
Stochastic Optimization of Convective-Fin Design
Authors: Marsh B. L. , Costello F. A.
Published: November 2010

In the design of convective fins, stochastic variations in fin dimensions have traditionally been handled by the use of safety factors. Often this process results in a multiplication of safety factors and thus an overly expensive design. This paper presents a probabilistic approach that not only analyzes the probability of system failure but also uses this analysis to synthesize the optimal design. Four methods of varying accuracy and difficulty are described and compared. The method based on the RMS approximation for the variances appears to be most useful for design purposes.
Heat and Momentum Transfers: Multiple-Disc Rotor Units
Authors: Charters W. W. S. , Lim T. M. , Dunkle R. V.
Published: November 2010

An investigation has been carried out to determine the performance characteristics of a multiple-disc rotor device used as a combined fan/heat exchanger. The advantages of such a system, when applied for example to an air-conditioning system, stem primarily from the simplicity of design and compact nature of the equipment. The assessment of the particular test unit as a fan was done under normal atmospheric conditions using air as the working fluid. A speed range from 550 to 1290 rpm was used in these tests. The maximum efficiency of the momentum transfer from the rotor to the fluid was about 14 percent. The unit capability as a heat exchanger using air flow under normal atmospheric conditions may be judged by the maximum heat transfer effectiveness of about 40 percent. Rotor speeds were varied in the range 700 to 1600 rpm, and at each rotational speed the ratio of the mass flow in the cool stream to that in the hot stream was varied from 0.48 to 1.30. Two different techniques were used in an endeavor to predict the performance of the experimental unit. Of these, the more successful was that based on the assumption that a turbulent boundary layer covered the rotating disc. However, the simpler approach, using calculated friction factors, may well prove acceptable for some engineering applications. The results from each of the prediction techniques are given for comparison with the test results.
Direct Contact Convection Between Liquid Jets and Air in Crossflow
Authors: Hassan Kamal-Eldin , Hilal Mohamed A.
Published: November 2010

Direct contact, or fluid-to-fluid heat convection in the absence of mass transfer is investigated experimentally. A large number of hot liquid jets were cooled by a cross stream of air. It was found that the heat flux thus exchanged is significantly less than that had the jets been enclosed in thin tubes of equal diameter, but larger than the heat flux due to pure conduction in the liquid jets. The results are presented in terms of the usual dimensionless criteria.
Phase Change Problems With Temperature-Dependent Thermal Conductivity
Authors: Cho S. H. , Sunderland J. E.
Published: November 2010

An exact solution is presented for the temperature distribution and phase change position of a semi-infinite body which is initially at a constant temperature different from the fusion temperature. The temperature of the free surface is instantaneously changed and held constant at a value that will cause either melting or solidification of the body. The thermal conductivity is assumed to vary linearly with temperature. The convection in the liquid phase due to density change is also considered.
An Experimental Study of Heat Transfer and Film Cooling on Large-Scale Turbine Endwalls
Authors: Blair M. F.
Published: November 2010

Experiments were conducted to determine the film cooling effectiveness and convective heat transfer coefficient distributions on the endwall of a large-scale turbine vane passage. The vane test models employed simulated the passage geometry and upstream cooling slot geometry of a typical first stage turbine. The test models were constructed of low thermal conductivity foam and foil heaters. The tests were conducted at a typical engine Reynolds number but at lower than typical Mach numbers. The film cooling effectiveness distribution for the entire endwall and the heat transfer distribution for the downstream one-half of the endwall were characterized by large gapwise variations which were attributed to a secondary flow vortex.
An Analytical Solution For a Planar Nongray Medium in Radiative Equilibrium
Authors: Lin C. C. , Chan S. H.
Published: November 2010

The problem of energy transfer through a nongray absorbing and emitting medium, bounded by two black surfaces, in radiative equilibrium is investigated. A nearly exact analytical solution for the temperature distribution within the nongray medium is found by an asymptotic matching technique. The nongray characteristics of the medium are accounted for by using the exponential wide-band model. The analytical solution is valid for all optical thickness and has an error of less than 0.5 percent as compared to the existing numerical solution.
Transport Phenomena in Thermally Stratified Boundary Layers
Authors: Pepper D. W. , Lee S. C.
Published: November 2010

Studies of heat, mass, and momentum transfer are made to analyze the formation of marine fogs in thermally stratified boundary layers in the atmosphere. The governing partial differential equations of continuity, momentum, temperature, and concentration are used to describe the transport phenomena. An additional equation of turbulence energy is introduced to account for the development of the turbulent motions. Simultaneous solution of this system of equations allows the turbulent exchange coefficients to be treated in the same way as all other dependent parameters. Verification of the theoretical approach is made by comparing the numerical predictions with wind tunnel simulations of neutral, stable, and unstable atmospheres. Application of the theory is extended to the investigation of the formation of advection fog over cold ocean surfaces. In addition to the established criteria obtained from wind tunnel data, the fog model takes into consideration the radiation and sedimentation of fog droplets as well as condensation and evaporation of liquid water.
Film Condensation on Inclined Plane Surfaces
Authors: Suryanarayana N. V. , Malchow G. L.
Published: November 2010

An experimental investigation of the effect of reduced gravity forces on film condensation heat transfer rates was carried out. Reduced gravity conditions parallel to the condensing surface were obtained by condensing saturated steam at atmospheric pressure on one surface of a copper block whose inclination to the vertical could be varied giving effective body forces from 0.1g to 1g in several discrete steps. Condensation heat transfer data were higher than predicted by Nusselt’s correlation. Such increases in heat transfer are shown to be well correlated by an empirical correlation suggested by Kutateladze.
Bouyancy Effects on Forced Convection Along a Vertical Cylinder
Authors: Chen T. S. , Mucoglu A.
Published: November 2010

The effects of buoyancy forces on the longitudinal forced convective flow and heat transfer along an isothermal vertical cylinder are studied analytically. This problem does not admit similarity solutions, the nonsimilarity arising both from the transverse curvature ξ = (4/r0) (νx/u∞)1/2 of the cylindrical surface and from the buoyancy effect expressible as Ω = Grx/Rex2 where Grx and Rex are, respectively, the Grashof and Reynolds numbers. The governing equations are solved by the local nonsimilarity method in which all the nonsimilar terms are retained in the conservation equations and only in the derived subsidiary equations are terms selectively neglected according to the two-equation or three-equation model. Numerical results for the velocity and temperature profiles, wall shear stress, and surface heat transfer for the case of assisting flow are presented for gases having a Prandtl number of 0.7 over a wide range of values of ξ from 0 (i.e., a flat plate) to 4.0 and Ω from 0 (i.e., pure forced convection) to 2.0. It is found that the wall shear and surface heat transfer rate increase with increasing buoyancy force and increasing curvature of the surface.
Laminar and Turbulent Free Convection Through Vertical Enclosures Filled With Non-Newtonian Fluids
Authors: Emery A. F. , Dreger W. W. , Wyche D. L. , Yang A.
Published: November 2010

Heat transfer and fluid flow experiments were made in narrow vertical enclosures of varying aspect ratio (5 ≤ H/W ≤ 40) filled with non-Newtonian fluids whose consistencies ranged from near that of water to several orders of magnitude more. Temperature and velocity profiles were obtained for thermal conditions of low convection augmentation to fully developed turbulent flow. The tests were run over periods of as much as 60 days, during which time the flow index and the consistency of the fluids changed markedly according to their thermal histories. Local hot and cold wall and average enclosure heat transfer rates and wall shear stresses were evaluated. For all the fluids, including the abnormal fluids (those which thickened with increasing temperature) the heat transfer could be correlated by Nu=CRab although the constant C differed for the two classes of fluids. These correlations were valid over the entire flow regimes studied even in the presence of multiple boundary layers and secondary vortices.
Laminar and Turbulent Free Convection From Elliptic Cylinders, With a Vertical Plate and Horizontal Circular Cylinder as Special Cases
Authors: Raithby G. D. , Hollands K. G. T.
Published: November 2010

Heat transfer by free convection from thin elliptic cylinders is predicted, accounting for both the effect of thick boundary layers at low Rayleigh numbers and the influence of turbulence at higher Rayleigh numbers. Isothermal and constant heat flux boundary conditions are treated. The results are compared with experimental data, which are available for the limiting cases of large eccentricity (vertical plate) and small eccentricity (horizontal circular cylinder); the agreement is excellent. Accurate correlation equations, from which the average heat transfer can be calculated, are given.
The Effect of the London-Van Der Waals Dispersion Force on Interline Heat Transfer
Authors: Wayner P. C.
Published: November 2010

A theoretical procedure to determine the heat transfer characteristics of the interline region (junction of liquid-solid-vapor) from the macroscopic optical and thermophysical properties of the system is outlined. The analysis is based on the premise that the interline transport processes are controlled by the London-van der Waals dispersion force between condensed phases (solid and liquid). Numerical values of the dispersion constant are presented. The procedure is used to compare the relative size of the interline heat sink of various systems using a constant heat flux mode. This solution demonstrates the importance of the interline heat flow number, A¯h/fgν−1, which is evaluated for various systems.
Augmentation of Horizontal In-Tube Condensation by Means of Twisted-Tape Inserts and Internally Finned Tubes
Authors: Royal J. H. , Bergles A. E.
Published: November 2010

Low pressure steam was condensed inside horizontal tubes of different internal geometries to investigate passive heat transfer augmentation techniques. A smooth tube, the smooth tube having two twisted-tape inserts, and four internally finned tubes were tested. The twisted-tape inserts were found to increase average heat transfer coefficients by as much as 30 percent above smooth tube values on a nominal area basis. The best performing internally finned tube increased average heat transfer coefficients by 150 percent above the nominal smooth tube values. Techniques were developed to correlate the improved heat transfer performance of the two twisted-tape inserts and the four internally finned tubes. The equations developed provide a reasonably accurate description of both the sectional and the average heat transfer coefficients. The finned tube correlation was also reasonably successful in predicting the data from the one other investigation of this augmentation technique for which detailed data were available.
Transient Temperature Distributions Within Porous Slabs Subjected to Sudden Transpiration Heating
Authors: Burch D. M. , Allen R. W. , Peavy B. A.
Published: November 2010

This paper investigates the transient temperature distribution within packed beds after being subjected to single blow heating. Numerical solutions are derived for the fluid and solid temperatures that include the effect of forced convection heat transfer at the fluid-exit surface. An inlet-face heat transfer coefficient is specified that includes both the effect of small scale inlet-face convective heat transfer and heat conduction in the oncoming transpirant. The boundary conditions do not require fluid or solid temperatures to be specified at the bounding surfaces. Charts are presented for predicting the response times for packed bed heat exchangers and chemical reactors covering a wide range of parameters.
A Correction to Noncircular Duct Hot Patch Data
Authors: Maneri C. C. , Schneider R. E.
Published: November 2010

Noncircular duct hot patch data, extensively referred to in the literature, have been found to be in error. When these data are corrected and compared with predictions of hot patch dryout using the most recent form of the Tong F factor, it is found that physically unintelligible results are obtained. It is not clear whether the Tong F factor, the method of predicting the equivalent uniform dryout flux, or the method of reducing the hot patch dryout data is at fault.
Theoretical Determination of Band Absorption With Specific Application to Carbon Monoxide and Nitric Oxide
Authors: Hashemi A. , Hsieh T. C. , Greif R.
Published: November 2010

Results are derived for infrared absorption in a fundamental manner directly from the basic spectroscopic variables. Comparison with the experimental data for carbon monoxide and nitric oxide shows very good agreement. Further work is suggested which includes the effect of variable line spacing.
Mass Transfer and Pressure Rise in Moist Porous Material Subjected to Sudden Heating
Authors: Saito H. , Seki N.
Published: November 2010

In this paper the authors treat heat and mass transfer which may occur in a moist porous material when it is subjected to a sudden heating of a prescribed temperature at the surface. The basic equations describing the heat and mass transfer and their dimensionless forms are presented. Thereafter, a procedure to solve the basic equations is mentioned by using their finite difference equations. Referring to the results of the numerical computations, the influences of various parameters including thermal conductivity, heat capacity, void fraction, mobility, and initial water content of the material upon temperature, pressure, and moisture distributions in the material are discussed in detail. As a conclusion of these discussions, the authors present an empirical formula to predict the maximum pressure. The proposed formula is compared with experimental results and it is found that the formula is useful for the prediction of the maximum pressure occurring in the material during heating.
Temperature Distributions in Fire-Exposed Building Columns
Authors: Lie T. T.
Published: November 2010

A procedure based on a finite difference method is described for calculating the temperature history of fire-exposed protected steel columns with rectangular cross section and heat generation or absorption in the insulation. Comparison with results of tests and those obtained from an analytical solution of the heat transfer equations indicates that the accuracy of the method is adequate for fire engineering purposes. The method is also suitable for the calculation of temperatures in monolithic building components such as solid concrete columns, beams, and walls. It can also be used for the calculation of temperatures of any system in which a perfect conductor or well stirred fluid is enclosed in an encasement, for example, water-filled hollow steel columns or beams, and exposed to a radiative heat source of varying temperature.
Experimental Evaluation of a Cylindrical Parabolic Solar Collector
Authors: Ramsey J. W. , Gupta B. P. , Knowles G. R.
Published: November 2010

Results are presented for a series of solar collector experiments in which the incident solar flux was concentrated by a single-axis tracking parabolic trough mirror. The concentrated solar flux was directed onto an absorber tube whose axis coincided with the focal axis of the concentrator. The performance of the collector was evaluated using three different absorbers; a black painted tube designed to operate near ambient temperature, a heat pipe which had a selective solar absorber coating applied to its surface, and a heat pipe which had its surface coated with a nonselective black paint. The peak efficiency for the collector in the absence of heat losses is approximately 62 percent when the incoming solar energy is normal to the collector aperture. The heat losses which occurred at elevated temperatures (300°C) decreased the peak efficiencies to 50 and 30 percent, respectively, for the selectively coated and black painted tubes. The experimental results establish the technical feasibility of using parabolic trough collectors for applications requiring thermal energy at temperatures up to 300°C.
Transient Pool Boiling Heat Transfer—Part 1: Incipient Boiling Superheat
Authors: Sakurai A. , Shiotsu M.
Published: November 2010

Incipient boiling superheat for exponentially increasing heat inputs to a platinum wire supported horizontally in a pool of water was measured for exponential periods ranging from 5 ms to 10 s and for subcoolings ranging from 25 to 75K under atomospheric pressure. The heat transfer coefficient before the initiation of boiling was related to those by conduction and by natural convection. The heat flux at the incipient boiling point increased with the decrease in the period. The log-log plot of the heat flux against the superheat at the incipient boiling point had a single asymptotic line of slope 2 which was independent of subcoolings in the high heat flux region. On the other hand, as the heat flux decreased to zero, the superheat tended to approach to a constant value for each subcooling. This asymptotic superheat at zero heat flux was higher for higher subcooling. Transient incipient boiling superheat was reasonably explained by the combination of two kinds of incipient boiling models.
Thermoconvective Motion of Low Prandtl Number Fluids Within a Horizontal Cylindrical Annulus
Authors: Custer J. R. , Shaughnessy E. J.
Published: November 2010

Steady natural convection in very low Prandtl number fluids is investigated using a double perturbation expansion in powers of the Grashof and Prandtl numbers. The fluid is contained in a horizontal cylindrical annulus, the walls of which either are held at constant temperature or support a constant heat flux. In both cases the evolution of the flow for increasing Grashof number is of interest. It is found that the basic flow pattern consists of one eddy. For both boundary conditions the center of this eddy falls into the lower half of the annulus as the Grashof number increases. Such behavior is directly opposite to experimental results obtained in fluids of higher Prandtl number.
Choked Expansion of Subcooled Water and the I.H.E. Flow Model
Authors: Collins R. L.
Published: November 2010

The isentropic, homogeneous, equilibrium (I.H.E.) model for two-phase flows is discussed with special regard to recent experimental and theoretical information. Over the past years, the I.H.E. model has been misrepresented many times and its deficiencies have been overstated. More recent studies have indicated that the I.H.E. model may be quite valid for certain types of flows and this paper is presented to amplify these results. It is noted here that the I.H.E. model, under certain reservoir conditions, will over-predict flow rates, that an essential discontinuity of the I.H.E. sound speed may play an important role in choking, that the mass flux-pressure derivative is not continuous at the saturation line, and that the maximum error of the I.H.E. flow rate is about 60 percent at the liquid saturation line.
Interferometric Investigation of Turbulently Fluctuating Temperature in an LMFBR Outlet Plenum Geometry
Authors: Bennett R. G. , Golay M. W.
Published: November 2010

A novel optical technique is developed for the measurement of turbulently fluctuating temperature is a transparent fluid flow. The turbulent sodium mixing in the ANL 1/15-scale FFTF outlet plenum is investigated with a scale-model outlet mixing plenum, using flows of air. The electrical analogue and the power spectral density of the fluctuating temperature are observed experimentally at seven stations in the flow.