bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of System Rotation on the Performance of Two-Dimensional Diffusers
Authors: Rothe P. H. , Johnston J. P.
Published: November 2010

Experiments with incompressible flow are reported concerning the effects of Coriolis acceleration on flow separation and on separated flow in plane-wall diffusers of rectangular cross section. The diffusers were rotated about an axis perpendicular to the plane of the nearly two-dimensional flow in order to simulate some features of the blade-to-blade flow distribution in the radial portion of the centrifugal impeller. Various stall regimes are mapped on coordinates of rotation number and diffuser area ratio (at fixed wall length). Diffuser pressure-recovery coefficient is reported as a function of area ratio and rotation number. These data demonstrate that, by suppressing turbulent mixing and shear stress in the suction-side boundary layers, the Coriolis acceleration field greatly enhances the tendency for stall to appear in a diffuser. This effect causes a corresponding reduction in the throat-to-exit pressure recovery as compared to that of nonrotating diffusers of the same geometry and inlet flow blockage.
The Suppression of Flow Separation by Sequential Wall Jets
Authors: North P.
Published: November 2010

The performance of many fluid flow devices is limited by the separation of the turbulent boundary layer. This separation may be suppressed or delayed by use of wall jets, raising questions of jet location and strength. A numerical analysis of a single wall jet gave results in close agreement with experiment. The same analysis of a single wall jet gave results in close agreement with experiment. The same calculation procedure indicated that two sequential wall jets, with the same total kinetic energy flux as the single jet, would suppress separation under conditions where the single jet would not. The best two-jet arrangement would be achieved with 63 percent of the total kinetic energy flux in the first jet. It is possible that three-jet arrangements could provide some further improvement.
Static Characteristics of Shrouded Acoustically Controlled Turbulence Amplifiers
Authors: Rankin G. W. , Sridhar K.
Published: November 2010

The static characteristics of shrouded, acoustically controlled turbulence amplifiers are investigated. The main variables are control sound pressure level and frequency, shroud diameter, gap length and supply flow conditions. Existing analytical and empirical relationships are evaluated. It is found that Bell’s analytical procedure [1] for unshrouded, flow controlled turbulence amplifiers reasonably describes the laminar jet pressure recovery of the amplifiers used in this investigation. The turbulent recovery pressure given by Bell’s procedure is not in agreement with the experimental results of this investigation. A “jump” in the characteristic frequency (defined as the control sound frequency to which the device is most sensitive) occurs as the Reynolds number of the emitter tube is increased. The lower characteristic frequency can be predicted by an advanced Helmholtz resonator theory. Further, the acoustically controlled, unlike the flow controlled, turbulence amplifier can be operated in the proportional mode over a limited range of experimental variables.
The Hydrodynamics Laboratory at the California Institute of Technology—1976
Authors: Ward Thomas M.
Published: November 2010

The High Speed and Free Surface Water Tunnels are the principal research facilities of the Hydrodynamics Laboratory at the California Institute of Technology. Significant changes have been made to these facilities since their erection in 1945. This paper presents a description of these facilities, and their operating characteristics, as they exist today. Recent projects, new instrumentation, and support facilities are also described.
Velocity Distribution in an Abruptly Expanding Circular Duct
Authors: Moon L. F. , Rudinger G.
Published: November 2010

The behavior of recirculating flows typical of advanced air-breathing and rocket injectors has been experimentally investigated. The configuration used consisted of a circular duct having a sudden increase of its diameter. Step size and flow velocity were chosen to be of a magnitude representative of “sudden-dump” combustion chambers. The recirculation, which occurred in the separation region behind the sudden expansion, was investigated using a laser-Doppler velocimeter. Detailed measurements of mean axial velocities were made. Sets of partial differential equations—including continuity, axial and transverse momentum, turbulence energy, and turbulence dissipation—were simultaneously solved using finite differencing techniques. Predictions made using these equations were brought into good agreement with the data taken from the recirculating flows under investigation by selection of appropriate “constants” in the models.
Loss Coefficients for Fluid Meters
Authors: Benedict R. P.
Published: November 2010

A generalized equation is derived which describes the loss coefficient for any differential pressure type fluid meter. This loss coefficient is given in terms of dimensionless factors including: meter geometry, discharge coefficient, contraction coefficient, and diffuser efficiency. The equation applies equally well for venturis, nozzles, and orifices, installed in pipes or with plenum inlets. Another equation is derived which relates the previously published ASME loss parameter for fluid meters to this new generalized loss coefficient.
The 1976 Freeman Scholar Lecture: Some Current Research in Unsteady Fluid Dynamics
Authors: McCroskey W. J.
Published: November 2010

Important unsteady fluid dynamic effects occur in a wide range of modern engineering problems. A review and critical appraisal has been made of the current research activities on topics that contain essential and unique unsteady features, especially those which cannot be approximated by quasi-steady analyses. A synopsis of the main areas covered in this paper is given below. Linear potential theory is well advanced and most of the fundamental concepts are well understood. The theory has been specially adapted for engineering purposes to many complex geometries and flow environments, but its limitations are not well established in most cases. Transonic flows have received considerable attention in recent years, and the profusion of numerical analyses of nonlinear unsteady flows has outstripped measurements. However, new experimental investigations are underway. Numerical codes are becoming much more efficient, and efforts are being made to incorporate viscous effects into them. Unsteady boundary layers have been computed with almost no complementary experimental guidance, and this deficiency is particularly acute in the turbulent case. A major conceptual difference between steady and unsteady separation has been identified and is continuing to be studied. Unsteady stall is currently under detailed examination, and recent experiments have shed considerable new insight on the fundamental mechanisms of dynamic stall on oscillating airfoils. New attempts to treat unsteady stall as a strong viscous-inviscid interaction problem are needed. Vortex shedding from bluff bodies is difficult to predict, especially in cases where body oscillations are self-induced by the fluctuating fluid dynamic forces. Nonlinear oscillator models are limited by a lack of understanding of the basic fluid dynamic phenomena. The trailing edge condition of Kutta and Joukowski for thin airfoils has been called into question recently for unsteady flows at high frequencies or with trailing-edge separation. The correct modeling of this condition is important in predicting the fluid dynamic forces on all thin lifting surfaces that fluctuate. Considerable progress has been made in each of these subjects, but none of them has been mastered. The questions that remain unanswered pose intriguing challenges to the fluid dynamics community.
Linearized Theory of Supercavitating Hydrofoils in Subsonic Liquid Flow
Authors: Nishiyama Tetsuo
Published: November 2010

In order to clarify the compressibility effect, the perturbed flow field of the supercavitating hydrofoil in subsonic region is examined by a linearized technique and, as a result, the general corresponding rule of the compressible flow to the incompressible one is proposed to obtain the characteristics of the supercavitating hydrofoil. The main contents are summarized as follows: (i) Basic relations between velocity, pressure, and sound speed are shown in subsonic liquid flow within the framework of linearization. (ii) The correspondence of the steady, characteristics of the two and three dimensional supercavitating hydrofoils in subsonic liquid flow to ones in incompressible flow is clarified. Hence we can readily calculate the characteristics by simple correction to ones in incompressible flow. (iii) Numerical calculations are made to show the essential differences of the compressibility effect between liquid and gas flow, and also the interrelated effect between cavitation number and Mach number on the characteristics of the supercavitating hydrofoils.
Response of Fluid-Elastically Coupled Coaxial Cylindrical Shells to External Flow
Authors: Au-Yang M. K.
Published: November 2010

The dynamics of a system of two fluid-elastically coupled coaxial cylindrical shells is studied theoretically. The general equations of motion for free and forced-damped vibration are derived in terms of virtual mass, coupling coefficients, and uncoupled natural frequencies of the individual cylindrical shells. For free vibration, numerical solutions to the coupled equations of motion are given as a function of these parameters. For forced-damped vibration, solution is given to the special case when the external force is a normal one acting on the surface of the outer shell, such as the dynamic pressure forces arising from an external turbulent axial flow. It is shown that the coupled system can then be reduced to an equivalent single cylindrical shell. However, the effective force acting on the equivalent single cylinder, as well as its natural frequencies and effective damping ratios, are all modified from the corresponding uncoupled values. The response of the system can then be predicted by established methods in flow-induced random vibration analysis. Curves are included. The study aims mainly at applications to the vibration analysis of hydraulically coupled internal components of a pressurized nuclear reactor but is general enough to find application in other engineering disciplines.
Prediction of Flow Separation in a Diffuser by a Boundary Layer Calculation
Authors: Senoo Y. , Nishi M.
Published: November 2010

From a consideration of flow stability, it is shown that the onset of separation in a diffuser depends upon the local blockage factor. Using performance data for two-dimensional diffusers from the literature, the shape factor of the boundary layer at the separation point Hs is related to the blockage factor Bs at that section, and the formula Hs = 1.8+3.75Bs is deduced as the separation-limit relation. It is proved that this separation-limit relation is also applicable to conical diffusers. Furthermore, a simple theory is derived to evaluate the time-mean pressure recovery in the separated region. Using this method, it is possible to predict whether a separation occurs in a diffuser and to evaluate the pressure recovery.
Increased Turbulent Jet Mixing Rates Obtained by Self-Excited Acoustic Oscillations
Authors: Hill W. G. , Greene P. R.
Published: November 2010

A new device, capable of greatly increasing subsonic jet mixing rates, has been discovered. This device, which we have named the “whistler nozzle,” consists of a convergent nozzle section, a constant area section, and a step change to an exit section with a larger constant area. The exit section excites a standing acoustic wave in the constant area section, in a way similar to the action of an organ pipe. The result of this resonance is a loud pure tone and a greatly increased rate of jet mixing. The increased mixing rates appear related to the acoustically stimulated vortex shedding character (large scale structure or superturbulence) observed by Crow and Champagne [1] in their pioneering study of jets excited by a loudspeaker, and others utilizing upstream valves and pistons, except that the whistler nozzle is self-excited. The standing wave and the resulting increased mixing rates occur for a wide range of exit plane configurations and jet parameters.
Direct Measurement of Wall Shear Stress With Mass Transfer in a Low Speed Boundary Layer
Authors: Depooter K. , Brundrett E. , Strong A. B.
Published: November 2010

A porous plate floating element is used to obtain direct measurements of shear stress in a transpired zero pressure gradient boundary layer from laminar asymptotic suction to blow-off. The thrust balance incorporates a feedback system which provides self centering of the porous element from zero shear stress up to the maximum encountered. Shear stress data obtained for suction and blowing conditions agree well with previously determined indirect data. The floating element data are well correlated by two equations, one for the suction mode, and one for the blowing mode, via simple modifications of an existing correlation.
Numerical Simulation of Natural Convection in Closed Containers by a
Fully Implicit Method
Authors: Pepper D. W. , Harris S. D.
Published: November 2010

Numerical solutions have been obtained for two-dimensional free convective flow in rectangular and annular cavities by the strongly implicit procedure (SIP) and the cyclic reduction-fast Fourier transform (CR-FFT) technique. Rayleigh numbers range from 104 to 106, Prandtl numbers from 0.713 to 103, radius ratios from 1 to 3 (annular cavities), and aspect ratios (height/width) from 1 to 15. Motion is generated by either uniformly heating the bottom wall or heating a vertical wall and cooling the opposite wall. Both time-dependent and steady-state solutions confirm results previously obtained by others. Because SIP uses a common set of matrix algorithms, the governing equations of motion can be solved simultaneously without major modification to the method for each equation.
Numerical Modeling of Unsteady, Separated Viscous
Flow
Authors: Giaquinta A. R.
Published: November 2010

Numerical solutions of the equations governing the laminar flow of an incompressible fluid through a two-dimensional sudden expansion are discussed. The fluid motion is started impulsively from rest and is examined in detail during the transient phase to the steady-state condition. Solutions are obtained by two independent finite-difference methods which are discussed. The development of the flow in the zone of separation is investigated, and, during the earliest phases of motion, the generation of vorticity at the solid boundaries and its spatial diffusion is studied in the region of uniform flow. The numerical treatment of the boundary conditions is discussed. Characteristics of the transient solution for two different Reynolds numbers in the laminar range are presented. Included with the results is the temporal development of the streamline dividing the zone of separation from the main flow.
Prediction of the Three-Dimensional Velocity Field of a Deflected
Turbulent Jet
Authors: Patankar S. V. , Basu D. K. , Alpay S. A.
Published: November 2010

The paper describes the results of a finite-difference solution for the three-dimensional flow field generated by a round turbulent jet deflected by a main stream normal to the jet axis. The Reynolds stresses in the time-averaged momentum equations are calculated by a “two-equation turbulence model” in which differential equations are solved for the kinetic energy of turbulence and for the rate of its dissipation. The solution procedure employs an elliptic finite-difference scheme with the three velocity components and the pressure as the main dependent variables. Results are presented for the cases in which the ratio of the jet velocity to the main-stream velocity ranges from 2 to 10. The numerical predictions are shown to agree well with available experimental data.
Laminar Free Convection From Vertical Cylinders With Uniform Heat Flux
Authors: Nagendra H. R. , Tirunarayanan M. A. , Ramachandran A.
Published: November 2010

The boundary-layer analysis of free-convection heat transfer from a vertical cylinder with uniform heat flux at its surface is made. The transformed ordinary coupled equations form a two-parameter system (ηw and Pr). The two search type of equations is solved using an iterative scheme developed for the isothermal case. Numerical solutions obtained for parametric values of Pr and ηw indicate that the cylinders can be classified as short cylinders, long cylinders, and wires. Heat transfer correlations are presented and compared with experimental data. The results suggest that correlations for the isothermal case may be used for the present case also if a discrepancy of about 6 percent can be tolerated.
An Induced-Convection Effect Upon the Peak-Boiling Heat Flux
Authors: Lienhard J. H. , Keeling K. B.
Published: November 2010

An induced-convection effect upon the peak pool-boiling heat flux is identified and described. A method is developed for correlating this effect under conditions of variable gravity, pressure and size, as well as for various boiled liquids. The effect is illustrated, and the correlation verified, with a large number of peak heat-flux data obtained on a horizontal ribbon heater. The data, obtained in a centrifuge, embrace an 87-fold range of gravity, a 22-fold range of width, a 15-fold variation of reduced pressure, and five liquids.
The Effect of Thermocapillary Flow on Heat Transfer in Dropwise Condensation
Authors: Lorenz J. J. , Mikic B. B.
Published: November 2010

The effect of fluid flow induced by surface tension forces on heat transfer through a drop was considered. The model is a hemispherical liquid drop growing on a flat isothermal-surface. The solution was obtained by finite-difference techniques for different values of the Marangoni number (Nm) associated with surface tension forces and the Biot number (Bi) associated with heat transfer at the liquid-vapor interface. The ranges of parameters covered by this investigation include the regimes of most practical interest for water. The results show that the contribution of internal circulation in the drops to the increase of heat transfer in dropwise condensation is insignificant.
The Transient Response of Heat Exchangers Having an Infinite Capacitance Rate Fluid
Authors: Myers G. E. , Mitchell J. W. , Lindeman C. F.
Published: November 2010

The transient response of heat exchangers to a step change in the temperature of the infinite capacitance rate fluid temperature is discussed. This work applies to condensers, evaporators, precoolers, and intercoolers. Analytical and finite difference methods are used to obtain solutions. The procedure for making useful hand calculations for the entire range of practical values of the parameters is presented.
Profile Development With Mixed Convection in a High Prandtl Number Fluid
Authors: Allen P. H. G. , Finn A. H.
Published: November 2010

The paper deals with entry-length conditions for transformer oil in vertical laminar flow through a uniformly heated duct allowing for changes in density, viscosity, and thermal conductivity. The calculation method uses a fundamental property of high Prandtl number fluids and assumes a series of truncated temperature profiles. Calculated wall mean temperature rises have been verified experimentally for a simple case. Local and mean Nusselt numbers have been derived and an empirical correlation relating mean and limiting Nusselt numbers applied. The analysis includes evaluation of the free-convective component of pressure head which causes flow and distinguishes this from free-convective effects within the duct.
The Effects of Upstream Mass Injection on Downstream Heat Transfer
Authors: Wolfram W. R. , Walker W. F.
Published: November 2010

The present study was performed in order to determine the effects of upstream mass injection on downstream heat transfer in a reacting laminar boundary layer. The study differs from numerous previous investigations in that no similarity assumptions have been made. The complete set of coupled reacting laminar boundary layer equations with discontinuous mass injection was solved for this problem using an integral-matrix technique. The effects of mass injection on heat transfer to both sharp and blunt-nosed isothermal flat plates were studied for a Mach 2 freestream. The amount of injection and the length of the injected region were varied for each body. Heat transfer rates were found to decrease markedly in the injected region. A sharp rise in heat transfer was found immediately downstream of the region of injection followed by an asymptotic approach to the heat transfer rates calculated for the case of no injection. An insulating effect was found to persist for a considerable distance downstream from the injection region. The distance required for this insulating effect to die out was found to depend on the length of the injection region as well as the rate of injection.
Thick Film Analysis of Radiative Transfer Between Parallel Metallic Surfaces
Authors: Domoto G. A. , Tien C. L.
Published: November 2010

The radiative transfer between two infinite parallel metallic surfaces separated by a nonconducting ideal dielectric is calculated on the basis of electromagnetic wave theory. The solution is restricted to the case of large spacing (thick film) wherein the effects of interference and radiation tunneling can be neglected. The optical properties of the metals are predicted via the anomalous skin effect theory, the Drude single electron theory and the Hagen-Rubens relation. A comparison of the predicted radiative fluxes indicates the large disparities which result from the three different specifications of the optical properties of metals. For practical applications at cryogenic temperatures, approximations are obtained for the thick film solution using the anomalous skin effect theory of the optical properties.
Axial Distribution of Bulk Temperature and Void Fraction in a Heated Channel With Inlet Subcooling
Authors: Ahmad S. Y.
Published: November 2010

A theoretical model is developed to determine the axial temperature distribution of subcooled liquid. It is a simple function of a heat transfer and a condensation parameter. The proposed model satisfactorily correlates the measured bulk temperature profiles. The corresponding mid fraction is computed by using a new empirical slip correlation, valid in both subcooled and bulk boiling regions. The resulting axial void profile has been compared (over the entire heated length) with steam and water data from six different sources, covering a wide range of pressure, mass flux, surface heat flux, inlet subcooling and channel geometry. The method gives satisfactory agreement with experimental data.
Surface Roughness Effects on Radiant Energy Interchange
Authors: Hering R. G. , Smith T. F.
Published: November 2010

Radiant interchange between opaque interacting surfaces is formulated for unequal temperature adjoint plates with a one-dimensional surface roughness profile. Rough surface bidirectional reflectance and directional emittance depend on material emittance, roughness element slope, and roughness element specularity. Numerical solution to simultaneous integral equations governing the dimensionless radiant intensities lead to local and overall absorption factors for selected values of the influencing parameters. Absorption factor results show a strong dependence on surface roughness and indicate that roughness effects are more important in the evaluation of radiant interchange than radiant heat loss. Absorption factor values differing by a factor of two to four are commonly observed for identical emittance materials as a result of roughness. The diffuse emission-diffuse reflection property model employing rough surface apparent hemispherical emittance gave the closest agreement to rough surface absorption factor results. Simple property model results, however, were often significantly in error.
Transpiration Cooling of the Constrictor Walls of an Electric High-Intensity Arc
Authors: Heberlein J. , Pfender E.
Published: November 2010

In this paper transpiration cooling of a porous tube exposed to a high-temperature plasma is discussed. The plasma is generated by a high-intensity d-c arc which reaches a thermally and hydrodynamically fully developed state in the porous constrictor tube. From an energy balance over a tube cross section in this regime using a semiempirical relationship between pressure drop and mass flow rate across the porous wall, the temperature distribution in the porous material as well as local heat fluxes are determined. Properties of the porous material which are of particular importance for the performance of a transpiration-cooled arc arc determined independently. The experiments provide a check on the reliability of these data. Analytical predictions of arc and constrictor performance are compared with experimental results. A large discrepancy exists in most of the results which is mainly attributed to turbulent-flow components in the tube which, in turn, can be confirmed by other diagnostic measurements. Finally, various sources for possible errors are discussed and the limitations imposed on the performance of a transpiration-cooled arc by imperfections of porous materials and the technology involved are indicated.
Infrared Radiation Properties of Sulfur Dioxide
Authors: Chan S. H. , Tien C. L.
Published: November 2010

The low resolution measurements of infrared absorption are presented for ν1, ν3, 2ν1, and ν1 + ν3 bands of sulfur dioxide. These measurements were performed at room temperature and at the optical pathlengths such that the data cover the transition and strong absorption regions. The spectral data were correlated in terms of the line-strength and the line-shape parameters by use of the Elsasser model while the Edwards exponential wide-band model was employed to correlate the total band absorptance data. The total emissivity was then calculated from these total band absorptance correlations to compare with Hottel’s result. It is found that Hottel’s result is much higher than the present calculations. Possible causes for such a large discrepancy in Hottel’s result are discussed.
Mass Flux and Enthalpy Distribution in a Rod Bundle for Single- and Two-Phase Flow Conditions
Authors: Lahey R. T. , Shiralkar B. S. , Radcliffe D. W.
Published: November 2010

Diabatic multirod subchannel data have been obtained in a 9-rod bundle for operating conditions typical of a boiling water reactor. These data have been used to obtain both the natural flow and enthalpy distribution in a rod bundle and information on the flow diversion enthalpy and the effective flow diversion length.
Heat Transfer to the Insulator Wall of a Linear MGD Accelerator
Authors: Cochran Robert A. , Fay James A.
Published: November 2010

An experimental investigation of the rate of heat transfer to the insulator wall of a quasi-steady magnetogasdynamic accelerator is described. The experiments were conducted in an accelerator section attached to the end of a shock tube using argon as the test gas. The measurements are compared with a Hartmann boundary-layer analysis, which correlates the data within the experimental scatter. Based on this theory, estimates of the current shorting through the boundary layer and energy fluxes to the wall are made and compared with the accelerator’s overall performance.
Highly Accelerated Compressible Laminar Boundary Layer Flows With Mass Transfer
Authors: Wortman A. , Mills A. F.
Published: November 2010

Exact numerical solutions have been obtained for highly accelerated self-similar laminar boundary layer flows with and without mass transfer. Values of the acceleration parameter β in the range 0 to 20 were considered. Variable gas properties were realistically modeled by assuming ρ ∝ h−1, μ ∝ hω, and Pr = constant. The results presented show the dependence of wall shear stress, heat transfer rate, and displacement thickness on the problem parameters which include β, Mach number, wall enthalpy ratio, mass transfer rate, ω and Pr. The inadequacy of solutions obtained under the simplifying assumptions of Pr = 1.0 and ω = 1.0 is clearly displayed. The numerical solution procedure employed proved quite adequate for a class of problem which has presented serious difficulties to previous investigators.
A Model of Heat Transfer in Fluidized Beds
Authors: Chung Benjamin T. F. , Fan L. T. , Hwang C. L.
Published: November 2010

An expression for estimating the heat transfer coefficient in a fluidized bed has been developed based on the surface renewal and penetration concept. The predicted heat transfer coefficients between walls and beds agree well with experimental results. The result of this analysis shows that, in general, the effect of thermal conductivity of particle on heat transfer is insignificant. The maximum possible Nusselt number for the gas fluidized system is determined theoretically as 13.5. This value appears to be reasonable in light of the majority of available experimental data.
A Probe Technique for Determining the Thermal Conductivity of Tissue
Authors: Cooper T. E. , Trezek G. J.
Published: November 2010

A small needle-like probe has been developed for the determination of the thermal conductivity of either in-vitro or in-vivo tissue. This probe consists of a copper cylinder having a diameter of 1.5 mm and a length of 22.5 mm. Constantan and copper leads are attached to the center and top of the cylinder, respectively, and as a consequence the probe acts as a thermocouple. The distinguishing characteristic of this probe is that when it is suddenly embedded into a medium at a different temperature, the duration of its temperature–time response is such that it can be related to the thermal properties of the medium. This is accomplished by a match with an analytically determined response curve which accounts for metabolic heat generation, blood flow, and conductive effects. By nondimensionalizing the governing equations for the probe–tissue system, three nondimensional groups for time, temperature, and blood flow emerge. The results of a parametric study of these effects are presented in tabular form. Initially, the probe technique was used to determine the thermal conductivity of a 1 percent agar–water mixture and the results were within 5 percent of water. Subsequently, experimental thermal-conductivity data were obtained on the following in-vitro human organs: liver, kidney, heart, spleen, whole brain, brain gray matter, and brain white matter. In addition, density, specific-heat, and water-content measurements were also obtained on these organs. In-vivo conductivity data have recently been obtained for canine liver with and without blood flow. These data indicate that the in-vivo value without blood flow is approximately the same as the in-vitro value after the organ had been removed and refrigerated for 24 hr. Blood flow, if not considered, resulted in apparent conductivities which were 15 to 25 percent higher than that of the tissue.
Thermal-Conductivity Measurements of Propane and N-Butane in the Range 300 to 1000 deg K
Authors: Ehya H. , Faubert F. M. , Springer G. S.
Published: November 2010

Using a thermal-conductivity column the thermal conductivity of propane and normal butane were measured at 760 mm Hg in the range 300–1000 deg K. The thermal-conductivity values obtained were compared with existing data and with the Misic-Thodos formula.
Surface-Tension Effects in Boiling from a Downward-facing Surface
Authors: Huplik V. , Raithby G. D.
Published: November 2010

An experimental investigation of the effect of surface-tension variation around air and vapor bubbles on a downward-facing heated surface is reported. For air bubbles, and vapor bubbles at moderate heat fluxes, regimes of flow where surface-tension forces and buoyancy forces respectively dominate are defined. For boiling at heat fluxes near the burnout limit, flow driven by surface-tension forces appears to play a large role in cooling the heated surface. It is shown that small amounts of surfactant added to the liquid result in dramatic changes in the boiling mechanism, and at high heat fluxes a substantial improvement in the heat transfer. Most of the experiments were conducted with the liquid at temperatures less than the saturation temperature.
Optimization of the Directional Emission from V-Groove and Rectangular Cavities
Authors: Black W. Z.
Published: November 2010

Specially designed cavities are known to produce directional emissivities that have large variations with direction. Surfaces with large variations in radiative properties offer a means of controlling radiative exchange between surfaces. In this paper a measure of the directionality, or degree of focusing, is defined. Possible combinations of directionality and hemispherical emissivity are identified. Two limiting cases for the directional emissivity are discussed which provide collimation of emitted energy in directions which graze and are normal to the cavity opening area, respectively. For a given strength of emission these idealized situations provide maximum focusing of the emission pattern. A V-groove and a rectangular groove are selected as cavities which provide directional emissivities that approach the characteristics of the two limiting cases. Hemispherical emissivity and directionality results for both cavities are presented. Geometries and surface properties of both cavities are optimized to produce maximum focusing of emitted energy. Comparisons are made among the emission characteristics of the V-groove, rectangular groove, and the two idealized limiting cases.
A Numerical Study of Laminar Combined Convective Flow over Flat Plates
Authors: Oosthuizen P. H. , Hart R.
Published: November 2010

The boundary-layer equations for combined forced- and free-convective flow over flat plates have been numerically solved using a simple implicit finite-difference scheme. The method of analysis has been developed for flow over plates for which either the surface temperature distribution or the surface heat-flux distribution is arbitrarily specified. Both assisting flow, in which the longitudinal component of the buoyancy force is in the same direction as the forced flow, and opposing flow, in which it is opposite in direction to the forced flow, have been considered. Numerical results have been obtained for plates having a uniform temperature and a uniform heat-flux distribution, and for fluids with Prandtl numbers of 0.7, 3, and 10.
Incipient-boiling Superheats for Sodium in Turbulent Channel Flow: Effect of Rate of Temperature Rise
Authors: Dwyer O. E. , Strickland G. , Kalish S. , Hlavac P. J. , Schoener G. A.
Published: November 2010

Using sodium, an experimental study was carried out to determine the effect of rate of temperature rise on the incipient-boiling superheat for fully developed, forced turbulent flow. Three different methods of achieving boiling inception were used. The magnitude of the incipient-boiling superheat was found to be quite reproducible and independent of the experimental method as long as the rate of temperature rise (temperature ramp) was kept constant and kept the same. Moreover, the value of the superheat was found to have a strong dependency on the temperature ramp—the greater the ramp, the larger the superheat. The failure to carefully measure and control temperature ramp is apparently one reason why incipient-boiling-superheat data generally show so much scatter, and those from different laboratories so much disagreement.
Mass Rate of Flow in the Natural-Convection Plume above a Heated Horizontal Cylinder Immersed in a Liquid
Authors: Fand R. M. , Keswani K. K.
Published: November 2010

In this paper, an empirical formula is determined whereby the mass rate of flow in the natural-convection plume above a heated horizontal cylinder immersed in a liquid can be calculated. The formula is based upon experimental data obtained for a heated horizontal cylinder immersed in a tank of water. It is anticipated that the formula will be useful in the design of heaters for liquids stored in tanks.
Transient Heat Conduction in Laminated Composites
Authors: Horvay G. , Mani R. , Veluswami M. A. , Zinsmeister G. E.
Published: November 2010

The layers are stacked parallel to the x axis. On the half-space x ⩾ 0 there is applied, at x = 0, a boundary temperature of y-periodicity conforming to the periodicity of the layered composite. The response is determined in the form of a normal mode expansion. A complex eigenvalue problem must be solved first, then the Fourier coefficients are determined from a biorthogonal expansion formula. The series converges to both the real and the imaginary parts of the prescribed input simultaneously. It is found that at low frequencies and not too small distances the static equivalent thermal constants kav, (ρc)av are applicable also in the non-static problem. This ceases to be true at high frequencies.
Optimization of Finned Tubes for Heat Transfer in Laminar Flow
Authors: Hu M. H. , Chang Y. P.
Published: November 2010

The heat transfer of fully developed laminar flow in internally finned tubes is investigated analytically. If there is no heat generation in the fluid, the highest Nusselt number is obtained for the tube with 22 fins extended to about 80 percent of the tube radius. Its value is almost 20 times that for the finless tube. When there is heat generation at sufficiently large rate, the number of fins is reduced from 22 to 16 in order to obtain the highest Nusselt number.
Unsteady, Combined Radiation and Conduction in an Absorbing, Scattering, and Emitting Medium
Authors: Weston K. C. , Hauth J. L.
Published: November 2010

The transient cooldown of a gray, absorbing, isotropic scattering, emitting, and conducting medium bounded by gray, diffusely emitting and reflecting parallel plates is considered. Numerical solutions are obtained for the initial boundary-value problem with a discontinuous decrease in temperature at one boundary. The quasi-steady equation of radiative transfer is solved using Gaussian quadrature and a matrix eigenvector technique together with explicit numerical solution of the unsteady energy equation. Temperature and energy flux distributions are presented for variations of optical thickness, boundary emissivity, albedo, and conduction–radiation parameter.
On the Minimum Size of Large Dry Cooling Towers With Combined Mechanical and Natural Draft
Authors: Moore F. K.
Published: November 2010

The gasdynamic performance equation for large-scale dry cooling towers is derived relating size, shape, fan power, and drag and heat-transfer performance of heat exchangers. Induced-, forced-, or natural-draft towers are special cases. The general result consists of a zero-order scaling formula involving a size function having a minimum for a particular combination of temperatures, together with a set of correction terms of first order in temperature rise. Thus systems that are nearly equivalent gasdynamically can be compared. Technical requirements for small tower size or fan power are expressed in terms of heat-exchanger parameters.
Configuration Factors for Radiant Heat Exchange in Cavities Bounded at the Ends by Parallel Disks and Having Conical Centerbodies
Authors: Holchendler J. , Laverty W. F.
Published: November 2010

Using contour integration, radiation configuration factors are derived and presented in closed form solution for the case of a differential area to a parallel disk with conical blockage and for the case of the same differential element to the conical centerbody.
An Asymptotic Study of the Nusselt-Graetz Problem—Part I: Large x Behavior
Authors: Hickman H. J.
Published: November 2010

A method is given for determining the large x behavior of the Nusselt number for a variety of Nusselt-Graetz problems. Exploitation of properties of the Laplace transform of the temperature yields analytic expressions for Nu as explicit functions of the other parameters of the problem. Accurate results (<1 percent error) are deduced for problems involving the laminar flow of a Newtonian flow between parallel plates and in a circular pipe (valid for all values of the wall Nusselt number).
The Influence of Twisted Tapes in Subcritical, Once-Through Vapor Generators in Counter flow
Authors: Cumo M. , Farello G. E. , Ferrari G. , Palazzi G.
Published: November 2010

The swirl flow of Freon 12 in a tubular heat exchanger, indirectly heated by forced convection of water in an annular gap, is studied. Two identical situations are compared, with and without a twisted tape, to deduce the influence of the swirl flow in the particularly interesting boundary condition of indirect heating by another fluid (and not simply of uniform Joule heating). The heat transfer is greatly increased by the swirl flow, up to a factor of two at the burnout or dryout point.
Continuous Slug Flow in Vertical Tubes
Authors: Clift R. , Grace J. R. , Sollazzo V.
Published: November 2010

A method of simulating the behavior of continuously slugging vertical columns is presented. Slugs are introduced at regular time intervals at some reference level near the bottom of a column and their subsequent motion and coalescence is simulated numerically. Experiments on coalescing slug pairs are used to supply information on slug interactions, while the relationship between slug length and volume is obtained from experiments on single slugs. The numerical predictions are in reasonable agreement with experimental results for continuously slugging liquids.
Natural Convective Heat Transfer Rates During the Solidification and Melting of Metals and Alloy Systems
Authors: Chiesa F. M. , Guthrie R. I. L.
Published: November 2010

Analysis of experiments involving a cylindrical column of lead in the process of freezing downward or alternatively, of melting upward from the base of the container, showed that heat transfer rates associated with Be´nard convection are less under transient conditions than at steady-state. Analysis of experiments involving the freezing of lead-tin alloys (0.2 – 1.6 wt. percent Sn) showed that the same heat transfer correlation for Be´nard convection could be applied, provided the upper bounding “interface” was located on the solidus isotherm for planar and cellular alloy growth, and on the liquidus, for cellular-dendritic alloy growth.
Radiative Transfer in Homogeneous Nongray Gases With Nonisotropic Particle Scattering
Authors: Domoto G. A. , Wang W. C.
Published: November 2010

A perturbation technique is presented to treat the problem of radiative transfer in homogeneous, plane parallel, nongray gases with nonisotropic particle scattering. The technique allows use of nongray narrow-band or wide-band models as well as Mie and Rayleigh scattering coefficients and asymmetry factors. Results are obtained in the form of monochromatic transmittance, reflectance, and absorptance of water clouds typical of those in the earth’s atmosphere.
On Two-Phase Highly Dispersed Flows
Authors: Cumo M. , Farello G. E. , Ferrari G. , Palazzi G.
Published: November 2010

Experimental research on highly dispersed, two-phase, turbulent flows was performed employing Freon 12 at different pressures up to the critical value. By means of visualization techniques it was possible to study the droplet size distribution, their spatial concentration, and the relationships among the deduced law of distribution and the main thermo-hydraulic parameters for different thermo-hydraulic conditions (pressure, mass velocity, and quality). Simple relations were developed which make it possible to determine, at least for some reference thermo-hydraulic situations, all of the characteristics of the liquid dispersed phase.
The Influence of Radiation on Arc Constriction in the Anode Region
Authors: Pfender E. , Schafer J.
Published: November 2010

An improved analytical model for the description of the anode contraction zone of a high intensity arc takes radiation effects into account. The conservation equations for the anode contraction zone and the adjacent undisturbed arc column are solved numerically with a relaxation method. Results for atmospheric pressure argon arcs at three different currents demonstrate that radiation losses reduce temperature peaks substantially and, at the same time, provide a smooth matching of arc column and contraction zone solutions. Although the model seems to be adequate for a large portion of the anode contraction zone, the results indicate that refinements of the model are necessary for the region close to the anode, in particular, deviations from LTE have to be taken into account.
Measurement of the Condensation Coefficient of Mercury by a Molecular Beam Method
Authors: Narusawa U. , Springer G. S.
Published: November 2010

The condensation coefficient of mercury was determined by measuring the number flux of a mercury vapor beam incident on, and reflected from, a liquid mercury surface. For a clean surface the condensation coefficient was found to be between 0.65 and 1.
Effects of a Transverse Magnetic Field on a Constricted Electric Arc
Authors: Ahrens F. W. , Powell H. N.
Published: November 2010

The interaction of a constricted electric arc (argon at 1 atm) with an applied perpendicular magnetic field has been investigated analytically. The resulting (two-dimensional) flow and temperature fields, conductive and radiative wall heat transfer, and voltage-current characteristics of the arc are predicted. Three characteristic parameters are isolated: (I/a = current/tube radius), (Re = Lorentz and viscous force parameter), (RT = radiation parameter). When radiation is negligible, the first two are sufficient to scale the effects of any combination of current, tube radius, and applied magnetic field strength. A twin vortex flow pattern is predicted, with the displacement of the vortex “eyes” greatest for high applied magnetic fields and low currents. Comparisons with experimental results from the literature are good to satisfactory.
Heat Transfer in Rotary Combustion Engines
Authors: Atesmen K. M.
Published: November 2010

In the first part of this study, a one-dimensional quasi-steady-state heat transfer model is developed for an axial forced flow system in rotary combustion engines. This computer model is useful in optimizing the cooling system in accordance with the heat input from the combustion chambers. In the second part of this study, a two-dimensional quasi-steady-state heat transfer model is developed for an axial forced flow cooling system in a rotor housing in an effort to minimize the thermal stresses and the thermal distortions of the trochoidal surfaces. In the third part of this study, a two-dimensional transient heat transfer model is developed for an axial forced flow cooling system in a critical portion of the rotor housing in order to determine the critical thermal loads that occur in the through-bolts during the sudden acceleration of a cold rotating combustion engine.
Effect of Precursory Cooling on Falling-Film Rewetting
Authors: Sun K. H. , Dix G. E. , Tien C. L.
Published: November 2010

An analytical model for falling-film wetting of a hot surface has been developed to account for the effect of cooling by droplet-vapor mixture in the region immediately ahead of the wet front. The effect of precursory cooling is characterized by a heat transfer coefficient decaying exponentially from the wet front. Based on the present model, the wet front velocity, as well as the temperature profile along a thin slab, can be calculated. It is demonstrated that the precursory cooling can increase the wet front velocity by an order of magnitude. Existing experimental data with variable flow rates at atmospheric pressure are shown to be successfully correlated by the present model.
Normal and Hemispherical Thermal Emittances of Cylindrical Cavities
Authors: Alfano G. , Sarno¨ A.
Published: November 2010

Normal and hemispherical thermal emittances of cylindrical cavities closed by a circular diaphragm have been evaluated. Diaphragms are diffuse or specular reflectors, at the cavity temperature or at a very low temperature. Results are reported and discussed.